EX-99.1 2 d323919dex991.htm EX-99.1 EX-99.1

Exhibit 99.1

 

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BARRICK GOLD CORPORATION

 

TECHNICAL REPORT ON THE

LAGUNAS NORTE MINE,

LA LIBERTAD REGION, PERU

NI 43-101 Report

Qualified Persons:

Luke Evans, P.Eng.

Glen Ehasoo, P.Eng.

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

March 16, 2012

 

ROSCOE POSTLE ASSOCIATES INC.


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Report Control Form

 

Document Title    Technical Report on the Lagunas Norte Mine, La Libertad Region, Peru    
Client Name & Address   

Barrick Gold Corporation

Brookfield Place, TD Canada Trust Tower

Suite 3700, 161 Bay Street, P.O. Box 212

Toronto, Ontario

M5J 2S1

  

  

  

  

  

Document Reference    Project # 1681    Status &
Issue No.
   Final

Version

     Rev 0   
Issue Date    March 16, 2012   
Lead Author   

Luke Evans

Glen Ehasoo

Kathleen Ann Altman

   (Signed)

(Signed)

(Signed)

     
              (   
Peer Reviewer   

Graham G. Clow

Deborah McCombe

   (Signed)

(Signed)

     
Project Manager Approval    Luke Evans    (Signed)      
Project Director Approval    Graham Clow    (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   

Accessibility

     5-1   

Climate

     5-1   

Local Resources

     5-2   

Infrastructure

     5-2   

Physiography

     5-3   

6 HISTORY

     6-1   

7 GEOLOGICAL SETTING AND MINERALIZATION

     7-1   

Regional Geology

     7-1   

Local Geology

     7-3   

Property Geology

     7-5   

Mineralization

     7-11   

Material Classification

     7-15   

8 DEPOSIT TYPES

     8-1   

9 EXPLORATION

     9-1   

Exploration Potential

     9-1   

10 DRILLING

     10-1   

11 SAMPLE PREPARATION, ANALYSES AND SECURITY

     11-1   

Sampling Method and Approach

     11-1   

Sample Preparation, Analyses and Security

     11-2   

12 DATA VERIFICATION

     12-1   

13 MINERAL PROCESSING AND METALLURGICAL TESTING

     13-1   

14 MINERAL RESOURCE ESTIMATE

     14-1   

Summary

     14-1   

Geological Models

     14-2   

Geological Domains

     14-6   

Grade Domains

     14-6   

Density Data

     14-8   

Cut-Off Grades

     14-8   

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

Technical Report NI 43-101 – March 16, 2012

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Assay Statistics and Capping of High Grades

     14-9   

Composites

     14-12   

Contact Plot Analysis

     14-14   

Variography

     14-14   

Resource Estimation Methodology

     14-18   

Resource Estimate Validation

     14-28   

Resource Classification

     14-33   

15 MINERAL RESERVE ESTIMATE

     15-1   

16 MINING METHODS

     16-1   

Summary of Mining Operations

     16-1   

Mine Design

     16-4   

Ground Conditions/Slope Stability

     16-10   

Production Schedule

     16-14   

Waste Rock

     16-15   

Heap Leach Facility

     16-16   

Mine Equipment

     16-17   

Manpower

     16-19   

Mine Infrastucture

     16-19   

17 RECOVERY METHODS

     17-1   

Process Description

     17-1   

18 PROJECT INFRASTRUCTURE

     18-1   

Buildings and Facilities

     18-2   

Communications

     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   

Environmental Studies

     20-1   

Project Permitting

     20-1   

Reclamation

     20-2   

Social or Community Requirements

     20-2   

21 CAPITAL AND OPERATING COSTS

     21-1   

Capital Costs

     21-1   

Operating Costs

     21-1   

Manpower

     21-3   

22 ECONOMIC ANALYSIS

     22-1   

23 ADJACENT PROPERTIES

     23-1   

24 OTHER RELEVANT DATA AND INFORMATION

     24-1   

25 INTERPRETATION AND CONCLUSIONS

     25-1   

26 RECOMMENDATIONS

     26-1   

27 REFERENCES

     27-1   

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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28 DATE AND SIGNATURE PAGE

     28-1   

29 CERTIFICATE OF QUALIFIED PERSON

     29-1   

LIST OF TABLES

 

     PAGE  

Table 1-1 Mineral Resources – December 31, 2011

     1-2   

Table 1-2 Mineral Reserves – December 31, 2011

     1-2   

Table 1-3 Capital Costs Summary

     1-15   

Table 2-1 List of Abreviations

     2-4   

Table 4-1 Mining Concessions

     4-3   

Table 7-1 Material Classification

     7-18   

Table 10-1 DDH and RC Drilling Details

     10-1   

Table 10-2 Drilling Summary

     10-1   

Table 11-1 QC Insertion Rates

     11-4   

Table 12-1 2008 to 2011 Data Verification

     12-2   

Table 13-1 Ore Types

     13-1   

Table 13-2 Metallurgical Model Recoverable Recovery Algorithms

     13-2   

Table 13-3 Recovery Evaluation

     13-3   

Table 14-1 Mineral Resources – December 31, 2011

     14-1   

Table 14-2 Lithology Codes

     14-3   

Table 14-3 Geostructural Codes

     14-3   

Table 14-4 Grade Domain Codes

     14-6   

Table 14-5 Resource Internal Cut-off Grades

     14-8   

Table 14-6 Au Capping Levels

     14-10   

Table 14-7 Gold Composite Statistics By lithology

     14-13   

Table 14-8 Gold Estimation Parameters

     14-20   

Table 14-9 Tonnage Factors

     14-27   

Table 15-1 Mineral Reserves – December 31, 2011

     15-1   

Table 16-1 Lagunas Norte Production History

     16-1   

Table 16-2 Ore Type Classification

     16-5   

Table 16-3 Mine Optimization Parameters

     16-6   

Table 16-4 Internal Cut-off Grades, Mine Reserves

     16-9   

Table 16-5 Mine Design Parameters

     16-10   

Table 16-6 Summary of Piteau Highwall Slope Design Recomendations

     16-11   

Table 16-7 Summary of Footwall Slope Design Recomendations

     16-11   

Table 16-8 Mine Production Schedule

     16-14   

Table 16-9 Heap Leach Placement Schedule

     16-15   

Table 16-10 Mine Equipment Fleet

     16-19   

Table 21-1 Capital Costs Summary

     21-1   

Table 21-2 Mine Operating Costs

     21-2   

Table 21-3 Process Operating Costs

     21-2   

Table 21-4 G&A Costs

     21-3   

Table 21-5 Mine Site Manpower

     21-3   

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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LIST OF FIGURES

 

     PAGE  

Figure 4-1 Location Map

     4-2   

Figure 4-2 Property Map

     4-4   

Figure 4-3 Royalty Map

     4-5   

Figure 7-1 Regional Geology

     7-2   

Figure 7-2 Local Geology

     7-6   

Figure 7-3 Property Geology

     7-7   

Figure 7-4 Stratigraphic Column

     7-8   

Figure 7-5 Shulcahuanca Dome

     7-9   

Figure 7-6 Cross-Section Looking Northwest

     7-10   

Figure 7-7 Gold Grade Thickness Contours

     7-13   

Figure 7-8 TCM Versus Gold Recovery

     7-16   

Figure 7-9 In-Pit Material Type Flag System

     7-19   

Figure 9-1 Satellite Deposits

     9-2   

Figure 10-1 DDH and RC Drilling by Year

     10-2   

Figure 10-2 Drill Hole Plan

     10-3   

Figure 14-1 Lithological Domains on 4,050 m Bench

     14-4   

Figure 14-2 Geostructural Domains on 4,050 m Bench

     14-5   

Figure 14-3 Grade Domains on 4,050 m Bench

     14-7   

Figure 14-4 Assay Cumulative Frequency Distribution – Gold

     14-11   

Figure 14-5 Gold Contact Plot for Volcanic and Sandstone Rocks

     14-15   

Figure 14-6 Gold Contact Plot for GS1 and GS2

     14-16   

Figure 14-7 Lagunas Norte Gold Indicator Variogram

     14-17   

Figure 14-8 Block and Composite Au Grades

     14-29   

Figure 14-9 Gold Block Versus Composite Graphs

     14-31   

Figure 14-10 Gold Swath Plot

     14-32   

Figure 16-1 Lagunas Norte General Site Arrangement

     16-2   

Figure 16-2 Lagunas Norte Final Pit Slope Domains in Plan

     16-13   

Figure 17-1 Simplified Process Flow Sheet

     17-5   

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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1 SUMMARY

EXECUTIVE SUMMARY

Roscoe Postle Associates Inc. (RPA) was retained by Barrick Gold Corporation (Barrick) to prepare an independent Technical Report on the Lagunas Norte Gold Mine (the Project) in Peru. The purpose of this report is to support public disclosure of Mineral Resource and Mineral Reserve estimates at the Project as of December 31, 2011. This Technical Report conforms to National Instrument 43-101 Standards of Disclosure for Mineral Projects. RPA visited the property from November 28 to 30, 2011.

Barrick is a Canadian publicly traded mining company with a large portfolio of operating mines and projects across five continents. The Lagunas Norte Mine is located in the District of Quiruvilca in the Province of Santiago de Chuco and the Department of La Libertad, in north-central Peru. The mine site is approximately 90 km east of the coastal city of Trujillo.

Lagunas Norte is a large open-pit, heap leach gold and silver mine in the high Andean Cordillera. Operations include open pit mining of gold-silver ore, crushing, and extraction of precious metals using heap leaching and Merrill-Crowe recovery. Since Lagunas Norte started production in March 2005, the mine has recovered 6.5 million ounces of gold and over three million ounces of silver from approximately 137 million tonnes of ore averaging 1.81 g/t Au and 3.6 g/t Ag.

Mining an average of approximately 23 million tonnes per year of ore and an average of approximately 20 million tonnes of waste per year is scheduled for Lagunas Norte over the next eight years. Leaching will continue for two years after mining ceases, with mine operations concluding in 2021. Most of the ore is crushed prior to placement on the heap leach facility.

The Project is owned and operated by Minera Barrick Misquichilca S.A. (MBM), a wholly-owned Peruvian subsidiary of Barrick. The mine is part of the Alto Chicama property. A 2.51% net smelter royalty is paid to Peruvian state company Activos Mineros S.A.C., formerly Centromin Peru S.A. (Centromin). In December 2006, Centromin transferred all of its rights and obligations with respect to the mine to Activos Mineros S.A.C. (Activos Mineros), a state mining company.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Table 1-1 summarizes open pit Mineral Resources exclusive of Mineral Reserves as of December 31, 2011.

TABLE 1-1 MINERAL RESOURCES – DECEMBER 31, 2011

Barrick Gold Corporation – Lagunas Norte Mine

 

     Tonnage      Grade      Contained Metal  

Category

   (Mt)      (g/t Au)      (g/t Ag)      (000 oz Au)      (000 oz Ag)  

Measured

     0.8         0.47         1.9         12         50   

Indicated

     31.1         0.49         1.8         493         1,778   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total Measured and Indicated

     31.9         0.49         1.8         505         1,828   

Inferred

     7.2         0.47         1.7         109         397   

Notes:

 

1. CIM definitions were followed for Mineral Resources.
2. Mineral Resources are estimated using a gold price of US$1,400 per ounce and a US$/PEN exchange rate of 2.75.
3. Mineral Resources are estimated at gold cut-off grades that vary by material type from approximately 0.119 g/t to 0.692 g/t.
4. Mineral Resources are exclusive of Mineral Reserves.
5. Numbers may not add due to rounding.

Table 1-2 summarizes the open pit Mineral Reserves, including existing stockpiles scheduled for processing and inventory, as of December 31, 2011.

TABLE 1-2 MINERAL RESERVES – DECEMBER 31, 2011

Barrick Gold Corporation – Lagunas Norte Mine

 

Category

   Tonnage
(Mt)
     Au (g/t)      Ag (g/t)      Contained
Metal

(Moz Au)
     Contained
Metal

(Moz Ag)
 

Proven

     8.7         1.06         4.0         0.30         1.1   

Probable

     179.0         0.96         3.8         5.53         21.9   

Stockpiles

     5.6         1.49         3.1         0.27         0.6   

Inventory

     1.2         1.47         8.5         0.06         0.3   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Proven & Probable

     194.5         0.98         3.8         6.15         23.9   

Notes:

 

1. CIM definitions were followed for Mineral Reserves.
2. Mineral Reserves are estimated at a variable cut-off grade based on process cost, recovery and profit. The cut-offs vary from approximately 0.14 g/t Au to 0.80 g/t Au.
3. Mineral Reserves are estimated using an average long-term gold price of US$1,200 per ounce and an US$/PEN exchange rate of 2.75.
4. The Mineral Reserve estimate includes inventory.
5. Numbers may not add due to rounding.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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CONCLUSIONS

Based on the site visit and subsequent review, RPA offers the following conclusions:

MINERAL RESOURCE ESTIMATION

 

   

The 2011 year-end Measured and Indicated Mineral Resources, exclusive of Mineral Reserves, total 31.9 million tonnes averaging 0.49 g/t Au and 1.8 g/t Ag and contain 505,000 ounces of gold and 1.83 million ounces of silver.

 

   

The 2011 year-end Inferred Mineral Resources total 7.2 million tonnes averaging 0.47 g/t Au and 1.7 g/t Ag and contain 109,000 ounces of gold and 397,000 ounces of silver.

 

   

Mineral Resource estimates have been prepared utilizing acceptable estimation methodologies. The classification of Measured, Indicated, and Inferred Resources, stated in Table 1-1, conform to CIM Definition Standards for Mineral Resources and Mineral Reserves dated November 27, 2010 (CIM definitions).

 

   

The current drill hole database is reasonable for supporting a resource model for use in Mineral Resource and Mineral Reserve estimation.

 

   

The methods and procedures utilized by MBM at the Lagunas Norte Mine to gather geological, geotechnical, assaying, density, and other information are reasonable and meet generally accepted industry standards. Standard operating protocols are well documented and updated on a regular basis for most of the common tasks. MBM developed and implemented its own laboratory information management system (LIMS) for the mine laboratory. The mine carries out regular comparisons with blast hole data, previous models, and production reconciliation results to calibrate and improve the resource modelling procedures.

 

   

Exploration and development sampling and analysis programs use standard practices, providing generally reasonable results. The resulting data can effectively be used for the estimation of Mineral Resources and Mineral Reserves.

 

   

The positive gold reconciliation variance of approximately 20% in the past has improved significantly to only 3% due mostly to infill reverse circulation (RC) drilling and procedural improvements to the resource model.

 

   

Overall, RPA is of the opinion that MBM has done very high quality work that exceeds industry practice.

MINING AND MINERAL RESERVES

 

   

The open pit Proven and Probable Reserves, including existing stockpiles scheduled for processing and inventory, are estimated to be 194.5 million tonnes grading 0.98 g/t Au and 3.8 g/t Ag, containing 6.2 million ounces of gold and 23.9 million ounces of silver.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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The Mineral Reserve estimates have been prepared utilizing acceptable estimation methodologies and the classification of Proven and Probable Reserves, stated in Table 1-2, conform to CIM definitions.

 

   

The operating data and the supporting documents were prepared using standard industry practices and provide reasonable results and conclusions.

 

   

Recovery and cost estimates are based upon actual operating data and engineering to support a Mineral Reserve statement. Economic analysis using these estimates generates a positive cash flow, which supports a statement of Mineral Reserves.

 

   

The current Lagunas Norte production schedule provides reasonable results and, in RPA’s opinion, meets the requirements for statement of Mineral Reserves. In addition to the Mineral Reserves within the ultimate pit, there are Mineral Resources and potential sulphide resources that represent opportunities for the future.

ENVIRONMENTAL CONSIDERATIONS

 

   

The environmental and social practices at Lagunas Norte appear to be very effective. The use of ranches/farms, including the trout farm, to demonstrate the viability of the coexistence of agriculture and mining appears to be very effective. Also, the transparency of the water sampling along with representatives from the local community and the voluntary reclamation and remediation of the historic coal mining areas have clearly enabled Barrick to have a strong “social licence to operate” Lagunas Norte.

PROCESS

 

   

RPA confirmed that the formulae used to estimate gold and silver recovery meet industry standards.

 

   

The Lagunas Norte operation is an excellent operation where the staff have made intelligent and innovative use of the available resources. For example, using solution recirculation to increase the amount of solution going to the leach pad is an excellent idea. It not only provides additional solution to meet the required ratio of solution to ore, but increases the gold grade of the solution which makes the Merrill-Crowe zinc cementation process work more efficient and reduces costs.

 

   

The solution management practices exceed industry standards under extremely difficult conditions. Not only is there a high net positive water balance, but there is an effective, efficient water management system that includes acid rock drainage (ARD) water treatment, secondary water treatment, and other processes. It is clear that a lot of thought went into the development and integration of all of the solution management processes.

 

   

One of the processing constraints is difficulty in reducing the ammonia concentration to less than 10 ppm in the effluent from the water treatment facilities prior to discharge from the mine. While it is accepted that much of the ammonia comes from cyanide and cyanate, a portion of it may be residue from

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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the blasting. If the amount of ammonium nitrate used in blasting is reduced, it may be beneficial to the water treatment process and, correspondingly, enhance the remaining processing operations.

 

   

The installation of the carbon-in-column (CIC) circuit will be very beneficial in the detoxification and closure of the leach pad, in RPA’s opinion. Activated carbon recovery of gold and silver does not add zinc to the circuit, as the Merrill Crowe circuit does. It removes residual metals from the solution and reduces the cyanide concentration since some of the metals are present as cyanide complexes that adsorb onto the surface of the activated carbon. So, the CIC circuit will not only increase the solution flow but will also be very helpful when the mine moves into final closure of the leach pads.

RECOMMENDATIONS

RPA makes the following recommendations:

MINERAL RESOURCE ESTIMATION

 

   

In RPA’s opinion, the resource modelling work is very good and no significant procedural changes are warranted. The resource model is performing very well, so it is best not to make any significant procedural changes. RPA notes, however, that the modelling procedures include hundreds of interpolation runs, the use of length weighted composites to simulate semi-soft boundaries, multiple interim block sizes, and other advanced features that collectively result in a very complex process that may be difficult for potential newcomers to the site to follow. Consequently, RPA’s sole recommendation on resources estimation would be to try to simplify the modelling procedures in the future without sacrificing the model reliability.

MINING

 

   

The Life of Mine (LOM) plan is robust and Barrick should proceed to implement the plan as presented. Production haul truck and drill fleets should be monitored closely in future years to ensure adequate capacity is in place to meet production targets while annual production requirements increase.

 

   

MBM should review the potential of reducing powder factor and its impact on mining productivity and costs along with crushing throughput and costs; the rationale being that at present a significant amount of material passed through the crusher does not require crushing but still contributes to wear.

 

   

MBM should review the conveyor belt extension to the heap leach facility (HLF) for LOM operations to reduce the haulage cycle and corresponding demand on haul trucks.

PROCESS

 

   

The contribution of ammonia from blasting agents should be evaluated to determine if a reduction in the powder factor may reduce the ammonia concentration in the leach solution and if that would lead to a positive impact on production.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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In response to the mining discussion about switching to blasting using only emulsion instead of the combination of ANFO and emulsion, RPA recommends that the impact on the water treatment processes be carefully and fully investigated. The emulsion is specifically designed such that it will not dissolve in water, however, it will still contribute to the total ammonia in the solution and it will most likely not respond to the water treatment processes in the same way. RPA recommends investigating whether the use of emulsion will plug up the reverse osmosis membranes and if the concentration of ammonia due to the emulsion will be reduced using the existing plant.

 

   

MBM should evaluate if there is any benefit to accelerating the construction of the CIL facility to improve gold recovery from the higher grade clean oxide ore before the pressure oxidation circuit is operational. Although permitting may be a time constraint, it is worth considering.

