EX-99.1 2 d325652dex991.htm EX-99.1 EX-99.1

Exhibit 99.1

 

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TECHNICAL REPORT ON THE

GOLDSTRIKE MINE, EUREKA AND ELKO

COUNTIES, NEVADA, USA

PREPARED FOR BARRICK GOLD

CORPORATION AND FRANCO-NEVADA

CORPORATION

Report for NI 43-101

Rev. 0

Qualified Persons:

Chester M. Moore, P.Eng.

R. Dennis Bergen, P.Eng.

Wayne W. Valliant, P.Geo.

Stuart E. Collins, P.E.

Kathleen Ann Altman, Ph.D., P.E.

March 16, 2012


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Report Control Form

 

Document Title

   Technical Report on the Goldstrike Mine, Eureka and Elko Counties, State of Nevada, USA.

Client Name & Address

  

Mr. Rick Sims

Senior Director Reserves and Resources

Barrick Gold Corporation

10371 N. Oracle Road

Suite 201

Tucson, AZ 85737

  

Franco-Nevada Corporation

Exchange Tower

130 King Street West, Suite 740

P.O. Box 467

Toronto, Ontario M5X 1E4

Document Reference

   Project #1663    Status &

Issue No.

     

Final

Version

   Rev 0

Issue Date

   March 16, 2012            

Lead Author

  

Chester M. Moore, P.Eng.

R. Dennis Bergen, P.Eng.

Wayne W. Valliant, P.Geo.

Stuart E. Collins, P.E.

Kathleen Ann Altman, P.E.

  

(Signed)

(Signed)

(Signed)

(Signed)

(Signed)

           

Peer Reviewer

   Graham G. Clow, P.Eng.    (Signed)      

Project Manager Approval

  

Chester M. Moore, P.Eng.

Wayne W. Valliant, P.Geo.

  

(Signed)

(Signed)

     

Project Director Approval

   Richard J. Lambert, P.E.    (Signed)      

Report Distribution

           Name       No. of Copies   
   Client         
   RPA Filing       1 (project box)   

Roscoe Postle Associates Inc.

55 University Avenue, Suite 501

Toronto, Ontario M5J 2H7

Canada

Tel: +1 416 947 0907

Fax: +1 416 947 0395

mining@rpacan.com

 

  
  


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TABLE OF CONTENTS

 

     PAGE   

1 SUMMARY

     1-1   

Executive Summary

     1-1   

Technical Summary

     1-7   

2 INTRODUCTION

     2-1   

3 RELIANCE ON OTHER EXPERTS

     3-1   

4 PROPERTY DESCRIPTION AND LOCATION

     4-1   

5 ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY

     5-1   

6 HISTORY

     6-1   

7 GEOLOGICAL SETTING AND MINERALIZATION

     7-1   

Regional Geology

     7-1   

Property Geology

     7-4   

Mineralization

     7-12   

8 DEPOSIT TYPES

     8-1   

9 EXPLORATION

     9-1   

10 DRILLING

     10-1   

Open Pit

     10-1   

Underground

     10-5   

11 SAMPLE PREPARATION, ANALYSES AND SECURITY

     11-1   

Sampling Method and Approach

     11-1   

Sample Preparation, Analyses and Security

     11-3   

Quality Assurance and Quality Control

     11-9   

12 DATA VERIFICATION

     12-1   

Open Pit

     12-1   

Underground

     12-1   

13 MINERAL PROCESSING AND METALLURGICAL TESTING

     13-1   

Metallurgical Testing

     13-1   

Mineral Processing

     13-1   

Recovery

     13-1   

Allocation and Reconciliation

     13-2   

14 MINERAL RESOURCE ESTIMATE

     14-1   

Open Pit Mineral Resources

     14-2   

Underground

     14-12   

15 MINERAL RESERVE ESTIMATE

     15-1   

Open Pit

     15-1   

Underground

     15-8   

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page i
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16 MINING METHODS

     16-1   

Open Pit

     16-1   

Underground

     16-7   

17 RECOVERY METHODS

     17-1   

Mineral Processing

     17-1   

Process Description

     17-3   

18 PROJECT INFRASTRUCTURE

     18-1   

Open Pit

     18-1   

Underground

     18-3   

19 MARKET STUDIES AND CONTRACTS

     19-1   

Markets

     19-1   

Contracts

     19-1   

20 ENVIRONMENTAL STUDIES, PERMITTING, AND SOCIAL OR COMMUNITY IMPACT

     20-1   

Tailings Storage Facility

     20-1   

Project Permitting

     20-2   

Surface Disturbance

     20-4   

Social or Community Requirements

     20-6   

Mine Closure Requirements

     20-6   

21 CAPITAL AND OPERATING COSTS

     21-1   

Capital Costs

     21-1   

Operating Costs

     21-3   

22 ECONOMIC ANALYSIS

     22-8   

23 ADJACENT PROPERTIES

     23-1   

24 OTHER RELEVANT DATA AND INFORMATION

     24-1   

25 INTERPRETATION AND CONCLUSIONS

     25-1   

Open Pit

     25-1   

Underground

     25-2   

26 RECOMMENDATIONS

     26-1   

27 REFERENCES

     27-1   

28 DATE AND SIGNATURE PAGE

     28-1   

29 CERTIFICATES OF QUALIFIED PERSONS

     29-1   

LIST OF TABLES

 

     PAGE   

Table 1-1 Goldstrike Mineral Resources—December 31, 2011

     1-2   

Table 1-2 Goldstrike Mineral Reserves—December 31, 2011

     1-3   

Table 1-3 Goldstrike Open Pit Mineral Resources—December 31, 2011

     1-13   

Table 1-4 Underground Mineral Resources—December 31, 2011

     1-13   

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page ii
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Table 1-5 Betze-Post Open Pit Mineral Reserves—December 31, 2011

     1-15   

Table 1-6 Goldstrike Underground Reserves—December 31, 2011

     1-15   

Table 1-7 Alkaline CaTS Recovery Calculations for LOM Plan

     1-20   

Table 1-8 Roaster Recovery Calculations for LOM Plan

     1-20   

Table 6-1 Past Production—Underground Mine

     6-3   

Table 6-2 Past Production—Open Pit Mine

     6-3   

Table 6-3 Past Production—Plant Facilities

     6-4   

Table 10-1 Drill Hole Database Statistics

     10-2   

Table 10-2 Downhole Survey Statistics

     10-4   

Table 10-3 Underground Drilling to EOY2011

     10-5   

Table 11-1 Core Sample Control Assay Statistics

     11-13   

Table 11-2 Chip Sample Control Assay Statistics

     11-13   

Table 13-1 Alkaline CaTS Recovery Calculations for LOM Plan

     13-2   

Table 13-2 Roaster Recovery Calculations for LOM Plan

     13-2   

Table 13-3 Summary of Head Grade Adjustments

     13-4   

Table 14-1 Goldstrike Mineral Resources—December 31, 2011

     14-1   

Table 14-2 Open Pit Mineral Resources—December 31, 2011

     14-2   

Table 14-3 Open Pit Mineralization Domains

     14-3   

Table 14-4 Open Pit Grade Contour Zones

     14-4   

Table 14-5 Capping of High Grade Values—Open Pit

     14-7   

Table 14-6 Grade Interpolation Parameters for Open Pit Resource Estimation

     14-9   

Table 14-7 Open Pit Resource Classification

     14-11   

Table 14-8 Underground Mineral Resources—December 31, 2011

     14-13   

Table 14-9 Underground Inferred Mineral Resources—December 31, 2011

     14-14   

Table 14-10 Tonnage Factor/Density – Goldstrike Underground

     14-18   

Table 14-11 Underground Sample Statistics

     14-19   

Table 14-12 Underground Composite Statistics

     14-20   

Table 14-13 Underground Resource Classification Distances

     14-23   

Table 15-1 Goldstrike Mineral Reserves—December 31, 2011

     15-1   

Table 15-2 Betze-Post Open Pit Mineral Reserves—December 31, 2011

     15-2   

Table 15-3 Autoclave and Roaster Stockpile Accounting Summary for November 2010 YTD

     15-6   

Table 15-4 Open Pit Cut-off Grade Parameters—2011

     15-7   

Table 15-5 Rodeo/Meikle Underground Mineral Reserves—December 31, 2011

     15-8   

Table 15-6 Underground Cut-off Grade Estimates

     15-10   

Table 15-7 Reconciliation Data for Goldstrike Underground

     15-11   

Table 15-8 DOM Compared to Reserve Model

     15-12   

Table 15-9 Rodeo Stope Statistics October 2010

     15-13   

Table 15-10 Rodeo Stope Performance

     15-14   

Table 16-1 Open Pit Mine Design Parameters

     16-2   

Table 16-2 Open Pit Mine Equipment Fleet

     16-6   

Table 16-3 Open Pit Equipment Productivity

     16-6   

Table 16-4 Open Pit Life of Mine Production Summary

     16-7   

Table 16-5 Goldstrike Underground Zones

     16-8   

Table 16-6 Underground Production Data

     16-10   

Table 16-7 Underground Zone Dimensions

     16-11   

Table 16-8 Underground Waste Development Compared to Plan

     16-14   

Table 16-9 Underground Dilution EOY2011

     16-14   

Table 16-10 Mining Extraction—2011

     16-16   

Table 16-11 Underground Equipment

     16-17   

Table 16-12 Underground Production Schedule—Reserves Only

     16-19   

Table 16-13 Underground Reserve and Resource Production Schedule

     16-20   

Table 20-1 Goldstrike Permits

     20-3   

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page iii
Technical Report NI 43-101 – March 16, 2012   


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Table 20-2 Barrick Goldstrike Mine Disturbance Estimate

     20-5   

Table 21-1 2012 Life of Mine Capital Cost Estimate

     21-2   

Table 21-2 2012 Life of Mine Capital Cost Estimate by Year (Not including Reclamation)

     21-3   

Table 21-3 Actual Reported Open Pit Operating Costs—YTD November 30, 2011

     21-4   

Table 21-4 Average LOM Operating Cost (2012-2026)

     21-4   

Table 21-5 October 2011 YTD Performance

     21-5   

Table 21-6 Underground LOM Operating Costs

     21-6   

Table 21-7 Project 2012 Manpower

     21-6   
LIST OF FIGURES   
     PAGE   

Figure 4-1 Location Map

     4-3   

Figure 4-2 Land Ownership

     4-4   

Figure 4-3 Footprint of Mineralization

     4-5   

Figure 7-1 Regional Geology

     7-2   

Figure 7-2 Open Pit Geology

     7-5   

Figure 7-3 Open Pit Geology Cross Sections

     7-6   

Figure 7-4 Underground Geology Long and Cross Sections

     7-11   

Figure 7-5 Open Pit Zone Locations

     7-13   

Figure 7-6 Underground Longitudinal Section

     7-16   

Figure 10-1 Drill Hole Location Plan

     10-3   

Figure 10-2 Downhole Survey Measurement Intervals

     10-4   

Figure 10-3 Drill Hole Locations

     10-6   

Figure 14-1 Bench 4290 Grade Zone Contours

     14-5   

Figure 14-2 Open Pit Composite Length Statistics

     14-8   

Figure 14-3 Isometric View of Underground Block Models

     14-17   

Figure 15-1 Goldstrike Open Pit General Material Routing Flow Chart

     15-4   

Figure 16-1 Ultimate Open Pit Outline

     16-3   

Figure 16-2 Pit Slope Design Criteria

     16-5   

Figure 16-3 Underground Section and Plan

     16-9   

Figure 17-1 POX Process Flow Diagram

     17-2   

Figure 17-2 Roaster Process Flow Diagram

     17-6   

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page iv
Technical Report NI 43-101 – March 16, 2012   


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1 SUMMARY

EXECUTIVE SUMMARY

Roscoe Postle Associates Inc. (RPA) was retained by Barrick Gold Corporation (Barrick) Franco-Nevada Corporation (Franco-Nevada) to prepare an independent Technical Report on the Goldstrike Open Pit and Underground Mine (the Project), in Eureka and Elko Counties, Nevada, USA. The purpose of this report is to support public disclosure of Mineral Resource and Mineral Reserve estimates at the Project. This Technical Report conforms to NI 43-101 Standards of Disclosure for Mineral Projects. RPA visited the open pit between December 7 and 9, 2010, and the underground operation between December 13 and 15, 2010.

Barrick is a Canadian publicly traded mining company with a portfolio of operating mines and projects across five continents. Franco-Nevada is a Canadian publicly traded company focused on gold royalties and revenue streams. The Goldstrike Mine property is located within the northern Carlin Trend on the western flank of the Tuscarora Mountains in Eureka and Elko Counties, northeastern Nevada, USA, approximately 38 mi northwest of Elko and 27 mi north-northwest of the town of Carlin.

The Goldstrike Mine contains both open pit and underground operations. The Betze-Post open pit is a large scale operation utilizing a traditional truck and shovel fleet. The current open pit production plan shows that 47.6 million tons of ore grading 0.108 oz/st Au will be mined between 2012 and 2025. The ultimate pit will measure approximately two miles east to west, 1.5 mi north to south, and have an average depth of approximately 1,300 ft. The underground mine consists of ten separate zones stretching over a length of 12,000 ft and a vertical distance from 600 ft to 1,925 ft below surface. Underground mine production is planned from the Rodeo, Meikle, North Post, and Banshee mine areas. Underground Mineral Reserves totalling 11.9 million tons at 0.255 oz/st are projected to sustain the mine operations until 2020. Barrick maintains a second mining plan which includes conversion of resources and totals 18.1 million tons grading 0.277 oz/st Au and has projected production between 2012 and 2024.

Table 1-1 summarizes the total Mineral Resources, exclusive of Mineral Reserves, at the Goldstrike Mine.

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page 1-1
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TABLE 1-1 GOLDSTRIKE MINERAL RESOURCES—DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

     Measured Resources      Indicated Resources     

Measured + Indicated

Resources

 
     Tons      Grade      Contained
Gold
     Tons      Grade      Contained
Gold
     Tons      Grade      Contained
Gold
 

    Area    

   (000)      (oz/st Au)      (000 oz)      (000)      (oz/st Au)      (000 oz)      (000)      (oz/st Au)      (000 oz)  

Within Reserve Pit

     783         0.032         25         3,368         0.032         108         4,151         0.032         133   

Within Resource Pit

     103         0.032         3         358         0.032         12         462         0.032         15   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Open Pit Subtotal

     886         0.032         28         3,726         0.032         119         4,612         0.032         147   

Underground

     985         0.341         336         5,092         0.293         1,492         6,077         0.301         1,828   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total

     1,867         0.195         364         8,818         0.183         1,611         10,685         0.185         1,975   

 

     Inferred Resources  
     Tons      Grade      Contained
Gold
 

    Area    

   (000)      (oz/st Au)      (000 oz)  

Within Reserve Pit

     531         0.055         29   

Within Resource Pit

     34         0.049         2   
  

 

 

    

 

 

    

 

 

 

Open Pit Subtotal

     564         0.055         31   

Underground

     2,698         0.298         805   
  

 

 

    

 

 

    

 

 

 

Total

     3,263         0.256         835   

Notes:

 

  1. CIM Definitions were followed for Mineral Resources.

 

  2. Mineral Resources are estimated using a long-term gold price of $1,400 per ounce.

 

  3. Mineral Resources are exclusive of Mineral Reserves.

 

  4. Open pit Mineral Resources are based on cut-off grades of 0.030 oz/st Au for roaster feed, 0.040 oz/st Au for acid POX, 0.045 oz/st Au for alkaline POX, and 0.040 oz/st Au for CaTs.

 

  5. Underground Mineral Resources are reported at an incremental cut-off grade of 0.10 oz/st Au.

 

  6. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.

 

  7. Totals may not add due to rounding.

The Mineral Reserves for the Goldstrike Mine are shown in Table 1-2. These Mineral Reserves are a combination of the open pit and underground operations and the stockpiles.

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page 1-2
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TABLE 1-2 GOLDSTRIKE MINERAL RESERVES—DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

     Proven Reserves      Probable Reserves      Proven and Probable Reserves  
Process    Tons      Grade      Contained
Gold
     Tons      Grade      Contained
Gold
     Tons      Grade      Contained
Gold
 

Route

   (000)      (oz/st Au)      (000 oz)      (000)      (oz/st Au)      (000 oz)      (000)      (oz/st Au)      (000 oz)  

Open Pit and Underground

                          

CaTs

     4,361         0.117         509         18,902         0.101         1,900         23,263         0.104         2,410   

Roaster

     4,753         0.148         704         19,538         0.103         2,015         24,291         0.112         2,719   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Combined Total

     9,114         0.133         1,214         38,440         0.102         3,915         47,555         0.108         5,129   

Stockpiles

                          

Roaster/Autoclave/BRSO

     49,810         0.084         4,179                  49,810         0.084         4,179   
  

 

 

    

 

 

    

 

 

             

 

 

    

 

 

    

 

 

 

Stockpiles Total

     49,810         0.084         4,179                  49,810         0.084         4,179   
  

 

 

    

 

 

    

 

 

             

 

 

    

 

 

    

 

 

 

Inventory Total

           38                        38   
        

 

 

                   

 

 

 

Total

     58,924         0.092         5,427         38,440         0.102         3,915         97,325         0.096         9,342   

Notes:

 

  1. CIM definitions were followed for Mineral Reserves.

 

  2. Mineral Reserves are estimated using an average long-term gold price of US$1,200 per ounce.

 

  3. Totals may not add due to rounding.

 

  4. CaTs—Thiosulphate Leach Conversion Process; BRSO—Barrick Roaster Sub Ore

 

  5. Open pit CaTs cut-off grade is 0.045 oz/st Au and the open pit roaster cut-off grade is 0.035 oz/st Au. The majority of the ore material in stockpile was generated at higher cut-off grades because of lower gold prices.

 

  6. Underground cut-off grades are between 0.134 oz/st Au and 0.155 oz/st Au.

CONCLUSIONS

OPEN PIT

Geology and Mineral Resource Estimation

 

   

The Goldstrike deposits are Carlin style deposits.

   

The sampling, sample preparation, and analyses are appropriate for the style of mineralization and mineral resource estimation.

 

   

The parameters, assumptions, and methodology used for mineral resource estimation are appropriate for the style of mineralization.

 

   

Open pit Measured plus Indicated Mineral Resources total 4.6 million tons grading 0.032 oz/st Au, containing 147,000 oz Au. Inferred Mineral Resources are estimated to be 0.6 million tons grading 0.055 oz/st Au, containing 31,000 oz Au. Mineral Resources are exclusive of Mineral Reserves.

 

   

The Goldstrike open pit Mineral Resource estimates meet the requirements of NI 43-101.

 

   

Mineral Resources are reported exclusive of Mineral Reserves and are estimated effective December 31, 2011.

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page 1-3
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Mining and Mineral Reserves

 

   

Open pit Proven and Probable Mineral Reserves total 97.3 million tons grading 0.096 oz/st, containing 9.34 million oz Au.

 

   

The Goldstrike Mineral Reserves stated for the EOY2011 meet Canadian NI 43-101 and US SEC Industry Guide 7 requirements to be classified as Mineral Reserves.

 

   

Mine planning for the Goldstrike open pit mine follows industry standards.

 

   

Ore control procedures for the Goldstrike open pit are well documented, and the ore control results have also been well documented. All records have been kept in good condition and are readily accessible.

 

   

No out-of-the-ordinary major equipment purchases are scheduled from the current Life of Mine (LOM) plan.

 

   

The workforce is well trained and capable of achieving the necessary production targets established by the engineering department in a safe manner.

 

   

The Proven Reserves located in 34 different stockpiles are estimated to be 49.8 million tons grading 0.084 oz/st Au, containing 4.2 million ounces of gold, as of December 31, 2011. RPA agrees with the ore control rationale for creating the stockpiles, and the accounting methods used to track the stockpile quantities and grades. Ongoing confirmation of the stockpile grades should be part of the mill’s quality control process. Most of the stockpiles were generated from grade control boundaries generated at much lower gold prices, thus, the ore stockpile grades should be adequate to sustain the projected mill head grades.

Process

 

   

Planning the process feed is a well-coordinated and complex operation to ensure ore going to the processing operation provides optimum results. The milling operations are well run, safe, and environmentally sound and meet industry standards. Addition of the CaTs (Thiosulphate Leach Conversion Process) has the potential to extend the useful life of the POX circuit and to substantially increase gold production by bringing forward production from ores that were previously only amenable to roasting. RPA did not have full access to data regarding the CaTs project. This is likely due to the fact that the project is in development and also due to the proprietary nature of the process. Therefore, it is not possible for RPA to evaluate the metallurgical implications and recovery projections associated with CaTs.

Environmental Considerations

 

   

The Goldstrike operation is within compliance, except for one monitor well associated with the AA pad. Monitoring and remediation of this situation has been addressed by the Goldstrike environmental department. Goldstrike has an experienced staff of professionals who are diligent in the maintenance of their permits. Reclamation estimates are realistic, in RPA’s opinion.

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page 1-4
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UNDERGROUND

Mineral Resource Estimation

 

   

The EOY2011 underground Mineral Resources as stated by Goldstrike management are estimated in a manner consistent with industry practices.

 

   

The sampling, sample preparation, and analyses are appropriate for the style of mineralization and mineral resource estimation.