 

   

RPA recommends that Barrick continue to conduct routine metallurgical tests to try to improve the accuracy of the calculations used to estimate recovery of gold and silver.

 

   

RPA understands the rationale for trying to lower the mine laboratory 0.05% detection limit for the sulphur assays, however, RPA would like to emphasize that changes to the classification of potentially acid generating ore should be thoroughly evaluated prior to the time any changes are made in the operation. Representative samples should be used to conduct acid-base accounting and humidity cell tests to ensure that a change will not result in ARD that is uncontrolled. RPA observed that Lagunas Norte is currently doing an excellent job of managing ARD, collecting and treating the drainage efficiently, and maintaining an operation that has not created environmental problems due to ARD. RPA recommends that every care should be taken to ensure that this does not change in the future.

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 Lagunas Norte Mine is currently in production, and a material expansion is not being planned. RPA has performed an economic analysis of the Lagunas Norte 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.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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TECHNICAL SUMMARY

PROPERTY DESCRIPTION AND LOCATION

The Project is located on the 185 km2 Alto Chicama property in the La Libertad Region, north-central Peru, approximately 90 km east of the coastal city of Trujillo and 175 km north of Barrick’s Pierina Mine. The mine is located at 7º50’ S latitude and 78º15’ W longitude and lies on the western flank of the Peruvian Andes at an elevation of 4,000 MASL to 4,260 MASL.

Access is by public roads from Trujillo for a total driving distance of approximately 150 km.

LAND TENURE

The Alto Chicama property includes four mining concessions (Acumulación Alto Chicama, Los Angeles, Las Lagunas 15 and 16) totalling 19,181.3 ha. The Lagunas Norte Mine is located on the 18,002.3 ha “Acumulación Alto Chicama” mining concession. MBM acquired this concession in December 2002 from Centromin, the Peruvian state mining company, pursuant to an international bid process. Production at Lagunas Norte is subject to 2.51% Net Smelter Return (NSR) royalty, payable semi-annually to Activos Mineros on the extraction of gold and all other minerals.

The Acumulación Alto Chicama has no expiry date since it is in exploitation phase. In order to maintain its validity, however, a Validity Fee, of $3.00/ha, must be paid no later than June 30 each year. Non-fulfillment for two consecutive years results in expiration of a mining concession. The Validity Fee payments for the Alto Chicama property were up to date as of December 2011.

On December 29, 2004, Barrick entered into a Tax Stability Agreement with the Peruvian government, which provides increased certainty with respect to tax, administrative, and exchange stability to MBM for 15 years until December 31, 2020.

MBM controls surface rights totalling 3,779.6 ha in the mine area, which are sufficient to mine the current reserves.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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EXISTING INFRASTRUCTURE

Lagunas Norte infrastructure and services have been designed to support an operation of 63,000 tpd of ore to an HLF and a nominal 140,000 tpd of total material mined. Due to the remote location, the property is self-sufficient with regard to the infrastructure needed to support the operation.

Site infrastructure includes the open pit, heap leach pads, crushing facilities, Merrill Crowe recovery plant, on-site facilities (safety/security/first aid/emergency response building, assay laboratory, plant guard house, dining facilities, and offices); related mine services (truckshop, truck wash facility, warehouse, fuel storage and distribution facilities, reagent storage and distribution facilities), and other facilities to support operations. Permanent accommodations are available for all Lagunas Norte employees and visitors and are located approximately three kilometres east and downslope of the Lagunas Norte open pit operations at approximately 3,800 MASL.

The water for process and mining consumptive needs is delivered rain captured on two small lakes. There is plenty of water available for consumptive use now and for the future. At Lagunas Norte, a water management group is in place to carry out all dewatering including pumping, distribution, delivery, and disposal. Lagunas Norte has a positive water balance.

Electricity is provided by a private-owned generation company and delivered to Lagunas Norte through a high voltage power line connected to the National Grid in Trujillo.

HISTORY

MBM commenced a field program at Alto Chicama in March 2001, which included geologic mapping, geochemical sampling, and ground geophysics. This work resulted in the identification of targets for drill testing. Drilling commenced in mid-2001 and the initial program identified the Las Lagunas Norte area as justifying detailed follow-up. Subsequent drilling was concentrated in the Las Lagunas Norte area.

On April 2, 2004, the Alto Chicama environmental impact assessment (EIA) received regulatory approval and on April 12, 2004, the Plant Construction Authorization was granted which authorized MBM to construct and install the Alto Chicama process plant and related facilities.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Construction started in 2004 and the first ore tonne was placed on the leach pad in March 2005. First pour was realized in June 2005. As of the end of 2011, the mine has recovered 6.5 million ounces of gold and over 3.0 million ounces of silver from approximately 137 million tonnes of ore averaging 1.81 g/t Au and 3.6 g/t Ag.

GEOLOGY AND MINERALIZATION

The regional geology is dominated by a thick sequence of Mesozoic marine clastic and carbonate sedimentary rocks, which are bounded to the west by the Mesozoic to Early Tertiary Coastal Batholith and to the east by the Precambrian metamorphic rocks of the Marañón Complex. The Mesozoic sequence has been affected by at least one and possibly two stages of deformation during the Andean Orogeny. The volcanic rocks of the Tertiary Calipuy Group unconformably overlie the Mesozoic rocks.

Mineralization is the result of multiple volcanic and hydrothermal events. It occurs in the southeast portion of the Alto Chicama property and is hosted in both the Tertiary volcanics of the Calipuy Group and the underlying Cretaceous sedimentary rocks of the Chimú Formation. The deposit is locally faulted by relatively steeply dipping structures and is primarily controlled by stratigraphy and lithologic contacts.

The mineralization within the present pit extends for approximately two kilometres in the north-northwest direction by approximately two kilometres in the east-northeast direction and for more than 200 m vertically. Most of the mineralization (75%) occurs as oxide material, with approximately 25% occurring as sulphide material.

A significant characteristic of the Lagunas Norte deposit is the variable carbonaceous content found within the siliclastic sedimentary strata.

EXPLORATION

Field exploration on the Alto Chicama property by MBM commenced in March 2001. Following detailed mapping, geophysical and geochemical surveys, PIMA analysis, and channel sampling, drilling commenced in June 2001. In 2002, environmental, metallurgical, and engineering studies, together with cost estimation and economic analysis, were started, and by January 31, 2003, the first reserve estimate for Lagunas Norte was completed.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Approximately half of the metreage drilled up to 2011 was done in 2002 and included almost entirely diamond drill holes. Since 2007, there has been much more RC drilling after the discovery that the gold grades from core samples were biased low relative to production and to RC samples.

In 2006, resource definition drilling commenced at the satellite deposits of Lagunas Sur and Tres Cruces. It resulted in a small resource estimated at Lagunas Sur, which is now included in the Lagunas Norte resource estimate.

MBM has begun evaluating the economic potential of the primary sulphide mineralization located below the current resources.

MINERAL RESOURCES

The 2011 year-end Measured and Indicated Mineral Resources total 31.9 million tonnes averaging 0.49 g/t Au and 1.8 g/t Ag and contain 505,000 ounces of gold and 1.83 million ounces of silver. In addition, the 2011 year-end Inferred Mineral Resources total 7.2 million tonnes averaging 0.47 g/t Au and 1.7 g/t Ag and contain 109,000 ounces of gold and 397,000 ounces of silver.

The modelling work was carried out by Barrick. The current resource model combines the 2010 year-end model for gold, silver, mercury, and geology interpretation, all based on the drill holes available up to October 2010, with the 2011 mid-year model for copper, arsenic, sulphur, and TCM. The sulphide surface was updated for the 2011 mid-year copper model.

RPA reviewed the resource assumptions, input parameters, geological interpretation, and block modelling procedures and is of the opinion that the Mineral Resource estimate is appropriate for the style of mineralization and that the resource model is reasonable and acceptable to support the 2011 year-end Mineral Resource and Mineral Reserve estimates.

RPA is not aware of any environmental, permitting, legal, title, taxation, socio-economic, marketing, political, or other issues that could materially affect the Mineral Resource and Mineral Reserve estimates.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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MINERAL RESERVES

RPA reviewed the reported resources, production schedules, and cash flow analysis to determine if the resources meet the CIM definitions. Based on this review, it is RPA’s assessment that the Measured and Indicated Mineral Resource within the final pit design at Lagunas Norte can be classified as Proven and Probable Mineral Reserves.

The open pit Proven and Probable Reserves, including existing stockpiles scheduled for processing, are estimated to be 194.5 million tonnes at 0.98 g/t Au and 3.8 g/t Ag, containing 6.2 million ounces of gold and 23.9 million ounces of silver as presented in Table 1-2.

MINING METHOD

The Lagunas Norte Mine is a traditional open pit truck/shovel heap leach operation that has been in continuous production since 2005. To date, Lagunas Norte has produced 6.5 million ounces of gold and 5.1 million ounces of silver.

Open pit mining operations are located on a mountain top with gentle to extreme terrain between elevations of 3,800 MASL and 4,200 MASL. Mining is from a single open pit, with an average of approximately 23.5 million tonnes per year ore scheduled over the next eight years to 2019, the final year of open pit operations.

The Lagunas Norte ultimate pit measures approximately 2.5 km along strike, typically 0.8 km to 1.2 km across with a surface footprint of approximately 240 ha, and has a maximum depth of approximately 250 m. There are four main areas of development identified within the ultimate pit: Dafne, Josefa, Alexa, and the moraines furthest to the north. The open pit is overlooked by the Shulcahuanca Dome, a sacred feature, and there is an approximate 50 m standoff from the base of the Shulcahuanca Dome for mine planning and operations.

Final arrangement of the Lagunas Norte waste rock facilities is for the continued development of surface dumps surrounding the Lagunas Norte ultimate pit other than to the south-southeast where the HLF is located, resulting in a relatively compact overall footprint.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Processing is based on two adjacent heap leach pads designed to merge into a single HLF. Various ore types, both crushed and ROM, are delivered to the HLF by haul truck. Solution from the HLF is pumped to the Merrill Crowe process facilities for production of gold bars with silver credits. The HLF is located less than 0.5 km south of the existing pit limits. Final HLF dimensions are up to 1.7 km north-south and up to 1.7 km east-west, for an ultimate footprint of approximately 280 ha.

MINERAL PROCESSING

The recovery process used at Lagunas Norte is a two-stage conventional crushing circuit, followed by heap leaching, and a Merrill Crowe zinc cementation plant for recovery of the precious metals. The major components of the process are primary crushing, secondary crushing, heap leaching, recovery plant, refinery, and water discharge treatment plant.

The crushing circuit was originally designed to crush 42,000 tpd, but the capacity is permitted to 63,000 tpd. Historically, it was determined that the gold recovery from heap leaching at Lagunas Norte is not overly dependent on crush size, so the size has been increased over time to allow more material to be processed through the crushing circuit. The crushed ore is conveyed to a 2,000 tonne live capacity stockpile, from which it is fed to the secondary crushers. From the secondary crusher, the ore is loaded into haul trucks that transport it to the leach pad. Lime is added to the trucks to raise the pH of the leach solution.

At the leach pad, stacking of the crushed ore is done in 10 m high lifts with assistance from a high precision GPS dozer. Ore classified as contaminated based on the concentration of total carbonaceous material is stacked on a separate area of the leach pad. Some of the contaminated ore is crushed and some is not, depending on the type of ore. Once the cell has been prepared, a drip irrigation system is laid on top of the ore. Cyanide solution is trickled through the pad at the rate of 20 L/m2/h. After passing through the pad, pregnant solutions are temporarily stored in the pregnant leach solution pond, then pumped to the process plant using vertical turbine pumps at the rate of 2,700 m3/h. The plant and pumping systems have been modified to increase the flow rate to 3,000 m3/h, which is adequate to maintain the optimum solution to ore ratio.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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The pregnant solution is pumped to the Merrill Crowe zinc cementation recovery plant. The suspended solids are removed in the clarifier and the dissolved oxygen concentration is reduced to less than one part per million by the de-aerator. From the de-aerator the solution passes through a cone where powdered zinc is added and the gold and silver precipitate out of the solution. The precipitate is recovered from the solution using filter presses and put into trays that are placed in mercury retorts. In the retorts, the precipitate is gradually heated so that it dries and the mercury is evaporated, condensed, and recovered under a vacuum system. After retorting, the precipitate is mixed with flux and placed in a smelting furnace. The impurities are removed from the precious metals in the slag and the mixture of gold and silver is recovered as doré. The doré is transportation to a refinery for further processing.

Lagunas Norte’s water treatment facilities include cyanide destruction plant and acid rock drainage pond and treatment plant. At the time of the site visit, a secondary water treatment plant was under construction to further improve the treatment facilities and the quality of the water that is discharged from the property. The plant design includes ferric sulphate precipitation to remove metals and reverse osmosis to remove ammonia.

At the time of the site visit, installation of the CIC circuit to accommodate a flow rate of 3,000 m3/h was planned for 2012. The purpose of the installation is to further increase the solution flow to the leach pad to 4,000 m3/h. The excess available flow, i.e., 2,000 m3/h, from the CIC circuit will be used to wash the areas of the leach pad where leaching is completed.

ENVIRONMENTAL, PERMITTING AND SOCIAL CONSIDERATIONS

Environmental studies at Lagunas Norte are ongoing and extensive. For example, MBM has done significant work proving that cattle can grow to large sizes at high elevations using MBM’s ranches to demonstrate effective methods to the local communities.

The EIA for the Project was approved in 2004. In August 2010, an amendment to the former EIA was approved and that allowed expansion of the east waste dump, new leach pad, new ponds (doubling of size for process leach solution, process overflow, ARD, and sediment ponds).

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Permits to discharge from the sedimentation ponds and the rotating bio-contactor (RBC) sewage treatment plant at El Sauco expire every two years. Permits for pit dewatering and the trout farm are on-going. The trout farm is in construction. Water use permits to begin operation are anticipated in March 2012.

Water monitoring is completed at 31 points in three basins. Groundwater is monitored at ten points and surface water is monitored at 16 points. Mine effluent is monitored at three points and potable water and wastewater are monitored at two points. The data is reported every three months. Air monitoring is required at four points primarily for dust. Reports are due quarterly. Additional permits are required for hazardous waste disposal, e.g., fire assay cupels, which is done off site by experts. Wildlife is monitored every two years and aquatic life is monitored annually during the operating phase of the mine for internal purposes.

Lagunas Norte is in compliance with the International Organization for Standardization (ISO) 14001 Environmental Management System and the International Cyanide Code. ISO certification is renewed every five years. Cyanide Code audits and renewals are completed every three years.

The closure cost in 2011 was estimated to be a total of US$199.49 million. This includes US$111.0 million for concurrent reclamation, US$56.4 million for final closure and US$32.1 million for post closure costs. The current closure plan estimates that treatment of ARD water will continue for approximately 34 years.

The primary social program at Lagunas Norte is employment programs that are designed to train unemployed workers. The focus is on local communities and suppliers. The Lagunas Norte social and community programs are participative. They encourage representatives from the local communities to take water samples in conjunction with the company employees and to submit them to laboratories of their own choice.

Voluntary reclamation of Callacuyan, a historic coal mine located in the area of the Project, has been enthusiastically received by the local community and regulators. As a result of the reclamation process, the camp was reclaimed, the loadout facility was removed, and acidic water is being treated using passive wetlands treatment.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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CAPITAL AND OPERATING COST ESTIMATES

Remaining capital costs at Lagunas Norte are primarily sustaining capital, which includes mine equipment replacement and leach pad expansion. Total remaining capital costs are a nominal $704 million (Table 1-3). Mine pre-stripping costs were considered an operating cost.

TABLE 1-3 CAPITAL COSTS SUMMARY

Barrick Gold Corporation – Lagunas Norte Mine

 

Department

   Sustaining
Capital

US$
Millions
 

Engineered Facilities

     235   

Sustaining Capital

     298   

Other

     5   

Subtotal

     538   

Contingency

     27   

Closure

     139   
  

 

 

 

Total Capital Expenditures

     704   

Notes:

 

1. Numbers may not add due to rounding.

Mine operating costs are $2.69 per tonne of material mined or $4.80 per tonne of ore mined. Process operating costs are dependent on ore type and processing method and include the heap leach, crushing and conveying, stacking, Merrill Crowe process plant, power, and consumables. Process operating costs for the LOM are $2.84 per tonne ore processed. General and Administrative (G&A) costs average $1.21 per tonne ore processed over the LOM. The total project operating cost is $8.85 per tonne processed. The total operating cash cost per ounce of gold production over the LOM is $474/oz. Total production cost per ounce, including capital, over the LOM is $656/oz.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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2 INTRODUCTION

Roscoe Postle Associates Inc. (RPA) was retained by Barrick Gold Corporation (Barrick) to prepare an independent Technical Report on the Lagunas Norte Gold Mine (the Project) in Peru. The purpose of this report is to support public disclosure of Mineral Resource and Mineral Reserve estimates at the Project as of December 31, 2011. This Technical Report conforms to National Instrument 43-101 Standards of Disclosure for Mineral Projects. RPA visited the property from November 28 to 30, 2011.

Barrick is a Canadian publicly traded mining company with a large portfolio of operating mines and projects across five continents. The Lagunas Norte Mine is located in the District of Quiruvilca in the Province of Santiago de Chuco and the Department of La Libertad, in north-central Peru. The mine site is approximately 90 km east of the coastal city of Trujillo.

Lagunas Norte is a large open pit, heap leach gold and silver mine in the high Andes Cordillera. Operations include open pit mining of gold-silver ore, crushing, and extraction of precious metals using heap leaching and Merrill-Crowe recovery. Since Lagunas Norte started production in March 2005, the mine has recovered 6.5 million ounces of gold and over five million ounces of silver from approximately 137 million tonnes of ore averaging 1.81 g/t Au and 3.6 g/t Ag.

Mining an average of approximately 23 million tonnes per year of ore and an average of approximately 20 million tonnes of waste per year is scheduled for Lagunas Norte over the next eight years. Leaching will continue for two years after mining ceases, with mine operations concluding in 2021. Most of the ore is crushed prior to placement on the heap leach facility.

The Project is owned and operated by Minera Barrick Misquichilca S.A. (MBM), a wholly-owned Peruvian subsidiary of Barrick. The mine is part of the Alto Chicama property. A 2.51% net smelter royalty is paid to Peruvian state company Activos Mineros S.A.C. (Activos Mineros), formerly Centromin Peru S.A. (Centromin). In December 2006, Centromin transferred all of its rights and obligations with respect to the mine to Activos Mineros S.A.C. (Activos Mineros), a state mining company.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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SOURCES OF INFORMATION

RPA Principal Geological Engineer Luke Evans, M.Sc., P.Eng., RPA Senior Mining Engineer Glen Ehasoo, P.Eng., and RPA Principal Metallurgist, Kathleen Ann Altman, Ph.D., P.E., visited the mine from November 28 to 30, 2011 and held meetings at the Barrick office in Lima on December 1 and 2, 2011. Discussions were held with the following Barrick and MBM personnel:

 

   

Sergio Cruz – General Manager, Operations

 

   

Esteban Garcia – Superintendent Regional Engineering and Mine Planning

 

   

Jose Nizama – Superintendent of Technical Services

 

   

Wilmer Cancho – Chief Engineer

 

   

Michel Sanchez – Chief Geologist

 

   

Paul Gómez – Senior Resource Geologist

 

   

Benjamin Sanfurgo – Superintendent of Resource and Reserve Modelling

 

   

Mario Rojas – Senior Ore Control Geologist

 

   

Angela Zapana – Ore Control Geologist

 

   

Melissa Vasquez – Modelling Geologist

 

   

Cicino Sernaque – Modelling Geologist

 

   

Christel Beceria – AcQuire Database Manager

 

   

Carlos Aguirre – Senior Geotechnical Engineer

 

   

Jose Luis Vidarte -Chief Process

 

   

Wesley Ubillus – Superintendent, Metallurgy

 

   

Pedro Bobadilla – Senior Supervisor, Process

 

   

Carlos Venegas – Superintendent, Environment

 

   

Mark Ernesto Prieto – Junior Supervisor, Environment

 

   

Paolo Muschi – Operations Assistant

 

   

Richard Collanque – Chief Chemist Laboratory

 

   

Claudia Valdivia – Flexicadastre Administrator

 

   

Carlos Diaz – Senior Supervisor Mining Properties

The Lagunas Norte Mine has been the subject of resource/reserve technical audits as follows:

 

   

March 2009, NI 43-101 Technical Report, Barrick Gold Corporation.

 

   

May 2008, Reserve Audit, Scott Wilson Roscoe Postle Associates Inc. (Scott Wilson RPA, a predecessor company to RPA).

 

   

April 2006, Reserve Procedure Audit, RPA.

 

   

February 2005, Reserve Procedure Audit, RPA.

 

   

March, 2003, NI 43-101 Technical Report, Barrick Gold Corporation.

Mr. Evans is responsible for the overall preparation of this report. Mr. Evans reviewed the geology, sampling, assaying, and resource estimate work and is responsible for Sections 1 to 12 and 14. Mr. Ehasoo reviewed the mining, reserve estimate, and economics and is responsible for Sections 15, 16, 19, 21, and 22. Dr. Altman reviewed the metallurgical, environmental, and permitting aspects and is responsible for Sections 13, 17, and 20. RPA would like to acknowledge the excellent cooperation in the transmittal of data by Barrick and MBM personnel.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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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.

TABLE 2-1 LIST OF ABREVIATIONS

Barrick Gold Corporation – Lagunas Norte Mine

 

µm    micron    km2    square kilometre
°C    degree Celsius    kPa    kilopascal
°F    degree Fahrenheit    kVA    kilovolt-amperes
µg    microgram    kW    kilowatt
A    ampere    kWh    kilowatt-hour
a    annum    L    litre
bbl    barrels    L/s    litres per second
Btu    British thermal units    m    metre
C$    Canadian dollars    M    mega (million)
cal    calorie    m2    square metre
cfm    cubic feet per minute    m3    cubic metre
cm    centimetre    min    minute
cm2    square centimetre    MASL    metres above sea level
d    day    mm    millimetre
dia.    diameter    mph    miles per hour
dmt    dry metric tonne    MVA    megavolt-amperes
dwt    dead-weight ton    MW    megawatt
ft    foot    MWh    megawatt-hour
ft/s    foot per second    m3/h    cubic metres per hour
ft2    square foot    opt, oz/st    ounce per short ton
ft3    cubic foot    oz    Troy ounce (31.1035g)
g    gram    PEN    Nuevo Sol
G    giga (billion)    ppm    part per million
Gal    Imperial gallon    psia    pound per square inch absolute
g/L    gram per litre    psig    pound per square inch gauge
g/t    gram per tonne    RL    relative elevation
gpm    Imperial gallons per minute    s    second
gr/ft3    grain per cubic foot    st    short ton
gr/m3    grain per cubic metre    stpa    short ton per year
hr    hour    stpd    short ton per day
ha    hectare    t    metric tonne
hp    horsepower    tpa    metric tonne per year
in    inch    tpd    metric tonne per day
in2    square inch    US$    United States dollar
J    joule    USg    United States gallon
k    kilo (thousand)    USgpm    US gallon per minute
kcal    kilocalorie    V    volt
kg    kilogram    W    watt
km    kilometre    wmt    wet metric tonne
km/h    kilometre per hour    yd3    cubic yard
      yr    year

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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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). 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. RPA has not researched property title or mineral rights for the Lagunas Norte property 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 Lagunas Norte.

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.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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4 PROPERTY DESCRIPTION AND LOCATION

LOCATION

The Lagunas Norte Mine site is located on the 185 km2 Alto Chicama property in the district of Quiruvilca in the Province of Santiago de Chuco, La Libertad Region, north-central Peru, approximately 90 km east of the coastal city of Trujillo and 175 km north of Barrick’s Pierina Mine (Figure 4-1). The property is located at 7º50’ S latitude and 78º15’ W longitude and lies on the western flank of the Peruvian Andes at an elevation of 4,000 MASL to 4,260 MASL.

LAND TENURE

The Alto Chicama mining property encompasses four mining concessions (Acumulación Alto Chicama, Los Angeles, Las Lagunas 15 and 16) totalling 19,181.3 ha (Table 4-1). In December 2002, MBM acquired the mining concession “Acumulación Alto Chicama” encompassing 18,002.3 ha from Centromin, the Peruvian state mining company, pursuant to an international bid process. The Lagunas Norte Mine is located on this mining concession. Production at Lagunas Norte is subject to 2.51% Net Smelter Return (NSR) royalty, payable semi-annually to Activos Mineros S.A.C., formerly Centromin, on the extraction of gold and all other minerals. Under the terms of agreement with Centromin, MBM paid Centromin an advance contractual royalty of $2 million. In December 2006, Centromin transferred all of its rights and obligations with respect to the mine to Activos Mineros, a state mining company.

The “Los Angeles” mining concession was acquired by MBM from Pan American Silver Peru S.A.C. through a Transference Contract dated June 28, 2004. The “Las Lagunas 15” and “Las Lagunas 16” mining concessions were granted by the Peruvian government on January 30, 2001. The Acumulación Alto Chicama mining concession has no expiry date since it is in exploitation phase. In order to maintain its validity, however, a Validity Fee, of $3.00/ha, must be paid no later than June 30 each year. Non-fulfillment for two consecutive years results in expiration of a mining concession. The Validity Fee payments for the Alto Chicama property were up to date as of December 2011.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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TABLE 4-1 MINING CONCESSIONS

Barrick Gold Corporation – Lagunas Norte Mine

 

Code

  

Mining Concession Name

   Area (ha)      Effective
Area (ha)
     Royalty
(%)
     Title Date  

010000204L

  

Acumulación Alto Chicama

     18,002.3         18,002.3         2.51         04/10/2004   

10204000

  

Las Lagunas 15

     800         534.8         0         30/01/2011   

10204100

  

Las Lagunas 16

     900         572.1         0         30/01/2011   

15005489X01

  

Los Angeles

     72         72         0         01/10/1969   
     

 

 

    

 

 

       

Totals

        19,774.3         19,181.3         

On December 29, 2004, Barrick entered into a Tax Stability Agreement with the Peruvian government. The Tax Stability Agreement provides increased certainty with respect to tax, administrative, and exchange stability to MBM, regarding the four mining concessions, for 15 years. The 15 year period commenced as of January 1, 2006 and ends on December 31, 2020.

The mining concessions are shown in Figure 4-2. Note that the Las Lagunas 15 and Las Lagunas 16 mining concessions overlap with Acumulación Alto Chicama, so the effective area for the four combined mining concessions is 19,181.3 ha. MBM controls surface rights totalling 3,779.6 ha in the mine area and the mine area has a fenced perimeter (Figure 4-2). Surface rights are sufficient to mine the current reserves and all reserves lie within MBM controlled lands.

The Acumulación Alto Chicama mining concession, subject to a 2.51% NSR payable semi-annually to Activos Mineros S.A.C., formerly Centromin,, is shown in Figure 4-3.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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5 ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY

ACCESSIBILITY

The Lagunas Norte Mine is accessed from Trujillo, the capital of the La Libertad Region, by driving on a public paved road heading east-northeast from Trujillo to Otuzco for approximately 75 km. At Otuzco, the road splits and a rough, all season public gravel road heads east towards the mine site and beyond. It is approximately 70 km to the mine site turnoff along the gravel road, which currently has sections being upgraded and paved. Approximately 7.0 km before the mine site turnoff is the mine airfield, which has a compacted gravel runway approximately 1.6 km long at 4,180 MASL. From the mine site turnoff it is 1.0 km to the main gate at 4,155 MASL. From the main gate it is approximately 3.0 km to the Lagunas Norte open pit and 6.0 km to the camp facilities at 3,800 MASL. The total driving distance from Trujillo is approximately 150 km one way, and it takes four to five hours for a light vehicle to access the mine site in typical driving conditions. Trujillo is serviced by daily commercial flights from Lima.

Most consumables and people working at the mine are transported along this route.

CLIMATE

The property is considered to have mountain climate. The air temperature ranges from -4°C to +16°C, with an average daily temperature of 7°C. The recorded seasonal air temperature fluctuations are small. The prevailing wind direction is from the north-northeast to east-northeast. The average wind velocity at Lagunas Norte is 17 km/hr, with a maximum recorded of 51 km/hr. Precipitation at Lagunas Norte occurs primarily in the form of rainfall. Dry, wet, and transitional periods can be distinguished during the year. The dry period is observed from June through August, with the average monthly rainfall less than 40 mm. The driest month is July, with the average monthly rainfall of 20 mm. The wet period is observed from October through April, with the average monthly rainfall greater than 100 mm. The wettest month is March, with the average monthly rainfall of 230 mm. The months of May and September may be classified as transitional, with the average monthly rainfall amounts of 89 mm and 79 mm, respectively. The maximum daily rain on record for the period from 1965 through 2002 is 61 mm. Strong electric storms are frequent during the wet period.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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LOCAL RESOURCES

La Libertad Region has a long history of mining activity, and mining suppliers and contractors are locally available. Both experienced and general labour is readily available from the La Sarre area, a municipality of 7,728 inhabitants (2001 census). Most of the workforce lives in the nearby towns, Trujillo and Lima.

Lagunas Norte has generally had success in hiring and retaining experienced staff and personnel with good mining expertise, despite tight current labour markets experienced industry-wide. Lagunas Norte makes extensive use of contract and temporary employees as well as local community day labourers. Processing and mine facilities operate on a 24-hour, seven days per week schedule, with four crews rotating on a 12-hour, two shift basis. Most of the maintenance personnel work on the day shift, with a small breakdown crew on the night shift to provide 24-hour coverage. Operating and technical personnel work on a rotating eight-days-on and six-days-off schedule with staggered crew changes to minimize transportation costs. Middle and upper management operate on a five-days-on and two-days-off schedule.

The Project is supported by the local communities. Barrick has a progressive social policy framework, stressing communication and respect, which is inclusive of the local population as well as employees. Environmental, health and safety, and social responsibilities are the cornerstones of the program.

INFRASTRUCTURE

Lagunas Norte infrastructure and services have been designed to support an operation of 63,000 tpd of ore to a heap leach facility (HLF) and a nominal 140,000 tpd of total material mined. Site infrastructure is discussed in more detail in Section 18. Due to the remote location, the property is self-sufficient with regard to the infrastructure needed to support the operation.

 

 

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Mine camp facilities are located approximately three kilometres east and downslope of the Lagunas Norte open pit operations at approximately 3,800 MASL. Permanent accommodations are available for all Lagunas Norte employees and visitors. Contractor accommodations are also provided near the Lagunas Norte accommodations. Site accommodations are sufficient for the Lagunas Norte workforce, contractors, and consultants. RPA was impressed with the camp food, recreation, and accommodation facilities.

Site infrastructure includes the open pit, HLF, crushing facilities, Merrill Crowe recovery plant, on-site facilities (safety/security/first aid/emergency response building, assay laboratory, plant guard house, dining facilities, and offices); related mine services facilities (truckshop, truck wash facility, warehouse, fuel storage and distribution facilities, reagent storage and distribution facilities), and other facilities to support operations.

The water for process and mining consumptive needs is delivered rain captured on two small lakes. There is plenty of water available for consumptive use now and for the future. At Lagunas Norte, a water management group is in place to carry out all dewatering including pumping, distribution, delivery, and disposal. Lagunas Norte has a positive water balance.

Electricity is provided by a private-owned generation company and delivered to Lagunas Norte through a high voltage power line connected to the National Grid in Trujillo.

PHYSIOGRAPHY

The mine area is dominated by rolling hills and rugged mountains with steep-sided valleys. The area is vegetated with natural grasses and small shrubs. Rock outcrops and shallow soils predominate in the valleys. The Project is located in a region of high seismic activity.

 

 

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6 HISTORY

MBM executed an Option Contract to acquire the Acumulación Alto Chicama mining concession on February 28, 2001 following an auction held by Centromin. Centromin and MBM signed the Public Deed of the Mining Option Contract on March 28, 2001. The option had a one-year term extendable three times until February 28, 2005, and included minimum exploration investment commitments.

MBM commenced a field program at Alto Chicama in March 2001, which included geologic mapping, geochemical sampling, and ground geophysics. This work resulted in the identification of targets for drill testing. Drilling commenced in mid-2001 and the initial program identified the Las Lagunas Norte area as justifying detailed follow-up. Subsequent drilling was concentrated in the Las Lagunas Norte area.

Pursuant to the mining option contract, MBM exercised its purchase option on December 2, 2002, over the Acumulación Alto Chicama mining concession. The transfer agreement and its Public Deed were executed on December 12, 2002, and MBM’s title to the concessions was registered before the Trujillo Public Registry on March 21, 2003.

On April 2, 2004, the Alto Chicama environmental impact assessment (EIA) received regulatory approval by means of Directorate Resolution No. 118-2004-MEM/AAM.

On April 12, 2004, MBM was granted the Plant Construction Authorization by means of Directorate Decree No. 174-2004-MEM-DGM/PDM, which authorized MBM to construct and install the Alto Chicama beneficiation plant and related facilities.

The construction started immediately in 2004. A total amount of US$321 million was invested and during March 2005 the first ore tonne was placed on the leach pad. First pour was realized in June 2005, ahead of schedule and within budget. As of the end of 2011, the mine has recovered 6.5 million ounces of gold and 5.1 million ounces of silver from approximately 137 million tonnes of ore averaging 1.81 g/t Au and 3.6 g/t Ag.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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7 GEOLOGICAL SETTING AND MINERALIZATION

REGIONAL GEOLOGY

The regional geology is dominated by a thick sequence of Mesozoic marine clastic and carbonate sedimentary rocks, which are bounded to the west by the Mesozoic to Early Tertiary Coastal Batholith and to the east by the Precambrian metamorphic rocks of the Marañón Complex. The Mesozoic sequence has been affected by at least one and possibly two stages of deformation during the Andean Orogeny. The volcanic rocks of the Calipuy Group unconformably overlie the Mesozoic rocks. There are four recognized stages of volcanism in the area:

 

  1. Island arc volcanism in the Lower Jurassic

 

  2. Island arc volcanism in the Lower Cretaceous

 

  3. Plutonism in the Upper Cretaceous and Lower Tertiary

 

  4. Continental volcanism and associated intrusions in the Tertiary

The Jurassic island arc developed 100 km west of the current coastline of Peru. During this time, a marine basin developed between the magmatic arc and the emergent cratonic zone to the east. The Chicama Formation, which consists of shales and bituminous shales and arenites, was deposited in the basin during this period. This formation hosts coal deposits that have been exploited since the early 1900s.

Island arc volcanism continued during the Lower Cretaceous with migration of the arc to the east. Active volcanism resulted in deposition of a thick sequence of volcanic and volcaniclastic rocks. In the Alto Chicama region, the Lower Cretaceous is characterized by deposition of clastic sediments of the Chimú (quartz sandstones intercalated with mudstones) and Carhuaz formations (dirty sandstones interbedded with shales).

The regional geology is shown in Figure 7-1. The Lagunas Norte Mine is on the Alto Chicama property, which is located approximately mid-way between the Pierina gold mine to the south and Yanacocha gold mine to the north.

 

 

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LOCAL GEOLOGY

The local geology consists of sedimentary rocks from the Jurassic to Cretaceous age overlain by younger volcanic rocks. The local stratigraphy and structure is described below and is mostly excerpted from MBM (2009).

STRATIGRAPHY

JURASSIC

Chicama Formation

The Chicama Formation comprises thinly interbedded mudstone, bituminous mudstone, siltstone, and minor sandstone with local intercalations of clay and reworked tuffaceous material. These terrigenous sediments were deposited in a shallow, inland-sea basin flanked to the east by the emerged continent and to the west by a volcanic arc. The sediments eroded from the continental side are mainly quartz sands, while the sediments derived from the volcanic arc are typically clay-rich and tuffaceous material. The shallow, restricted nature of this basin resulted in the development of a reducing environment, which favoured the formation of organic deposits. These organic deposits are present as bituminous and anthracitic material or as coal beds.

CRETACEOUS

Lower Cretaceous

The Lower Cretaceous is characterized by clastic sedimentation in a highly oxygenated open sea environment. To the east, the continent was affected by continuous uplift concurrent with basin subsidence. These conditions resulted in a significant accumulation of detrital sediments. Also, during this period, the island arc to the west of the sedimentary basin was subjected to intense erosion due to a reduction in magmatic activity. This resulted in the formation of a highly oxygenated, open sea environment as opposed to the reducing conditions created by the inland sea during the Jurassic.

Chimú Formation

The Chimú Formation rocks are almost exclusively composed of very clean quartz sand. This formation is characterized by a second order, fining upwards sequence beginning with deposition of coarse, angular, thickly bedded sands followed by upwardly thinning beds of finer sand terminating in clay size material. These rocks have been regionally metamorphosed into highly resistant grey to white quartzite. Coal and mudstone sequences were deposited in associated deltaic environments. The Chimú Formation is the main host rock at the Lagunas Norte deposit.

 

 

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Santa Carhuaz Formation

The Santa Carhuaz Formation overlies the Chimú and records sediment deposition during a relatively passive tectonic period. The Carhuaz Formation consists of grey, dirty sandstone with a red and purple hue interbedded with grey mudstone. White quartzite beds are interbedded with sandstone and mudstone in the upper portion of this sequence.

Farrat Formation

The Farrat Formation consists of thick, white sandstone beds that commonly display planar cross stratification and locally develop pebble conglomerates. The Farrat Formation is similar to the Chimú Formation, however, the Farrat Formation lacks the coal beds and grey colour observed in the latter.

During the Upper Cretaceous and part of the Lower Tertiary, extensional tectonism facilitated the emplacement of plutons along the length of the coast, culminating in the emplacement of the Coastal Batholith west of the Project area.

TERTIARY (MIOCENE)

Calipuy Group

During the Tertiary, the magmatic arc migrated further east initiating the onset of continental volcanism and the development of small volcanic arcs oriented in a south-southwest/north-northeast direction. This event resulted in the present day alignment of the volcanic structures of the Calipuy in the area southwest of Huamachuco, east of the deposit area. The Calipuy Group rocks are calc-alkaline in composition and are predominately andesite, with lesser dacite and rhyolite observed. The volcanic structures are predominantly domes or dome complexes.

STRUCTURE

The Mesozoic sequence has been affected by at least one and probably two stages of Early Tertiary deformation during the Andean orogeny (Lewis, 2002). The earlier stage is inferred from a regional angular unconformity between the base of the Calipuy Group (Eocene epoch) and the folded Mesozoic rocks. This deformation event generated

 

 

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northeasterly verging folds and southwest dipping thrust faults (Lewis, 2002). The second stage is inferred from an unconformity within the Calipuy Group at 44 to 40 Ma (Noble et al., 1990). The local geology and stratigraphy is shown in Figure 7-2.

PROPERTY GEOLOGY

A property geology map and generalized stratigraphic column are provided in Figures 7-3 and 7-4. The unit thicknesses in the stratigraphic column are shown for clarity but are not representative of actual thickness.

The round Shulcahuanca Dome is a prominent and sacred topographic feature that is located immediately west of the Lagunas Norte pit. This feature has been preserved for the local communities and restricts the pit wall in this area (Figure 7-5).

Figure 7-6 presents a northwest looking cross-section through the deposit. The deposit area lies within the Chimú Formation, exposed along the northeast limb of an anticlinal fan cored by Chicama Formation rocks. The deposit is locally faulted by relatively steeply dipping structures. The mineralization is primarily controlled by stratigraphy and lithologic contacts; although both high and low angle structures acted as conduits for mineralizing fluids and are important mineralization controls on a local scale.