 

   

The resource estimation practices are considered to be generally appropriate for the deposit and mining methods.

 

   

Underground Measured plus Indicated Mineral Resources total 6.1 million tons grading 0.301 oz/st Au, containing 1.8 million oz Au. Inferred Mineral Resources are estimated to be 2.7 million tons grading 0.298 oz/st Au, containing 805,000 oz Au. Mineral Resources are exclusive of Mineral Reserves.

 

   

The Goldstrike EOY2011 Underground Mineral Resource estimate meets the requirements of Canadian NI 43-101.

Mining and Mineral Reserves

 

   

The EOY2011 underground Mineral Reserves as stated by Goldstrike management are estimated in a manner consistent with industry practices.

 

   

Underground Proven plus Probable Mineral Reserves are estimated to be 11.9 million tons grading 0.255 oz/st Au, containing 3.0 million oz Au.

 

   

The Goldstrike EOY2011 Underground Mineral Reserve estimate meets the requirements of NI 43-101 and SEC Industry Guide 7.

 

   

RPA considers the selection of mining methods and the design practices to be appropriate for the deposits.

 

   

The LOM plan is in place and is based upon current operating experience. The plan shows a positive cash flow to support the definition of the Mineral Reserves.

 

   

The reconciliation between production and Mineral Reserves is completed in a comprehensive manner on a monthly basis. RPA considers this to be a “best practice”.

Process

 

   

The roaster operation was running well during the site visit.

 

   

Planning the process feed is a well-coordinated and complex operation to ensure ore going to the processing operation provides optimum results. The milling operations are well run, safe, environmentally sound and meet industry standards.

 

   

The adjustments made to the process production data and mill head grades based on actual gold production conform to industry standards.

 

 

Barrick Gold and Franco-Nevada - Goldstrike Mine, Project #1663    Rev. 0 Page 1-5
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Environmental Considerations and Health and Safety

 

   

Goldstrike has an experienced staff of professionals who are diligent in the maintenance of their permits.

 

   

Reclamation estimates are realistic, in RPA’s opinion.

RECOMMENDATIONS

Based on the site visits and review of available data, RPA presents the following recommendations.

OPEN PIT

Geology

 

   

Additional density test work should be done in all ore and waste types to optimize mineral resource estimation.

Mining

Perform more analysis of the stockpile grades for a confirmation of the grades in coordination with the mill department. The stockpiles represent approximately 45% of the Mineral Reserve. Some of the stockpiles are over 20 years old, and RPA recommends that it would be prudent to re-sample a portion of the stockpiles that will be processed within the short term (less than one year) in order to verify the grades as the stockpiles are re-handled.

 

   

Sample, test, and review the metallurgical characteristics of the ore stockpiles on a periodic basis to ascertain how they may affect the process and impact recovery and costs.

 

   

Change the resource and reserve models to reflect more accurate tonnage factors of the material to be encountered in the future, Post-Betze pit laybacks. Historically, the same tonnage factor has been used for all rock types within the Post-Betze pit, which has been acceptable. Future laybacks in the pits will begin to encounter rock types that are heavier than previously mined rock types. Therefore, the tonnage factors in the resource model should be adjusted.

 

   

Develop a comprehensive mine planning procedure manual.

UNDERGROUND

RPA recommends that:

Geology

 

   

Wireframes be snapped to the drill holes to allow proper selection of assays for the grade interpolation process.

 

   

Tonnage factor determinations be collected in the various ore and waste types at Banshee and North Post.

 

 

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Mining

 

   

The reconciliation results and the stope performance analysis be used to evaluate stope designs to determine where improvements in mine planning would be most advantageous.

 

   

The long term underground productivity estimates be reviewed for the next LOM plan as the tons per man year in the current plan are forecast to increase over time.

ECONOMIC ANALYSIS

Under NI 43-101 rules, producing issuers may exclude the information required in this section on properties currently in production, unless the Technical Report includes a material expansion of current production. RPA notes that Barrick is a producing issuer, the Goldstrike Mine is currently in production, and a material expansion is not being planned. RPA has performed an economic analysis of the Goldstrike Mine using the estimates presented in this report and confirms that the outcome is a positive cash flow that supports the statement of Mineral Reserves.

TECHNICAL SUMMARY

PROPERTY DESCRIPTION, LOCATION, AND LAND TENURE

The Goldstrike Mine property is located within the northern Carlin Trend on the western flank of the Tuscarora Mountains in Eureka and Elko Counties, Nevada, USA, approximately 38 mi northwest of Elko and 27 mi north-northwest of the town of Carlin.

The Goldstrike Mine area is composed of approximately 10,372 acres of surface rights of which approximately 1,922 acres are public lands administered by the Bureau of Land Management (BLM) and 8,450 acres are patented and private lands owned by Goldstrike. There are approximately 8,736 acres of mineral rights ownership/control made up of 1,962 acres of public lands and 6,774 acres of private land. These rights are owned or controlled through ownership of various forms of patents issued by the USA and by ownership of unpatented mining and millsite claims held subject to the paramount title of the USA.

 

 

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A total disturbance of 8,590 acres is currently authorized for the mine. The majority (88%) of the total authorized disturbance would occur on private lands owned by Goldstrike. The remainder (12%) of the authorized disturbance would occur on public lands administered by the BLM.

The Goldstrike property has various royalty shareholders with a nominal overriding Net Smelter Royalty (NSR) of between 4% and 5% and a Net Profit Interest Royalty (NPI) of between 2.4% and 6% over various parts of the property. Key royalty shareholders are Franco-Nevada and Royal Gold, Inc.

INFRASTRUCTURE

Goldstrike is located in a major mining region and local resources including labour, water, power, and local infrastructure for transportation of supplies are well established. The majority of the workforce lives in the nearby towns of Elko, Spring Creek, Carlin, and Battle Mountain.

The surface rights secured for Goldstrike are sufficient to provide the necessary space required for all mining and quarrying activities. Enough land area also exists on the property to accommodate all foreseeable processing plants, tailings impoundments, and waste disposal areas.

Currently, the major assets and facilities associated with the Project are:

 

   

Underground (16 years old) and open pit mines (34 years old) with production from several mineralized structures.

 

   

The physical plant site including the administrative office complex and associated facilities, the open pit and underground mine workings and associated facilities, ore processing plants (autoclave pressure oxidation and roaster circuit) and associated facilities such as the laboratories, ore stockpiles, waste dumps, coarse ore storage, tailings storage, workshops, warehouses.

 

   

Facilities providing basic infrastructure to the mine, including electric power, water treatment and supply, and sewage treatment.

 

   

Surface and underground infrastructure including mine ramps, headframes, hoists, ventilation raises, maintenance shops, and mobile equipment fleets.

The water for process and mining is delivered from dewatering production wells and is more than adequate for present and planned requirements. Active dewatering operations are required and a water management group is in place to carry out all dewatering including pumping, distribution, delivery, and disposal.

 

 

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Barrick has a 115 MW natural gas-fired power plant, located near Reno, Nevada, that allows the flexibility to provide power through a combination of self-generation and market purchases.

HISTORY

The earliest gold mining activity in the northern part of the Carlin Trend occurred at the Bootstrap and Blue Star mines prior to the discovery of gold at Goldstrike. At Bootstrap, just northwest of Goldstrike, antimony was discovered in 1918, followed by gold in 1946. Gold was produced at the Bootstrap during 1957 to 1960. At Blue Star, immediately south of Goldstrike, gold was identified in 1957 in areas that had been mined for turquoise.

The first discovery of gold in the Goldstrike property was in 1962 by Atlas Minerals. Soil samples and drilling discovered low-grade gold mineralization. In 1973 to 1974, the Nevada Syndicate (funded by Lac Minerals) outlined shallow mineralization in the Long Lac and Winston areas. Polar Resources (Polar) in 1975, followed by Pancana Minerals Ltd. (Pancana) from 1976 to 1977, delineated the Number 9 deposit and several low-grade zones within the Goldstrike intrusion to the east of Nevada Syndicate property. From 1975 to 1977, Polar and Pancana operated a small open pit and heap leach.

In 1978, Western States Minerals Corporation (Western States) entered into a 50/50 joint venture with Pancana, which had consolidated the various claims and leases in the Goldstrike area. The bulk of the production was from oxidized zones, chiefly from the Long Lac, Bazza, and West Bazza deposits, plus some production from deposits within the Goldstrike intrusion. The Post deposit was discovered in 1982. Exploration continued until 1986 when a deep core hole was drilled at Post and the Deep Post deposit was discovered.

American Barrick Resources Corporation acquired the mine and properties from Western States (50%) in December 1986 and subsequently purchased Pancana’s interest (50%) in January 1987 for a total purchase price of $62 million. A deep drilling program outlined the large, high-grade Deep Post deposit, which was subsequently

 

 

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found to continue onto the adjacent property owned by Newmont Gold Company (Newmont). Exploration drilling in 1987 to 1988 led to the discovery of a number of other deposits similar to Deep Post. These included Betze and Screamer, which, together with Deep Post, comprise the Betze-Post deposit. Other discoveries in 1987 and 1988 included Deep Star, Rodeo, Meikle, South Meikle, and Griffin.

Heap leach ore production from the Betze-Post pit continued from the time of purchase to the end of 1998. Oxide mill ore processing started in August 1988 and the autoclave portion of the mill commenced operation in early 1990. The processing of ores by the roaster began in 2000.

The 1999 Asset Exchange with Newmont resulted in the acquisition of the Goldbug (the southern portion of Rodeo), West Rodeo, Barrel, and North Post deposits. These deposits were in the Newmont land corridor separating the Betze-Post and Meikle mines. The Banshee property north of the Meikle was also part of the exchange.

Past production from the underground operations to the end of 2011 totals 19.5 million tons grading 0.488 oz/st Au for 9.5 million ounces of gold. Past production from the open pit operations to the end of 2011 totals 65.9 million tons grading 0.157 oz/st for 10.4 million ounces of gold.

GEOLOGY AND MINERALIZATION

The Goldstrike Mine is located in the eastern Great Basin (Basin and Range Province) within the northern Carlin Trend on the western flank of the Tuscarora Mountains. The Carlin Trend is an alignment of gold mines located in a northwest-southeast belt extending five miles wide and 40 mi long, which accounts for more gold production than any other mining district in the United States. The northern trends account for in excess of twenty gold mines and deposits.

Carlin deposits comprise stratabound disseminated gold mineralization hosted by Silurian-Devonian carbonate rocks that have been metamorphosed to varying extents. The deposits are hydrothermal in origin and are usually structurally controlled. The carbonate host rocks are part of an autochthonous miogeoclinal carbonate sequence exposed as tectonic windows beneath the Roberts Mountains allochthon. The allochthonous rocks are a sequence of lower Paleozoic dominantly siliciclastic eugeoclinal rocks that were displaced eastward along the Roberts Mountains Thrust over younger units during the Upper Paleozoic Antler orogeny.

 

 

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The western or siliciclastic allochthonous assemblage consists of mudstone, chert, siltstone, and minor limestone and includes imbricate thrust slices of Devonian Slaven, Silurian Elder, and Ordovician Vinini formations. The eastern autochthonous assemblage of carbonate rocks consists of calcareous mudstone, siltstone and sandstone of the Rodeo Creek unit, muddy limestone of the Devonian Popovich Formation, silty limestone to massive fossiliferous limestone of the Silurian-Devonian Roberts Mountains Formation, sandy dolomite of the Ordovician Hanson Creek Formation, quartzite of the Ordovician Eureka Quartzite, and limestone, cherty limestone and dolomite of the Ordovician Pogonip Group.

Jurassic quartz diorite, as plugs, sills, and dikes, has intruded the Paleozoic sedimentary rocks. Dikes and sills of Jurassic monzonite and lamprophyre, and Tertiary dacite and rhyodacites, are mapped in the area.

Gold mineralization was emplaced approximately 39 Ma ago along favourable stratigraphy and structural features such as faults and folds, and along contacts between sedimentary rocks and the Goldstrike stock. Faulting provided major conduits for mineralizing fluids and may also have produced clay alteration that can act as a mineralizing barrier. Intense fracturing around the contact zone of the Goldstrike stock caused solution collapse and brecciation of the surrounding sedimentary units. Secondary fracture permeability was generated along the crests of anticlines, creating focal points for collapse breccia and dissolution zone formation. Finally, lithology and alteration contacts act as permeability barriers to fluids causing mineralization to pond along them particularly where feeder structures intersect these contacts. Alteration is characterized by decalcification of limestone, silicification of all rock types, and clay development in structurally disturbed areas.

The gold mineralization is associated with silicification, argillization, and sulphide mineralization. In sulphide ore, the gold is intimately associated with very fine-grained pyrite and marcasite and is refractory. Over time, the pyrite oxidized, freeing the gold and making its extraction relatively easy, as in the historic Post Oxide deposit. Associated sulphide minerals include arsenopyrite, realgar, orpiment, and stibnite.

 

 

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Gangue minerals include quartz, calcite, and barite. Realgar and orpiment are generally low in abundance; however, these minerals are locally common in stockwork veinlets, fracture fillings and breccia matrices.

EXPLORATION STATUS

To date, surface geological mapping and prospecting has been completed on the property, with pit mapping ongoing. In excess of 14,000 diamond and reverse circulation (RC) holes have been drilled on the property to the end of 2010. Geochemical soil and rock sampling was carried out on the property in early exploration. Geophysical surveys include airborne and ground magnetometer; gravity; time domain pole-dipole induced polarization (IP); DC resistivity; CSAMT (controlled source audio magnetotellurics) and MT (magnetotellurics); time domain MT/IP using a distributed assay system; electrical logging of drill holes; and downhole IP. Gold mineralization is not directly detectable by geophysical methods; however, surveys map subsurface properties that are useful in interpreting lithology, alteration, and structure as guides to gold mineralization. Aerial photographic surveys are performed every one to two years for open pit survey control.

MINERAL RESOURCES

OPEN PIT

The open pit block model has been created using Mintec Inc.’s MineSight® software supplemented by custom programs derived from Geostatistical Software Library (GSLIB) software from Stanford University. Three-dimensional solids representing fault traces and lithologic units have been created from drill hole logging, and blasthole and bench mapping information. These solids and the understanding of mineralization controls are used as reference features in guiding the generation of grade contours used in estimating the gold resource model.

Table 1-3 lists the open pit Mineral Resources.

 

 

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TABLE 1-3 GOLDSTRIKE OPEN PIT MINERAL RESOURCES —

DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

Category

   Tons
(000)
     Grade
(oz/st Au)
     Contained Gold
(000 oz)
 

Measured

     886         0.032         28   

Indicated

     3,726         0.032         119   
  

 

 

    

 

 

    

 

 

 

Measured + Indicated

     4,612         0.032         147   

Inferred

     565         0.055         31   

Notes:

 

  1. CIM Definitions were followed for Mineral Resources.

 

  2. Mineral Resources are estimated using a long-term gold price of $1,400 per ounce.

 

  3. Mineral Resources are exclusive of Mineral Reserves and are contained within and below the reserve pit.

 

  4. Mineral Resources are based on cut-off grades of 0.030 oz/st Au for roaster feed, 0.040 oz/st Au for acid POX, 0.045 oz/st Au for alkaline POX, and 0.040 oz/st Au for CaTs.

 

  5.

Mineral Resources based on tonnage factor of 13.5 ft3/st.

 

  6. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.

 

  7. Totals may not add correctly due to rounding.

UNDERGROUND

The underground Mineral Resources are estimated using block models constrained by three-dimensional wireframe models of the mineralized bodies and underground workings. The grade is interpolated into the blocks using Inverse Distance to the Fifth Power (ID5) weighting. There are four block models which encompass 18 individual mineralized zones at Goldstrike underground. The models are constructed using Maptek Vulcan 3D software, version 7.5.

Table 1-4 lists the underground Mineral Resources at Goldstrike.

TABLE 1-4 UNDERGROUND MINERAL RESOURCES – DECEMBER 31, 2011

Barrick Gold Corporation– Goldstrike Mine

 

Category

   Tons
(000)
     Grade
(oz/st
Au)
     Contained
Gold

(000 oz)
 

Measured

     985         0.341         336   

Indicated

     5,092         0.293         1,492   
  

 

 

    

 

 

    

 

 

 

Measured + Indicated

     6,077         0.301         1,828   

Inferred

     2,698         0.298         805   

Notes:

 

  1. CIM Definitions were followed for Mineral Resources.

 

  2. Mineral Resources are reported using a long-term gold price of US$1,400 per ounce.

 

  3. Mineral Resources are reported at an incremental cut-off grade of 0.10 oz/st Au.

 

  4. A minimum mining width of 15 ft was used.

 

  5. Mineral Resources are exclusive of Mineral Reserves.

 

  6. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.
7. Totals may not add correctly due to rounding.

 

 

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MINERAL RESERVES

The Mineral Reserves are generated based upon the mine designs applied to the Mineral Resources. The design methodology uses both the cut-off grade estimation and economic assessment to design and validate the mineable reserves. Overall, RPA finds the Mineral Reserve estimates to be reasonable, acceptable, and compliant with NI 43-101.

Goldstrike maintains a complex system of ore and low grade stockpiles, which have been growing since the late 1980s. There are primarily three major stockpile categories: Autoclave, Roaster, and Barrick Roaster Sub Ore (BRSO).

The Proven Reserves located in 34 different stockpiles are estimated to be 49.8 million tons grading 0.084 oz/st Au, containing 4.2 million ounces of gold, as of December 31, 2011. RPA agrees with the ore control rationale for creating the stockpiles, and the accounting methods used to track the stockpile quantities and grades.

Two separate stockpile reports are maintained, one for the roaster and the other for the autoclaves. The amount of material processed from each stockpile is tracked throughout the month. At the end of the month, the tonnage of material processed from each stockpile is adjusted to reflect the total tons processed through the roaster and/or autoclave. In a similar fashion, the contained ounces are adjusted based on the production from each plant.

The monthly stockpile reports also track the amount of material from each stockpile that is crushed and estimate the number of ounces of gold contained in the crushed material based on the average gold grade in each stockpile. At the end of the month, the tonnage of the crushed material is adjusted to match the tonnage of material processed as reported by the process department. In general, the adjustments are less than one percent.

OPEN PIT

EOY2011 Mineral Reserves for the open pit are shown in Table 1-5.

 

 

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TABLE 1-5 BETZE-POST OPEN PIT MINERAL RESERVES — DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

     Proven Reserves      Probable Reserves      Proven and Probable Reserves  

Process

Route

   Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
 

Open Pit Total

     9,114         0.133         1,214         38,440         0.102         3,915         47,555         0.108         5,129   

Stockpiles Total

     49,810         0.084         4,179                  49,810         0.084         4,179   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total

     58,924         0.092         5,393         38,440         0.102         3,915         97,325         0.096         9,308   

Notes:

 

  1. CIM definitions were followed for Mineral Reserves.

 

  2. Mineral Reserves are estimated using an average long-term gold price of US$1,200 per ounce.

 

  3. Numbers may not add due to rounding.

 

  4. CaTs – Thiosulphate Leach Conversion Process; BRSO – Barrick Roaster Sub Ore

 

  5. Open pit CaTs cut-off grade is 0.045 oz/st and the open pit roaster cut-off grade is 0.035 oz/st. The majority of the ore material in stockpile was generated at higher cut-off grades because of lower gold prices.

 

UNDERGROUND

EOY2011 Mineral Reserves for the underground are shown in Table 1-6.

TABLE 1-6 GOLDSTRIKE UNDERGROUND RESERVES — DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

     Proven Reserves      Probable Reserves      Proven and Probable Reserves  
     Tons
(000)
     Grade
(oz/st
Au)
     Contained
Gold
(000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
 

U/G

     4,038         0.330         1,334         7,824         0.216         1,691         11,861         0.255         3,026   

Stockpiles

     33         0.293         10                  33         0.293         10   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total

     4,070         0.330         1,344         7,824         0.216         1,691         11,894         0.255         3,035   

Notes:

 

  1. CIM definitions were followed for Mineral Reserves.

 

  2. Mineral Reserves are estimated at $1,200/oz Au.

 

  3. Numbers may not add due to rounding.

 

  4. Underground cut-off grades are between 0.134 oz/st Au and 0.155 oz/st Au.

MINING METHOD

OPEN PIT

Barrick’s Betze-Post open pit is a large scale operation utilizing a traditional truck and shovel fleet. The open pit has seven remaining phases, with the ultimate pit to measure approximately two miles east to west, 1.5 mi north to south, and have an average depth of approximately 1,300 ft. The Bazza Waste Dump is located to the southwest of the open pit. The LOM plan includes the addition of the Clydesdale Dump to the west and backfilling of the southeast portion of the open pit. Internal to the pit are the Betze

 

 

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Portal, which connects to the Rodeo underground mine, and previously the Post Portal, which connected to Newmont’s Deep Post underground mine but has since been backfilled.

Ultimate pit limits were determined by generating Whittle pit shells based on the net cash generated and the pit slopes recommended by Piteau Associates Engineering Ltd. Haul ramps were designed to be 120 ft wide, including the safety berm for double lane traffic accommodating the 330 ton class haul trucks, and have a maximum grade of 10%. Mining thickness is 40 ft in waste and 20 ft in ore to help minimize dilution. In ore, double and triple benching is utilized creating 40 ft and 60 ft faces between catch benches.