 

 

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FIGURE 7-5 SHULCAHUANCA DOME

 

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MINERALIZATION

The Lagunas Norte mineralization occurs in the southeast portion of the Alto Chicama property. The mineralization is finely disseminated and is hosted mostly by siliclastic sedimentary strata.

The mineralization within the present pit extends for approximately two kilometres in the north-northwest direction by approximately two kilometres in the east-northeast direction and for more than 200 m vertically.

MBM has defined an alteration and mineralization sequence involving up to four distinct stages, including the following;

Stage 1:        an early period of massive silicification

Stage 2:        intense acid leaching accompanied by finely-disseminated sulphide

Stage 3:        deposition of druzy quartz in vugs and open fractures

Stage 4:        a second stage of sulphide mineralization with coarse pyrite, enargite, and sulphosalts

Mineralization is the result of multiple volcanic and hydrothermal events. It is hosted in both the Tertiary volcanics of the Calipuy Group and the underlying Cretaceous sedimentary rocks of the Chimú Formation. The alteration associated with the mineralization is typical of a high-sulphidation epithermal environment, characterized by silica (SiO2), surrounded by alunite [KAl3(SO4)2 (OH)6], dickite [Al2Si 2O5(OH)4] and pyrophyllite [Al2Si4 O10(OH)2]. Trace elements typically associated with these deposits include copper, arsenic, barium, bismuth, zinc, lead, and variable amounts of mercury (Silberman and Berger, 1985). The deposit has very low concentrations of carbonate minerals or other potentially acid neutralizing minerals.

There are both stratigraphic and structural controls on the mineralization. Mineralizing fluids ascended along the main fault systems and migrated laterally along stratigraphic contacts in both the sedimentary and volcanic rocks. At least two stages of sulphide mineralization are recognized. The sulphide assemblage comprises mainly pyrite (FeS2) with lesser amounts of enargite (Cu3AsS4) and occurs as replacement structures, veins, and disseminations in volcanic breccias and highly fractured and locally brecciated

 

 

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Chimú sandstones. Most of the mineralization (75%) occurs as oxide material, with approximately 25% occurring as sulphide material. Supergene oxidation has altered a large part of the sulphide assemblage to iron oxides and, to a lesser extent, sulphates. The extent of this oxidation ranges from a few metres to more than 300 m below surface. Approximately 90% of the mineralization is contained within the Chimú sediments and the balance is hosted in the Calipuy volcanic rocks.

The gold grade times thickness contours clearly show the Lagunas Norte deposit is approximately two kilometres by one kilometre wide (Figure 7-7).

DEPOSIT MINERALOGY

Sulphide occurrences are dominantly pyrite and enargite but also include traces of arsenopyrite, chalcopyrite, and covellite, with oxidation and alteration states through to iron oxides, iron sulphates, and elemental copper.

Gold occurs primarily as fine discrete particles in open silicified vugs, fine particles or disseminated gold within iron oxides, in gold-silver electrum, and as fine free gold along fracture surfaces. Silver mineralization is noted as occurring primarily as an electrum with gold, as finely disseminated native silver, or as a solid solution within remnant sulphides. Copper mineralization is present primarily as enargite, with lesser copper associations as chalcopyrite, or oxidized species including native copper.

Carbonaceous mudstones are composed chiefly of pyrophyllite with lesser amounts of quartz and minor amounts of nacrite clay, aluminum oxide and phosphate, and zirconium-bearing silicates. Coal seams typically have the appearance of a moderate-grade coal, with significant preg-robbing potential. Samples of the least sulphidic coal seams (<5% sulphur) with highest grade (>40% total carbonaceous material (TCM)) returned an average 24.9% ash content which far exceeds the 5% average of local informal operations and this represents a potential problem for coal burning furnaces.

 

 

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COAL AND CARBONACEOUS MATERIAL

Uncommon to most gold deposits, the Lagunas Norte deposit overprints both Tertiary volcanic rocks and basement Cretaceous sedimentary rocks, including variably carbonaceous, fine grained sedimentary rocks. Footwall rocks to the Lagunas Norte deposit of both the Chicama and Carhuaz formations are dominated by black carbonaceous mudstones but host no significant amounts of mineralization known to date. As some of the Tertiary volcanic rocks ripped through underlying carbonaceous sedimentary rocks of the Chicama Formation, some of these also carried carbonaceous material in their matrix (finely ground), or as coarser individually distinguishable fragments.

In the geological interpretations on sections and level plans, fine grained sediments, such as mudstones, siltstones, and interbedded sandstones, are grouped together. The Chimú Formation sediments are hence divided up in the geological model as sandstone, non-carbonaceous fine grained units, carbonaceous fine grained units, and coal. Even the narrowest carbonaceous intervals are described in the drill logs to aid the interpretation work.

The carbonaceous content has been described both qualitatively in geologic descriptions and quantitatively in terms of TCM in selected LECO analysis of carbonaceous and potentially carbonaceous rocks.

TCM contents range from over 67% for anthracitic coal down to 0% for non-carbonaceous lithology such as sandstone, which is the dominant lithology at Alto Chicama.

There is a good correlation between rocks described as carbonaceous by Alto Chicama geologists and measured TCM values. Many checks have been done to confirm this and a detailed re-logging campaign was carried out so as not to miss significant carbonaceous units.

Although carbonaceous materials do occur adjacent to mineralized rocks, there is little significant gold within the carbonaceous rocks themselves. A few notable exceptions exist to this rule, but generally plots of TCM versus gold content clearly show inverse relationships.

 

 

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It appears that the same fluids responsible for depositing the gold mineralization probably destroyed or leached out carbonaceous material from fine grained sedimentary rocks as part of the alteration process. Therefore, the best mineralized zones have the least amount of associated carbonaceous materials. Conversely, at depth where mineralization becomes more structurally controlled, there is an increase in the abundance of carbonaceous units.

MATERIAL CLASSIFICATION

The results of metallurgical testwork indicate that the metal recovery of the materials at Alto Chicama decreases with increased carbonaceous material content and/or increased content of sulphur or copper. The aforementioned materials are therefore referred to as “contaminants”.

CARBONACEOUS MATERIAL

Carbonaceous material, as defined by TCM data, has been collected in many campaigns at Alto Chicama in order to improve the geometallurgical model and has been demonstrated by metallurgists to have a strong preg-robbing effect on gold rich sodium-cyanide leaching. To evaluate this effect, sampling of carbonaceous lithologies for analysis of TCM, for recovery and for preg-robbing potential has been carried out to date on more than 4,400 samples covering potentially carbonaceous intervals within the pit.

Recovery is simply a measure of what percent of the gold is extracted by cyanide-leach from the original sample. Preg-robbing potential has been measured with several ”spike” tests consisting of adding a fixed amount of gold to a cyanide leach test and measuring how much gold remains in the solution. If the recoverable gold plus the fixed amount added remains in solution the sample is not considered to be preg-robbing. If on the other hand there is less gold than the fixed amount added plus the recoverable amount, the percent robbed is calculated by determining the amount that is missing as a fraction of the amount that should have remained in solution.

Based on analysis at Alto Chicama, it could be argued that up to 6% preg-robbing potential values based on “spike” tests are not significant as samples in the low preg-robbing range are almost as likely to return up to 6% more gold as they are of returning

 

 

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with 6% less gold. At 10% preg-robbing, the values become somewhat significant. Hence, samples are not considered to be “significantly” preg-robbing if they return values under 10% (MBM, 2009).

The effect of TCM on recovery is obvious when TCM analysis is plotted against recovery as shown on Figure 7-8.

FIGURE 7-8 TCM VERSUS GOLD RECOVERY

 

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From MBM (2009)

The average recovery drops sharply somewhere after 0.1% TCM, stabilizing around a 30% recovery above approximately 1.0% TCM. Ongoing testwork by the mine metallurgical group suggests that no significant preg-robbing occurs for materials with less than 0.2% TCM.

COPPER AND SULPHIDES

Copper and sulphides are presented as contaminants as a result of their affinity for cyanide absorption and acid rock drainage (ARD) potential. Assays for copper and Leco S% are used to determine the classification of material contaminated with these minerals.

 

 

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WASTE

With respect to the classification of waste, LECO S% limits have been set to segregate potentially acid generating (PAG) waste from non-acid generating (NAG) waste to ensure that all PAG material is deposited in the waste rock facility (WRF), whose drainage is collected in the collection pond and treated in the adsorption-desorption and refining (ADR) plant.

Coal was originally planned to be stockpiled separately, with a constantly rotating inventory, reflecting the assumed use of this product in some possible economic or social manner. However, high carbonaceous materials with acceptable amounts of sulphur and ash content have not been encountered in significant mining widths to serve this propose.

MATERIAL CLASSIFICATION SYSTEM

Materials with acceptable levels of contaminants are crushed and processed in the Clean Heap Leach Facility (CHLF), while those with elevated contaminant levels are processed as run-of-mine (ROM) in a Single Pass Heap Leach Facility (SPHLF) where the effect of the contaminants on the recovery of metal can be minimized.

The specific metallurgical classification system for the various ore and waste material types is shown in Table 7-1 and the complex flag system used to identify different material types in the pit are shown in Figure 7-9.

 

 

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FIGURE 7-9 IN-PIT MATERIAL TYPE FLAG SYSTEM

 

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8 DEPOSIT TYPES

Lagunas Norte differs from many other large high-sulphidation epithermal gold deposits of the Andes in that a majority of the known resource is contained within Cretaceous siliciclastic sedimentary rocks, and a relatively small portion is within the Tertiary volcanic sequence that is the primary host elsewhere (e.g., Yanacocha, Pierina). The main host rock sequence at Lagunas Norte consists of quartz sandstones and subordinate interlayered mudstone, siltstone, and carbon-rich siltstone, correlated with the Lower Cretaceous Chimú Formation (Lewis, 2002).

Another significant characteristic of the Lagunas Norte deposit is the variable carbonaceous content found within the siliclastic sedimentary strata.

 

 

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9 EXPLORATION

Field exploration on the Alto Chicama property by MBM commenced in March 2001. Following detailed mapping, geophysical and geochemical surveys, PIMA analysis, and channel sampling, drilling commenced in June 2001. By mid-September 2002, 298 holes had been drilled and twelve drill rigs were active. By the end of December 2002, 452 holes had been completed for a total of 113,338 m of drilling. Most of the Lagunas Norte area was diamond drilled on a grid of approximately 50 m by 100 m (or 72 m average spacing). In 2002, environmental, metallurgical, and engineering studies, together with cost estimation and economic analysis, were started, and by January 31, 2003, the first reserve estimate for Lagunas Norte was completed.

Drilling has been concentrated principally in the Lagunas Norte area, in the southeast portion of the Alto Chicama property. First pass reconnaissance exploration was completed outside Lagunas Norte over the Alto Chicama land holdings in 2004. The principal exploration targets defined and drill tested by MBM were the Lagunas Sur and the Tres Cruces deposits, both located southwest of the current deposit (Figure 9-1).

In 2006, resource definition drilling commenced at the satellite deposits of Lagunas Sur and Tres Cruces. The infill drill program confirmed and upgraded the continuity of wide spaced mineralization for both prospects. Focus of the 2007 perimeter exploration projects was to expand both the mineralized strike extent and to infill the existing wider spaced intersections for confirmation of mineralization continuity.

The Lagunas Sur deposit has a small resource that is included with the current Lagunas Norte resource estimate.

EXPLORATION POTENTIAL

MBM has begun evaluating the economic potential of the primary sulphide mineralization located below the current resources and at Tres Cruces.

 

 

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10 DRILLING

The drill hole database has 937 diamond drill holes (DDH) totalling 176,837 m and 481 reverse circulation (RC) drill holes totalling 41,426 m (Table 10-1). Approximately 66% of the drill holes are DDH and the balance are RC. Overall, 1,418 drill holes totalling 218,263 m and comprising 166,655 samples were completed from 2001 to 2010 (Table 10-2).

TABLE 10-1 DDH AND RC DRILLING DETAILS

Barrick Gold Corporation – Lagunas Norte Mine

 

 

     DDH      DDH      DDH      RC      RC      RC  

Year

   Holes      Metres      Samples      Holes      Metres      Samples  

2001

     17         2715         2127         0         0         0   

2002

     438         109,074         80,459         21         1,847         1,500   

2003

     273         48,517         36,456         35         3,425         1,945   

2004

     43         5,864         4,809         4         142         138   

2005

     10         837         713         0         0         0   

2006

     72         3,145         1,997         16         1,701         1,691   

2007

     26         1,063         7         69         6,778         6,755   

2008

     28         1,435         0         309         23,748         21,946   

2009

     19         3,487         2,011         0         0         0   

2010

     11         701         320         27         3,785         3,781   

Totals

     937         176,837         128,899         481         41,426         37,756   

TABLE 10-2 DRILLING SUMMARY

Barrick Gold Corporation – Lagunas Norte Mine

 

Description

   DDH &  RC
Holes
     DDH &  RC
Metres
     DDH &  RC
Samples
 

Grand Total

     1,418         218,263         166,655   

Approximately half of the metreage drilled up to 2010 was done in 2002 and it was almost entirely DDHs (Figure 10-1). Since 2007, there has been much more RC drilling relative to diamond drilling after the discovery that the gold grades from core samples were biased low relative to production and to RC samples.

 

 

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FIGURE 10-1 DDH AND RC DRILLING BY YEAR

 

LOGO

From MBM (2011d)

Drill hole collars have been surveyed and downhole surveys have been completed with a number of survey instruments, including mostly Sperry Sun and some Maxibor II up to approximately 2008, GyroSmart and MultiSmart in 2009, DeviFlex in 2010, and a Reflex gyroscopic instrument in 2011. Most of the DDH have HQ size core and a number of holes were completed with NQ diameter rods to facilitate hole completion. Average core recovery is in excess of 95%.

Both core and RC holes are logged for lithology, stratigraphy, basic structural data, and sample recovery. The degree of alteration (argillization, silicification, carbon content, etc.) and the content of various elements, like pyrite and carbonaceous material, are also recorded. The core drilling is interpreted for more detailed structural data and to measure faults and bedding angles as well as rock mechanic properties (RMR) and core recoveries whenever possible. This data is entered directly into a geological database from handheld computers using standardized rock codes and descriptive information and is used for the interpretation of the geology, structure and alteration, as well as for the modelling of the mineralized zones.

The typical spacing for DDH holes is approximately 60 m, with lengths generally ranging from 200 m to 350 m. The RC drill holes are spaced approximately 50 m apart and the RC hole lengths vary from approximately 100 m to 200 m. The mineralized zones display variable dip, and holes are mostly drilled with steep dips, generally from -65° to -85°. Drill section lines are oriented at N60°E with holes drilled parallel to the sections. The drill holes are shown in Figure 10-2.

 

 

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LOGO

 

10-3


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11 SAMPLE PREPARATION, ANALYSES AND SECURITY

SAMPLING METHOD AND APPROACH

DIAMOND DRILL CORE

All core samples are tagged, bagged, sealed in sample bags and forwarded to the sample preparation laboratory. Core is placed in metal trays at the drill site and transported to the core room where it is sorted, photographed, and examined for rock quality designation (RQD). The sample lengths are selected to honour both gross geological units and obvious geological features. Core sample lengths varied from 0.12 m to 8.1 m, with an average sample length of 1.28 m. Sampled core is sawn into equal halves. One half is placed in a sample bag and the other half remains in the core box, which is stored in a secure location on site.

REVERSE CIRCULATION SAMPLES

All the chips from the drilling are collected and sent to the assay laboratory, except for a handful that are placed in a chip tray for geological logging. The samples are collected in either one or two metre intervals, and are identified with the hole number and the distance from the collar. The RC samples are approximately 35 kg to 40 kg. They are usually assayed for Au and for LECO (sulphur, sulphide, TCM, total carbon, total sulphur, CO3, and arsenic).

BLAST HOLE SAMPLES

Cuttings from each blast hole are sampled and analyzed for grade and contaminant constituents (sulphur or carbon). The Lagunas Norte technical department has carried out extensive testing and evaluation of blast hole sampling methods and techniques and has developed a set of documented procedures for the entire process. The current sampling method involves cutting a cross-sectional sample through the cone of cuttings with the collected 6 kg to 10 kg sample bagged and tagged and logged using a digital palm pilot data collection system. Blast hole sampling locations are surveyed using a GPS system.

 

 

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The data collected from the logging of the sample, the laboratory analysis, and the blast hole survey are incorporated directly into the acQuire grade control database system. The data are ultimately used to develop a grade control model for estimation of grades and material classification according to ore characteristics into digging polygons. Each polygon contains a single material type designation based on gold grade, carbonaceous content, and sulphur content.

The polygons are staked out on the mining bench and flagged according to material type. As excavation operations progress, the material that is loaded and hauled from each polygon and material type is tracked through the dispatch system through to its ultimate disposition location (crusher, stockpile, ROM leach pad, or waste dump).

RPA is of the opinion that the core, RC, and blast hole sampling procedures at Lagunas Norte are reasonable.

SAMPLE PREPARATION, ANALYSES AND SECURITY

SAMPLE PREPARATION

ALS Chemex installed a sample preparation laboratory at the Alto Chicama field camp in 2002 and performed all gold assays at its commercial laboratory in Lima. The sampling, sample preparation, and quality control procedures at the site have been reviewed and approved independently (Smee, 2002). Dr. Smee also conducted unannounced audits of the ALS Chemex laboratory in Lima in May 2002 and February 2003 and concluded that the facility is well-designed and well-operated. Dr. Smee recommended additions to the existing quality control procedures being used at the laboratory in May 2002 and all his recommendations were implemented (MBM, 2009).

Since the mine laboratory was commissioned in 2005, samples were prepared both on-site as well as off-site at commercial laboratories. The same sample preparation protocols were followed. ALS Chemex has been the primary laboratory except in mid- 2009 and 2010 when SGS became the primary laboratory and ALS Chemex was switched to the secondary laboratory.

Samples are first counted and checked against the sample submission sheet. The samples are dried and weighed and are then crushed to 70% passing two millimetres

 

 

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and split to approximately 800 g in a Jones riffle splitter. The entire 800 g split is pulverized to 85% passing 200 mesh in an LM-2 pulverizer. A 250 g to 300 g split of the pulverized pulp is shipped to the laboratory analysis. All remaining crusher rejects and pulverized pulps are retained at site and stored. The pulverizer is cleaned with barren quartz and coarse and fine sieve tests are carried out on a regular basis.

ASSAYING

The exploration samples are sent to a commercial laboratory and the fire assay gold determinations use 50 g aliquots with atomic absorption spectrometer (AAS) finish. For results greater than 5 g/t Au, a second fire assay using a gravimetric finish is performed. The exploration samples are analyzed for gold, silver, copper, TCM, sulphide sulphur (S2), arsenic, and mercury.

The blast hole samples are analyzed at the mine laboratory using a 30 g aliquot with an AAS finish. Results greater than 5 g/t Au are rerun using a gravimetric finish. A one gram sample is dissolved in two acids and AAS is used for silver and copper. An Eltra CS-2000 generates the sulphur and carbon results automatically. All production blast holes drilled in zones modelled as ore are sampled for gold, silver, and copper as well as for sulphur and carbon. Samples with greater than 0.1% sulphur are reanalyzed for sulphide sulphur and samples with greater than 0.05% carbon are reanalyzed for TCM. In material that is clearly waste, only one in four drill holes are assayed for gold and total sulphur. Holes that may contain ore or are near ore are sampled as if they were ore.

SAMPLE SECURITY

The core is logged and cut by MBM personnel within the secure Lagunas Norte mine site complex. Drill core is moved from the drill rig to the core shack by MBM personnel. Geological data recorded on the handheld computers is reviewed, field checked if necessary, and then uploaded to the main server at the end of every shift. Samples are delivered by MBM personnel to the sample preparation on-site or off-site facilities where the laboratory assumes sample custody.

MBM has tight database security protocols for the acQuire exploration and blast hole databases that control the level of access to authorized users. The acQuire database is backed up on a regular basis. The GVMapper logging software has full security levels controlled by the Database Administrator.

 

 

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QUALITY ASSURANCE AND QUALITY CONTROL

MBM has very good quality control (QC) and quality assurance (QA) procedures that include the regular insertion of in-house standards, blanks, field duplicates, reject duplicates, and pulp replicates. In addition, pulps are sent to external laboratories on a regular basis. MBM has had QA/QC procedures in place since drilling commenced in 2001. In mid-2002, following a full audit of the Alto Chicama Project’s sampling, analytical, and reporting procedures, Dr. Barry Smee implemented improvements to the QA/QC procedures.

A follow-up audit was conducted in July 2003 by Lynda Bloom of Analytical Solutions Ltd. The scope of this audit included a review of sampling, sample preparation, assaying, and quality control procedures. Ms. Bloom concluded that the sampling, sample preparation, and assaying procedures used for the Lagunas Norte drill core samples met or exceeded industry standards (Bloom, 2003).

The approximate insertion rates for exploration samples are summarized in Table 11-1. The actual insertion rates vary slightly by year and sample type. The QC insertion rates for blast hole samples sent to the Lagunas Norte laboratory also have similarly high levels, particularly when the large numbers of samples analyzed are considered.

TABLE 11-1 QC INSERTION RATES

Barrick Gold Corporation – Lagunas Norte Mine

 

Description

   Approximate
Insertion
Rate
 

Standards

     5

Blanks

     5

Pulp Replicates

     2

Reject Duplicates

     2

Field Duplicates

     3

Sieve Tests (on rejects and pulps)

     3

External pulp replicates (more blanks and standards sent as well)

     5

Smee (2010) completed an independent review of the QC results from 2007 to 2010. The gold precision for field, reject, and pulp duplicates was approximately ±17%, ±8%, and ±7%, respectively, at 0.2 g/t Au. The external check assays compiled annually from 2007 to 2010 revealed no significant biases. The 2010 results indicated that the SGS gold assays were slightly higher than those at ALS Chemex and the certified reference material (CRM) results confirmed that the SGS gold assays had a minor positive bias.

 

 

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Barrick personnel use a number of control charts and graphs to closely monitor the QA/QC results and reanalyses are periodically requested. The insertion rates and results are well documented and reveal no significant biases or precision problems.

RPA is of the opinion that the QA/QC procedures are very good and exceed standard industry practice. Reduction in the QC insertion rates, particularly for the blast hole samples, might be warranted.

In RPA’s opinion, the sample preparation, analyses, and security are reasonable and appropriate.

 

 

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12 DATA VERIFICATION

Smee (2003) used signed assay certificates to verify 15,600 assays in the database over a two day period and found only one error.

In 2007, MBM exported all of the collar coordinates in acQuire and verified them with the hard copy data available in the hard copy files. A small number of errors were found and corrected (Gómez, 2011). In 2007, all of the Sperry Sun photographic discs were reread and compared with the downhole survey values in acQuire. A small number of errors and invalid tests were found and corrected (Gómez, 2011).

In 2007, Scott Wilson RPA did some database spot checks and found no errors.

In 2009, MBM used the electronic assays certificates to check 7,902 assays, which represented approximately 5% of the assays in the acQuire database from 2001 to 2008 (Zapana, 2009). A relatively small number of errors were found including six samples that still had 10 g/t Au overlimit values that had not been replaced with the gravimetric finish reassays. Other errors were related to inconsistent handling of below detection limit values, reanalyses, and other minor inconsequential discrepancies.

Smee (2010) chose eleven drill holes at random from 2007 to 2010 and checked 1,410 samples for database entry errors by comparing the original assay certificates against the acQuire data. No significant errors were found. A minor problem related to not updating some 5 g/t Au and 10 g/t Au overlimit values with the follow-up gravimetric fire assay results was noted. Smee (2010) also noted that some of the drill hole hard copy folders were incomplete and that some of the assay certificates were only available as .csv files and not signed .pdf files. MBM subsequently requested and has now received signed .pdf assay certificates directly from the assay laboratories for most of the assays.

In 2011, MBM checked a minimum of 5% of the collar coordinate and downhole survey data in acQuire for 2008 to 2011 drill holes (Becerra 2011a and 2011b). Overall, MBM checked 11% of the drill hole collar coordinates and downhole surveys for this time period (Table 12-1).

 

 

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TABLE 12-1 2008 TO 2011 DATA VERIFICATION

Barrick Gold Corporation – Lagunas Norte Mine

 

Year

   Total
Holes
     Collars
Checked
     Percent
of
Collars
Checked
    Downhole
Surveys
Checked
     Percent
of
Surveys
Checked
 

2008

     336         21         6     21         6

2009

     19         9         47     8         42

2010

     38         10         26     10         26

2011

     82         11         13     11         13
  

 

 

    

 

 

    

 

 

   

 

 

    

 

 

 

Totals

     475         51         11     50         11

The ultimate validation of the reliability of the exploration drill hole database is provided by the very good reconciliation between the resource model and production.

RPA used a number of data validation queries in Access and Vulcan and did some visual checks and found essentially no database validation problems, which is remarkable considering the database size. RPA is of the opinion that the drill hole database is valid and acceptable for resource estimation.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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13 MINERAL PROCESSING AND METALLURGICAL TESTING

Metallurgical testing was completed prior to the start-up of Lagunas Norte and metallurgical recovery calculations were developed at that time. Lagunas Norte is continuously and routinely testing the ore that is being mined using column leach tests and bottle roll tests in the on-site metallurgical laboratory.

The gold recovery is forecast using a set of formulae outlined by Steve Haggarty and Rodolfo Espinel in a 2004 memo that are routinely updated using the information generated from the testwork. The estimated gold extraction for clean oxide ore is established using a 5th order polynomial equation based upon grade-recovery relationships for clean oxide ore that is crushed. The formula is:

x = Au (g/t)

There are ten ore types that are classified based on gold grade (Au, g/t), total carbonaceous material (TCM), sulphide sulphur (S, %), and copper concentration (Cu, ppm). They are defined in Table 13-1.

TABLE 13-1 ORE TYPES

Barrick Gold Corporation – Lagunas Norte Mine

 

Type

  

Definition

   Au
(g/t)
     TCM
(%)
   S
(%)
     Cu
(ppm)
 
M1   

crush, clean

     ³0.40       < 0.10      < 0.25         —     
M1 LG   

low grade crush clean

     < 0.40       < 0.10      < 0.25         —     
M1A   

crush, clean

     —         < 0.10      <0.40         <350   
M2AL   

crush, clean

     —         ³ 0.10 & < 0.20      < 0.25         —     
M3   

crush, sulphide

     —         < 0.10      ³ 0.40         <350   
M3A   

crush, sulphide

     —         < 0.10      ³ 0.25         >350   
M2AH   

crush, low TCM

     —         ³ 0.20 & < 0.50      < 0.25         —     
M2B   

ROM, contaminated

     —         ³ 0.50 & < 1.50      < 0.25         —     
M3B   

low crush, contaminated

     —         ³ 0.10 & < 0.50      ³ 0.25         —     
M3B   

Mid ROM contaminated

     —         ³ 0.50 & < 1.50      ³ 0.25         —     

Note: TCM – total carbonaceous material

 

 

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Revised metallurgical models have been updated by the Process Department for specific material types based on testwork undertaken since 2004, with updated algorithms issued in subsequent memoranda (Vidarte, 2008a, 2008b, 2009). The Process Department maintains the backup justification of the new algorithms.

A summary of the current algorithms utilized for the Au and Ag recovery calculations is presented with source documentation for the algorithms presented (Table 13-2).

TABLE 13-2 METALLURGICAL MODEL RECOVERABLE RECOVERY ALGORITHMS

Barrick Gold Corporation – Lagunas Norte Mine

 

Type

  

Algorithm

  

Source

Gold

     

CHLF - Crushed

     

M1

  

AuR

  

April 2004

M1_LG

  

AuR

  

April 2004

M1A

  

AuR

  

April 2004

M2AL

     

0.5 ³ Au (g/t)

  

= (0.5740-0.7300*TCM(%))*Au(g/t)

  

August 2009

0.5 < Au (g/t) £ 4.0

  

= (0.7200+0.0498*Au(g/t)-0.7358*TCM(%))*Au(g/t)

  

December 2008

4.0 £ Au (g/t)

  

= (0.9200-0.7358*TCM(%))*Au(g/t)

  

December 2008

SPHLF – Crushed

     

M3

  

= 0.7700*Au(g/t)

  

May 2008

M3A

  

= 0.4000*AuR

  

April 2004

M2AH

     

4.0 > Au (g/t)

  

= (0.7200+0.0498*Au(g/t)-0.7358*TCM(%))*Au(g/t)

  

August 2009

4.0 £ Au (g/t)

  

= (0.9200-0.7358*TCM(%))*Au(g/t)

  

August 2009

M3B_Low

  

= 0.4000*AuR

  

April 2004

SPHLF – ROM

     

M2B

  

= 0.5000*AuR

  

April 2004

M3B_Mid

  

= 0.4000*AuR

  

April 2004

Silver

     

CHLF - Crushed

     

M1

  

= 0.3000*Ag(g/t)

  

April 2004

M1_LG

  

= 0.3000*Ag(g/t)

  

April 2004

M1A

  

= 0.1500*Ag(g/t)

  

April 2004

M2AL

     

0.5 ³ Au (g/t)

  

= 0.1500*Ag(g/t)

  

April 2004

0.5 < Au (g/t) £ 4.0

  

= 0.1500*Ag(g/t)

  

April 2004

4.0 £ Au (g/t)

  

= 0.0750*Ag(g/t)

  

April 2004

 

 

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Type

  

Algorithm

  

Source

SPHLF – Crushed

     

M3

  

= 0.0750*Ag(g/t)

  

April 2004

M3A

  

= 0.0750*Ag(g/t)

  

April 2004

M2AH

     

4.0 > Au (g/t)

  

= 0.1375*Ag(g/t)

  

4.0 £ Au (g/t)

  

= 0.1375*Ag(g/t)

  

April 2004

M3B_Low

  

= 0.0750*Ag(g/t)

  

April 2004

SPHLF – ROM

     

M2B

  

= 0.1250*Ag(g/t)

  

April 2004

M3B_Mid

  

= 0.0750*Ag(g/t)

  

Note:

ACCURACY OF RECOVERY ESTIMATES

RPA has reviewed the budgeted recovery, based on the recovery calculations, and the actual recovery for the past three years. The data is shown in Table 13-3.

TABLE 13-3 RECOVERY EVALUATION

Barrick Gold Corporation – Lagunas Norte Mine

 

     2009     2010     2011  

Au Estimated Recovery

     78.2     74.3     76.5

Au Actual Recovery

     79.0     80.7     81.1

Variance

     1.05     8.60     5.99

Ag Estimated Recovery

     24.1     25.9     24.3

Ag Actual Recovery

     22.6     32.0     37.1

Variance

     6.2     23.7     52.5

Based on the data, RPA confirms that the formulae used to estimate gold and silver recovery meet industry standards, however, RPA recommends that Barrick continue to conduct routine metallurgical tests to try to improve the accuracy of the calculations.

 

 

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14 MINERAL RESOURCE ESTIMATE

SUMMARY

Table 14-1 summarizes open pit Mineral Resources exclusive of Mineral Reserves as of December 31, 2011, based on a $1,400/oz gold price. The 2011 year-end Measured and Indicated Mineral Resources total 31.9 million tonnes averaging 0.49 g/t Au and 1.8 g/t Ag and contain 505,000 ounces of gold and 1.83 million ounces of silver. In addition, the 2011 year-end Inferred Mineral Resources total 7.2 million tonnes averaging 0.47 g/t Au and 1.7 g/t Ag and contain 109,000 ounces of gold and 397,000 ounces of silver.

TABLE 14-1 MINERAL RESOURCES – DECEMBER 31, 2011

Barrick Gold Corporation – Lagunas Norte Mine

 

            Grade      Contained Metal  

Category

   Tonnage
(Mt)
     (g/t
Au)
     (g/t
Ag)
     (000
oz
Au)
     (000
oz Ag)
 

Measured

     0.8         0.47         1.9         12         50   

Indicated

     31.1         0.49         1.8         493         1,778   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total Measured and Indicated

     31.9         0.49         1.8         505         1,828   

Inferred

     7.2         0.47         1.7         109         397   

Notes:

 

  1. CIM definitions were followed for Mineral Resources.
  2. Mineral Resources are estimated using a gold price of US$1,400 per ounce and a US$/PEN exchange rate of 2.75.
  3. Mineral Resources are estimated at gold cut-off grades that vary by material type from approximately 0.119 g/t to 0.692 g/t.
  4. Mineral Resources are exclusive of Mineral Reserves.
  5. Numbers may not add due to rounding.

Silver recoveries are very low at Lagunas Norte, so silver is not considered for the resource and reserve cut-off grades. The resource internal gold cut-off grades range from 0.119 g/t to 0.692 g/t depending on the material type.

The current resource model combines the 2010 year-end model for Au, Ag, Hg, and geology interpretation, all based on the drill holes available up to October 2010, with the 2011 mid-year model for Cu, As, S, and TCM. The sulphide surface was updated for the 2011 mid-year copper model. The modelling work was completed by Barrick Senior Resource Geologist Paul Gómez, MBM Modelling Geologists Melissa Vasquez, and Hugo Rios under the supervision of Barrick Superintendent of Resource and Reserve Modelling Benjamin Sanfurgo.

 

 

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RPA reviewed the resource assumptions, input parameters, geological interpretation, and block modelling procedures and is of the opinion that the Mineral Resource estimate is appropriate for the style of mineralization and that the resource model is reasonable and acceptable to support the 2011 year-end Mineral Resource and Mineral Reserve estimates. The Qualified Person for the resource estimate is Luke Evans, M.Sc., P.Eng.

RPA is not aware of any environmental, permitting, legal, title, taxation, socio-economic, marketing, political, or other issues that could materially affect the Mineral Resource and Mineral Reserve estimates.

GEOLOGICAL MODELS

The Lagunas Norte Geology Department has developed a very good understanding of the Lagunas Norte geology. Geological models were constructed to provide geologic control for grade estimation and to provide parameters for mine planning. Geology models for lithological and geostructural domains were built using Vulcan software. The ten main faults have also been modelled. Interpretations were made by mine geology personnel on a set of 51 cross sections spaced 50 m apart and oriented at N60°E. The sectional interpretations were checked and adjusted on 47 benches spaced ten metres apart. Diamond drill holes, RC holes, blast holes, and pit mapping were used in Vulcan to create 3D geological wireframes. The geological wireframes were inspected by mine personnel and minor revisions were made locally. The geological modelling work for the current resource model was completed in late 2010. In early 2011, MBM began working with Leapfrog Mining software to investigate using it to build future geology models.

The main lithology wireframes were constructed by extrusion from the final interpretation lines on the ten metre benches. The mudstone, the carbonaceous mudstone, and the coal units in the Chimú Formation were also extruded following local strike and dip. The sandstone in the Chimú Formation was left as the background default rock type.

Wireframes were built for the main lithology and geostructural domain zones are listed in Tables 14-2 and 14-3, respectively. These wireframes were used to assign codes to the block model.

 

 

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TABLE 14-2 LITHOLOGY CODES

Barrick Gold Corporation – Lagunas Norte Mine

 

Code

   Description

1

   Volcanic (Volc)

2

   Andesite (And)

3

   Carhuaz

4

   Chicama

5

   Sandstone (SS)

6

   Mudstone (MS)

7

   Carbonaceous Mudstone (CBMS)

8

   Coal (Coal)

9

   Overburden (Ovb)

10

   Breccia (Bx)

TABLE 14-3 GEOSTRUCTURAL CODES

Barrick Gold Corporation – Lagunas Norte Mine

 

Code

   Description

1

   GS1 (Azimuth: 150, dip: -25)

2

   GS2 (Azimuth: 150, dip: -30)

3

   GS3 (Azimuth: 150, dip: -40)

4

   GS4 (Azimuth: 150, dip -50)

5

   GS5 (Azimuth: 155, dip: -60)

6

   GS6 (Azimuth: 155, dip: -35)

7

   GS7 (Azimuth: 340, dip: -65)

8

   GS8 (Azimuth: 150, dip: -50)

9

   GS9 (Azimuth: 145, dip: -30)

10

   GS10 (Azimuth: 185, dip: -50)

The lithological and geostructural domains models are shown in Figures 14-1 and 14-2, respectively.

 

 

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GEOLOGICAL DOMAINS

The main mineralization controls are the lithology and the structural domains. Approximately 85% of the gold is contained within the Chimú sediments and the remaining 15% of the gold is hosted in the Calipuy volcanic rocks. Alteration has a secondary mineralization control and is very local. Alteration was not modelled.

GRADE DOMAINS

The drill hole and blast hole data were used to build gold envelopes from 0.2 g/t Au and 1.0 g/t Au bench contours spaced 10 m apart. Three separate grade indicator envelopes were also created based on blocks with a greater than 40% probability of grading over 0.15 g/t Au, 1.0 g/t Au, and 5.0 g/t Au. The indicator envelopes were used to expand the 0.2 g/t Au and 1.0 g/t gold envelopes locally along strike and down dip and the 5.0 g/t Au indicator outlined internal higher grade areas. This resulted in four grade domains (Figure 14-3) and they were used to assign codes to the block model (Table 14-4).

TABLE 14-4 GRADE DOMAIN CODES

Barrick Gold Corporation – Lagunas Norte Mine

 

Code

   Description
0    Low (<0.15 g/t Au)
1    Normal (0.15 to 1.0 g/t Au)
2    Medium (1.0 to 5.0 g/t Au)
3    High (>5.0 g/t Au)

RPA found that the additions related to the indicator envelopes were reasonable. RPA’s preference, however, would be to construct future gold envelopes manually from the drill hole and blast hole data.

 

 

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DENSITY DATA

Core density is determined using a Digital Core Model (DCM) developed by CODELCO Chile and Geovectra. The system has been audited by both company personnel and external consultants, and results are consistent with pre-existing density measurements determined by conventional (ASTM) methods. Approximately half of the sampled cores (72,000 m) have Módulo Digital de Testigos (MDT) density values. The procedure for density determination is as follows:

 

  1. The core is cleaned, dried, and placed in specially designed weighing trays of consistent and predetermined weight, containing approximately 4.5 m of core. Core recovery is again measured at the time of density determination.

 

  2. The sample tray is suspended over the tank, and the weight of the tray in air is recorded, using a calibrated balance. The tray is then lowered into a tank containing water of a measured density for a short period of time. The weight of the tray in water is recorded, as is the nature and relative abundance of bubbles effusing from the core.

 

  3. All of the measurements (weights, recovery, lithology, and “porosity factor” for correction) are entered into the DCM database, and a corrected density is calculated for each tray.

CUT-OFF GRADES

The resource cut-off grades are based on a $1,400/oz gold price and the cost, recovery, and other parameters discussed in the reserve section. The cut-off grade estimates vary by material type (Table 14-5).

TABLE 14-5 RESOURCE INTERNAL CUT-OFF GRADES

Barrick Gold Corporation – Lagunas Norte Mine

 

Ore Type

   Internal
Cut-Off

g/t Au
M1: crush, clean    0.400
M1_LG: crush, clean    0.152
M1A: crush, clean    0.119
M2AL: crush, clean    0.144
M3: crush, sulphide    0.141
M3A: crush, sulphide    0.692
M2AH: crush, low TCM    0.180
M2B: ROM, contaminated    0.285
M3B_Low: crush, contaminated    0.371
M3B_Mid: ROM, contaminated    0.414

 

 

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The resource cut-off grade estimate details are very well documented in Garcia (2011). The resource internal gold cut-off grades range from 0.119 g/t to 0.692 g/t depending on the material type.

ASSAY STATISTICS AND CAPPING OF HIGH GRADES

The assay statistics for gold are summarized in Table 14-6. The assays for 147,010 m of drilling average 0.80 g/t Au and have a very high coefficient of variation (CV) equal to 5.4. Approximately 68% of the assays are situated in sandstone and average 0.62 g/t Au. The second most abundant rock type is the breccias at 10% and they average 1.35 g/t Au.