Barrick optimizes mining by using a multi-phased approach which maximizes stripping rates to keep an ore producing face always available. This multi-phase technique consists of a primary ore layback, a primary stripping layback, and a secondary stripping layback. Historically, this approach was put in place to maintain a consistent mill feed, and keep mine production in the range of 14 to 15 benches per layback per year. There are approximately 135 million tons per year mined.

UNDERGROUND

The poor rock conditions are the key factor in the underground mine design and mining method selection. This has led to two mining methods both of which rely on cemented backfill for support. Where long hole stoping is used, the wall and back exposure is reduced by taking short long hole sections and filling before taking the next section. The underhand drift and fill stoping provides a backfill roof for subsequent lifts in the mining cycle. In the 2012 forecast, 79% of the ore is planned to come from long hole stoping. The proportion of ore to be obtained by long hole stoping drops every year in the current LOM plan, with an average of 48% of the production from long hole stoping in the complete LOM plan.

Transverse long hole stoping is used where the mineralized zone has a significant width. Footwall drifts are driven parallel to the strike of the ore to provide access for stoping. Mining with transverse stopes requires a primary, secondary, and sometimes tertiary extraction to completely mine out the area. Longitudinal stopes are utilized in areas of the mine with adequate ground conditions to support a stope rib greater than 15 ft in height but do not have mineralized widths greater than 25 ft. The stopes are accessed

 

 

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from a footwall drive and then driven parallel to the strike of ore. Each section is mined and filled before the next section is mined. If ground conditions are poor, the long hole stope section length can be reduced.

The underhand drift and fill method is utilized in areas of fair to poor ground conditions regardless of the width of the zone. The underhand drifts are nominally designed as 15 ft wide by 15 ft high. The minimum width is 15 ft. The primary drift is driven with increased ground support to hold the ground open, then backfilled with a high strength cemented rock fill (CRF). Where the ore width exceeds the nominal drift width, subsequent drifts are developed (parallel or at oblique angles to the primary drift) and then backfilled. This process continues until the entire ore shape at a given elevation has been excavated and filled. Successive lifts are taken beneath the primary workings, utilizing the backfill as an engineered back.

MINERAL PROCESSING

There are two ore processing facilities at Goldstrike. They are:

 

   

The autoclave pressure oxidation (POX) circuit; and

 

   

The roaster circuit.

Depending on various factors, including gold content, carbonate content, carbonaceous carbon reactivity, and sulphide sulphur content, the Betze-Post open pit ore is dispatched to various stockpiles located at either the POX area or the roaster area. Planned distribution of ore from the stockpiles is an extensive exercise which is carried out monthly by the strategic planning department to maintain optimal operations designed to maximize gold recovery. All of the underground ore is processed in the roaster.

ACID/ALKALINE POX CIRCUIT

The grinding circuit was developed in two phases with the total capacity of both phases being 17,500 stpd. In both circuits, the crushed ore is fed to semi-autogenous grinding (SAG) mills operating in closed circuit with pebble cone crushers. The SAG mill discharge is pumped to the ball mill circuit operating in closed circuit with a bank of cyclones. The overflow from the cyclones feeds a ball mill operating in closed circuit with a bank of cyclones. The cyclone overflow feeds one of the three thickeners that are common to both grinding circuits.

 

 

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The thickener underflow is fed to a series of acidulation tanks where sulphuric acid is added to reduce the carbonate content, thereby reducing the potential carbon dioxide gas that will be generated in the autoclaves.

The ground, acidified slurry is fed to a series of preheaters where hot steam is contacted with the new feed in order to preheat the material. The sulphide oxidation reaction is carried out under high pressure and temperature in autoclaves. High purity oxygen is also added as the oxidant. The autoclave discharge passes through a series of flash vessels to let down the pressure and is then sent to a series of tube and shell slurry coolers. The heat from the flash vessels is the primary steam source used for heating the slurry in the preheaters.

The autoclave products are very acidic due to the generation of sulphuric acid by the sulphide oxidation reaction that occurs in the autoclaves. The pH of the slurry is increased to at least 9.5 by the addition of milk-of-lime in a series of neutralization tanks, in order to operate the carbon-in-leach (CIL) circuit safely when adding cyanide (to minimize the generation of hydrogen cyanide gas).

As the carbonate levels in a portion of the Goldstrike ores have increased, Goldstrike has converted its autoclaves such that they can operate in an alkaline environment, as needed. Due to the high carbonate concentration, the autoclave reaction does not generate acid and the designated flash tank discharge, after being cooled in the slurry coolers, goes directly to CIL, bypassing the neutralization circuit.

The slurry from neutralization is pumped to one of two CIL circuits, each made up of eight tanks. Cyanide is added. The slurry flows by gravity through the series of eight tanks and carbon is pumped counter-current to the slurry. From the first tank, carbon is transferred to the elution and refining circuit for recovery of the gold. The slurry exiting the eighth tank in the series is sent to a cyanide destruction circuit, which uses Caro’s acid as the cyanide destruction medium, and then pumped to the tailings storage facility.

The loaded carbon is transferred to acid wash tanks where inorganic materials are removed and then to carbon strip vessels where it is soaked in a solution containing cyanide and sodium hydroxide. Hot fresh water is then pumped through the carbon,

 

 

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under pressure and at elevated temperature, to strip the gold from the carbon. The pregnant solution containing the gold is forwarded to the electrowinning and gold smelting circuit. The stripped carbon is transferred to the carbon regeneration kiln where organic contaminants are removed before the carbon is returned to a CIL circuit.

ROASTER OPERATION

Fluid bed roasters were constructed to treat carbonaceous refractory ores that could not be treated effectively by the existing POX circuit at Goldstrike. The roasters use high purity oxygen to react with organic carbon and sulphide sulphur prior to processing in a conventional CIL circuit.

After crushing, the ore is conveyed to one of the two grinding circuits. Lime and/or coal is added for roaster fuel and fed to the double rotator dry grinding mill. The ore is dried and then flows toward the centre of the mill where it is removed through screens for classification into product size material. The roaster material has a target product size of 80% passing (P80) 74 µm.

The ore is primarily oxidized in the first stage of the roasters and then solids discharge by gravity continuously to the second stage. The temperature is maintained in the range of 524oC to 561oC. Oxidation is essentially completed in the second stage, achieving approximately 99% oxidation of the sulphide sulphur and 89% oxidation of the organic carbon. Material from the second stage of the roaster discharges by gravity to the calcine quench system.

The exhaust gas from each stage is classified using dry cyclones. The coarse material recovered from the exhaust gas is returned to the roaster for further treatment and the fine material is forwarded to gas quenching and final dust scrubbing. The off-gas from the final dust scrubbers from both circuits are recombined for final off-gas cleaning. The final gas cleaning circuit removes mercury, sulphur dioxide, carbon monoxide, and nitrous oxides. The gas then exits through a stack to the atmosphere.

The treated calcine from the roaster is sent to a quench tank to reduce temperature. Water recovered from the neutralization circuit is used to cool the calcine. The slurry feeds neutralization tanks where milk-of-lime is added for pH control in order to safely leach the ore with cyanide. After leaving the neutralization tanks, the material is sent to a thickener to recover excess water for cooling and reuse in the quench tanks. The thickener underflow reports to the roaster CIL circuit.

 

 

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The slurry from neutralization tanks is pumped to a CIL circuit, which has six agitated tanks. Activated carbon is pumped counter-currently from the sixth tank to the first tank. The carbon then is transferred to a loaded carbon holding bin and taken to the main elution and refining operation located adjacent to the POX operations. The slurry exiting the final CIL tank is sent to a cyanide destruction reactor before being transferred to the tailings storage facility.

RECOVERY

Barrick has developed recovery calculations based on evaluation of historical data. They have changed over time as the ore and operations have changed. The most recent recovery calculations for the autoclave are shown in Table 1-7 and the recovery calculations for the roaster are shown in Table 1-8.

TABLE 1-7 ALKALINE CATS RECOVERY CALCULATIONS FOR LOM PLAN

Barrick Gold Corporation– Goldstrike Mine

 

Head Grade (oz/s)t

  

Equation

HG > 1.3

  

Rec. = 95.0 percent - 6.86

0.28 < HG <= 1.30

  

Rec. = 6.4334*HG*HG*HG - 23.02*HG*HG + 28.56*HG + 82.247 - 6.86 - 1.5

0.065 <= HG <= 0.28

  

Rec. = 661.36*HG*HG*HG - 628.91*HG*HG + 208.23*HG + 65.114 - 6.86 - 1.5

TABLE 1-8 ROASTER RECOVERY CALCULATIONS FOR LOM PLAN

Barrick Gold Corporation – Goldstrike Mine

 

Head Grade (oz/st)

  

Equation

HG > 1.15

  

Rec. = 93.0 percent + 0.3 + As Impact

0.35 < HG <= 1.15

  

Rec. = 3.1719LN(HG) + 92.592 + 0.3 + As Impact

0.125 < HG <= 0.35

  

Rec. = -95.006*HG*HG + 67.038*HG + 77.446 + 0.3 + As Impact

0.055 <= HG <= 0.125

  

Rec. = -1017.2*HG*HG + 377.14*HG + 53.439 + 0.3 + As Impact

As Impact (>1,200 ppm) = -0.0000004*As*As - 0.0005*As + 1.176

The process recovery for the roaster ranged between 84% and 90% and the autoclave recovery was between 67% and 86%.

RPA has completed an analysis of historical data and confirmed that the recovery estimates are reasonable.

 

 

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MARKET STUDIES

Gold is the principal commodity at Goldstrike and is freely traded, at prices that are widely known, so that prospects for sale of any production are virtually assured. The doré produced at Goldstrike is shipped to commercial refineries, which are located in a major city like Salt Lake City, Utah.

ENVIRONMENTAL, PERMITTING AND SOCIAL CONSIDERATIONS

The Goldstrike operations consist of operating open pit and underground mines plus process plant facilities. The mines and the corporation have environmental groups and management systems to ensure that the necessary permits and licences are obtained and maintained. These groups also carry out the required monitoring and reporting required.

TAILINGS STORAGE FACILITY

Tailings from both the POX and roaster operations are deposited in the North Block Tailings Disposal Facility (NBTDF) located immediately to the east of the roaster facility and the Meikle mine. The NBTDF operates as a zero discharge facility under a Water Pollution Control Permit with the Nevada Division of Environment Protection (NDEP). The NBTDF is expanded approximately every two years and is currently permitted through a Stage 9 expansion in 2011.

PROJECT PERMITTING

The BLM issued the Draft Environmental Impact Statement (EIS) (BLM/NV/EK/PL-GI-08/22 + 1793) on August 22, 2008. Subsequently, the BLM issued an abbreviated Final EIS (BLM/NV/EK/ES-GI-09/10 + 1793) on March 27, 2009; it includes comments, responses to comments, and revisions to the Draft EIS. The approval of this EIS ensured the continuance of mining and processing for the Goldstrike operations.

CAPITAL AND OPERATING COST ESTIMATES

CAPITAL COSTS

Current LOM capital costs for the Project are estimated to be $1.793 billion. The major capital cost for the open pit will be the capitalized waste stripping, which is estimated to be $360 million. Expansion of the process facilities is estimated to be $264 million, which consist primarily of replacement capital. Underground mine development is projected to be $122 million.

 

 

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OPERATING COSTS

Open Pit

The total open pit operating cost has been estimated by RPA to be approximately $667 million over the remaining mine life. Over the same time period, the average operating cost per ton is estimated to $1.59 per ton mined, and a projected open pit mining cash cost is estimated to be $91 per ounce of the total gold ounces produced from the Goldstrike open pit and stockpiles.

Underground

The total operating cost has been estimated to be approximately $1.2 billion over the remaining mine life. Over the same time period, the average operating cost per ton is estimated to be $103 per ton mined, and the cash cost is estimated to be $577 per ounce of gold directly produced from the underground operations.

Processing—General and Administration (G&A)

The total operating costs for the processing department and G&A were estimated to be $4.34 billion and $775 million, respectively. A total of 38.6 million short tons of ore supplied by other Barrick projects and contract ore is planned to be milled by the Goldstrike Project. Goldstrike also acts as the principal mine administration facility for Barrick’s northern Nevada exploration and production projects.

 

 

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2 INTRODUCTION

Roscoe Postle Associates Inc. (RPA) was retained by Barrick Gold Corporation (Barrick) and Franco-Nevada Corporation (Franco-Nevada) to prepare an independent Technical Report on the Goldstrike Mine (the Project), in Eureka and Elko Counties, Nevada, USA. The purpose of this report is to support public disclosure of Mineral Resource and Mineral Reserve estimates at the Project. This Technical Report conforms to NI 43-101 Standards of Disclosure for Mineral Projects.

Barrick is a Canadian publicly traded mining company with a portfolio of operating mines and projects across five continents. Franco-Nevada is a Canadian publicly traded company focused on gold royalties and revenue streams. The Goldstrike Mine property is located within the northern “Carlin Trend” on the western flank of the Tuscarora Mountains in Eureka and Elko Counties, northeastern Nevada, USA, approximately 38 mi northwest of Elko and 27 mi north-northwest of the town of Carlin.

The Goldstrike Mine contains both open pit and underground operations. The Betze-Post open pit is a large scale operation utilizing a traditional truck and shovel fleet. The current open pit production plan shows that 47.6 million tons of ore grading 0.108 oz/st Au will be mined between 2012 and 2025. The ultimate pit will measure approximately two miles east to west, 1.5 mi north to south, and have an average depth of approximately 1,300 ft. The underground mine consists of ten separate zones stretching over a length of 12,000 ft and a vertical distance from 600 ft to 1,925 ft below surface. Underground mine production is planned from the Rodeo, Meikle, North Post, and Banshee mine areas. Underground Mineral Reserves totalling 11.9 million tons at 0.255 oz/st are projected to sustain the mine operations until 2020. Barrick maintains a second mining plan which includes conversion of resources and totals 18.1 million tons grading 0.277 oz/st Au and has projected production between 2012 and 2024.

SOURCES OF INFORMATION

RPA visited the open pit between December 7 and 9, 2010, and the underground operation between December 13 and 15, 2010. The RPA team consisted of the following members:

 

   

Wayne Valliant, Principal Geologist

 

 

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Stuart Collins, Principal Mining Engineer

 

   

R. Dennis Bergen, Associate Principal Mining Engineer

 

   

Chester Moore, Principal Geologist

 

   

Kevin Scott, Principal Metallurgist with RPA

During the visit, discussions were held with the following people:

OPEN PIT

 

   

Dan Banghart, Open Pit Mine Manager

 

   

Jim Byars, Senior Production Geologist

 

   

Russ Downer, Open Pit Engineering Superintendent

 

   

Richard Hipsley, Chief Geologist – Exploration

 

   

Theophilus Kandawasvika, Mining Engineer

 

   

Lynnette Kleinsasser, Reserve Modeller

 

   

Robert Malloy, Senior Database Administrator, Barrick Gold Exploration Inc.

 

   

Keith Testerman, Senior Mine Geologist, Open Pit Division

UNDERGROUND

 

   

Nigel Bain, Mine Manager

 

   

Don Colli, Senior Geological Advisor

 

   

Todd Esplin, Superintendent Metallurgical Services

 

   

Jodi Esplin, Chief Metallurgist

 

   

Jeff Evans, Chief Geologist

 

   

Joe Giraudo, Environmental Superintendent

 

   

Erik Langenfeld, Senior Geologist

 

   

Janna Linebarger, Senior Systems Engineer

 

   

Julian Manuel, Senior Geologist

 

   

Sam Marich, Chief Engineer

 

   

Brandon Short, Senior Long Range Engineer

 

   

Graeme Stroker, Senior Geologist

 

   

Gilles Tousignant, Senior Geologist

 

   

Mark Wonenberg, General Supervisor, Metallurgical Services

 

   

Steve Yopps, Metallurgical Manager

The Goldstrike Betze-Post and Meikle operations have been the subject of resource/reserve technical audits as follows:

 

   

December 2008, Mineral Reserve & Resource Review, Scott Wilson Roscoe Postle Associates Inc. (Scott Wilson RPA, a predecessor company to RPA)

 

   

June 29, 2008, 2008 Mid-year Model Review, Resource Modeling Inc.

 

   

January 2006, Reserve Procedure Audit, Scott Wilson RPA.

 

   

February 7, 2005, Review of Mineral Reserve Estimation Procedures, Scott Wilson RPA November 2004, Sarbanes Oxley Review, Scott Wilson RPA

Mr. Valliant is responsible for the overall preparation of this report and reviewed the geology, sampling, assaying, and resource estimate of the open pit part of the operation described in Sections 7 to 12 and 14. Mr. Moore reviewed the geology, sampling,

 

 

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assaying, and resource estimate of the underground part of the operation described in Sections 7 to 12 and 14. Mr. Collins reviewed the mining practices, reserve estimate, and economics of the open pit division and is responsible for the open pit portions of Sections 15, 16, 18, 19, 21, and 22. Mr. Bergen reviewed the mining practices, reserve estimate, and economics of the underground division and is responsible for the underground portions of Sections 15, 16, 18, 19, 21, and 22. Mr. Scott and Dr. Kathleen Ann Altman, P.E., Principal Metallurgist with RPA, reviewed the metallurgical and environmental aspects of the operation and is responsible for Sections 13, 17, and 20.

The documentation reviewed, and other sources of information, are listed at the end of this report in Section 27 References.

 

 

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LIST OF ABBREVIATIONS

Units of measurement used in this report conform to the Imperial system. All currency in this report is US dollars (US$) unless otherwise noted.

 

µm

   micron    k    kilo (thousand)

°C

   degree Celsius    kVA    kilovolt-amperes

°F

   degree Fahrenheit    kW    kilowatt

A

   ampere    kWh    kilowatt-hour

a

   annum    L    litre

bbl

   barrels    L/s    litres per second

Btu

   British thermal units    M    mega (million)

C$

   Canadian dollars    mi    mile

cal

   calorie    min    minute

cfm

   cubic feet per minute    mph    miles per hour

d

   day    MVA    megavolt-amperes

dia.

   diameter    MW    megawatt

dwt

   dead-weight ton    MWh    megawatt-hour

ft

   foot    oz/st    ounces per short ton

ft/s

   feet per second    oz    Troy ounce (31.1035g)

ft2

   square foot    ppm    parts per million

ft3

   cubic foot    psia    pounds per square inch absolute

g

   gram    psig    pounds per square inch gauge

G

   giga (billion)    RL    relative elevation

Gal

   Imperial gallon    s    second

g/L

   grams per litre    st    short ton

g/t

   grams per tonne    stpa    short tons per year

gpm

   Imperial gallons per minute    stpd    short tons per day

gr/ft3

   grains per cubic foot    US$    United States dollar

hr

   hour    USg    United States gallon

ha

   hectare    USgpm    US gallons per minute

hp

   horsepower    V    volt

in

   inch    W    watt

in2

   square inch    yd3    cubic yard

J

   joule    yr    year

 

 

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3 RELIANCE ON OTHER EXPERTS

This report has been prepared by Roscoe Postle Associates Inc. (RPA) for Barrick Gold Corporation (Barrick) and Franco-Nevada Corporation (Franco-Nevada). The information, conclusions, opinions, and estimates contained herein are based on:

 

   

Information available to RPA at the time of preparation of this report,

 

   

Assumptions, conditions, and qualifications as set forth in this report, and

 

   

Data, reports, and other information supplied by Barrick and other third party sources.

For the purpose of this report, RPA has relied on ownership information provided by Barrick. The properties and mineral rights are owned or controlled through ownership of various forms of patents issued by the USA and by ownership of unpatented mining and millsite claims held subject to the paramount title of the USA. RPA has not researched property title or mineral rights for the Goldstrike Mine and expresses no opinion as to the ownership status of the property.

RPA has relied on Barrick for guidance on applicable taxes, royalties, and other government levies or interests, applicable to revenue or income from the Goldstrike Mine

Except for the purposes legislated under provincial securities laws, any use of this report by any third party is at that party’s sole risk.

 

 

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4 PROPERTY DESCRIPTION AND LOCATION

The Goldstrike Mine property is located within the northern “Carlin Trend” on the western flank of the Tuscarora Mountains in Eureka and Elko Counties, northeastern Nevada, USA, approximately 38 mi northwest of Elko and 27 mi north-northwest of the town of Carlin (Figure 4-1).

Barrick acquired the interest of Western States Minerals Corporation (Western States) in the Goldstrike Mine in December 1986. In 1994, Barrick Goldstrike Mines, Inc. (Goldstrike), a wholly-owned subsidiary of Barrick received patents under the General Mining Law to 1,793 acres of land on which the Betze-Post Mine, the Meikle Mine, and most of Goldstrike’s milling and beneficiation operations are situated. In June 1995, Goldstrike acquired title to 1,657.5 acres of public lands in a land exchange with the Bureau of Land Management (BLM) that were subject to Goldstrike’s unpatented millsite claims within or adjacent to Goldstrike’s mining and milling operation. A second land exchange to consolidate land ownership occurred between Goldstrike and the BLM in 1995. The Section 31 land exchange (BLM 1995) resulted in Goldstrike acquiring title to 1,279 acres of public land that was subject to Goldstrike’s unpatented mining claims within or adjacent to Goldstrike’s mining and milling operations.