Lagunas Norte capped high Au, Ag, Cu, TCM, S, As, and Hg assays prior to compositing based on experience, production reconciliation results, checking for high grade spatial continuity, and examining log probability plots of the assays for the main lithology types. The log probability plot for all of the gold assays is shown in Figure 14-4 and the gold capping levels applied to each lithology are listed in Table 14-6. The gold capping levels range from 7 g/t in andesite to 65 g/t in mudstone. The CVs after capping range from 1.9 in coal to 3.5 in mudstone. Excluding the overburden, the approximate amount of gold removed by capping ranges from 1.5% in the andesite to 69% in the coal.

 

 

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FIGURE 14-4 ASSAY CUMULATIVE FREQUENCY DISTRIBUTION – GOLD

 

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From MBM (2011a)

RPA concurs with the capping levels and restricted search conditions selected by Lagunas Norte. Some of the capping levels appear to be too high based on the statistics but they may actually be slightly too low based on production reconciliation. Investigating separate capping levels for the RC and DDH may be warranted. Very high grade blast hole gold grades are very rare but when encountered they are capped to 50 g/t.

 

 

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COMPOSITES

Drill hole sample data were composited into five metre lengths starting at the drill hole collars. No geology breaks were applied in the compositing.

Nine percent of the total composites that are located in portions of diamond drill holes that are twinned by RC holes and within a five metre distance were excluded. In 2008, MBM twinned a number of DDH with RC drill holes and confirmed that the DDH gold grades were significantly understated relative to the RC and blast holes (Gómez, 2008).

The composite statistics for each lithology are summarized in Table 14-7 (see next page).

The relative abundance of composites in each lithology is also summarized in Table 14-7. For example, 68% of the composites occur in sandstone rocks with a block model lithology code equal to 5 and 7% of the composites are in volcanic rocks with a block model lithology code equal to 1.

 

 

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CONTACT PLOT ANALYSIS

Contact plots were generated for Au, Ag, Cu, TCM, and S values to explore the relationship between the grade variable when moving from one geological domain to another. One of the results showed that the volcanic rocks with the sedimentary rocks were hard boundaries.

The contact plots are constructed with Vulcan software. Vulcan searches for data with a given lithology code and then for data with another specified lithology code and groups the grades according to the distance between the two points. This allows for a graphical representation of the grade trends away from a “contact.” If average grades are reasonably similar near a boundary and then diverge as distance from the contact increases, then the particular boundary should probably not be used as a grade constraint (“soft”). If the averages are distinctly different across a boundary, then the boundary may be important in constraining the grade estimation (“hard”). Examples of contact plots with hard boundaries are shown in Figures 14-5 and 14-6.

Domains with hard boundaries were interpolated separately and domains with soft boundaries were combined during grade interpolation.

VARIOGRAPHY

Lagunas Norte built a number of omni-directional correlograms and indicator variograms using the composites for each lithological domain. The range of the indicator variogram was used in the search parameters. The resulting indicator variogram for five metre composites greater than 0.2 g/t Au is shown in Figure 14-7.

 

 

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RESOURCE ESTIMATION METHODOLOGY

The step by step resource estimation methodology is well described in MBM (2011a). The Vulcan C shell file (adch0511.csh) provides an excellent record of all the steps done in Vulcan to build the resource block model.

The Lagunas Norte mineral resource model extends from 802,400 m to 805,445 m east, 9,119,600 m to 9,122,974 m north, and 3,750 m to 4,300 m in elevation. The 5 m high by 5 m by 5 m block model is populated directly with the lithology, structural domains, and 3D grade envelopes and a separate script is run to assign grade domain codes.

The capped assays were composited into five metre lengths. Composites for Au, Ag, Cu, TCM, S2, As, Hg, and gold recovery (Aurec) were created. The composite lithology, grade domain, and geological domain codes are back-flagged from the block model.

Lagunas Norte used multiple pass inverse distance squared (ID2) to interpolate Au, Ag, Cu, TCM, S2, Aurec, and density for all domains. The As and Hg estimation procedures are not discussed in this report.

GOLD ESTIMATION

Gold estimation parameters were developed for each of the grade domains. Length-weighted composites are used. Weighted boundaries using 0.1 and 1 values in the composite length fields were used to simulate semi-hard boundaries. These semi-hard boundaries were used for passes corresponding to grade domains 1 and 2. The 0.1 value was selected after repeated comparisons with production reconciliation data. RPA concurs with this innovative approach.

The search ellipsoids for gold are generally horizontal pancakes for lithological domains 1, 2, 3, 4, and 9 and sub-horizontal to sub-vertical pancakes oriented at 145° to 340° with a range of dips (-25° to -65°) for lithological domains 5, 6, 7, and 8. The search orientations vary for each lithological and for each geostructural domain within the Chimú sedimentary rocks. The longest radii are 180 m by 180 m by 90 m for the final pass and the shortest pass radii are 35 m by 35 m by 10 m for the second pass radii.

 

 

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There are six ID2 passes used for each of grade domain within each lithological domain and within each structural domain. The first one is the general box pass, which is based on 2.5 m by 2.5 m by 2.5 m distances and a minimum of one composite and the last pass is the fill pass, which is based on 180 m by 180 m by 90 m radii and a minimum of one composite and a maximum of five composites, with a maximum of one composite per hole.

The second passes use a minimum of two composites and a maximum of three composites, with a maximum of one composite per hole. The second pass radii are the distances defined by 80% of the omni-directional sill. The third pass radii are the distances defined by 60% of the omni-directional sill. The third pass uses a minimum of one composite and a maximum of three composites, with a maximum of one composite per hole. The fourth pass radii are the distances defined by 90% of the omni-directional sill. The fourth passes use a minimum of two composites and a maximum of three composites with a maximum of one composite per hole. The fifth pass radii are longer than the fourth pass radii. The fifth pass uses a minimum of one composite and a maximum of five composites with a maximum of one composite per hole. This pass was run only for grade domain 1.

The multi-pass interpolation parameters are summarized in Table 14-8.

 

 

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TABLE 14-8 GOLD ESTIMATION PARAMETERS

Barrick Gold Corporation – Lagunas Norte Mine

 

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From MBM (2011a)

 

 

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GOLD RECOVERY GRADE ESTIMATE

A gold recovery model was created using primarily bottle roll recovery tests as well as the extensive cyanide amenability (CNA) database. Indicators were used to create two recovery domains (high recovery > 50%, and low recovery <50%). Length-weighted composites are used. Recoveries were calculated within each domain by estimating head grades and recovered grades.

The search ellipsoids for recoveries are generally horizontal pancakes for lithological domains 1, 2, 3, 4, and 9 and sub-horizontal to sub-vertical pancakes oriented at 145° to 340° with a range of dips (0° to -65°) for lithological domains 5, 6, 7, and 8. The search orientations vary for each lithological domain and for each geostructural domain located within the Chimú sedimentary rocks. The longest radii are 300 m by 300 m by 300 m for the second pass and the shortest pass radii are 150 m by 150 m by 75 m for the first pass.

There are two ID2 passes used for each of the gold recovery domains within each lithological domain and within each geostructural domain. The first pass radii are the distances defined by the approximate range of the omni-directional sill and the second pass radii are double of the first pass radii. Both passes use a minimum of three composites and a maximum of nine composites, with a maximum of two composites per hole.

To compare the estimation, a second recovery value was derived from a polynomial curve based mostly on bottle rolls results. Whenever both values were within ±12% of each other, the polynomial calculation was kept; otherwise the estimated result was used.

SILVER GRADE ESTIMATE

Indicators were used to create two silver grade domains (high grade > 2 g/t, and low grade <2 g/t). Length-weight composites were used.

The search ellipsoids for silver are generally horizontal pancakes for lithological domains 1, 2, and 9 and sub-vertical pancakes oriented at 330° with a dip of -60° for lithological domains 3, 4 and a dip of -65° for lithological domains 5, 6, 7, and 8. The longest radii are 350 m by 350 m by 200 m for the final pass and the shortest pass radii are 70 m by 70 m by 35 m for the first pass.

 

 

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There are two ID2 passes used for each of the silver grade domains within each lithology grouping (5 and 6, 7 and 8, and 3 and 4) and within east and west geostructural grouping defined on either side of the Central Fault (East Group: 1 and 2, West Group: 3, 4, 5, 6, 7, 8, 9, and 10).

The first passes use a minimum of five composites and a maximum of eleven composites, with a maximum of two composites per hole. The first pass radii are the distances defined by approximately 90% of the omni-directional sill. The second pass radii are the double of the first pass radii. The second pass uses a minimum of three composite and a maximum of seven composites with a maximum of two composite per hole.

COPPER ESTIMATE

Copper is considered as a contaminant because it has a negative impact on the gold recovery. An indicator at 25 ppm was created to generate the copper grade domains (high grade >25 ppm Cu and low grade <25 ppm Cu). There are two main copper zones defined by the oxide-sulphide limit (oxide and sulphide). Length-weighted composites were used.

The search ellipsoids for copper are generally horizontal pancakes for lithological domains 1, 2, 3, and 9 and sub-horizontal to sub-vertical pancakes oriented at 15° to 330° with a range of dips (-29° to -64°). The search radii vary for each lithological domain, and for each geostructural grouping (East Group: 1 and 2; North West and Central Group: 3, 4, 5, 6, 7, 8, and 9; and South West Group: 10). The longest radii are 400 m by 400 m by 400 m for the sixth pass and the shortest pass radii are 30 m by 20 m by 15 m for the third pass.

There are five ID2 passes used for each of the copper grade domains within each lithological domain, within each geostructural grouping and within each copper zone.

The first pass is the general box pass, which is based on 2.5 m by 2.5 m by 2.5 m radii and a minimum of one composite and a maximum of 99 composites.

 

 

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The second pass uses a minimum of two composites and a maximum of three composites with a maximum of one composite per drill hole. The second pass radii are the distance defined by approximately the range at 80% of the omni-directional sill. The third pass radii are the distance defined by approximately 60% of the second pass radii. The third pass uses a minimum of one composite and a maximum of three composites with a maximum of one composite per hole. The fourth pass radii are the double of the second pass radii. The fourth passes use a minimum of two composites and a maximum of three composites with a maximum of one composite per hole. The fifth pass radii are the double of the fourth pass radii. The fifth pass uses a minimum of two composites and a maximum of three composites with a maximum of one composite per hole. The sixth pass radii are the double of the fifth pass radii. The fifth pass uses a minimum of two composites and a maximum of three composites with a maximum of one composite per hole. The fifth pass is only for the low copper grade domains.

TOTAL CARBONACEOUS MATERIAL ESTIMATE

TCM is considered as a contaminant because it has a negative impact on the metallurgical recovery. It has a strong preg-robbing effect on gold rich sodium cyanide leaching. There is a good correlation between rocks described as carbonaceous (lithology codes: 6, 7 and 8) and measured TCM values.

Two estimations were completed on one metre and five metre blocks. Length-weighted composites were used. The one metre estimation was generated for the carbonaceous rocks using one metre blocks with original length assays. The five metre estimation was generated for the other lithologies using five metre blocks and five metre composites.

For the one metre estimation, indicators were used to define TCM grade domains:

 

   

2% TCM Indicator in coal rocks (high grade domain)

 

   

0.1% TCM Indicator in carbonaceous mudstone rocks (medium grade domain)

 

   

0.1% and 5% TCM Indicators in mudstone rocks (low, medium, and high grade domains inside the mudstone)

The search ellipsoids for TCM are generally horizontal pancakes for lithological domains 6, 7, and 8 with no restriction by structural domain, and sub-horizontal to sub-vertical pancakes oriented at 145° to 340° with a range of dips (-25° to -65°) when there is

 

 

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restriction by structural domain. The search orientations vary for each lithological domain and for each geostructural domain within the Chimú sedimentary rocks. The longest radii are 500 m by 500 m by 500 m for the second pass and the shortest pass radii are 25 m by 25 m by 5 m for lithology domain 6 inside the high grade domain.

There are two inverse distance cubed (ID3) passes used for each grade domain within lithology domains 7 and 8 and two ID2 passes used for each grade domain within lithology domain 6. The first pass is run for each lithological domain within each geostructural domain and the second pass has the same parameters without restriction by geostructural domain.

For the two ID3 passes, the first passes use a minimum of one composite and a maximum of 15 composites and a maximum of three composites by drill hole. The first pass radii (200 m by 200 m by 40 m) are based on approximately the range of the omni-directional sill. The second passes use a minimum of one composite and a maximum of 21 composites with a maximum of three composite per drill hole. The second pass radii are 500 m by 500 m by 500 m.

For the two ID2 passes, the first pass uses a minimum of one composite and a maximum of 15 composites and a maximum of three composites by drill hole. The first pass radii are the distances defined by approximately the range at 80% of the omni-directional sill. The second pass uses a minimum of one composite and a maximum of 21 composites with a maximum of three composites per drill hole. The second pass radii are the distances defined by approximately the range at 90% of the omni-directional sill.

For the five metre estimation, there are two ID2 passes used for each lithological domain and for each geostructural domain in the Chimú sedimentary rocks. Also, there is one ID3 pass used for the third pass in each lithological domain with no restriction by structural domain.

The first passes use a minimum of one composite and a maximum of 15 composites and a maximum of three composites by drill hole. The first pass radii are the distances defined by the 80% of the omni-directional sill. The second pass uses a minimum of four composites and a maximum of 21 composites with a maximum of three composite per drill hole. The second pass radii are the distances defined by approximately the range at

 

 

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the omni-directional sill. The third passes use a minimum of one composite and a maximum of 21 composites and a maximum of three composites by drill hole. The third pass radii are longer than the second pass radii.

Mudstone, carbonaceous mudstone, and coal wireframes were populated into a 1 m high by 1 m by 1 m block model. Then, they were reblocked to five metre blocks based on their majority percentages. The TCM grades values, estimated in the one metre block model, were reblocked into the 5 m high by 5 m by 5 m based on tonnage weighting from the original block grades. Dilution was incorporated into the five metre block model combining the estimated five metre TCM values with the estimated one metre TCM values that were reblocked into the five metre block model. The final diluted TCM values are based on percentages of carbonaceous rocks and the estimated TCM values from both models. The final TCM grades in the five metre blocks are diluted with the background TCM values of the sandstone.

SULPHIDE SULPHUR ESTIMATE

S2 is considered as a contaminant because it has a negative impact on the metallurgical recovery. Since the carbonaceous rocks carry much higher S2 grades than sandstone, a diluted S2 grade is calculated for each block using an approach similar to that developed to estimate TCM grades.

Two estimation processes were carried out on one metre and five metre blocks. Length-weighted composites were used. The one metre estimations were generated for the carbonaceous rocks using one metre blocks and the original length assays. Five metre estimations were generated for the other lithologies using five metre blocks with five metre composites.

For the one metre estimation, the search ellipsoids for S2 are generally sub-horizontal to sub-vertical pancakes oriented at 145° to 340° with a range of dips from -25° to -65°. The search orientation radii vary for each structural domain. The longest radii are 240 m by 240 m by 80 m for the third pass with no restriction by geostructural domain and the shortest pass radii are 60 m by 60 m by 20 m for the second pass.

There are three ID3 passes used for lithology domains 6, 7, and 8 within each structural domain. The third pass does not have restriction by geostructural domain.

 

 

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The first passes use a minimum of three composite and a maximum of 11 composites and a maximum of two composites by drill hole. The first pass radii are the distances defined by approximately the range of the omni-directional sill. The second pass uses a minimum of one composite and a maximum of five composites with a maximum of two composite per drill hole. The second pass radii are the distances defined by approximately the range at 90% of the omni-directional sill. The third passes use a minimum of three composite and a maximum of 21 composites and a maximum of two composites by drill hole. The third pass radii are double the first pass radii.

For the five metre estimation, an indicator at one percent was created to generate the S2 high and low grade domains. Weighted boundaries using 0.1 and 1 values in the composite length fields were used for the indicator 1.0 to generate semi-hard boundaries.

There are six ID3 passes used for each of the grade domains within a number of lithology groupings and within each geostructural domain in the Chimú sedimentary rocks. The first one is the general box pass, which is based on 2.5 m by 2.5 m by 2.5 m radii and a minimum of one sample, and the last pass is the fill pass, which is based on 1,000 m by 1,000 m by 500 m and a minimum of one composite and a maximum of five composites with a maximum of one composite per hole.

The second passes use a minimum of two composites and a maximum of three composites and a maximum of one composite by drill hole. The second pass radii are the distance defined by the range at 90% of the omni-directional sill. The third pass uses a minimum of one composite and a maximum of three composites with a maximum of one composite per drill hole. The third pass radii are the distance defined by the range at 80% of the omni-directional sill. The fourth passes use a minimum of two composites and a maximum of three composites and a maximum of one composite by drill hole. The fourth pass radii are the double of the second pass radii. The fifth passes use a minimum of one composite and a maximum of three composites and a maximum of one composite by drill hole. The fifth pass radii are the same as the fourth pass radii.

The 1 m high by 1 m by 1 m blocks are reblocked into the 5 m high by 5 m by 5 m blocks. The reblocked S2 grades are assigned based on tonnes weighting from the original block grades. Then, the diluted S2 grades are calculated based on percentages

 

 

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of carbonaceous rocks and the estimated S2 values. Dilution was incorporated into the five metre block model combining the estimated five metre block S2 values with the estimated one metre block S2 values (reblocked into the five metre block model). The final diluted S2 values are based on percentages of carbonaceous rocks and the estimated S2 values from both models.

DENSITY ESTIMATE

Lithology domains based on logged lithology codes were used as the main estimation domains. Length-weighted composites were used. Only composite density values that were within plus or minus two standard deviations of the density means were used. For the carbonaceous rocks, composites with less than 35% carbonaceous material were excluded. Default density values were assigned to all blocks with no interpolated densities (Table 14-9).

TABLE 14-9 TONNAGE FACTORS

Barrick Gold Corporation – Lagunas Norte Mine

 

Rock Type

   Main  Model
(t/m³)
 

Volcanic

     2.43   

Andesite

     2.48   

Carhuaz & Chicama

     2.64   

Sandstone, Mudstone, and Carbonaceous Mudstone

     2.58   

Coal

     2.47   

Overburden & Breccia

     2.26   

The search ellipsoids for density are generally horizontal pancakes for lithological domains 1, 2, 3, 4 and 9, and sub-horizontal to sub-vertical pancakes oriented at 150° to 330° with a range of dips from -25° to -65°. The search orientations vary for each lithological domain and for each geostructural domain (just within the Chimú sedimentary rocks).

There is an ID2 pass used for each lithological domain and for each geostructural domain (just in the sedimentary rocks). It uses a minimum of five composites and a maximum of 13 composites and a maximum of two composites per drill hole. The pass radii are the distance defined by the range at 95% of the omni-directional sill.

 

 

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REBLOCKING TO FINAL RESOURCE MODEL

The 5 m high by 5 m by 5 me blocks are reblocked into the final resource model, which has 10 m high by 10 m by 10 m blocks. The reblocked grades are assigned based on tonnage weighting the original block grades and the geology and other codes are assigned based on majority rules. Over time, Lagunas Norte has developed a sophisticated multi-pass interpolation process that works well. RPA is of the opinion that the Lagunas Norte resource estimation methodology is reasonable and acceptable.

RESOURCE ESTIMATE VALIDATION

Lagunas Norte has validated the resource block model using six separate validation procedures. The results are provided in MBM (2011a) and some examples of the validation results are included below.

 

  1. Visual inspection of block and composite values on sections and plans

 

  2. Reconciliation with the ore control model

 

  3. Block versus composite statistics

 

  4. ID versus Nearest Neighbour (NN) swath plots

 

  5. ID versus NN global means

 

  6. Comparison between 2010 and 2011 estimates

MBM and RPA visually compared the composite and block grades on plans and sections and found that they correlate very well spatially (Figure 14-8).

The reconciliation data for the first eleven months of 2011 indicate that the resource model overestimates the tonnage by approximately 0.8%, and underestimates the gold grade by approximately 3.3% and contained gold ounces by approximately 2.6% compared to the grade control blast hole model (Table 14-10). The positive gold reconciliation variance of approximately 20% in the past has improved significantly to only 3% due mostly to infill RC drilling and procedural improvements to the resource model. In RPA’s opinion, the resource model reconciles very well with the grade control model.

 

 

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TABLE 14-10 2011 RECONCILIATION RESULTS

Barrick Gold Corporation – Lagunas Norte Mine

 

     2011 Grade Control      2011 Resource Model  
          Au      Au      Ag      Ag            Au     Au     Ag     Ag  

Month

   Tonnes      (g/t)      (ozs)      (g/t)      (ozs)      Tonnes     (g/t)     (ozs)     (g/t)     (ozs)  

Jan

     20,07,150         1.38         88,816         1.69         108,736         2,023,006        1.40        90,934        2.80        182,365   

Feb

     14,60,699         1.21         56,967         3.77         176,976         1,501,808        1.39        66,733        2.50        120,814   

Mar

     16,50,341         1.26         66,987         3.03         160,838         1,641,798        1.15        60,336        2.66        140,325   

Apr

     17,12,449         1.56         86,110         2.44         134,537         1,729,265        1.12        62,463        2.59        144,093   

May

     19,18,932         1.44         88,783         3.61         222,464         1,971,878        1.57        99,339        3.01        191,006   

Jun

     19,35,387         1.64         102,046         3.72         231,447         2,024,438        1.51        98,428        3.35        218,138   

Jul

     21,68,990         1.57         109,420         4.09         285,153         2,234,341        1.38        99,405        3.80        272,705   

Aug

     19,39,595         1.44         89,684         3.73         232,648         2,025,879        1.37        89,123        2.51        163,604   

Sep

     18,87,355         1.05         63,576         4.20         254,849         1,825,358        1.06        62,391        3.39        198,742   

Oct

     1,535,734         1.52         75,281         5.10         251,794         1,409,639        1.46        66,010        4.11        186,289   

Nov

     2,084,425         1.52         101,957         5.64         377,907         2,068,369        1.65        109,805        4.16        276,734   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

   

 

 

   

 

 

   

 

 

   

 

 

 

Totals

     20,301,057         1.42         929,628         3.73         2,437,352         20,455,781        1.38        905,431        3.19        2,094,815   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

   

 

 

   

 

 

   

 

 

   

 

 

 

Percent Differences

  

     0.8     -3.3     -2.6     -14.7     -14.1

Graphs that compare the composite and block gold grades show that the two populations have similar distributions with not much grade smoothing evident (Figure 14-9). The composites and blocks for the main lithology domains generally have similar gold means (MBM, 2011a). The block means are generally slightly lower, which is normal.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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FIGURE 14-9 GOLD BLOCK VERSUS COMPOSITE GRAPHS

 

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The NN and current gold block models have very similar swath plots, again indicating very little grade smoothing (Figure 14-10).

At the end of every year, MBM compares and tabulates variances with the previous year’s estimate. This is a good practice that helps ensure that all variances are explainable. The 2011 year-end Proven and Probable Mineral Reserves increased slightly, by approximately 7%, compared to 2010 and this change can be mostly attributed to higher gold prices.

 

 

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RESOURCE CLASSIFICATION

The classification criteria are based on distances from composites to block centroids and the number of holes. The 35 m, 60 m, and 90 m distances correspond to the ranges at approximately 60%, 80%, and 90% of the omni-directional correlogram sill, respectively. Figure 14-7 shows the omni-directional correlogram. In RPA’s opinion, constraining the classification runs by the structural domains is very good practice. This means that composites located one side of a fault cannot influence the classification of a block located on the other side.

Measured Mineral Resources:

 

   

Blocks containing a 10 m composite (based on a separate 10 m cube box search classification pass using 10 m composites).

Indicated Mineral Resources:

 

   

Supported by composites from two holes situated within 60 m of a block or by composites from one drill hole within 35 m of a block.

Inferred Mineral Resources:

 

   

Supported by composites from two holes situated within 90 m of a block.

Categories assigned to each block were post-processed to reduce isolated blocks enveloped in a different category and produce more continuous areas with similar classification categories. It is RPA’s opinion that the application of a classification category clean-up script is best practice. RPA’s view is that the Inferred classification criteria are conservative. Overall, RPA’s opinion is that the MBM classification criteria are reasonable and slightly conservative.

 

 

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15 MINERAL RESERVE ESTIMATE

The resource estimates discussed in Section 14 were prepared using industry standard methods and appear to provide an acceptable representation of the deposit. RPA reviewed the reported resources, production schedules, and cash flow analysis to determine if the resources meet the CIM Definition Standards for Mineral Resources and Mineral Reserves, to be classified as reserves. Based on this review, it is RPA’s assessment that the Measured and Indicated Mineral Resource within the final pit design at Lagunas Norte can be classified as Proven and Probable Mineral Reserves.

The open pit Proven and Probable Reserves, including existing stockpiles scheduled for processing and inventory, are estimated to be 194.5 million tonnes at 0.98 g/t Au and 3.8 g/t Ag, containing 6.2 million ounces of gold and 24 million ounces of silver as presented in Table 15-1. The Qualified Person for this Mineral Reserve estimate is Glen Ehasoo, P.Eng.

TABLE 15-1 MINERAL RESERVES – DECEMBER 31, 2011

Barrick Gold Corporation – Lagunas Norte Mine

 

Category

   Tonnage
(Mt)
     Au
(g/t)
     Ag
(g/t)
     Contained
Metal

(Moz Au)
     Contained
Metal

(Moz Ag)
 

Proven

     8.7         1.06         4.0         0.30         1.1   

Probable

     179.0         0.96         3.8         5.53         21.9   

Stockpiles

     5.6         1.49         3.1         0.27         0.6   

Inventory

     1.2         1.47         8.5         0.06         0.3   

Proven & Probable

     194.5         0.98         3.8         6.15         23.9   

Notes:

 

1. CIM definitions were followed for Mineral Reserves.
2. Mineral Reserves are estimated at a variable cut-off grade based on process cost, recovery and profit. The cut-offs vary from approximately 0.14 g/t Au to 0.80 g/t Au.
3. Mineral Reserves are estimated using an average long-term gold price of US$1,200 per ounce and an US$/PEN exchange rate of 2.75.
4. The Mineral Reserve estimate includes inventory.
5. Numbers may not add due to rounding.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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16 MINING METHODS

SUMMARY OF MINING OPERATIONS

The Lagunas Norte Mine is a traditional open pit truck/shovel heap leach operation that has been in continuous operation since 2005. Table 16-1 summarizes the production history through December 2011. To date, Lagunas Norte has produced 6.5 million ounces of gold and 5.1 million ounces of silver.

TABLE 16-1 LAGUNAS NORTE PRODUCTION HISTORY

Barrick Gold Corporation – Lagunas Norte Mine

 

     Ore Placed      Production      Waste      Total      Strip  

Year

   (Mt)      (g/t Au)      (g/t Ag)      (Moz Au)      (Moz Ag)      (Moz Au)      (Moz Ag)      (Mt)      (Mt)      Ratio  

2005

     12.5         2.03         1.0         0.82         0.40         0.55         0.1         8.0         20.5         0.6   

2006

     19.4         2.26         2.1         1.41         1.28         1.08         0.4         5.2         24.7         0.3   

2007

     19.6         2.16         3.7         1.37         2.32         1.09         0.8         3.0         22.7         0.2   

2008

     22.9         1.87         3.5         1.38         2.57         1.17         1.2         1.6         24.5         0.1   

2009

     23.0         1.66         5.2         1.23         3.84         1.01         0.9         1.7         24.7         0.1   

2010

     20.0         1.35         4.1         0.87         2.64         0.81         0.8         5.3         25.3         0.3   

2011

     19.4         1.47         4.2         0.91         2.60         0.76         1.0         7.6         27.0         0.4   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Total

     136.8         1.81         3.6         7.98         15.64         6.47         5.1         32.5         169.3         0.2   

Notes:

 

1. Numbers may not add due to rounding.

Open pit mining operations are located on a mountain top with gentle to extreme terrain between elevations of 3,800 MASL and 4,200 MASL. Production is from a single open pit and is scheduled to be complete in 2019, followed by two additional years of stockpile rehandle. This requires the excavation of 339 million tonnes of material over the next eight years.

Figure 16-1 presents a general site layout diagram of Lagunas Norte.

 

 

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The Lagunas Norte ultimate pit measures approximately 2.5 km along strike, typically 0.8 km to 1.2 km across with a surface footprint of approximately 240 ha, and has a maximum depth of approximately 250 m. The open pit is overlooked by the Shulcahuanca Dome (see Figure 7-5), rising 200 m above the west wall pit rim with a base diameter of approximately 350 m and slopes of over 70o facing the open pit. There is an approximate 50 m standoff from the base of the Shulcahuanca Dome for mine planning and operations.

There are four main areas of development identified within the ultimate pit: Dafne, Josefa, Alexa, and the moraines furthest to the north. The Shulcahuanca directly overlooks the Dafne area where the ultimate pit will be at its deepest. The Alexa area is to the northwest, north of the Shulcahuanca. Mining benches in Alexa form a north-south striking plateau with the pit wall stepping down on the east side and a steep natural rock face on the west side. The current vertical exposure to the west is up to 185 m, with the top 50 m in slopes typically between 60o and 80o. The moraines consist of gold bearing deposits of free digging material.

Final arrangement of the Lagunas Norte waste rock facilities (WRF) is for the continued development of surface dumps surrounding the Lagunas Norte ultimate pit other than to the south-southeast where the HLF is located, resulting in a relatively compact overall footprint.

Processing is based on two adjacent heap leach pads designed to merge into a single HLF. Various ore types both crushed and ROM are delivered to the HLF by haul truck. Solution from the HLF is pumped to the Merrill Crowe process facilities for production of gold bars with silver credits. The HLF is located starting less than 0.5 km south of the existing pit limits. Final HLF dimensions are up to 1.7 km north-south and up to 1.7 km east-west, for an ultimate footprint of approximately 280 ha.

Over 90% of remaining reserves are scheduled for crushing to a P80 of -50 mm prior to placement on the HLF as this offers a higher profit margin than ROM placement. The crushing facilities are located at the south end of the open pit, approximately 200 m from the existing pit rim and haul ramp exit. After crushing, the ore is stored in an overhead bin for loadout to the production fleet haul trucks. The haul trucks deliver the ore to the HLF for placement. The current haul distance is approximately 1.0 km uphill to the top of the existing HLF, followed by an increment of 0.5 km to 1.5 km to the destination.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Mining an average of approximately 23.5 million tonnes per year ore is scheduled for Lagunas Norte over the next eight years, with open pit mine operations concluding in 2019. Waste rock mining varies by year from a high of 30.0 million tonnes in 2018 to a low of 9.4 million tonnes in 2013, averaging 19.6 million tonnes per year. Annual ROM material movement increases steadily over the next seven years to a peak of approximately 50.6 million tonnes (139,000 tpd) in year 2018, falling to 44.6 million tonnes in the final year of open pit operations.

The current mine life and production schedule is based on the Mineral Reserve statement in Section 15 of this report. Therefore, the potential exists for Inferred Mineral Resources within the ultimate pit to be included in the production schedule reported as waste, as they currently do not meet the requirements to be considered reportable as Mineral Reserves.

MINE DESIGN

Mine operations are considered a typical truck/shovel open pit operation with a fleet of 184 tonne payload rigid frame haul trucks combined with diesel powered face shovel excavators and front end loaders as the primary loading equipment. Haul trucks are also utilized to transport ROM ore directly to the HLF, along with crushed ore to the HLF for stacking. A fleet of large diesel powered blast hole rigs are employed for production drilling of blast patterns.

The Mineral Resource model, described in Section 14 of this report, is exported from Vulcan software and imported into Q’Pit Ltd.’s Q’Pit software (Q’Pit). The mine model is prepared in Q’Pit, applying metallurgical recoveries based on material types, calculating potential block revenue, and defining slope sectors based on geotechnical domains in the model. The mine model is exported from Q’Pit and imported into Gemcom’s Whittle 4.X software (Whittle) for open pit optimization using the Lerchs-Grossmann algorithm. Pit shells generated by Whittle are imported into Q’Pit for mine design, Life of Mine (LOM) production scheduling, and Mineral Reserve reporting.

 

 

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There are ten different material type classifications for ore at Lagunas Norte, along with multiple classifications for waste material, some of which is designated for potential future processing via other process methods thus stockpiled separately as waste. In addition, waste material is identified as non-acid generating (NAG) or potentially acid generating (PAG) in order to determine destination.

The ten material type classifications for ore are a function of gold grade, carbon content (TCM), sulphur content, and copper content; each has a set of defined metallurgical properties with recoveries and operating costs. Material type classification is based primarily on logging and analysis of production blast hole cuttings.

In general, the ore is considered to be clean or contaminated, depending on the quantity of TCMs and sulphur present, with ore being considered contaminated if it is preg-robbing in the HLF. Table 16-2 presents a detailed breakdown of the ten ore material type classifications. In addition, the average metallurgical gold recovery for each ore type is presented based on the year end 2011 cut-off grade report for the current reserves.

TABLE 16-2 ORE TYPE CLASSIFICATION

Barrick Gold Corporation – Lagunas Norte Mine

 

Ore Type

   g/t Au      TCM %    S %      ppm
Cu
     Au Process
Recovery
 

M1: crush, clean

     >= 0.40       < 0.10      < 0.25         —           85.3

M1_LG: crush, clean

     < 0.40       < 0.10      < 0.25         —           85.3

M1A: crush, clean

     —         < 0.10      <0.40         < 350         84.5

M2AL: crush, clean

     —         ³ 0.10 & < 0.20      < 0.25         —           70.0

M3: crush, sulphide

     —         < 0.10      ³ 0.40         < 350         77.0

M3A: crush, sulphide

     —         < 0.10      ³ 0.25         ³350         15.7

M2AH: crush, low TCM

     —         ³0.20 & < 0.50      < 0.25         —           60.3

M2B: ROM, contaminated

     —         ³ 0.50 & < 1.50      < 0.25         —           42.4

M3B_Low: crush, contaminated

     —         ³0.10 & < 0.50      ³ 0.25         —           29.2

M3B_Mid: ROM, contaminated

     —         ³ 0.50 & < 1.50      ³ 0.25         —           29.2

Notes:

 

1. For the g/t Au column the prevailing cut-off grade overrides all entries as the minimum gold grade required to be considered as ore, otherwise there are no restrictions for gold.
2. A ‘-’ symbol in the ppm Cu column indicates there are no restrictions for copper.
3. All ore types with TCM ³ 1.5% are not considered as Mineral Reserves due to low gold/silver recovery and preg-robbing properties.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Clean ore is designated for the clean heap leach facility (CHLF), while contaminated ore is designated for the single pass heap leach facility (SPHLF). Both the CHLF and the SPHLF are located within the single footprint of the HLF. The overall weighted gold recovery for CHLF ores is 83%, and for SPHLF ores it is 49%.

In general, all CHLF ore is sent to the crusher prior to HLF placement. In addition, SPHLF ores with TCM < 0.5% are sent to the crusher prior to HLF placement permitting an increase in metal recovery over ROM placement, whereas SPHLF ores with TCM ³ 0.5% are sent to the HLF without crushing.

Table 16-3 presents the parameters used for developing the mine model and running the open pit optimizations in Whittle. The overall gold and silver recovery is presented for the Mineral Reserve statement grades. Actual gold and silver recovery is calculated on a block by block basis dependent on ore type (see Table 16-2) and grade.

TABLE 16-3 MINE OPTIMIZATION PARAMETERS

Barrick Gold Corporation – Lagunas Norte Mine, Peru

 

Input Parameter

   Units    Value  

Revenue Factors:

     

Au Price

   US$/oz      1,200.00   

Ag Price

   US$/oz      22.00   

Au Pay Factor

   %      100   

Ag Pay Factor

   %      100   

Exchange Rate

   PEN:US$      2.75   

Selling Costs:

     

Refining

   US$/oz      2.18   

Royalty

   %      2.51   

Pit Slopes (Inter-ramp) by Rocktype:

     

By Zone

   degrees      Variable   

Mining Parameters:

     

Mining Reference Cost

   US$/t moved      1.958   

Re-handle: M1_LG ores

   US$/t moved      1.22   

Re-handle: Colluvial ores

   US$/t moved      0.50   

Mining Recovery

   %      100   

Mining Dilution

   %      0   

Processing Parameters:

     

Au Recovery, Overall

   %      64   

 

 

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Input Parameter

   Units    Value  

Ag Recovery, Overall

   %      21   

Process Cost, CHLF Ore

   US$/t Crush      2.09   

Process Cost, SPHLF Ore

   US$/t Crush      2.43   

Process Cost, SPHLF Ore

   US$/t ROM      2.18   

Heap Leach, Placement

   US$/t process      0.38   

Heap Leach, Re-handle

   US$/t moved      0.80   

Heap Leach Expansion

   US$/t process      0.78   

G&A Cost

   US$/t process      1.11   

Operating Assumptions:

     

HLF Placement Rate

   tpd      63,000   

Average Specific Gravity

   t/m3      2.54   

Diesel, FOB Site

   US$/L      0.91   

Explosives, Average FOB Site

   US$/kg      0.76   

Cyanide, FOB Site

   US$/kg      2.36   

Lime, FOB Site

   US$/kg      0.16   

Electricity, FOB Site

   US$/kWhr      0.07   

The Whittle optimizations are run at gold prices between US$960/oz and $1,440/oz for use in pit phase selection for production sequencing and test sensitivity to pit limits at higher gold prices. The cash optimum pit at US$1,200/oz gold is selected for use in the ultimate pit design as it maximizes reportable ounces and is very similar to the best Net Present Value (NPV) pit.

Mining cost is an average of all tonnes moved based on a detailed LOM operating cost estimate with cost sensitivities run up to ± 20%. No mining recovery or mining dilution is assumed in the Whittle optimization as this is factored into the resource model by a combination of block size selection and continuity of the mineralization. In some instances, diluting material will grade above the cut-off but will not be considered ore due to TCM content. Mining factor assumptions are verified through good reconciliation performance of the resource model to the ore control model and dispatch reporting.

Mining of the Shulcahuanca is not permitted. In order to deal with this and still produce an optimized open pit result, the cost of mining blocks within the restricted Shulcahuanca area are adjusted to force the optimum pit boundaries to work around the restricted area.

A separate process cost is applied to CHLF and SPHLF ore types as SPHLF ores require a greater quantity of consumables. All ore types placed are charged a heap

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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leach placement cost which is variable over the LOM dependent on the haulage profile for the given period. SPHLF ores are charged a rehandle cost as spent material is relocated to another area of the HLF once the leach cycle has completed, in order to allow for placement of the next batch of SPHLF ore. Heap leach expansion costs are applied to all ore processed as an operating cost, along with general and administrative costs.

The HLF placement rate is the legal limit for placement based on Lagunas Norte’s operating permits; this includes all material placed whether crushed or ROM. The LOM production schedule considers crushing at 57,000 tpd plus 6,000 tpd of ROM contaminated ore placement. This schedule results in the build-up of approximately 30 million tonnes of contaminated ore in stockpile for processing at the end of the mine life.