On May 3, 1999, Newmont Gold Company (Newmont) and Goldstrike completed a transaction known as the asset exchange. The purpose of the asset exchange was to rationalize the ownership and control of both the surface and subsurface estates that were jointly owned by the parties and to reduce the number of complex agreements that were needed to permit efficient operation and development of properties owned by both companies.

As a result of these exchanges, Goldstrike obtained: (1) the land needed for the development of the west end of the Betze-Post open pit; (2) control of the open pit, including the right to backfill the pit; (3) control of other lands important to its security that were needed for waste rock facilities; and (4) the underground deposits adjacent to its Meikle and Rodeo mines. Current land ownership is shown in Figure 4-2.

The Goldstrike Mine area is composed of approximately 10,372 acres of surface rights of which approximately 1,922 acres are public lands administered by the Bureau of Land

 

 

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Management (BLM) and 8,450 acres are patented and private lands owned by Goldstrike. There are approximately 8,736 acres of mineral rights ownership/control made up of 1,962 acres of public lands and 6,774 acres of private land. These rights are owned or controlled through ownership of various forms of patents issued by the USA and by ownership of unpatented mining and millsite claims held subject to the paramount title of the USA.

Figure 4-3 shows the general surface arrangement of the property and the footprint of the Goldstrike mineralization relative to the property boundaries.

A total disturbance of 8,590 acres is currently authorized for the mine. The majority (88%) of the total authorized disturbance would occur on private lands owned by Goldstrike. The remainder (12%) of the authorized disturbance would occur on public lands administered by the BLM.

The Goldstrike property has various royalty shareholders with a nominal overriding Net Smelter Royalty (NSR) of between 4% and 5% and a Net Profit Interest Royalty (NPI) of between 2.4% and 6% over various parts of the property. Key royalty shareholders are Franco-Nevada and Royal Gold, Inc.

 

 

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FIGURE 4-1 LOCATION MAP

 

LOGO

 

 

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FIGURE 4-2 LAND OWNERSHIP

 

LOGO

 

 

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FIGURE 4-3 FOOTPRINT OF MINERALIZATION

 

LOGO

 

 

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5 ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY

ACCESSIBILITY

Goldstrike is accessed from Elko, Nevada, by travelling west approximately 26 mi on U.S. Interstate 80 to Carlin, Nevada, where State Route 766 provides access to the various mining operations, including Goldstrike. Access to the property is provided by access agreements with Newmont Mining Corporation that allow for the use of various roads in the area and a right-of-way issued by the BLM. Most of these roads are paved and well maintained.

CLIMATE

Annual temperatures range from minus 38ºF to plus 104ºF. Average annual snowfall averages 30 in., while annual rainfall averages eight to ten inches. The heaviest months of precipitation are during the winter, as snow, and in May and June, as rain. Summer precipitation occurs mostly as scattered showers and thunderstorms, making only a minor contribution to overall precipitation. The effect of climate on operations is minimal. Approximately two shifts per year are lost due to weather.

LOCAL RESOURCES

Goldstrike is located in a major mining region and local resources including labour, water, power, and local infrastructure for transportation of supplies are well established. The majority of the workforce lives in the nearby towns of Elko, Spring Creek, Carlin, and Battle Mountain.

The water for process and mining is delivered from dewatering production wells. The water supply is more than adequate for present and planned requirements. Active dewatering operations are required and a water management group is in place to carry out all dewatering including pumping, distribution, delivery, and disposal.

Barrick built a 115 MW natural gas-fired power plant that became operational in the fourth quarter of 2005. This allows Goldstrike the flexibility to provide power through a combination of self generation and market purchases.

 

 

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INFRASTRUCTURE

The surface rights secured for Goldstrike are sufficient to provide the necessary space required for all mining and quarrying activities. Enough land area also exists on the property to accommodate all foreseeable processing plants, tailings impoundments, and waste disposal areas.

Currently, the major assets and facilities associated with the Project are:

 

   

Underground and open pit mines with production from several mineralized structures.

 

   

The physical plant site including the administrative office complex and associated facilities, the open pit and underground mine workings and associated facilities, ore processing plants (autoclave pressure oxidation and roaster circuit) and associated facilities such as laboratories, ore stockpiles, waste dumps, coarse ore storage, tailings storage, workshops, and warehouses.

 

   

Facilities providing basic infrastructure to the mine, including electric power, water treatment and supply, and sewage treatment.

 

   

Surface and underground infrastructure including mine ramps, headframes, hoists, ventilation raises, maintenance shops, and mobile equipment fleets.

PHYSIOGRAPHY

The underground mine is located in the Great Basin of northeastern Nevada, USA. The mine is at an elevation of approximately 5,600 ft in the hilly terrain of the Tuscarora Mountains with elevations varying from 5,400 ft to 6,000 ft in the immediate area.

The combination of topography and a mid-latitude steppe climate, common to the Great Basin, has produced grass and shrub dominated vegetation. Disturbances to the vegetation, including overgrazing, large-scale range fires of the 1960s, past and present mining operations, and mineral exploration have converted much of the remaining native vegetation within the area to early non-native annuals, sagebrush, and rabbitbrush. Riparian vegetation exists in association with perennial stream flow in Bell, Brush, and Rodeo Creeks, as well as near springs located throughout the Little Boulder Basin.

 

 

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6 HISTORY

The following history of the Goldstrike property owned by Barrick was obtained from Keith Bettles’ report (Bettles, 2000).

The earliest gold mining activity in the northern part of the Carlin Trend occurred at the Bootstrap and Blue Star mines prior to the discovery of gold at Goldstrike. At Bootstrap, just northwest of Goldstrike, antimony was discovered in 1918, followed by gold in 1946. Gold was produced at the Bootstrap during 1957 to 1960. At Blue Star, immediately south of Goldstrike, gold was identified in 1957 in areas that had been mined for turquoise. At Goldstrike, the only evidence of early mining activities is small workings for mercury of unknown age, located along the Post fault zone, south of the Meikle deposit.

The first discovery of gold in the Goldstrike property was in 1962 by Atlas Minerals. Soil samples and drilling discovered low-grade gold mineralization. No further work was conducted until an increase in gold price was seen in 1973 to 1974, which led the Nevada Syndicate (funded by Lac Minerals) to re-evaluate the area. Using various exploration methods, shallow mineralization in the Long Lac and Winston areas was outlined. Polar Resources (Polar) in 1975, followed by Pancana Minerals Ltd. (Pancana) from 1976 to 1977, delineated the Number 9 deposit and several low-grade zones within the Goldstrike intrusion to the east of Nevada Syndicate property. From 1975 to 1977, Polar and Pancana operated a small open pit and heap leach.

In 1978, Western States Minerals Corporation (Western) entered into a 50/50 joint venture with Pancana, which had consolidated the various claims and leases in the Goldstrike area. The bulk of the production was from oxidized zones, chiefly from the Long Lac, Bazza, and West Bazza deposits, plus some production from deposits within the Goldstrike intrusion. The Post deposit was discovered in 1982. Exploration continued until 1986 when a deep core hole was drilled at Post and the Deep Post deposit was discovered.

American Barrick Resources Corporation acquired the mine and properties from Western States (50%) in December 1986 and subsequently purchased Pancana’s interest (50%) in January 1987 for a total purchase price of $62 million. An aggressive deep drilling program outlined the large, high-grade Deep Post deposit, which was

 

 

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subsequently found to continue onto the adjacent property owned by Newmont. Exploration drilling in 1987 to 1988 led to the discovery of a number of other deposits similar to Deep Post. These included Betze and Screamer which, together with Deep Post, comprise the Betze-Post deposit. Other discoveries in 1987 and 1988 included Deep Star, Rodeo, Meikle (previously named Purple Vein), South Meikle, and Griffin.

Additional drilling in 1987 and 1988 expanded the reserve to justify bringing the Betze-Post deposit into production by open pit methods. Even though the deposit was deep, the size and grade allowed for economic development. Heap leach ore production from the Betze-Post pit continued from the time of purchase to the end of 1998. Oxide mill ore processing started in August 1988 and the autoclave portion of the mill, which oxidizes sulphide ores, commenced operation in early 1990. The processing of ores by the roaster began in 2000.

The Meikle deposit, formerly known as the Purple Vein, is located approximately 1.5 mi north-northwest of Barrick’s Post-Betze deposit and is currently in production. The deposit is approximately 800 ft to 2,000 ft below the surface. Although there is very little gold at the surface above the Meikle, Rodeo/Goldbug, and Griffin deposits, there is extensive silicification of the rocks along fault zones and a weak arsenic anomaly has been detected in soil samples. The Meikle deposit was discovered in September 1989 when the tenth deep drill hole EX-89-4 intersected 540 ft of 0.41 oz/st Au from 1,305 ft to 1,845 ft. This hole was targeted at an inferred structural intersection associated with induced polarization (IP) geophysical and soil geochemistry anomalies. Gold mineralization is absent at surface (in contrast to the Post-Betze deposit), although the area was the site of small-scale mercury workings in the 1940s.

Discovery of the Rodeo and Griffin deposits were part of the original deep exploration program. Both predate the discovery of Meikle. The discovery of the Rodeo deposit was in June 1988 and Griffin in July 1988. Their development since discovery has been significantly aided by the knowledge gained from the Meikle mine and from the underground access from the Meikle mine. Underground drilling has focused on exploration and reserve development in the Meikle, Rodeo, and Griffin areas.

The 1999 Asset Exchange with Newmont resulted in the acquisition of the Goldbug (the southern portion of Rodeo), West Rodeo, Barrel, and North Post deposits. These deposits were in the Newmont land corridor separating the Betze-Post and Meikle mines. The Banshee property north of the Meikle was also part of the exchange.

 

 

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PAST PRODUCTION

Past production (tons hoisted) from the underground operations is listed in Table 6-1.

TABLE 6-1 PAST PRODUCTION - UNDERGROUND MINE

Barrick Gold Corporation – Goldstrike Mine

 

Year

   Tons Produced
(000)
     Grade
(oz/st Au)
     Contained Gold
(000 oz)
 

1996

     161         0.584         94   

1997

     775         0.837         649   

1998

     877         1.098         963   

1999

     998         1.071         1,068   

2000

     1,257         0.724         909   

2001

     1,372         0.561         770   

2002

     1,635         0.427         697   

2003

     1,631         0.383         625   

2004

     1,573         0.401         631   

2005

     1,463         0.382         559   

2006

     1,420         0.373         530   

2007

     1,300         0.354         460   

2008

     1,388         0.342         476   

2009

     1,515         0.366         458   

2010

     978         0.307         300   

2011

     1,154         0.284         327   
  

 

 

    

 

 

    

 

 

 

Total

     19,497         0.488         9,516   

Past production from the open pit mine is listed in Table 6-2.

TABLE 6-2 PAST PRODUCTION - OPEN PIT MINE

Barrick Gold Corporation – Goldstrike Mine

 

Year

   Tons
Mined
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
 

2004

     9,434         0.156         1,472   

2005

     9,544         0.185         1,766   

2006

     8,519         0.177         1,508   

2007

     4,647         0.157         730   

2008

     12,952         0.155         2,008   

2009

     3,990         0.188         750   

2010

     13,734         0.134         1,840   

2011

     3,064         0.097         297   
  

 

 

    

 

 

    

 

 

 

Total

     65,883         0.157         10,370   

 

 

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Mine production at Goldstrike has varied on an annual basis with the largest annual variance in production being the open pit mining where ore production is a function of the ore availability in the pit. The large annual variance is smoothed through the use of stockpiles. The total annual gold production and the total gold mined on an annual basis are shown in Table 6-3. The difference between the contained gold mined and the gold production is a combination of metallurgical recovery, material taken from stockpiles that existed before 2004, and other minor items such as the inclusion of the Storm site in reported Goldstrike production after the first quarter of 2010.

TABLE 6-3 PAST PRODUCTION – PLANT FACILITIES

Barrick Gold Corporation – Goldstrike Mine

 

Year

   Gold Mined
(000 oz)
     Gold Produced
(000 oz)
 

2004

     2,103         1,943   

2005

     2,325         2,024   

2006

     2,038         1,865   

2007

     1,190         1,629   

2008

     2,484         1,706   

2009

     1,208         1,419   

2010

     2,140         1,239   

2011

     624         1,002   
  

 

 

    

 

 

 

Total

     14,112         12,827   

Note: In 2011, approximately 86,000 ounces of gold were also recovered at Goldstrike from ore originating at the nearby Storm operation.

 

 

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7 GEOLOGICAL SETTING AND MINERALIZATION

REGIONAL GEOLOGY

The Goldstrike Mine is located in the eastern Great Basin (Basin and Range Province) within the northern Carlin Trend on the western flank of the Tuscarora Mountains. The Carlin Trend is an alignment of gold mines located in a northwest-southeast belt extending five miles wide and 40 mi long, which accounts for more gold production than any other mining district in the United States. The northern trends account for in excess of twenty gold mines and deposits.

Two regionally recognized assemblages comprise the sedimentary strata of northeastern Nevada (Figure 7-1). The western or siliciclastic assemblage consists of mudstone, chert, siltstone, and minor limestone and includes imbricate thrust slices of Devonian Slaven, Silurian Elder, and Ordovician Vinini formations. The eastern assemblage of carbonate rocks consists of calcareous mudstone, siltstone and sandstone of the Rodeo Creek unit, muddy limestone of the Devonian Popovich Formation, silty limestone to massive fossiliferous limestone of the Silurian-Devonian Roberts Mountains Formation, sandy dolomite of the Ordovician Hanson Creek Formation, quartzite of the Ordovician Eureka Quartzite, and limestone, cherty limestone, and dolomite of the Ordovician Pogonip Group.

Jurassic quartz diorite, as plugs, sills, and dikes, has intruded the Paleozoic sedimentary rocks. Contact metamorphism affects the sedimentary rocks adjacent to the larger igneous bodies and is evident in the formation of marble, calc-silicates, hornfels, and skarn. Dikes and sills of Jurassic monzonite and lamprophyre, and Tertiary dacite and rhyodacites, are mapped in the area. Miocene rhyolite flows occur to the west in Boulder Valley. Tuffaceous fluvial and lacustrine semi-consolidated sediments of the Tertiary Carlin Formation and Quaternary alluvium unconformably top the stratigraphic section.

 

 

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FIGURE 7-1 REGIONAL GEOLOGY

 

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The Antler orogeny extensively deformed Paleozoic rocks of the Great Basin in Nevada and western Utah during Late Devonian and Early Mississippian time. In the late Devonian some 350 million years B.P., the Antler volcanic island arc terrane collided with what was then the west coast of North America and the North American Plate. The collision zone is marked by the Carlin Trend and the Roberts Mountains Thrust. The siliciclastic rocks were thrust eastward over the carbonate rocks during the Antler Orogeny (Roberts Mountains Thrust). Mesozoic compressional deformation was also important regionally as indicated by various east and west as well as north-northeast and south-southwest verging thrusts. Tertiary faulting developed basins and ranges with the former subsequently filled with volcanics and sediments during Tertiary time. Gold mineralization occurred at the onset of Tertiary volcanism, approximately 39 million years ago.

The stratigraphic section is cut by a series of north-northwest, northwest, northeast and north-northeast striking high and low-angle faults with extensive fracturing, brecciation, and folding. These faults both control and displace mineralization, with evidence for both dip-slip and oblique-slip displacements. Jurassic and Tertiary intrusives utilized both high and low angle faults as they intruded the Paleozoic section. Cenozoic Basin and Range deformation most likely reactivated the majority of faults in the area.

In terms of their regional tectonic setting, the Carlin Trend gold deposits are hosted in carbonate rocks within a thick sequence of Paleozoic miogeosynclinal sedimentary rocks coincident with:

 

  1) the thinned western margin of the North American craton in early Paleozoic times;

 

  2) the west-central portion of the Lower Devonian Antler foreland basin;

 

  3) the east edge of deformation related to the late Paleozoic Humboldt orogeny;

 

  4) an area of Jurassic plutonism, metamorphism and deformation;

 

  5) the hinterland of the early Tertiary Sevier orogenic belt; and

 

  6) the broad zone of Eocene to Miocene calc alkaline magmatism and tectonic extension that occurred throughout much of the Great Basin.

The collision between Antler terrane and the North America plate induced higher crustal temperatures and pressures which produced numerous hot springs along the suture zone. Several episodes of subsurface magmatism are known to have occurred subsequent to the collision. During these episodes, and particularly during the Eocene epoch, hot springs brought dissolved minerals toward the surface, precipitating them out

 

 

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along fissures. Among these minerals were gold and silver. Most of the largest gold deposits lie within 350 ft of the Roberts Mountain Thrust at the base of the allochthon. Geochronologic study indicates that most of the gold in the Carlin Trend was emplaced over a short interval of time between approximately 42 and 36 Ma. Analyses of the sulphosalt galkhaite from the Rodeo deposit at Goldstrike have yielded a mineralization age of 39.8 ± 0.6 Ma.

PROPERTY GEOLOGY

OPEN PIT

At the Betze-Post open pit, the stratigraphic sequence from the base is as follows: Ordovician Vinini Formation siltstones, mudstones and cherts; Silurian-Devonian Roberts Mountains Formation silty/fossiliferous/laminated limestones and sedimentary breccias; Devonian Popovich limestones, limey mudstones and sedimentary breccias; and Devonian Rodeo Creek siltstones and argillites (Figures 7-2 and 7-3). These formations have been intruded by the Goldstrike diorite dike and sill complex as well as by Tertiary sills and dikes. The Vinini Formation rocks, which lie mostly east of the pit, have been thrust over the younger units along the Roberts Mountains Thrust that is exposed in the wall of the Betze-Post open pit. Unconformably overlying the older units are volcaniclastic sedimentary rocks, tuffs, and gravels of the Tertiary-aged Carlin Formation in turn succeeded by Quaternary alluvium.

 

 

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FIGURE 7-2 OPEN PIT GEOLOGY

 

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FIGURE 7-3 OPEN PIT GEOLOGY CROSS SECTIONS

 

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The Slaven, Elder, and Vinini formations contain similar lithologies and are collectively referred to as the Vinini Formation. The regional Roberts Mountains Thrust fault separates the Vinini Formation and the Rodeo Creek unit. The Rodeo Creek unit has been subdivided into four units: (1) a lower calcareous mudstone-argillite unit; (2) a calcareous sandstone unit; (3) a calcareous mudstone, siltstone, and argillite unit; and (4) an upper carbonaceous limestone unit.

The Popovich Formation is subdivided into four units: (1) the lower Wispy unit, which consists of wispy laminated muddy to silty limestone with abundant interbedded debris flows; (2) the planar unit consisting of thin planar bedded muddy limestone, (3) the soft-sediment deformation unit of thick to medium bedded muddy to micritic limestone with occasional soft-sediment deformation features, and (4) the upper muddy limestone unit consisting of thin to medium bedded muddy limestone. The Roberts Mountains Formation is subdivided by a facies change from north to south. In the south, from the Betze-Post open pit through the Rodeo underground mine, a thin bedded, planar laminated silty limestone basinal facies predominates with an upper coarse wispy laminated horizon. To the north of the Rodeo underground mine, the Bootstrap massive fossiliferous limestone is present. This facies relationship reflects a Roberts Mountains high related to reef development along the Paleozoic continental margin. The Popovich Formation thins to the north in response to the Roberts Mountains high, and both the Popovich and the Roberts Mountains units show local facies transitions with the Bootstrap limestone. At Betze-Post through Rodeo, there is a full section of Popovich, but at the north end of Meikle, only the upper member of the Popovich is present. The Roberts Mountains high at Meikle has been exaggerated by high and low angle reverse faulting.

The Hanson Creek Formation is a medium to thick bedded to massive dolomite to sandy dolomite. Drilling to date on the property has intercepted only the top of the Hanson Creek Formation. The Eureka quartzite is a massive to thinly bedded orthoquartzite with local lenses of dolomite. The Pogonip Group contains thin to thick bedded limestone, cherty limestone, and dolomite. The Eureka quartzite and Pogonip Group have not been intercepted with drilling on the property but occur in outcrop to the southeast.

ALTERATION

Pre-mineralization alteration includes dolomitization of limestones and migration and maturation of hydrocarbons. Jurassic intrusive rocks are extensively sericitized, which

 

 

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may be due to retrograde metasomatic alteration in a pre-mineralization Cretaceous hydrothermal event. From east to west, the Deep Post is affected by argillic alteration, the Betze deposit by decarbonatization of its upper zone and silicification of the lower zone, with similar but weaker alteration affecting the Screamer deposit. Decarbonatization (decalcification) produced extensive zones of permeable collapse breccias, ground preparation for hydrothermal fluids and gold bearing pyrite mineralization. Ore stage alteration was accompanied by illite and quartz deposition followed by late quartz and kaolinite.

STRATIGRAPHY AND STRUCTURE

Structures on the property record a complex history of contractional and extensional tectonics and later reactivation during successive periods of deformation. Stratigraphic formations have gentle dips except in the vicinity of high angle faults and along the western margin of the Goldstrike Stock where bedding may be steeper. Mesozoic folding and thrust faults form important structural traps for the mineralization in the Betze-Post open pit.