Cut-off grades for reporting Mineral Reserves are calculated utilizing the following formula:

COG=[(Cp+Hle+Hlp+Cga)/((YAu*(SPAu-TRAu)+(YAg*(SPAg-TRAg))*(1-CR))]*31.1035

Where, COG = internal (breakeven in-pit) gold equivalent cut-off grade (g/t)

 

  Cp = processing cost ($/t processed)
  Hle = heap leach expansion cost ($/t processed)
  Hlp = heap leach placement cost ($/t processed)
  Cga = general and administrative cost ($/t processed)
  YAu = gold metal recovery (fraction)
  YAg = silver metal recovery (fraction)
  SPAu = gold metal selling price ($/oz)
  SPAg = silver metal selling price ($/oz)
  TR = metal TC/RC and transport cost ($/oz)
  CR = Centromin Royalty (fraction)

Table 16-4 details internal cut-off grades for each ore material type. Both resource and reserve cut-off grade estimate details for Lagunas Norte are very well documented in Garcia (2011).

 

 

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TABLE 16-4 INTERNAL CUT-OFF GRADES, MINE RESERVES

Barrick Gold Corporation – Lagunas Norte Mine, Peru

 

Ore Type

   Internal
Cut-Off

g/t Au
 

M1: crush, clean

     0.40   

M1_LG: crush, clean

     0.17   

M1A: crush, clean

     0.14   

M2AL: crush, clean

     0.17   

M3: crush, sulphide

     0.16   

M3A: crush, sulphide

     0.80   

M2AH: crush, low TCM

     0.21   

M2B: ROM, contaminated

     0.33   

M3B_Low: crush, contaminated

     0.43   

M3B_Mid: ROM, contaminated

     0.48   

Notes:

 

1. Cut-off grades are calculated for the 2011 Mid/End-Year Cut-off Grade Report.

In addition to the mine reserve cut-off grades used for production scheduling, a floating cut-off grade is employed in daily operations, which is updated every three months or as required to better reflect the current gold price market. Mineralized material which falls between the mine reserve cut-off and floating cut-off is dispatched to the HLF as long as it is not displacing higher grade ores or upsetting the CHLF – SPHLF balance, in which case it would be dispatched to a stockpile.

Ultimate pit design is based on the optimum cash pit shell from Whittle at US$1,200/oz gold. Additional pit shells are used as guides to design pit phases leading up to the ultimate pit, in order to maximize Project NPV while maintaining a practical mine sequence and production schedule. Pit designs, long term production scheduling, and reserve reporting are completed in Q’Pit. Pit mid-bench lines are digitized in Q’Pit, honouring the Whittle pit shell outline and all pit wall slope constraints, and include haulage ramps.

In RPA’s opinion, the ultimate pit design honours the Whittle optimum pit shell, except for a few minor areas where access ramps are required or walls need to be smoothed out for operability.

 

 

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Detailed mine design parameters are presented in Table 16-5. Pit wall slopes vary based on structural domain, as per recommendations provided by Piteau Engineering Latin America S.A.C. (Piteau) discussed later in this section.

TABLE 16-5 MINE DESIGN PARAMETERS

Barrick Gold Corporation – Lagunas Norte Mine, Peru

 

Parameter

   Units    Value

Haul Road Width

   m    30

Haul Road Gradient, Maximum

   %    10

Mining Bench Height

   m    10

Safety Berm Width, Highwall

   m    8 - 12.9

Bench Face Angle, Highwall

   degrees    60 - 80

Inter-ramp Slope Angle, Highwall

   degrees    36 - 52

The 30 m haul road width design includes a single shoulder berm and water collection ditch.

RPA has reviewed the pit designs and is of the opinion that they follow good engineering practice. All phases are designed with sufficient room to allow for operations, and roads and ramps have been delineated.

GROUND CONDITIONS/SLOPE STABILITY

The geotechnical analysis to develop slope design parameters for Lagunas Norte was completed by Piteau, with the most recent work completed in October 2010. Piteau developed the feasibility-level geotechnical design criteria for Lagunas Norte in 2003. The 2010 work updates the 2003 study to cover changes from the original pit configuration, primarily relating to pit expansion and deepening. In addition, Piteau performs a scheduled site review once a year.

Piteau states that due to the relatively competent nature of the rock mass and relatively low overall slope heights planned for the Lagunas Norte open pit, the potential for deep-seated rock mass failure is considered unlikely and overall slope instability is not expected to control slope design. Consequently, explicit overall slope stability analyses were not conducted. Piteau recommends a review to determine if deep-seated overall slope stability analyses is warranted based on the new ultimate pit plan.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

Technical Report NI 43-101 – March 16, 2012

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Although the maximum designed slope height at Lagunas Norte is relatively small at approximately 215 m, there is a complex array of various slope zones, geologic features, and exposures to deal with. Piteau has identified eight structural domains plus overburden, with design sectors identified for each domain by compass bearing. Structural domain boundaries follow geological contacts, major faults, and axial fold planes. Design sectors are identified as either highwall slopes or footwall slopes.

Table 16-6 summarizes the current highwall slope design recommendations for Lagunas Norte. Ranges for the inter-ramp slope angle (IRA), bench face angle (BFA), and catch berm width (CBW) are provided to cover each domain sector excluding footwall slopes. All design sectors are based on double benching to 20 m except for two, which are considered at 10 m single bench height.

TABLE 16-6 SUMMARY OF PITEAU HIGHWALL SLOPE DESIGN RECOMENDATIONS

Barrick Gold Corporation – Lagunas Norte Mine

 

Highwall

Structural Domain

   IRA
(o)
   BFA
(o)
   CBW
(m)

KCW-U

   40 – 48    60 – 70    10.7 – 12.9

KCW-L

   43 – 47    60 – 70    10.0 – 12.1

KCE-U

   36 – 52    60 – 80    8.0 – 12.9

KCE-L

   43 – 50    60 – 75    10.0 – 12.6

AND-E

   46 – 50    70 – 75    11.4 – 12.6

AND-SW

   36 – 45    60 – 70    8.0 – 12.7

VOLC-W

   43 – 52    65 – 80    10.7 – 12.1

VOLCANICS

   41 – 48    60 – 70    10.7 – 12.7

OVERBURDEN

  

Maximum Overall Slope Angle of 30 degrees

Table 16-7 summarizes the applicable footwall slope design recommendations for Lagunas Norte, based on expected domain sectors. In general, the BFA is set to follow the bedding dip angle, with bench height increasing as the bedding dip angle decreases.

TABLE 16-7 SUMMARY OF FOOTWALL SLOPE DESIGN RECOMENDATIONS

Barrick Gold Corporation – Lagunas Norte Mine, Peru

 

Footwall

Structural Domain

   Bench
Height

m
   IRA
degrees
   BFA
degrees
   CBW
m

KCW-O

   20    43.2    65    12

KCW-W

   20    33.1    44    10

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

Technical Report NI 43-101 – March 16, 2012

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Footwall

Structural Domain

   Bench
Height

m
   IRA
degrees
   BFA
degrees
   CBW
m

KCW-E

   20    38.6    53    10

KCE-W

   40    28.4    32    10

KCE-E

   40    28.4    32    10

AND-SW

   20    57.6    88    12

KCC-W

   20    33.1    44    10

Figure 16-2 presents a plan view of the slope domains on the Lagunas Norte ultimate pit.

As can be seen in Figure 16-2, the majority of the ultimate pit falls within the KCW-U slope domain, followed by KCW-L, AND-E, and AND-SW.

As part of regular operations, Lagunas Norte is performing trial benches on interim walls to gain experience with specialized mining methods as required and document and assess the slope performance for optimization of final design.

As part of the overall water management plan, pit slopes require depressurization, which is achieved through a combination of vertical and horizontal dewatering wells, and control of surface water.

RPA is of the opinion that the work completed by Piteau was of an appropriate scope and the pit design is based on reasonable engineering analysis and assumptions.

A sophisticated system of manual and automated data collection equipment has been installed at Lagunas Norte for monitoring pit wall activity. In addition to a network of prisms, piezometers, and extensometers, a radar system and photogrammetry are used in high risk zones, such as on the northeast wall. Also, an automated theodolite and electronic distance meter (EDM) system is scheduled to be installed in 2012 for use with installed prisms.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

Technical Report NI 43-101 – March 16, 2012

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LOGO

 

16-13


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PRODUCTION SCHEDULE

Only Mineral Resources with classification of Measured or Indicated can be converted to Proven or Probable Mineral Reserves for production scheduling. A mine production schedule was developed from the mine design that targets the permitted limit for heap leach placement of ore at Lagunas Norte of 63,000 tpd. During open pit mining operations, on average 19.8 Mtpa (54,000 tpd) of ore is placed to the HLF, the majority of which is crushed prior to placement. This is followed by two additional years of production from stockpiles. Total ore plus waste mining over this period ranges from 34 Mtpa (92,000 tpd) up to 51 Mtpa (139,000 tpd). Table 16-8 summarizes the open pit mine production schedule by year.

TABLE 16-8 MINE PRODUCTION SCHEDULE

Barrick Gold Corporation – Lagunas Norte Mine, Peru

 

Year

   Open Pit Mine Production Schedule                       
   (Mt)      (g/t
Au)
     (g/t
Ag)
     (Moz
Au)
     (Moz
Ag)
     Waste
(Mt)
     Total
(Mt)
     Strip
Ratio
 

2012

     21.5         1.28         3.6         0.9         2.5         12.2         33.7         0.6   

2013

     28.4         0.90         2.6         0.8         2.4         9.4         37.8         0.3   

2014

     25.9         0.88         3.0         0.7         2.5         13.7         39.5         0.5   

2015

     25.1         1.03         4.5         0.8         3.6         18.8         43.9         0.8   

2016

     23.8         0.86         4.1         0.7         3.1         21.8         45.6         0.9   

2017

     24.7         0.86         5.2         0.7         4.1         24.6         49.3         1.0   

2018

     20.6         0.99         4.1         0.7         2.7         30.0         50.6         1.5   

2019

     17.7         0.99         3.5         0.6         2.0         26.6         44.3         2.2   

2020

     0.0         0.00         0.0         0.0         0.0         0.0         0.0         0.0   

2021

     0.0         0.00         0.0         0.0         0.0         0.0         0.0         0.0   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Totals

     187.7         0.97         3.8         5.8         23.0         157.2         345         0.8   

Notes:

 

1. Numbers may not add due to rounding.

During regular mining operations and as part of the LOM plan, short term and long term stockpiles are utilized. Low grade CHLF ores are stockpiled during times when crusher capacity is fully utilized by higher grade CHLF ores. Similarly, SPHLF ores are stockpiled when required to prevent displacement of better quality CHLF ores and to minimize preg-robbing issues. Last, potentially economic mineralization with TCM ³ 1.5% is also stockpiled for potential future processing via other methods, these stockpiles are not processed in the current LOM production schedule. Table 16-9 summarizes the HLF placement schedule by year, which includes production from both open pit operations and stockpile reclaim.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

Technical Report NI 43-101 – March 16, 2012

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TABLE 16-9 HEAP LEACH PLACEMENT SCHEDULE

Barrick Gold Corporation – Lagunas Norte Mine, Peru

 

     Heap Leach Placement Schedule      Recovery      Recoverable Metal  

Year

   (Mt)      (g/t
Au)
     (g/t
Ag)
     (Moz
Au)
     (Moz
Ag)
     Au
(%)
     Ag
(%)
     (Moz
Au)
     (Moz
Ag)
 

2012

     20.3         1.24         3.6         0.8         2.3         84         25         0.7         0.6   

2013

     20.6         0.98         2.8         0.6         1.8         84         27         0.5         0.5   

2014

     20.2         0.93         3.2         0.6         2.1         78         23         0.5         0.5   

2015

     20.1         1.01         4.6         0.7         3.0         74         23         0.5         0.7   

2016

     19.9         0.87         4.0         0.6         2.6         77         22         0.4         0.6   

2017

     19.5         0.91         5.2         0.6         3.2         61         21         0.3         0.7   

2018

     18.8         1.11         4.2         0.7         2.5         47         15         0.3         0.4   

2019

     18.2         1.52         4.1         0.9         2.4         34         12         0.3         0.3   

2020

     26.1         0.78         3.5         0.7         2.9         40         18         0.3         0.5   

2021

     9.8         0.12         2.3         0.0         0.7         85         30         0.0         0.2   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Totals

     193.3         0.98         3.8         6.1         23.6         64         21         3.9         4.8   

Notes:

 

1. Numbers may not add due to rounding.

The difference between totals for Tables 16-8 and 16-9 represents the stockpile inventory at the start of 2012, which is approximately 5.6 million tonnes at 1.49 g/t Au.

WASTE ROCK

Waste rock from Lagunas Norte open pit mining operations is stored starting just past the ultimate pit rim extending from the southeast along the eastern edge and to the north forming one continuous WRF with a total footprint of approximately 200 ha. Elevations range from approximately 4,000 MASL up to 4,200 MASL, with individual dump faces typically less than 50 m vertical.

To the east and southeast, the WRF is referred to as Botadero de Desmonte Este. The southern face of this area, which extends approximately 1,000 m east of the ultimate pit rim, is currently final and in the process of being reclaimed with new vegetation in place.

Heading north, the WRF wraps around the eastern rim of the ultimate pit and is currently active. At the far north end of the ultimate pit is the Botadero Vizcachas WRF which will extend approximately 800 m north of the ultimate pit rim. This area is the footprint of current mining operations in the moraines area. Once moraine stripping is complete, this area will be backfilled as part of the final WRF layout.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

Technical Report NI 43-101 – March 16, 2012

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In addition to the WRF identified above, a relatively small, approximately 10 ha, low grade stockpile is developed during mining of the Alexa area of the pit. During blasting operations on the Alexa plateau, some material is cast to the western free face resulting in a build-up of low grade NAG material on the side of this slope. This material is currently not in the LOM production schedule, however, will be considered for processing at the end of the mine life dependent on market conditions. In the original mine plan feasibility study, this area was referred to as the west waste facility, and had a significantly greater footprint than the current mine plan.

Approximately 75% to 80% of waste material destined for the WRF is considered PAG. As part of the water management plan, a series of water diversion and collection ditches are constructed, allowing for the collection of PAG drainage so that it can be treated at the water treatment plant prior to discharge.

Above cut-off grade material with TCM ³ 1.5%, thus currently considered waste, is stockpiled within the WRF footprint in the event a new process flowsheet is enacted that can profitably extract the gold from this material.

Remaining capacity of the east WRF is approximately 85 million m3, while there is approximately 90 million m3 of waste material in the LOM production plan with consideration for a 50% swell factor. The shortfall in WRF capacity is covered by the west waste facility and partial backfilling of the ultimate pit limits near the end of open pit mining operations.

Sufficient waste rock storage capacity exists within the WRF and ultimate pit backfill to support the mine production schedule and Mineral Reserve statement.

A comprehensive WRF geotechnical report was prepared by Piteau in 2009 for the current arrangement.

HEAP LEACH FACILITY

A HLF is permitted which at its final build straddles a ridgeline and sits in two neighbouring drainages. Currently, a single drainage is occupied directly south of the ultimate pit limit, with foundation preparation of the second drainage in progress immediately to the east of the first.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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The footprint of the final HLF design is approximately 300 ha starting at approximately 4,000 MASL. The maximum bench elevation is approximately 4,270 m, built up with bench intervals of 10 m.

Proven and Probable Reserves in the LOM production schedule total approximately 194 million tonnes, less than the remaining HLF maximum design capacity of approximately 200 million tonnes. Combining all classifications of Mineral Resources with Mineral Reserves within the ultimate pit limits based on the current process totals approximately 200 million tonnes, which indicates there is sufficient capacity within the current HLF design for future increases in production tonnes.

A comprehensive HLF geotechnical report was prepared by Golder in 2004, and has been revised for the expanded footprint.

MINE EQUIPMENT

Lagunas Norte operations are typical truck/shovel open pit operations, with all major production equipment furnished with GPS and dispatch systems. For production scheduling, equipment horsepower is de-rated for the operating elevations.

The current haul truck fleet consists of 12 Komatsu 730E trucks rated for a 184 tonne payload, with a peak truck count of 18 scheduled in 2016. Two to four of the current 12 haul trucks are assigned to hauling crushed ore from the overhead ore bin to the HLF on a daily basis as required. Peak production occurs in 2018 requiring haulage of 51 million tonnes ROM plus 19 million tonnes crush to the HLF. This demands that each truck move an average of approximately 3.9 million tonnes, which is near the upper limit for the proposed fleet.

Loading operations are conducted using a variety of diesel powered machines for production with the current fleet scheduled as follows:

 

   

Two Komatsu PC 4000 face shovels with 23 m3 buckets; and

 

   

Two Komatsu WA1200 front end loaders with 20 m3 buckets.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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Two additional Komatsu WA1200 front end loaders are put into service, one in 2014 followed by the second in 2015, bringing the front end loader fleet to four. In addition, consideration is being made to convert one Komatsu PC 4000 face shovel to a backhoe setup to provide greater mining flexibility. The peak ROM loading requirement is 51 million tonnes in 2018, plus additional stockpile and dynamic rehandle of approximately 8 million tonnes. Annual loading capacity with all six primary production loaders operating is over 70 Mtpa, sufficient to meet production requirements.

The diesel powered production drill fleet currently consists of four Reedrill SKS 12 blast hole drills. Over the next few years, three of the drills are scheduled to be replaced with new units, along with a fifth unit added in 2013. All drills are equipped with a 251 mm drill bit and are capable of single pass drilling the 10 m bench height plus one metre of sub-drill. Peak production drill capacity will be approximately 35 Mtpa to 40 Mtpa. This may strain the proposed fleet at peak production requirements of 51 million tonnes ROM in 2018, however, there is sufficient time and build-up to this peak to observe how the fleet performs and if additional drill capacity will be required. In addition, up to four smaller secondary drills will be available for wall control blasting requirements and other duties.

One of the primary production drills is set up for remote control operation. Only this drill is deployed in the Alexa area of the ultimate pit when drilling close to the western plateau edge where there is increased potential for unstable ground conditions.

For blasting, a blend of emulsion and ANFO are loaded into each hole. Consideration is given for a rainy and dry season, adjusting the powder factor to suit. Average powder factor targets are 0.48 kg/t in ore and 0.41 kg/t in waste. Very good rock fragmentation was observed during the site visit in both ore and waste material.

Mine mobile equipment production rates were reviewed with availability and utilization to see if mining production rates and costs are appropriate. RPA is of the opinion that the equipment productivities for the production fleet are appropriate. The current mine equipment fleet is listed in Table 16-10, along with major support equipment.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

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TABLE 16-10 MINE EQUIPMENT FLEET

Barrick Gold Corporation – Lagunas Norte Mine, Peru

 

Equipment

   Manufacturer    Current
2012

Haul Truck, 730E

   Komatsu    12

Face Shovel, PC4000

   Komatsu    2

Wheel Loader, WA1200

   Komatsu    2

Drill, SKS 12

   Reedrill    4

Drill, ECM-370

   Ingersoll Rand    1

Drill, Ranger 700

   Sandvik    1

Track Dozer, D375A

   Komatsu    7

Motor Grader, GD825A

   Komatsu    4

Backhoe, PC300LC

   Komatsu    4

Backhoe, PC750

   Komatsu    1

Backhoe, WB140

   Komatsu    1

Wheel Loader, WA500

   Komatsu    1

Wheel Dozer, WD600

   Komatsu    3

Water Truck, 330M

   Komatsu    2

Utility Trucks, 20t

   —      5

MANPOWER

Lagunas Norte operates on a 24-hour per day, 365 days per year schedule. For most operating positions, there are four work crews with two on site at any time working two 12-hour shifts per day, 14 days on followed by 14 days off.

Mining operating manpower is based on approximately four operators for each operating position. Mining manpower for operations, maintenance including process maintenance, and technical services in 2012 is budgeted for 390 employees. RPA considers the manpower estimates to be reasonable.

MINE INFRASTUCTURE

Lagunas Norte has all necessary infrastructure for a large open pit mine operation in a remote location at high altitude. Mining related infrastructure includes a truck shop, truck wash facility, warehouse, fuel storage and distribution facility, explosives storage and magazine sites, and electrical power distribution and substations to support construction and mine operations.

 

 

Barrick Gold Corporation – Lagunas Norte Mine, Project # 1681

  

Technical Report NI 43-101 – March 16, 2012

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&