The strata are cut by a series of Tertiary north-northwest, northwest, northeast, and north-northeast striking high and low angle faults accompanied by extensive fracturing, brecciation, and drag folding. Primary high angle faults strike north-northwest and dip east and west. Secondary faults strike east to east-northeast and dip north. These faults both control and displace mineralization, with evidence for both dip-slip and oblique-slip displacements. The most prolific structure in the district is the Post Fault Zone, which is approximately 250 ft wide, and has over 2,000 ft of normal displacement at Betze-Post open pit and approximately 1,300 ft of normal displacement to the north at the Meikle deposit. The Carlin Formation basin east of the Post Fault is a good local example of Cenozoic deformation, with normal offsets up to 1,000 ft on east and west dipping Post-parallel faults.

Gold mineralization in the open pit occurs at fault intersections as well as where faults intersect anticlinal fold axes in decalcified rocks such as sedimentary and collapse breccias in the lower Popovich limestone.

UNDERGROUND

As in the Open Pit, the geology of the underground deposits is characterized by two regional lithologic assemblages: (1) the “eastern” or carbonate assemblage of the

 

 

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Devonian Popovich and Silurian-Devonian Roberts Mountains Formations, and (2) the transitional Rodeo Creek Formation (Figure 7-4). The allochthonous western assemblage, which includes the Ordovician Vinini, Silurian Elder, and Slaven Chert formations, is also present but does not host any of the underground ore bodies.

A brief description of the formations starting from the base and moving upwards is taken from Linebarger (2010):

 

   

Roberts Mountains Formation: Underlies most of the property and is mineralized when strongly brecciated or intersected by structural features. The Roberts Mountains Formation is predominantly a thin-bedded silty limestone, which is locally dolomitic. This limestone transforms into shallow water reef and shoal facies informally termed the Bootstrap Limestone to the north and northeast. The Bootstrap Limestone at Meikle occurs as a series of structural highs, upon which the Popovich and Rodeo Creek formations were deposited in an overall progradational environment. Gold mineralization is hosted primarily in rocks derived from the Bootstrap Limestone.

 

   

Popovich Formation: The Popovich Formation is a major host for gold mineralization, particularly in the southern mining areas such as the Rodeo deposit. Rocks of the Popovich setting are typically carbonaceous, somewhat permeable, and are part of a marine slope facies. They were products of a shallower water depositional environment than the Vinini Formation and the other western assemblage siliciclastics. This formation overlies the Roberts Mountains Formation and is subdivided into four distinct units (described from base):

 

   

WS: The dominant mineralization host in the Rodeo Lower Zone. It is a grey silty limestone with distinct undulation laminations intercalated with debris flow horizons. A clast supported collapse breccia often occurs near the base.

 

   

PL: A minor mineralization host in the Rodeo Lower Zone but the predominant host of the Barrel Zone. It is a black to dark grey, fine grained, variably calcareous, and fossiliferous mudstone.

 

   

SD: Light grey, thickly bedded micritic limestone that hosts some of the Barrel mineralization and is a minor host to the Rodeo Upper Zone. It displays distinctive swirled bedding, but the base can be fresher and better bedded than upper sections.

 

   

UM: The Upper Mud is the dominant host for Rodeo Upper Zone mineralization, for mineralized lamprophyre dykes in the South Meikle Zone, and for west dipping dykes in the South Griffin Zone. Characterized by finely bedded limey mudstone, it is interlayered near the upper contact with mudstone beds. There are sub-units of finely disseminated pyritic lamina and cherty and debris flow lenses.

 

   

Rodeo Creek Formation: Overlies the Popovich Formation and underlies the Roberts Mountains Thrust (RMT). This formation is represented by a sequence of argillites and a locally mineralized package of silts and sandstones (Bazza Sand). The rocks of the Rodeo Creek are slightly calcareous but much less so than those rocks of the carbonate assemblage and represent a deep water transitional facies between the eastern and western assemblages. It is the host to the Griffin and Griffin West zones. It is divided into three units (described from base to top).

 

 

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AM: The generally barren Lower Argillite unit could host narrow mineralization within silty interbeds if intersected by favourable structures. Composed of thick layers of fine to medium grained carboniferous mudstone and siltstone alternating with thin layers of fine grained siliceous mudstone.

 

   

BS: The Bazza Sands unit forms the main host for the East Griffin and West-Griffin deposits. It is composed of well bedded siltstone and sandstone beds and typically contains a narrow sub-unit of argillite called the Middle Argillite.

 

   

AA: A poor host for mineralization, the Upper Argillite shares characteristics with the Lower Argillite but with thinner bedding.

 

   

Intrusives: Jurassic-aged Rhyodacite Porphyry (MP), lamprophyre (LA) and Tertiary Rhyodacite Biotite Feldspar Porphyry (BFP) dykes and sills occur at various orientations. The MP and BFP host no significant mineralization. Mineralization is found in or near east and west dipping LA, the South Meikle Extension, South-Griffin, and the Rodeo Upper and Lower zones.

STRUCTURE

The fracturing, brecciation, folding, and mineralization observed underground is primarily controlled by high angle north-northwest and north-northeast trending fault systems. The most prominent system is the Post Fault Zone (PFZ) that strikes N30ºW and dips steeply to the east. The PFZ is a normal fault that down-drops the formations hundreds of feet and marks the eastern edge of known mineralization from Banshee to Betze-Post. North-northwest striking and west-northwest striking low angle faults also influence ore emplacement.

 

 

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FIGURE 7-4 UNDERGROUND GEOLOGY LONG AND CROSS SECTIONS

 

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MINERALIZATION

Gold mineralization was emplaced approximately 39 Ma ago along favourable stratigraphy and structural features such as faults and folds, and along contacts between sedimentary rocks and the Goldstrike stock. Faulting provided major conduits for mineralizing fluids and may also have produced clay alteration that can act as a mineralizing barrier. Intense fracturing around the contact zone of the Goldstrike stock caused solution collapse and brecciation of the surrounding sedimentary units. Secondary fracture permeability was generated along the crests of anticlines, creating focal points for collapse breccia and dissolution zone formation. Finally, lithology and alteration contacts act as permeability barriers to fluids causing mineralization to pond along them particularly where feeder structures intersect these contacts. Alteration is characterized by decalcification of limestone, silicification of all rock types, and clay development in structurally disturbed areas.

The gold mineralization is associated with silicification, argillization, and sulphide mineralization with little or no oxide mineralization remaining. In sulphide ore, the gold is intimately associated with very fine-grained pyrite and marcasite and is refractory. Over time, the pyrite oxidized, freeing the gold and making its extraction relatively easy, as in the historic Post Oxide deposit. Associated sulphide minerals include arsenopyrite, realgar, orpiment, and stibnite. Gangue minerals include quartz, calcite, and barite. Realgar and orpiment are generally low in abundance; however, these minerals are locally common in stockwork veinlets, fracture fillings and breccia matrices.

OPEN PIT

The Betze-Post mineralization, the largest deposit in the Carlin Trend, is subdivided into sub-deposits which, from east to west, are the Deep Post, Post, Betze, West Betze, and Screamer. Other zones within the pit are North Betze, West Barrel, and North Screamer. The locations of the mineralized zones are illustrated in Figure 7-5.

Overall, the open pit deposits consist of five stacked zones which, when combined, average 500 ft thick and 600 ft wide but may attain a thickness of 700 ft, a width of 1,100 ft, and a length of 3,400 ft.

 

 

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FIGURE 7-5 OPEN PIT ZONE LOCATIONS

 

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Five generations of pyrite mineralization have been recognized at the Betze-Post open pit. Early stages of diagenetic pyrite, and coarse grained pyrite in the metamorphic aureole of the Goldstrike diorite, are barren. Early hydrothermal, very fine grained pyrite and marcasite grains of the third generation are coated by a 25 µm thick rind and cut by micro-veinlets of arsenic and gold bearing pyrite of the fourth generation. Barren, late hydrothermal coarse grained pyrite and marcasite is accompanied by barite and stibnite. Sulphides make up approximately 5% by weight of the ore, locally up to 20%.

The gold bearing arsenian pyrite may be subdivided into coarse grained sulphides at ±200 µm diameter and fined grained at 10 µm to 20 µm, with the latter carrying proportionately much more gold. Gold at 0.05 µm to 0.1 µm is occluded in the iron sulphides. Approximately 10% to 20% of the gold is free, 20% to 30% is held in the fine grained pyrite/marcasite, a few percent is contained in coarse pyrite, and the balance is in very fine pyrite associated with clay.

Mineralization types are described by Leonardson and Rahn (1996) as:

 

   

Disseminated carbonaceous mineralization, sulphide breccia and siliceous sulphide breccias in the decalcified Popovich limestone consisting of carbonaceous siltstone and grey breccia with quartz veining and marcasite blebs accompanied by high values of Hg, Cr, Zn, and Cu. This type of mineralization occurs as an upper tabular zone of the Popovich Formation and carries high gold grades.

 

   

Siliceous stibnite breccia mineralization in limestone occurs as tabular zones up to 300 ft long and 150 ft thick and is characterized by partially brecciated, silicified limestone with disseminated pyrite and late stibnite occurring as coatings on pyrite and fractures and as vein and vug fillings with barite. This type is rich in Sb with moderate Hg, Tl, As, Ba, and Zn.

 

   

Seam mineralization is rich in realgar and orpiment and occurs as dark decalcified fractures and argillaceous zones in blocks of sheared marble and calc-silicate rocks at the Goldstrike intrusive margin.

Late stage mineralization is characterized by stibnite and barite in silicified zones and realgar, orpiment, calcite, marcasite, and rare fluorite in argillized zones. Other late stage minerals are pyrite, marcasite, gypsum, apatite, siderite, dolomite, sphalerite, and millerite.

Carbon content in the deposits is highly variable and carbon occurs generally in the Popovich Formation, except in the east area of the pit where it is removed or destroyed by contact metamorphism along the Goldstrike intrusive.

 

 

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Mineralization may be predominantly oxides, sulphides, or refractory or carbonaceous sulphides. Supergene alteration extends up to 655 ft in depth resulting in oxide mineralization which overlies the refractory sulphides. Alteration has liberated gold by the destruction of pyrite and resulted in the formation of oxide and secondary sulphate minerals, which include goethite, hematite, jarosite, scorodite, alunite, and gypsum. The alteration is deepest in the Post deposit due to extensive fracturing and high pyrite content.

UNDERGROUND

Gold mineralization in the underground mine is subdivided into Meikle, Griffin, Rodeo, Barrel, Banshee, and North Post deposits and sub-deposits (Figure 7-6). The sulphide mineralization is associated with silicification and argillization, and there is little or no oxide mineralization remaining. In sulphide mineralization, the gold is intimately associated with very fine-grained pyrite and marcasite and is refractory. Over time, the pyrite oxidized, freeing the gold and making its extraction relatively easy, as in the historic Post Oxide deposit. Associated sulphide minerals include arsenopyrite, realgar, orpiment, and stibnite. Gangue minerals include quartz, calcite, and barite. Realgar and orpiment are generally low in abundance; however, these minerals are locally common in stockwork veinlets, fracture fillings, and breccia matrices.

The orientation of the mineralization is different in each zone. Meikle, Meikle-East, Extension, Rodeo, and East-Griffin are characterized by steep and shallow angle east-dipping mineralization. South Griffin and part of Lower Rodeo are more moderately west dipping. South Meikle, West Griffin, and Barrel mineralization are relatively flat lying.

 

 

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FIGURE 7-6 UNDERGROUND LONGITUDINAL SECTION

Use new version.

 

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.\.\.\1622-Barrick Gold Corporation 2010 Reserve Audits\From Client\Goldstrike\UG\2010reserves-11X17 Plan Section RPA.PDF

 

 

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MEIKLE

Collapse and hydrothermal breccias in the Bootstrap Limestone member of the Roberts Mountains Formation, and to a lesser extent, the Popovich Formation are the dominant host for gold mineralization at Meikle. Breccia geometries are complex, with multiple breccia types observed. Mineralization is predominantly hosted in a breccia derived from a zone of dolomitic alteration that mantles the Bootstrap Limestone. Dolomite and other carbonate rich rocks occurring within the host breccia have been completely digested and replaced by silica. The gold enriched pyrite is disseminated throughout the siliceous breccia host. A rhyodacite dike, which pre-dates mineralization, also occurs in the Main Zone.

The Meikle deposit is divided into five distinct zones: Main Zone, East Zone, Meikle Extension, South Meikle, and the Lamprophyre Zone. The Main Zone, East Zone, and Meikle Extension parallel the PFZ and exhibit pipe-like geometry, which dip at high angles to the east. The Main Zone and East Zone are the high grade zones in the deposit. The South Meikle and Lamprophyre zones have a flatter geometry with a possible stratigraphic component along the Rodeo Creek-Popovich contact. A second component exhibits a pipe-like geometry, which dips 50o to 75o west.

The Main Zone parallels the PFZ and strikes N30°W. It has a strike length of 1,200 ft, an average thickness of approximately 300 ft, and extends from the 4,600 ft to the 3,200 ft elevation. The host breccias occur between a rhyodacite porphyry dike in the hanging wall and a block of Bootstrap Limestone in the footwall. These breccias are highly silicified and pyritized. Locally, large unmineralized dolomite blocks occur within the breccia, which often divide the mineralized zones. The mineralization proximal to the limestone footwall is very high grade in the dolomite breccias, dropping to low grade in the hanging wall rhyodacite dike.

The N30ºW striking East Zone mineralization occurs south of where the Post Fault is cut by northeast faults. It extends from the 4,400 ft to 3,300 ft elevation, with a strike length of 700 ft and an average thickness of approximately 80 ft. The zone contains several rhyodacite, dacite, and lamprophyre dikes with highly silicified and pyritized breccias similar to the Main Zone. The similar orientation and alteration of footwall breccias allowed for the incorporation of the East Zone into the Main Zone model.

 

 

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The South Meikle Zone is subparallel to and west of the East Zone, over a strike length of 1,400 ft. It has a relatively shallow dip and extends from 4,350 ft to 4,650 ft elevation, with an average thickness of approximately 50 ft. It is located directly above and west of the Bootstrap Limestone structural block. Economic grade mineralization occurs in lamprophyre bodies, adjacent silicified breccias, and on the west side also in the Bazza Sands unit. Lamprophyre dikes were emplaced along moderate to high angle structures and locally follow bedding and/or contacts within carbon rich Popovich and overlying Rodeo Creek mudstone and siltstone.

The Meikle Extension Zone represents the southeast portion of the deposit and parallels the Post Fault system. It is discontinuous over a 1,500 ft strike length, with an average thickness of approximately 40 ft and extends from 4,400 ft to 3,200 ft elevation. This zone marks the transition between the wide and high grade breccia lenses to the north and the East Griffin North Zone to the south. The mineralization is similar to that observed in the East Zone to the north, but is higher grade and becomes hosted in an east dipping lamprophyre dike further south. This lamprophyre dike is the footwall of an east dipping barren biotite-feldspar porphyry dike. The host rocks and limited thickness distinguish the Meikle Extension Zone from the East Zone.

The Lamprophyre Zone is the extension of the South Meikle Zone through and above the Main Zone, shows a north-northeast trend, and has been incorporated into the west dipping South Meikle model. The average thickness of this zone is approximately 30 ft, from elevation 4,650 ft to 4,400 ft, and along a strike length of 550 ft. The Lamprophyre Zone has a flat lying stratigraphic component along and underneath the Rodeo Creek-Popovich contact. A second component exhibits a pipe-like geometry and dipping of 50o to 75o to the west. This second component splits the Main Zone in two lenses in the west sector of this deposit.

GRIFFIN

The Griffin deposit includes four geologically distinct domains: Breccia-hosted (formerly described as the North Griffin), Bazza Sands (formerly described as the Griffin Main Zone), West Griffin, and the Lamprophyre Zone. Each zone contains typical Carlin-style gold mineralization captured in fine-grained iron sulphides. Silica-replaced breccias similar to those at Meikle, calcarenites, and lamprophyre are the various host rocks, each dominant in its respective domain. Feeder, boundary, and offsetting structures are the primary controls to mineralization in every case throughout Griffin.

 

 

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The Griffin Breccia-hosted domain contains similar rocks as the Meikle East Zone. It extends from elevation 4,400 ft to 3,200 ft, with an average thickness of approximately 50 ft and a strike length of 900 ft. Limestones of the Popovich Formation, and possibly of the Bootstrap unit, comprise the main source of clasts which constitute the heterolithic mineralized breccia body. Rhyodacite dikes bound the breccia to the east and the Barite Fault separates the breccia-hosted mineralization from the Bazza Sands-hosted mineralization on the west. Rhyodacite and lamprophyre clasts are also present in the breccia mass to a lesser degree. Pervasive silicification normally replaces all protolith fabric. Mineralization weakens to the south.

The Griffin Bazza Sands-hosted domain comprises the bulk of Griffin mineralization and occurs southwest of the Barite Fault in a flat-lying, 250 ft to 300 ft thick silty to sandy facies of the Rodeo Creek unit called the Bazza Sands. This stratigraphic member is sandwiched between two siliceous and carbonaceous mudstone horizons locally called “argillite”. Mineralization is controlled by subvertical structures that are associated with the northwest trending Barite Fault. It is from 30 ft to 65 ft wide, 1,100 ft along strike, and occurs between the 3,700 ft and 4,500 ft elevation. The gold content decreases away from the Post Fault Zone.

The West Griffin Domain is also hosted in the Bazza Sands unit of the Rodeo Creek Formation. Minor amounts of mineralization are also hosted by carbonaceous to siliceous argillites of the Rodeo Creek Formation. The mineralization is controlled by N25°W, 70°NE and N10°E, 65°NW trending faults, and extensively by northwest trending, east dipping low angle faults (Zappa faults). The host rock is variably decalcified with weak to moderate silicification. Quartz veins with strong pyrite and some kaolinite localized along fractures characterize alteration within this zone. The zone has an average thickness of approximately 35 ft, from elevation 4,100 ft to 4,700 ft with a strike length of 1,200 ft. Resource potential lies to the west along the Zappa faults, and north and south along strike with South Meikle and Barrel respectively.

Mineralization distribution in the Lamprophyre Zone tracks mainly along the Dormant Fault (approximately N25ºW strike, 45º to 65º dip to the SW) and is proximal to bodies of lamprophyre. Mineralization occupies an area between the 3,200 ft and 4,100 ft elevation with a strike length 1,700 ft. Gold occurs in multiple west-dipping lenses that

 

 

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vary in thickness from 10 ft to 70 ft. The Zappa and Post fault systems also demonstrate some control on mineralization, particularly where these patterns intersect the Dormant Fault. Lamprophyre is the chief hosting lithology with minor dissemination into the Popovich Formation country rock. Economical grade mineralization is not ubiquitous within the lamprophyre rock but appears to favour conspicuous regions of intense alteration.

RODEO

The Rodeo deposit is located approximately 4,500 ft south of the Meikle underground mine and 3,600 ft north of the Betze-Post open pit.

Economical grade mineralization occurs in two zones in the Rodeo area, the Upper and Lower zones. The combined dimensions of the two zones have a strike length of 2,300 ft. The zones extend from the elevation of 3,500 ft to 4,700 ft, with a true thickness of 100 ft to 200 ft.

The Upper Zone consists of four subzones: the Upper North, Middle, Upper South, and West subzones. The Upper Zone lies within a stratigraphic and structural antiform that has a shallow plunge to the north-northeast. Mineralization is hosted in the Upper Mud, Sediment Deformation, and Planar units of the Popovich Formation as well as Jurassic lamprophyre dikes. The morphology of the mineralized zone is dictated, in order of significance, by the proximity to favourable feeder structures, receptive lithologies, and structural preparation.

The Lower Zone occurs in the Wispy unit of the Popovich Formation. The Wispy unit in Rodeo is characterized by laminated limestone, debris flow horizons, and local collapse breccia zones associated with structural intersections and discontinuous lamprophyre dikes. The morphology of the zone is strongly influenced by the proximity of through-going northwest striking faults, north-northeast striking feeder faults, and favourable lithology.

BARREL

The Barrel mineralized zone is a tabular body located 200 ft northwest to approximately 1,000 ft west-northwest of the Rodeo deposit, between the 3,900 ft and 4,200 ft elevation. It has a strike length of 1,600 ft along a N30ºW orientation and varies in thickness from 30 ft to 50 ft. It is hosted mainly in the Planar unit of the Popovich

 

 

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Formation, with minor values within the overlying Sediment Deformation unit, as well as in the underlying Wispy unit at the south end of the zone. The zone is bounded by a series of low and high angle east dipping structures, and is also partly controlled by west dipping lamprophyre dikes.

BANSHEE

The East Banshee deposit is located 1,800 ft to 3,000 ft north of the Meikle deposit, between 3,200 ft and 3,900 ft elevation. The general orientation of high grade mineralization is north-northwest striking and low to moderately northeast dipping. High grade mineralization ranges from 10 ft to 80 ft thick. Gold mineralization is hosted in faulted or brecciated quartz-sericite-pyrite altered lamprophyre, silicified brecciated limestone, collapse breccias, and brecciated monzonite. The mineralization is focused on a low to moderate northeast dipping lamprophyre filled fault zone (East Banshee Shear Zone). The multiple intrusive rock types that characterize the deposit diverge from this fault zone to the Ren Fault, which is a large displacement normal fault with a north-northwest strike and moderate northeast dip. The Ren Fault merges with the Post Fault to the south at the Meikle deposit. East Banshee high grade mineralization is bound both to the east and west by north-northwest striking steep east dipping faults (similar to the PFZ at Meikle). Continuity of mineralization along strike is offset by east-northeast striking, steeply dipping faults. The strike extent of the high grade mineralization appears to be bound to the north and south by east-northeast striking, steeply south dipping faults. The down-dip extent of higher grade mineralization is primarily controlled by the intersection of the East Banshee shear zone and Post-parallel faults (hinge zone). The Post Fault is the eastern limit of mineralization. Significant mineralization continues to the north, but drilling indicates less continuity than in the southern portion of the deposit.

The West Banshee deposit is located between 600 ft northwest and 1,800 ft north-northwest of the Meikle deposit, between the 3,900 ft and 4,300 ft elevation. Gold mineralization is hosted in north-northwest trending, moderate to steeply west dipping lamprophyre dikes up to 40 ft wide. Continuity along the 1,500 ft strike length appears to be offset by subvertical east-northeast striking faults. Continuity along dip appears to be approximately 200 ft at the northern end and less than 100 ft at the southern end. The East Banshee shear zone appears to limit the upper and lower extent of high grade mineralization. Low grade mineralization is relatively continuous between East Banshee and West Banshee deposits along the East Banshee shear zone.

 

 

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NORTH POST

The North Post deposit is located between the southern end of the Rodeo deposit and the northeast final wall of the Betze-Post Pit, between the 3,100 ft and 4,600 ft elevation. North Post mineralization can be subdivided in three zones: the Upper Zone, Main Zone, and Lower Zone. The Main Zone is partially split by a property boundary with Newmont.

Upper Zone gold mineralization is hosted in the Popovich Formation limestone along west dipping lamprophyre filled faults. The Main Zone is hosted primarily in the Roberts Mountains limestone, footwall to the Post Fault, between interpreted moderate east dipping reverse faults at intersections with Dormant Fault splays. The Lower Zone or Deep North Post Zone is hosted in the Roberts Mountains Formation limestone, footwall to the Post Fault, between interpreted moderate east dipping reverse faults and between splays of the Dormant Fault.

 

 

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8 DEPOSIT TYPES

The Goldstrike deposits are Carlin style deposits. Carlin deposits comprise stratabound disseminated gold mineralization hosted by Silurian-Devonian carbonate rocks that have been metamorphosed to varying extents. The deposits are hydrothermal in origin and are usually structurally controlled. The carbonate host rocks are part of an autochthonous miogeoclinal carbonate sequence exposed as tectonic windows beneath the Roberts Mountains allochthon. The allochthonous rocks are a sequence of lower Paleozoic dominantly siliciclastic eugeoclinal rocks that were displaced eastward along the Roberts Mountains Thrust over younger units during the Upper Paleozoic Antler orogeny.

Current models attribute the genesis of the deposits to:

 

   

Epizonal plutons that contributed heat and possibly fluids and metals;

 

   

Meteoric fluid circulation resulting from crustal extension and widespread magmatism;

 

   

Metamorphic fluids, possibly with a magmatic contribution, from deep or mid crustal levels; and

 

   

Upper crustal orogenic-gold processes within an extensional tectonic regime.

 

 

 

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9 EXPLORATION

To date, surface geological mapping and prospecting has been completed on the property, with pit mapping ongoing. In excess of 14,000 diamond and reverse circulation (RC) holes have been drilled on the property to the end of 2010. Geochemical soil and rock sampling was carried out on the property in early exploration. Geophysical surveys include airborne and ground magnetometer; gravity; time domain pole-dipole IP; DC resistivity; CSAMT (controlled source audio magnetotellurics) and MT (magnetotellurics); time domain MT/IP using a distributed assay system; electrical logging of drill holes; and downhole IP. Gold mineralization is not directly detectable by geophysical methods; however, surveys map subsurface properties that are useful in interpreting lithology, alteration, and structure as guides to gold mineralization. Aerial photographic surveys are performed every one to two years for open pit survey control.

Currently, exploration is exclusively by drilling, which is described in Section 10, Drilling.

 

 

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10 DRILLING

OPEN PIT

The current Mineral Reserves were defined by drilling from 1994 to 2005 with additional in-fill drilling from 2006 to present. Most of the drilling prior to 2003 was diamond drilling and RC drilling has been used since then.

The geometry of mineralization can be highly variable, controlled by fracturing related to faulting and folding as well as by favourable stratigraphy and variations in rock chemistry, porosity, permeability, bedding habit, etc. Drilling is done at various angles to structural and stratigraphic controls so as to determine true heights and widths of mineralization. Drill sampling and geological interpretations completed prior to mining are generally effective in predicting the orientation of mineralization.

The in-pit resource area has been explored by drilling on a grid pattern of 100 ft to 175 ft. Drill hole spacing through the Betze, West Betze, and Screamer deposits is approximately 150 ft to 175 ft, and at Post and North Betze is roughly 150 ft. West Barrel is drilled at roughly 130 ft spacing or less and the pattern has been tightened to 100 ft for the North Screamer Zone.

Murray et al. (2005) report that drilling on a regular spaced grid has underrepresented tightly controlled high grade mineralization in many cases (North and South walls) and overrepresented high grade mineralization in at least two cases (North Betze area and along the Dillon fault zone near the base of mineralization). Local downhole deviation has the possibility to influence the representivity of samples in deposits. Angled drill holes are used to deliberately drill opposed to the preferred direction of downhole deviation.

RC drilling (6 1/4 in.) accounts for approximately two thirds of the drilling, with one third diamond drilling at HQ to NQ (2 1/2 in. to 17/ 8 in.) core diameter. The database also contains some underground drilling collared north of the pit. Table 10-1 summarizes drill hole database statistics and Figure 10-1 illustrates the drill hole locations.

 

 

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TABLE 10-1 DRILL HOLE DATABASE STATISTICS

Barrick Gold Corporation—Goldstrike Mine

 

Count

     10,507   

Sum

     7,003,595 ft   

Minimum Length

     1 ft   

Maximum Length

     4,528 ft   

 

Subvertical (<-80o)

   Inclined (-20o to -80o)   Subhorizontal & Uppers (>-20o)

8,175

   1,693   639

5,135,961 ft

   1,575,639 ft   291,995 ft

73%

   23%   4%

As-planned drill hole collar locations are set out by the open pit surveyors using Trimble High Precision GPS to determine the location of every hole and to establish foresights for all angle holes. After the holes are drilled, the surveyors again pick up the as-built collars using GPS.

 

 

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FIGURE 10-1 DRILL HOLE LOCATION PLAN

 

LOGO

 

 

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Downhole surveys are performed on all new exploration drill holes except for very shallow (<200 ft) vertical holes. Downhole surveys by gyro instrumentation are performed under contract by International Directional Services LLC (IDS). Most of the diamond drill holes have been surveyed downhole, whereas less than a third of RC holes are surveyed for deviation. Of the 36% of the holes in the database that are surveyed downhole, most measurements have been taken at 25 ft, 10 ft, and 40 ft intervals. Table 10-2 and Figure 10-2 summarize the downhole survey statistics.

TABLE 10-2 DOWNHOLE SURVEY STATISTICS

Barrick Gold Corporation—Goldstrike Mine

 

Number of survey records (including collar)

     141,501   

Number of drill holes

     10,507   

Number of holes surveyed

     3,822   

Number of downhole readings

     130,994   

Number of holes not surveyed

     6,685   

FIGURE 10-2 DOWNHOLE SURVEY MEASUREMENT INTERVALS

 

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UNDERGROUND

Both RC and diamond drilling are used underground at Goldstrike. Over 13,400 underground holes have been drilled up to December 31, 2011 (Table 10-3) with the majority being RC holes. The drill hole locations are illustrated in Figure 10-3.

TABLE 10-3 UNDERGROUND DRILLING TO EOY2011

Barrick Gold Corporation—Goldstrike Mine

 

     Footage  

Type

   Rodeo      Meikle      North
Post
     Banshee      Utility      Total  

Underground Exploration

     160,830         167,359         73,722         71,539         —           473,450   

Underground

     671,424         1,306,300         80,886         24,910         15,855         2,099,375   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total

     832,254         1,473,659         154,608         96,449         15,855         2,572,825   
     Number of Holes  

Type

   Rodeo      Meikle      North
Post
     Banshee      Utility      Total  

Underground Exploration

     351         301         118         116            886   

Underground

     4,005         8,007         302         81         134         12,529   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total

     4,356         8,308         420         197         134         13,415   

 

 

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FIGURE 10-3 DRILL HOLE LOCATIONS

 

LOGO

 

 

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The majority of the stope definition drilling is performed using RC. The holes are drilled in areas where the geology and mineralization are generally well understood and serve the purpose of better defining the ore zones prior to extraction. Drill holes are designed for the best possible angle of intersection with the mineralization but are limited by availability of drilling platforms. Drill hole lengths vary from 50 ft to 600 ft.

For programs categorized as Capital Drilling (defined as drilling of stopes that will not be mined in the next two years) and for exploration/step-out drilling, the holes vary in length from 150 ft to more than 1,200 ft. These holes are usually pre-collared using RC and drilled as far as ground conditions will permit. The holes are then switched over to core drilling, usually starting with HQ and reducing to NQ as required, to achieve the target depth. Longer holes are given sight lines by underground surveyors based on planned azimuths. Dips are set by the drillers based on the designed collar orientations. When drilling is complete, the collars of the exploration holes are surveyed to determine their final elevation, northing, easting, azimuth, and dip. In the past, several of the longer core and RC holes were surveyed with a MAXIBOR downhole survey tool to determine hole deviation. Beginning in 2009, a new downhole survey tool, Flexit, was introduced. This new tool allows for the survey of RC holes. This information is later downloaded into a database where it is used in conjunction with the geological and assay data.

Drill spacing is initially done at 100 ft and 50 ft section spacings. Follow-up RC definition drilling is done on fans 25 ft apart, depending on the geologist’s specific requirements, and holes are oriented to hit the target at a spacing of 25 ft to 30 ft.

When possible, drill holes are designed for the best possible angle of intersection with mineralization. This is not always possible since drilling must be done from the available drill stations. The apparent thickness of any mineralized intersection varies greatly and is dependent on drill station location. In most instances, the angle will be between 45o and 90o to core axis, but in the case of holes reaching for step-out targets, this angle could be 30o or lower.

Stope test holes are logged as required. Core and RC holes are logged for lithology, stratigraphy, basic structural data, recovery, degrees of alteration, and mineralization. Core is further scrutinized for detailed structural information like faults and bedding angles as well as rock mass rating (RMR). This information is entered directly into a

 

 

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geological database and used for interpretation of lithologies, structure, alteration, and modelling of mineralized zones. Interpretations of drilling results are done continually by the mine geological staff.

In RPA’s opinion, the drilling, core handling, and logging protocols are appropriate and are being carried out to a reasonable standard.

In 2009, underground delineation drilling tested for expansion of the North Post deposit after completion of the 4330 drift. There was 15,300 ft of reserve conversion drilling in North Post. In 2010, reserve conversion drilling consisted of 23,005 ft in Banshee and 55,737 ft in North Post. In 2011, planned reserve conversion drilling includes 24,000 ft in North Post, 36,000 ft in Banshee and 15,000 ft below the water table (3,600 ft elevation) in the rest of the mine. Actual drilling in 2011 included reserve conversion drilling at Rodeo (23,227 ft in 129 holes), at Meikle (24,953 ft in 171 holes), and at North Post (8,994 ft in 38 holes). No reserve conversion drilling was reported at Banshee.

 

 

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11 SAMPLE PREPARATION, ANALYSES AND SECURITY

SAMPLING METHOD AND APPROACH

RPA visited the core logging facilities and in general found the arrangement clean and efficient. RPA noted that there is no ongoing density testing and recommends that this practice should be initiated to provide improved tonnage estimates for the variety of ore and waste types.

Core was washed and photographed prior to logging. After the logging was completed, the core was halved with a diamond saw and sampled in five foot intervals. Underground core samples were whole core. Samples were placed in a sample bag with a barcode that clearly identified the hole number and the starting and ending depth of the sample. This information was also written manually on the sample bags. In areas where mineralization was not expected, i.e., the beginning of longer drill holes, a 20 ft sample interval may be used by sampling a chip, approximately one inch, per one foot section. These 20 ft intervals may be further subdivided into the standard five foot sample interval if warranted by assay results from the 20 ft chip samples. The samples were then delivered by Goldstrike personnel to the Goldstrike laboratory for assaying. Occasionally, if Goldstrike’s laboratory is not able to process the samples in a timely manner, they will be sent to an outside commercial laboratory.

Exploration geotechnical logging is carried out in mineralization and 100 ft into the hanging wall and footwall. Underground geotechnical logging is completed for the total length of the hole.

Core samples are taken at five foot intervals as a standard to indicate variability in grade over a minimum mining height and width (20 ft for surface mining and 15 ft for underground mining). Studies have shown that smaller sampling lengths are not cost effective from a handling or processing perspective and core sampling to one foot intervals has shown little additional grade variability.

The upper portions of RC drill holes are sampled at lengths of 10 ft where there is no potential for significant mineralization. In mineralization, RC holes are sampled on five

 

 

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foot intervals similar to core holes. RC samples are returned through the cyclone and automated splitter and are collected by the drillers and inserted into marked bags and tagged by a plastic label with a unique barcode that includes the hole number and the sample interval.

OPEN PIT

Open pit blasthole samples are delivered by Goldstrike personnel to the Goldstrike on-site assay laboratory. Occasionally, if the site laboratory is over capacity, samples will be sent to an outside ISO 9000 registered commercial laboratory. These samples are delivered by Goldstrike personnel or are collected by laboratory employees.

In RPA’s opinion, the sampling methods and practices in the open pit are appropriate and are being carried out in a reasonable fashion. These samples are representative of the volumes included in the estimates of Mineral Resources and Mineral Reserves.

UNDERGROUND

For underground sampling where needed and accessible, chip channels are taken along the wall of the stope in five foot intervals at five feet above the sill (if possible) and placed in a sample bag. Sample bags are prepared with barcodes to identify the sample and track it through the database. The distance to the chip sample is measured from a known survey point. The samples are sent to surface where they are inventoried by the core-shed geotechnicians before being sent to the laboratory for analysis.

Muck samples are collected on a routine basis and provide information for grade control and monitoring development headings. These samples are collected by the scoop operators at a rate of one per ten buckets (approximately 70 tons). The grades from these samples are used to estimate production grade from the underground mine. The bucket counts are adjusted against the hoist scale and the weighted average grades estimated from the reconciled volumes.

Where there is a paucity of diamond drilling, short test holes are drilled underground using a production rig. Chips are collected and sent to the laboratory for gold analysis only. The purpose of this method is to quickly identify ore zone contacts for stope definition.

 

 

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Underground blasthole samples are delivered by Goldstrike personnel to the Barrick on-site assay laboratory. Occasionally, if the site laboratory is over capacity, samples will be sent to an outside ISO 9000 registered commercial laboratory. These samples are delivered by Goldstrike personnel or are collected by laboratory employees.

In RPA’s opinion, the sampling methods and practices in the underground operations are appropriate and are being carried out in a reasonable fashion. These samples are representative of the volumes included in the estimates of Mineral Resources and Mineral Reserves.

SAMPLE PREPARATION, ANALYSES AND SECURITY

OPEN PIT

Samples from the Betze-Post core drilling of 1991 to 1993 and exploration samples from drilling since mid-2003 have been consistently prepared and analyzed by contract assay laboratories. Sample preparation and analysis from drilling completed at other dates has been performed both on site at the Goldstrike Mine assay laboratory and by contract. Both internal and external check assays have been performed by independent laboratories. The 2003 and later exploration drilling samples have been sent exclusively to the ALS Chemex Assay Laboratories due predominantly to manpower issues.

SAMPLE PREPARATION

At the ALS Chemex Elko preparation laboratory, the Goldstrike exploration samples are dried, crushed to less than 70% minus 10 mesh, and riffle split with a 250 g subsample pulverized to greater than 85% minus 200 mesh. ALS Chemex ships the pulp samples to its Vancouver laboratory for assay or occasionally to its Reno laboratory if a rush is requested.

Sample preparation at the Goldstrike Mine laboratory is fully automated. It uses three state-of-the-art automated preparation systems. All of the samples are oven dried prior to crushing. Samples are logged in, weighed (prior to crushing), crushed to -10 mesh, and fed to an automated pulverizing/splitting/weighing system. When the samples come out of this unit, they are at +90% passing 100 mesh (µm) and they are already weighed for analysis. The system weighs several splits of each sample, five at 15 g and one at 100 g.

 

 

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ANALYSIS

At ALS Chemex, fire assay fusion is done on a 30 g aliquot (one assay ton) with an atomic adsorption spectrometry (AAS) finish. Samples that exceed the upper detection limits of 7 ppm for AAS are rerun using a gravimetric finish. ALS Chemex laboratories in Nevada are certified to standards within ISO 9001-2008. Internal quality assurance/quality control (QA/QC) batch duplicates showing wide variation are reassayed using the metallic screen method to improve assay confidence for possible free gold intervals.

In addition to gold assays, all blasthole samples, and specific exploration drill hole intervals identified for process route metallurgical characteristics, are analyzed for sulphide, carbonate, total carbon by LECO furnace, as well as preg-robbing carbon assays, at the Goldstrike Mine laboratory. For RC holes drilled since 2003, Goldstrike Mine personnel have identified intervals for compositing based on gold values. ALS Chemex creates 20 ft composites for these intervals from the five foot samples. The homogenized composites are then returned to the Goldstrike Mine laboratory for analysis of metallurgical characteristics. A program of identifying intervals for process route characteristics in pre-2003 drill holes and reanalyzing archived samples was carried out in the past several years to augment the database. The results are used as ore blending criteria for processing and are 3D computer block modelled.

CORE AND SAMPLE STORAGE

Drill core is stored in boxes located at the core laydown yard. Assay pulps are saved and stored inside the core handling facility.

Samples from mineralized intervals are selected for storage with the rest disposed at the mine waste dumps. The storage selection basis is:

 

  i. Select all intervals that contain in excess of 0.020 oz/st Au.

 

  ii. Select at least four intervals above and below the above intervals as a buffer.

 

  iii. Select intervals that outline small gaps of four (more or less) unselected intervals between other intervals that are selected.

 

  iv. Select any other interval that may require further analyses.

Sample rejects are saved for mineralized intervals and ± 20 ft above and below the ore intervals. Rejects are kept in sealed steel barrels that are stored at the core laydown yard.

 

 

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SAMPLE SECURITY

All blasthole samples remain in Goldstrike custody and control generally from the drill rig to the mine assay laboratory. Exploration drill core and RC chip samples sent to ALS Chemex laboratories for analysis are either picked up on site by ALS Chemex personnel or transported to the ALS Chemex facility by exploration personnel. Security is not an issue since Goldstrike employees hand off the samples directly to ALS Chemex or the Goldstrike main assay laboratory and the chain of custody is complete.

In RPA’s opinion, the sample preparation, security, and analytical procedures used in the open pit operations are appropriate and are being carried out in a reasonable fashion.

UNDERGROUND

SAMPLE PREPARATION

The majority of the samples are prepared at the Goldstrike Mine assay laboratory by Goldstrike employees. The samples remain in the custody of Goldstrike employees from the drill to the assay laboratory. Currently, the Barrick laboratory is not certified. If samples are sent to a commercial laboratory for preparation and analysis, they are directed to a laboratory that is ISO 9000 registered. Barrick has dispatched underground samples to American Assay Laboratory, and/or ALS Chemex when higher than normal volumes of samples are received on site.

Most sample preparation at the Goldstrike laboratory is fully automated, using three prepping systems: System 1, System 2, and System 3. A Bico Crusher/TM Pulverizer sample preparation system is also available for use as required.

Within System 1 and System 2, samples are scanned into the system and then poured into a drying pan which is sent into the drying ovens (120oC). When samples are dried according to protocol, the system then discharges the sample pans from the oven. The samples are moved along a conveyor to a balance to be weighed prior to crushing. This weight is used to determine the speed and cuts of the splitter. The sample is crushed to approximately 10 mesh and then goes through rotary splitter. Any reject is directed to the waste conveyor. The crushed sample split is then run through a continuous ring mill (CRM) pulverizer and is pulverized down to 100% passing 50 mesh. Then the sample is fed into another rotary splitter and a 500 g split is fed to another CRM. The secondary

 

 

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CRM pulverizes the sample to 90% passing 100 mesh and deposits the pulverized sample into a cup. The pulverized material is split into an udder which dumps into a sample cup.

The systems send sample information to the Laboratory Information Management System (LIMS), which then creates labels for each of the sample cups and a label for the project ID, which keeps the samples grouped together. It also creates batches for each required test. Samples are then blended in sample blender. After blending they are sent to the weigh room to be manually weighed for various analyses. Samples for fire assays are weighed at  1/2 assay ton.

System 3 is slightly different from System 1 and System 2. This system is used for larger sample sizes. The samples are loaded onto sample carts and are dried in an oven set to 120oC. Samples are weighed before being fed to a primary crusher and this weight plus the required sample size is used to determine the sample split at the secondary crusher. At the primary crusher, the sample is crushed to -3/8 in. before being taken by a conveyor belt to the secondary crusher where the sample is crushed to -10 mesh. The samples are then fed into a rotary splitter and the desired amount is sent to a CRM pulverizer. When the samples come out of this unit, they are 90% passing a 100 mesh screen. Samples are placed into sample cups and their sample tags are placed into the sample cup or stapled to the cup. Samples are then placed into a sample box, which is blended for approximately 20 minutes. They are sent to the weigh room to be logged and weighed for various analyses. Sample sizes that come out of this system can range from 250 g up to 2,000 g.

In the fourth sample preparation circuit, samples are crushed by a Bico crusher to  1/4 in. and then sent through a riffle splitter to obtain a representative split of approximately 500 g of crushed material. Samples are dried at a temperature of 120oC for two hours or until dry. This crushed material is then placed onto the TM pulverizer, which pulverizes it to +90% passing 100 mesh. The sample is then resplit in five 13 g to 16 g subsamples, which are blended for five minutes, and a reject split, which is stored. The samples are logged into the LIMS and pre-weighed at  1/2 assay ton by the system, placed into crucibles, and taken to the fire room for assay.

 

 

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ANALYSIS

Underground samples are routinely run for gold, with analysis for LECO (Sulphur, Sulphide, Total Carbonaceous Material, Total Carbon, Total Sulphur, CO3 and Arsenic) if time permits. Analyses are based on the specific deposit and purpose of sample. These are briefly summarized in the following subsections.

Rush Samples (Rodeo and Meikle)

Meikle Rush (MR) and Rodeo Rush (RR) must be prepped on the protocol followed for System 3 or for Bico Crusher/TM Pulverizer. The MR login automatically adds one gravimetric fire assay to each sample. Samples are weighed at  1/2 assay ton into crucibles and taken to the fire room for assay.

Meikle Deposit (Chip and Drill)

Meikle Chip (MC) and Meikle Drill (MD) samples are prepped on the protocol followed for System 1 and System 2. The MC and MD logins automatically add one fire assay with an atomic absorption finish (FA/AAS) to each sample. Any FA/AAS assay that is greater than 0.438 Au oz/st is automatically reprocessed for a gravimetric gold assay.

Muck (Composite and Bag samples)

The procedure is the same (System 3) for both Meikle Muck (MM) and Rodeo Muck (RM).

While the samples are being prepped on the sample prep systems, one sample from each batch of samples submitted is randomly selected for a Quality Control (QC) sample. This sample is processed through the sample prep as all others except the split weight is raised to 900 g to 1,000 g, blended using a roll cloth, and split into three representative samples. Each split is logged into LIMS, assayed by the production crew as a quality check and then the two quality control splits are submitted to the QC group. These QC samples are sent to outside laboratories for assay. Each quarter, QC reports are generated and the results given to the clients.

The MEK-COMP login assigns one gravimetric Au assay and a LECO Carbon/Sulphur (C/S) assay to each MM sample. The samples are then weighed at  1/2 assay ton for the fire assay and 0.1 g for the C/S assay.

The pulp is stored for seven days then discarded.

 

 

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Meikle and Rodeo Exploration (Five Foot Core and Rotary Samples)

The samples are processed either on System 1 or System 2 and split down to a subsample of up to 2,000 g depending on the original sample material. If the initial sample is 500 g or less, the entire split is used. Rejects are discarded.

The sample barcode ID is scanned into LIMS under the MEK-CORE N, MEK-CORE, ROD-CORE N, or ROD-CORE login depending on the sample type. The MEK-CORE N and ROD-CORE N login add one FA/AAS assay to each sample and the MEK-CORE and ROD-CORE add one FA/AAS and LECO Suite. The LIMS system automatically adds a gravimetric fire assay to a sample that has a gold grade greater than 0.438 oz/st, and subject to request.

MEIKLE AND RODEO EXPLORATION – FIVE FOOT PRODUCTION SAMPLES

Underground five-foot production samples have a 72 hour return time based on a budgeted 30 to 40 samples per day. The analytical protocols are according to the protocols for System 1 or System 2.

The sample barcode ID is scanned into LIMS under the MEK-CORE N, MEK-CORE, ROD-CORE N or ROD-CORE login depending on the sample type. The MEK-CORE N and ROD-CORE N login add one FA/AAS assay to each sample and the MEK-CORE and ROD-CORE add one FA/AAS and LECO Suite. The LIMS program automatically adds a gravimetric fire assay to a sample when the gold grade is greater than 0.438 oz/st.

Upon completion of all assays, the auto approval program in LIMS either approves the assays or labels them suspect and reprocesses the set for reassay. Upon approval in LIMS, the assays are automatically transferred to the Assay Repository database and become available for download by approved database users. Database access is limited to customer designations.

CORE AND SAMPLE STORAGE

Pulps from exploration and definition drilling are stored for six months. After this time, the pulps are discarded. Samples required from holes older than six months can be constructed from chip trays stored in numbered boxes. Both electronic and hard copy manifests of chip tray contents are maintained.

 

 

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Pulps from channels, mucks, and rush samples are usually discarded once the results have been approved. Underground sample rejects are routinely discarded once results have been confirmed by the Geology department.

Any remaining diamond drill core is either kept on site at the core shed or shipped to the exploration laydown yard.

SAMPLE SECURITY

Security is not an issue since underground samples remain in Goldstrike custody and control generally from the source to the mine assay laboratory and the chain of custody is complete.

In RPA’s opinion, the sampling, sample preparation, security, and analytical procedures used in the underground operations are appropriate and are being carried out in a reasonable fashion.

QUALITY ASSURANCE AND QUALITY CONTROL

GOLDSTRIKE EXPLORATION

Goldstrike Exploration is responsible for surface drilling and exploration drilling for the underground. Goldstrike has checks in place to prevent non-compliance with sampling procedures that include daily observation of contractor RC sampling techniques by geologists and drill supervisors. Immediate action is taken to correct any non-compliance with sampling procedures. A visual estimate of any downhole contamination is recorded by geologists on the drill hole log and the contractor, driller, and crew responsible are notified and proper drilling and sampling procedures are reviewed. Sample weights are monitored since low sample weights in RC drilling are normally due to low recovery. Any mineralized sample that is thought to be unreliable is assigned a no confidence factor and is not utilized in estimating resources.

Current QA/QC field procedures for RC and core drilling are summarized from Goldstrike documentation below.

Drill holes are designed and assigned DH numbers, planned collar coordinates, depth, and ten foot and five foot sample intervals. The targeted mineralized interval is used to assign the QA/QC standards, blanks, and duplicates for each drill hole. A list is

 

 

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prepared and bar coded sample tags are printed. Sample bags are written by a geotechnician and checked for accuracy. The bags are then given to the drillers. Duplicate sample intervals are marked by red flagging to warn the driller’s helper of an upcoming duplicate. Blank control samples are included in the sample sequence and reference standard samples are marked and prepared after completion of the drilling and prior to submittal to the laboratory. Samples are collected in bins and transported to the laboratory either by mine or laboratory vehicle accompanied by completed submittal forms for each drill hole.

Ten percent of the samples from the assaying stream are submitted for QA/QC on the following basis:

 

  a. Intervals modelled barren contain approximately 9% quality control samples.

 

  i. 3% duplicates

 

  ii. 3% control blanks

 

  iii. 3% reference standards

 

  b. Intervals modelled mineralized contain approximately 18% quality control samples.

 

  i. 6% duplicates

 

  ii. 6% control blanks

 

  iii. 6% reference standards

 

  c. For core drilling, the intervals are grab sampled first at 20 ft intervals to locate mineralization without QA/QC involved. The mineralized intervals are split and sampled using the same procedure listed above with the exception that no duplicates are taken to preserve the core for archive.

QA/QC data are tracked as returned from the laboratory and assays validated before finalizing them in the database. All variances are documented in:

 

   

Goldstrike Database

 

   

Hard copy filed in the Goldstrike exploration office.

 

   

Archived email, PDF, Word, and PDF files of the assay certificates, changes, explanations, and calculations.

DUPLICATE SAMPLES

Duplicate or check samples are used primarily to identify problems with field sampling procedures. A prescribed number of samples are allocated according to the anticipated mineralized intervals. The RC drill crew collects duplicate samples in a five gallon bucket with splitter baffles adjusted to allow for adequate sample collection. The sample is homogenized and then split in two equal, approximately three kilogram portions and placed in the assigned sample bags.

While there is no procedure in place now to flag problem holes, drill holes that have a large assay discrepancy (e.g., 0.5 g/t Au to 2.0 g/t Au) and no other problems are flagged for metallic screen assays, while problem holes with larger discrepancy are reassayed.

 

 

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STANDARD SAMPLES

Certified Reference Standard samples are purchased from Rocklabs as pulps that were assayed in a round robin of 28 laboratories. The average value and its standard deviation for the round robin are certified. The variation from the standard’s mean value in standard deviations defines the QA/QC variance and is used to determine acceptability of the standard sample assay. Approximately 150 g of sample material is submitted per QA/QC sample. The database administrator maintains documents for these samples.

 

  i. Assay value <certified mean ±2 Standard Deviations (STD) g Pass

 

  ii. Assay value > mean ±2 STD and < mean ±3 STD g Warning

 

  iii. Assay value > mean ±3 STD g Failure

The following reference standards are available to the open pit operations:

 

  1)    SI15    1.805 ± 0.067 ppm Au
  2)        SJ32        2.645 ± 0.068 ppm Au
  3)    SK33    4.041 ± 0.103 ppm Au
  4)    SN26    8.543 ± 0.175 ppm Au
  5)    SE19    0.583 ± 0.026 ppm Au
  6)    SE44    0.606 ± 0.028 ppm Au
  7)    SI42    1.761 ± 0.054 ppm Au
  8)    SL46    5.867 ± 0.170 ppm Au
  9)    SN38    8.573 ± 0.158 ppm Au
  10)    SP27    18.104 ± 0.429 ppm Au

The following certified standards are used by the underground division:

 

  1)    BCH-OX-01        0.214 ± 0.010 ppm Au
  2)        BCH-OX-02    0.338 ± 0.011 ppm Au
  3)    BCH-OX-03    0.338 ± 0.095 ppm Au
  4)    BCH-OX-04    0.338 ± 0.165 ppm Au
  5)    BCH-SR-01    0.338 ± 0.090 ppm Au
  6)    BCH-SR-02    0.338 ± 0.100 ppm Au
  7)    BCH-SR-03    15.980 ± 0.355 ppm Au

BLANK SAMPLES

Blank control (zero gold) samples are used to assess the level of analytical “background noise” and to identify “smearing” or sample carryover in subsequent samples caused by improper sample preparation techniques and lack of equipment cleaning. Blanks are prepared from barren drill hole reject cuttings of various colours and are submitted as one kilogram pulps. The blanks contain no detectable gold (<0.005 ppm Au). They are assigned to the sample stream series using a prescribed number of samples according to the anticipated mineralized intervals.

 

 

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Blanks are prepared by taking enough sample rejects to fill five gallon buckets. The 25 gallons of sample are thoroughly mixed in a clean cement mixer and poured back into the five gallon buckets. One sample is taken from each bucket and resubmitted to the assaying laboratory. If the assays returned are also below the detection limit for gold, the sample becomes a standard blank.

 

  i. Assay <0.030 ppm Au g Pass

 

  ii. 0.030 ppm Au <=Assay <0.060 ppm Au g Warning

 

  iii. 0.060 ppm Au <=Assay g Failure

OUTSIDE CHECK SAMPLES

At least five percent of the intervals from a hole are selected for reassay and submitted to a third party commercial laboratory on the following basis:

 

  i. Select all intervals that have had gravimetric finishes.

 

  ii. Select intervals that have significant assay variations that may impact on the resource/reserve estimate.

 

  iii. Randomly select intervals adjacent to the mineralized intervals.

 

  iv. Select intervals around the intervals that had QA/QC problems, whether resolved or not.

SCREEN CHECKS

At least two percent of the samples in the sample stream are selected for screen checks to ensure that no assaying problems occur with coarse gold:

 

  i. Intervals selected at random that lie near the mineralization but are not likely candidates for reassay and the rejects are selected for storage rather than disposal if possible.

 

  ii. At least 85% of the screened pulp should pass through a 200 mesh screen. (The laboratory crushes the entire sample to 10 mesh and then pulverizes 250 g of it to 200 mesh.)

GOLDSTRIKE ASSAY LABORATORY

One or two samples per shift of production sampling and one sample per shift of core are used in the QA/QC program. For each set of 24 samples, there is one blank, two standards, and a repeat assay. For samples that are sent to an external laboratory for QC evaluation, two standards are sent with each batch.

Standard QC charts are posted throughout the laboratory at the beginning of each shift. These display how the controls have been performing over the last several shifts. If issues are detected around a sample, the senior chemist engages the QC technician, the laboratory supervisor, and the analytical chemist, in an effort to remediate the problem. If an issue is detected in an external QC sample, the laboratory in question is contacted and assays are redone.

 

 

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The external laboratories for the QC program are Florin Analytical Services (Florin) and Inspectorate America Corporation (IA). Quarterly reviews are conducted comparing results from Florin, Acme, and Goldstrike assay laboratory on samples from both Meikle and Rodeo. Assay results from pulp duplicates are grouped according to broad grade ranges and the mean values of the groups are compared. A t-test for evaluation on paired sample means is conducted to confirm that there is no significant difference between them.

The results of the underground exploration core control assays for the second quarter of 2011 are shown in Table 11-1 and the results of definition drilling chip control assays are shown in Table 11-2.

TABLE 11-1 CORE SAMPLE CONTROL ASSAY STATISTICS

Barrick Gold Corporation—Goldstrike Mine

 

Sample

Grouping

(oz/st)

   No. of
Samples
   Goldstrike
(oz/st Au)
   Goldstrike QC
(oz/st Au)
   Florin Mean
(oz/st Au)
   IA Mean
(oz/st Au)

All Samples

   134    0.078    0.078    0.081    0.076

0.000-0.100

   100    0.029    0.028    0.028    0.028

0.101-0.500

   32    0.193    0.195    0.203    0.189

>0.500

   2    0.679    0.710    0.744    0.639

TABLE 11-2 CHIP SAMPLE CONTROL ASSAY STATISTICS

Barrick Gold Corporation – Goldstrike Mine

 

Sample

Grouping

(oz/st)

   No. of
Samples
   Goldstrike
(oz/st Au)
   Goldstrike QC
(oz/st Au)
   Florin Mean
(oz/st Au)
   IA Mean
(oz/st Au)

All Samples

   62    0.342    0.347    0.346    0.337

0.000-0.100

   11    0.048    0.047    0.044    0.054

0.101-0.500

   39    0.281    0.292    0.288    0.280

>0.500

   12    0.905    0.903    0.909    0.875

For the core sample control data, the Barrick Production Laboratory had only one low outlier and four high outliers and these were all in the 0.000 to 0.100 oz/st Au range. For the chip sample control data, the Barrick Production Laboratory had only one low outlier and one high outlier with the low outlier in the 0.101 to 0.500 oz/st Au range and the high

 

 

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outlier in the >0.500 oz/st Au range. In RPA’s opinion, the QA/QC practices are appropriate for the exploration and definition drilling data and are being carried out in a reasonable fashion.

 

 

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12 DATA VERIFICATION

OPEN PIT

Goldstrike assay data is first checked by the Goldstrike assay laboratory using its QA/QC program, and then visually by the geology department as the assays are received and downloaded into the database. Any anomalous assay is rechecked with the laboratory personnel and the pulps, or rejects when available, are reassayed if necessary.

RPA imported the open pit drill hole and block model databases into Vulcan 3D version 8.0.3 software for review. Vulcan validation routines found no errors in collar, survey, and assay files. Composite files provided by Goldstrike were consistently formatted and generally in good order. The file was reconstructed for import to Vulcan 3D, and two problems were identified by Vulcan 3D validation routines. Twenty-seven samples had lengths of zero feet with an associated gold grade by fire assay grade (AuFA) value and, although drill holes were composited on 30 ft intervals, there were two samples with lengths greater than 30 ft.

It is RPA’s opinion that the Goldstrike open pit database is well prepared and is adequate and suitable for Mineral Resource estimation.

UNDERGROUND

All sample information is captured and managed in a database system developed using acQuire software. This includes the RC, diamond drilling, chips, and muck samples. The geological staff enter information and generate reports as needed. The database administrator (DA) validates the databases and prepares them for use in wireframe modelling and Mineral Reserve estimation. Laboratory personnel (both external and internal) produce files with the assay results and these are loaded directly into the acQuire system by the DA. Once the acQuire database has been validated and finalized, it is ported to Vulcan for modelling purposes.

Assay reports are downloaded daily and merged with the acQuire system every few days. Suspicious results are flagged for review. Validation of the acQuire database is carried out on a random basis by means of spot checks to confirm that the files from the

 

 

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laboratories loaded correctly. Occasional failures do occur, often as a result of incorrect entry of sample location or identification information. The sample IDs are generally affixed to the sample bags by means of a barcode tag. Sometimes the barcodes become smeared or the tags themselves are torn off. The underground mine staff report that failures of this sort occur at a rate of “a couple of hundred” per year, for a total throughput of over 40,000 samples. In RPA’s opinion, this is an acceptable error rate.

Updates of the Vulcan database from acQuire are routinely done on a weekly basis. Planned drill holes are entered into Vulcan, then updated with the as-built information as they are completed. The hole traces are checked visually for gross errors. For the resource estimates, suspect drill holes are dropped. Assay data are checked against laboratory reports.

Once the data has been validated, it is “locked”, and cannot be changed by anyone except authorized staff members. Access to the Vulcan database used for resource and reserve estimation is restricted to only two members of the mine staff to ensure that the data integrity is preserved.

In RPA’s opinion, the management of the sampling data is being carried out in an efficient and capable manner. The validation routines meet a reasonable standard.

RPA imported the drill hole and block model databases from Banshee, Meikle, and North Post into Vulcan 3D version 8.0.3 software for review. Vulcan validation routines found a few errors in collar, survey, and assay files. No surveys were found for five holes at Banshee, 14 holes at Meikle, and one hole at North Post. Composite files provided by Goldstrike were consistently formatted and are generally in good order. However, one hole was found with overlapping intervals at Banshee.

It is RPA’s opinion that the Goldstrike underground database is well prepared and is suitable for Mineral Resource estimation.

 

 

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13 MINERAL PROCESSING AND METALLURGICAL TESTING

METALLURGICAL TESTING

Metallurgical testing has focused on development of the CaTs (Thiosulphate Leach Conversion) process to support a capital investment program which is planned to implement reconfiguration of the existing pressure oxidation circuits and adding a resin-in-leach circuit during 2011 and 2012. The testing included bench-scale and pilot-scale testing to develop the process design criteria and to estimate the operating costs associated with the proprietary process. Implementation of the CaTs process will extend the useful life of the pressure oxidation plant and may significantly increase the gold production by bringing forward gold production in the LOM plan by treating ores that were not previously amenable to pressure oxidation.

MINERAL PROCESSING

There are two ore processing facilities at Goldstrike. They are:

 

   

The autoclave pressure oxidation (POX) circuit;

 

   

The roaster circuit.

Depending on various factors, including gold content, carbonate content, carbonaceous carbon reactivity, and sulphide sulphur content, the Betze-Post open pit ore is dispatched to various stockpiles located at either the POX area or the roasters. Planned distribution of ore from the stockpiles is an extensive exercise which is carried out monthly by the strategic planning department to maintain optimal operations designed to maximize gold recovery. All of the underground ore is processed in the roasters.

RECOVERY

Barrick has developed recovery calculations based on evaluation of historical data. They have changed over time as the ore and operations have changed. The most recent recovery calculations for the autoclave are shown in Table 13-1 and the recovery calculations for the roaster are shown in Table 13-2.

 

 

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TABLE 13-1 ALKALINE CATS RECOVERY CALCULATIONS FOR LOM PLAN

Barrick Gold Corporation—Goldstrike Mine

 

Head Grade (oz/s)t

  

Equation

HG > 1.3

   Rec. = 95.0 percent - 6.86

0.28 < HG <= 1.30

   Rec. = 6.4334*HG*HG*HG - 23.02*HG*HG + 28.56*HG + 82.247 - 6.86 - 1.5

0.065 <= HG <= 0.28

   Rec. = 661.36*HG*HG*HG - 628.91*HG*HG + 208.23*HG + 65.114 - 6.86 - 1.5

TABLE 13-2 ROASTER RECOVERY CALCULATIONS FOR LOM PLAN

Barrick Gold Corporation—Goldstrike Mine

 

Head Grade (oz/st)

  

Equation

HG > 1.15

   Rec. = 93.0 percent + 0.3 + As Impact

0.35 < HG <= 1.15

   Rec. = 3.1719LN(HG) + 92.592 + 0.3 + As Impact

0.125 < HG <= 0.35

   Rec. = -95.006*HG*HG + 67.038*HG + 77.446 + 0.3 + As Impact

0.055 <= HG <= 0.125

   Rec. = -1017.2*HG*HG + 377.14*HG + 53.439 + 0.3 + As Impact

As Impact (>1,200 ppm) = -0.0000004*As*As - 0.0005*As + 1.176

ALLOCATION AND RECONCILIATION

Goldstrike undertakes comprehensive metallurgical accounting through month-end inventory measurements and calculations, and allocation procedures to reconcile differences between predicted head grade and actual head grades. This process involves formulae for predicting gold recovery in both the autoclave and the roaster. The data and procedures have been reviewed and appear to meet industry standards with no significant problems detected.

Goldstrike reconciles the differences between the predicted and actual head grades and recoveries for Betze and underground ores based on the actual gold production. The differences are allocated based on specified procedures and formulae.

Separate metallurgical balances are maintained at Goldstrike for the roaster, the autoclaves, and the refinery. The metallurgical balances are calculated on a monthly basis according to the equation:

IN = OUT + r Inventory

The monthly inventory is a key component of the metallurgical balance. At each month end, measurements are made of the amount of material contained in the circuits and representative samples of the material are taken and assayed to estimate the amount of gold contained in each circuit.

 

 

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The tonnages fed to the plants are measured using flow meters and densitometers. Automatic samplers are used to collect samples of the feed and the tails for both the autoclave and the roaster. Using this data, the “Ounce Calls” are estimated and reported on the Daily Safe Production Report (DSPR). The tonnages are not adjusted. The head grades are adjusted at the month end based on the actual gold production. Tailings grades may be adjusted based on bench-top autoclave test results, bench-top roaster test results, or contracted recovery rates for toll material. The actual production is reconciled with the Ounce Call for each plant based on the total actual gold production using the ratios determined from the Ounce Call.

AUTOCLAVE ADJUSTMENTS

In the autoclave, the different feed materials are campaigned so the tonnage of each is measured using the magnetic flow meter and the densitometer. The Betze tons from the open pit mine are estimated using the difference between the total tonnage and the tonnage of each of the toll processed materials according to the following equation.

Total Tons – Concentrate Tons – Toll Tons = Betze Tons

The head grade is adjusted based on the gold production numbers. No adjustment is made to the head grades of the toll material. This means that the entire adjustment is made to the Betze head grade since no underground ore is processed in the autoclaves.

The final plant tail grade comes from the DSPR with no adjustments. The tail grades for toll materials are determined using the estimated gold recovery based on either lab test results or the contracted recovery rate.

ROASTER ADJUSTMENTS

The total tonnage to the roaster is not adjusted; it is measured using a densitometer and a flow meter. The toll material is not campaigned; therefore, the tonnage of toll material is determined using scale weights and moisture determinations that are measured from representative samples. The tonnage of material coming from the underground mine is provided to the process division by the mine. Again, the tonnage of material from the Betze open pit is calculated by the difference according to:

 

 

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Total Tons – Concentrate Tons – Toll Tons – Underground Tons = Betze Tons

No adjustment is made to the head grades of toll material. The adjustments made based on actual production are applied to both the underground head grade and the Betze head grade using simple ratios.

The final roaster tail grade is taken from the DSPR with no adjustment. The tail grade from toll ore is determined using the estimated gold recovery based on either lab test results or the contracted recovery rate. The roaster recovery model is used to estimate tail grades for the underground and Betze ores. Estimated tail grades are corrected by applying a ratio to the actual DSPR tail grade less toll tail ounces.

The recovery is adjusted using the adjusted head grade and the corrected tail grade using the following equation:

Ounce Production = Tons x Adjusted Head Grade x Adjusted Recovery (%)

The minor adjustments made to the plant head grades for 2010 and 2011 are summarized in Table 13-3.

TABLE 13-3 SUMMARY OF HEAD GRADE ADJUSTMENTS

Barrick Gold Corporation—Goldstrike Mine

 

     2010      2011  
     Autoclave      Roaster      Overall      Autoclave      Roaster      Overall  

Calculated Plant Head Grade, oz/st Au

     0.112         0.236         0.194         0.129         0.205         0.180   

Adjusted Plant Head Grade, oz/st Au

     0.113         0.236         0.194         0.129         0.205         0.187   

Difference, oz/st Au

     0.001         0.000         0.000         0.000         0.000         -0.007   

Difference, %

     0.51         0.08         0.16         0.00         0.00         -3.74   

Based on the evaluation of the head grade adjustments, RPA believes that the recovery calculations and the estimated equations used to estimate gold recoveries are accurate.

 

 

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14 MINERAL RESOURCE ESTIMATE

Table 14-1 summarizes the total Mineral Resources, exclusive of Mineral Reserves, at the Goldstrike Mine.

TABLE 14-1 GOLDSTRIKE MINERAL RESOURCES—DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

     Measured Resources      Indicated Resources      Measured + Indicated Resources  
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold

(000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold

(000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold

(000 oz)
 

Within Reserve Pit

     783         0.032         25         3,352         0.032         107         4,131         0.032         132   

Within Resource Pit

     103         0.032         3         358         0.077         12         462         0.032         15   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Open Pit Subtotal

     886         0.032         28         3,711         0.032         119         4,612         0.032         147   

Underground

     985         0.341         336         5,092         0.293         1,492         6,077         0.301         1,828   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total

     1,867         0.195         364         8,818         0.183         1,611         10,685         0.185         1,975   

 

     Inferred Resources  
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
 

Within Reserve Pit

     531         0.055         29   

Within Resource Pit

     34         0.049         2   
  

 

 

    

 

 

    

 

 

 

Open Pit Subtotal

     564         0.055         31   

Underground

     2,698         0.298         805   
  

 

 

    

 

 

    

 

 

 

Total

     3,263         0.256         835   

Note:

  1. CIM Definitions were followed for Mineral Resources.

 

  2. Mineral Resources are estimated using a long-term gold price of $1,400 per ounce.

 

  3. Mineral Resources are exclusive of Mineral Reserves.

 

  4. Open pit Mineral Resources are based on cut-off grades of 0.030 oz/st Au for roaster feed, 0.040 oz/st Au for acid POX, 0.045 oz/st Au for alkaline POX, and 0.040 oz/st Au for CaTs.

 

  5. Underground Mineral Resources are reported at an incremental cut-off grade of 0.10 oz/st Au.

 

  6. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.

 

  7. Totals may not add due to rounding.

 

 

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OPEN PIT MINERAL RESOURCES

SUMMARY

Table 14-2 summarizes open pit Mineral Resources exclusive of Mineral Reserves. The Qualified Person for the open pit Mineral Resource estimate is Wayne W. Valliant, P.Geo.

TABLE 14-2 OPEN PIT MINERAL RESOURCES—DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

     Measured Resources      Indicated Resources      Measured + Indicated Resources  
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold
(000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold (000 oz)
     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold (000 oz)
 

Within Reserve Pit

     783         0.032         25         3,352         0.032         107         4,131         0.032         132   

Within Resource Pit

     103         0.032         3         358         0.032         12         462         0.032         15   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Open Pit Total

     886         0.032         28         3,711         0.032         119         4,612         0.032         147   

Inferred Resources

 

     Tons
(000)
     Grade
(oz/st Au)
     Contained
Gold

(000  oz)
 

Within Reserve Pit

     531         0.055         29   

Within Resource Pit

     34         0.049         2   
  

 

 

    

 

 

    

 

 

 

Open Pit Total

     564         0.055         31   

Notes:

 

  1. Mineral Resources estimated according to CIM Definitions.

 

  2. Mineral Resources are exclusive of Mineral Reserves and are contained within and below the reserve pit.

 

  3. Mineral Resources estimated at $1,400/oz Au.

 

  4. Mineral Resources based on cut-off grades of 0.030 oz/st Au for roaster feed, 0.040 oz/st Au for acid POX, 0.045 oz/st Au for alkaline POX, and 0.040 oz/st Au for CaTs.

 

  5. Tonnages factors vary depending on mineralization domain.

 

  6. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability.

 

  7. Columns may not exactly due to rounding.

GEOLOGICAL INTERPRETATION AND GRADE CONTOURING

The open pit block model has been created using Mintec Inc.’s MineSight® software supplemented by custom programs derived from Geostatistical Software Library (GSLIB) software from Stanford University. Three-dimensional solids representing fault traces and lithologic units have been created from drill hole logging, and blasthole and bench mapping information. These solids and the understanding of mineralization controls are used as reference features in guiding the generation of grade contours used in estimating the gold resource model.

 

 

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Creation of model domains and grade contouring was guided by geologic interpretation of mineral controls, i.e., fault and structure orientations, host rock control, grade clustering, etc. Blasthole grade control assay data are also used for contouring where available. Grade contours and grade interpolation domains have been established to control the block estimation by grouping composites and blocks into distinct geological and metallurgical regimes

GRADE DOMAINS AND ZONES

Assays and composites are grouped into domains based on the grade, structure, host rock, spatial location, etc., in an effort to define different types of ore. All composites within a domain solid are coded with the same domain value as summarized in Table 14-3.

TABLE 14-3 OPEN PIT MINERALIZATION DOMAINS

Barrick Gold Corporation—Goldstrike Mine

 

    Domain    

   Description

1

   Latite

2

   Unknown

3

   SW Bazza

4

   Northwest

5

   Bills

6

   South Buzzard

7

   Bridge

8

   North Betze East

9

   Betze

10

   Weird 2

11

   North Post

12

   JBE

13

   Post

14

   Rodeo

Grade contours are created from assay/composite, blasthole, and geologic model information. Goldstrike has implemented a program to continuously update and modify the grade contours based on blasthole assays, geologic bench mapping, and geologic model updates. Fourteen interpolation domains have been developed to represent portions of the model that display similar geologic or geostatistical properties. Variograms have been created for combinations and groupings of grade zones and kriging domains.

 

 

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The block model is coded with respect to rock type, grade zone, and kriging domain using either 2D polygons or 3D solids. A block is coded if 50% or more of the block falls inside the polygons or solids. Grade zone and interpolation domain codes are used directly for gold interpolation, while rock type is used for metallurgical parameters.

A grade zone code is assigned to composites according to its spatial location with respect to the grade contours as summarized in Table 14-4.

TABLE 14-4 OPEN PIT GRADE CONTOUR ZONES

Barrick Gold Corporation—Goldstrike Mine

 

    Zone    

   Grade Contour
Range (Moz/st Au)
   Grade Contour
Range (oz/st Au)

0

   0    0

1

   15-29    0.015-0.029

2

   30-64    0.030-0.064

3

   65-149    0.065-0.149

4

   150-199    0.150-0.199

5

   200-299    0.200-0.299

6

   300-399    0.300-0.399

7

   400-9,999    >0.400

8

   1-14    0.001-0.014

Figure 14-1 illustrates the grade zone contours for Bench 4290.

 

 

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FIGURE 14-1 BENCH 4290 GRADE ZONE CONTOURS

 

 

LOGO

 

 

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DOCUMENTATION

The methodology used in creating the EOY2010 resource model has been thoroughly documented by the Goldstrike resource team. They have created several documents that list model notes and step by step procedures for re-creating the model in MineSight®. These step by step notes include screen shots of all of the panels used in the software and descriptions of all of the data files used. RPA does note that the model documentation is not in a similar layout or format as some of the other regional Barrick sites.

DENSITY DATA

The density values used by Goldstrike’s modelling team for EOY2011 resource estimations originated from historical tests conducted on core for several area of the Betze-Post deposit. These tests have indicated an average tonnage factor for non-Carlin Formation ore and waste of approximately 13.5 cubic feet per ton (ft3/st). For Carlin Formation waste, a tonnage factor of 16.0 ft3/st is used and for waste dump material, a value of 18.2 ft3/st is used. These values are in line with those used by other operations in the immediate region.

RPA recommends collecting an updated suite of samples for density testwork on the entire range of types of ore and waste.

MINIMUM WIDTH

No minimum widths are employed per se except for the grade contour modelling in plan. The 50 ft. x 50 ft. x 20 ft. block dimensions are the implicit minimum width.

CUT-OFF GRADES

Breakeven cut-off grades are applied to resource blocks at the resource summary stage.

CAPPING OF HIGH GRADE VALUES

Grade capping employs Barrick software and is applied to individual assays. Variable capping thresholds are employed as determined from log-probability grade distributions domain by domain. Outlier high grade populations are identified from profile inflections and the inflection point grade taken as the capping threshold. The capping level is applied to the domain assays and statistics examined to ensure the coefficient of

 

 

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variation (CV) for the capped assays is less than 2. Capping thresholds for the EOY2011 resource estimate are summarized in Table 14-5. In RPA’s opinion the capping thresholds are reasonable.

TABLE 14-5 CAPPING OF HIGH GRADE VALUES – OPEN PIT

Barrick Gold Corporation—Goldstrike Mine

 

    Domain    

  

Capping Level

(oz/st Au)

  

CV Capped

Latite

   0.800    4.50

Unknown

   0.600    2.72

SW Bazza

   1.200    4.20

NW

   1.000    4.54

Bill’s

   1.000    3.73

S Buzzard

   0.500    3.99

Bridge

   1.200    3.39

NB East

   1.000    2.99

Betze

   1.125    2.25

Weird 2

   2.000    3.15

North Post

   1.000    2.13

JBE

   1.000    2.60

Post

   1.500    2.68

Rodeo

   1.000    1.60

Other

   1.800    3.01

COMPOSITING

Goldstrike used two methods to composite drill hole data, with the method selection being based on the dip angle of the drill hole. If the drill hole dip is equal to or greater than 45°, the hole is composited by bench. If the drill hole has a dip angle shallower than 45°, the hole is composited down the hole with a maximum composite interval of 30 ft. All compositing is performed using MineSight® software. Due to MineSight® limitations, composite data is manipulated in four separate files that are merged together to use in the creation of the resource model. Figure 14-2 illustrates the statistics of the composite lengths.

 

 

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FIGURE 14-2 OPEN PIT COMPOSITE LENGTH STATISTICS

 

LOGO

VARIOGRAPHY

RPA checked the variography by running horizontal variograms on all the domain coded composites and then on a few selected individual domains.

Goldstrike variography studies obtained ranges of 250 ft to 500 ft, depending on the domain. RPA obtained similar results with the horizontal variograms. There is a preferred orientation northwest-southeast, but Goldstrike has used the shorter range in all horizontal directions.

In RPA’s opinion, given the size of the deposit, the amount of drilling, and the drill hole spacing, the search distances used in the Mineral Resource estimation are reasonable.

INTERPOLATION STRATEGY

For the open pit resource estimate, the grade interpolation was carried out by Inverse Distance Squared (ID2), with a search ellipse consistent with the variography for each domain and grade zone. The interpolation uses a pancake like search ellipse that has equal search distances in both the X and Y directions with a constraining search distance in the Z direction to 50 ft for all domains. It is important to note that the grade contours are used to constrain the estimated gold grade. Table 14-6 lists key parameters used for grade interpolation.

 

 

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TABLE 14-6 GRADE INTERPOLATION PARAMETERS FOR OPEN PIT

RESOURCE ESTIMATION

Barrick Gold Corporation—Goldstrike Mine

 

          Search Distance      Samples  
Pass # (Category)    Domain    X      Y      Z      Min      Max      Per Hole  

Pass 1 (Measured)

   All      25         25         10         1         1         1   

Pass 2 (Indicated)

   1,2,9,10,11,12,13,14,99      300         300         50         2         3         1   
   3      90         90         50         2         3         1   
   4,7      225         225         50         2         3         1   
   5      275         275         50         2         3         1   
   6      100         100         50         2         3         1   
   8      250         250         50         2         3         1   

Pass 3 (Indicated)

   1,2,9,10,11,12,13,14,99      150         150         50         1         3         1   
   3      75         75         50         1         3         1   
   4,7      115         115         50         1         3         1   
   5      150         150         50         1         3         1   
   6      75         75         50         1         3         1   
   8      125         125         50         1         3         1   
  

 

  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Pass 4 (Inferred)

   1,2,9,10,11,12,13,14,99      400         400         50         2         3         1   
   3      150         150         50         2         3         1   
   4,7      400         400         50         2         3         1   
   5      450         450         50         2         3         1   
   6      200         200         50         2         3         1   
   8      400         400         50         2         3         1   

BLOCK MODEL

The Betze-Post open pit bock model properties are shown below. The origin is in mine grid coordinates. The model is oriented north-south, east-west, i.e., is unrotated and extends along each axis for:

 

Model Axis

   Ft.  

East (X)

     14,050   

North (Y)

     12,050   

Elevation (Z)

     2,300   

Model maximum depth from surface varies from approximately 1,750 ft in the west to approximately 2,330 ft in the east, depending on surface topography. Model extents are adequate for open pit design, but drilling depths extend well below the block model depth. Blocks have a height of 50 ft, a width of 50 ft, and a length of 50 ft.

 

 

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LOGO

In addition to the gold grade block model, block models have been prepared and interpolated for rock units and for process route parameters: sulphide content (S2), bleach test (BLCH), arsenic content (ARSEN), carbonaceous material (TCM), carbonate, pregnant solution robbing value (PRVAL), bond work index (BWI), SAG mill power index (SPIMN), and fuel consumption (FUEL).

OPEN PIT RESOURCE CLASSIFICATION

Resource classification is based on distance from the resource block centroid to the nearest composite. The distances are determined from variogram ranges at 80% and 90% of the sill, where Measured Resource is defined for distances up to 80% and Indicated Resource up to 90%. Variograms for gold have been prepared from the composites. The number of composites and spatial location of composites used for block grade interpolation are also criteria for Measured and Indicated classification and are summarized in Table 14-7.

 

 

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TABLE 14-7 OPEN PIT RESOURCE CLASSIFICATION

Barrick Gold Corporation - Goldstrike Mine

 

Category

   Estimation Pass
Number
   Classification    No. of Composites for Interpolation
         Minimum    Maximum    Max. Per Hole

1

   1    Measured    1    1    1

2

   2 and 3    Indicated    2    3    1

3

   4    Inferred    2    3    1

Blocks classed as Indicated generally form coherent areas within the resource/reserve pits with minor dispersed areas of Inferred. Characteristic of distance based classification schemes, the Measured blocks comprise coherent areas where drilling is closely spaced.

Mineral Resources are within a pit shell optimized at $1,400/oz Au.

RESOURCE ESTIMATE VALIDATION

In RPA’s opinion, the EOY2011 resource estimation is appropriate for the style of mineralization in the southeastern areas of the Carlin Trend. The following is a list of some of the checks performed on the resource model by RPA:

 

   

Checked for duplicate drill hole traces, twinned holes, etc.

 

   

Checked collar locations for zero/extreme values.

 

   

Checked assays in database for missing intervals, long intervals, extreme high values, blank/zero values, reasonable minimum/maximum values.

 

   

Ran validity report to check for out of range values, missing interval, overlapping intervals, etc.

 

   

Checked for overlapping wireframes to determine possible double counting.

 

   

Checked mineralization/wireframe extensions beyond last holes to see if they are reasonable and consistent.

 

   

Compared basic statistics of assays within wireframes with basic statistics of composites within wireframes for both uncut and cut values.

 

   

Checked for capping of extreme values and effect of Coefficient of Variance.

 

   

Checked for reasonable compositing intervals.

 

 

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Checked that composite intervals start and stop at wireframe boundaries.

 

   

Checked that assigned composite rock type coding is consistent with intersected wireframe coding.

 

   

Checked if block model size and orientation is appropriate to drilling density, mineralization, and mining method.

 

   

Checked search volume radii and orientations against available variography.

 

   

Checked kriging parameters against available variography.

 

   

Visually checked block resource classification coding for isolated blocks.

 

   

Compared block statistics (zero grade cut-off) with assay/composite basic statistics.

 

   

Visually compared block grades to drill hole composite values on sections and/or plans.

 

   

Visually checked for grade banding, smearing of high grades, plumes of high grades, etc., on sections and/or plans.

 

   

Conducted a block value calculation on trace blocks within the model.

CONCLUSIONS

In RPA’s opinion, the open pit Mineral Resource estimates are competently conducted using reasonable and appropriate parameters, assumptions, and methodology. The data collection system (i.e., the sample data) is well configured and maintained. Estimation procedures are very well organized and documented, as are the various sign-offs and validation checks. All personnel interviewed during the audit appeared to be comfortable and confident with their roles in the process.

RPA is not aware of any environmental, permitting, legal, title, taxation, socio-economic, marketing, political, or other relevant factors which could materially affect the open pit Mineral Resource estimates.

UNDERGROUND

SUMMARY

Tables 14-8 and 14-9 list the underground Mineral Resources exclusive of Mineral Reserves. These Mineral Resources could not be converted to Mineral Reserves due to operational constraints (e.g., Measured and Indicated Mineral Resources) or an insufficient level of confidence (e.g., Inferred Mineral Resources). The Qualified Person for the underground Mineral Resource estimate is Chester M. Moore, P.Eng.

 

 

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TABLE 14-8 UNDERGROUND MINERAL RESOURCES—DECEMBER 31, 2011

Barrick Gold Corporation—Goldstrike Mine

 

 

     Measured Resources      Indicated Resources      Measured and Indicated
Resources
 
     Tons      Grade      Contained
Gold
     Tons      Grade      Contained
Gold
     Tons      Grade      Contained
Gold
 

Area

   (000)      (oz/st)      (000 oz)      (000)      (oz/st Au)      (000 oz)      (000)      (oz/st Au)      (000 oz)  

Meikle

     289         0.423         122         440         0.298         131         729         0.348         254   

South Meikle

     19         0.469         9         64         0.241         15         83         0.294         24   

Extension

     35         0.551         19         263         0.444         117         298         0.457         136   

East Griffin

     51         0.291         15         100         0.268         27         151         0.276         42   

West Griffin

     57         0.265         15         119         0.206         25         176         0.225