EX-99.1 2 d325561dex991.htm EX-99.1 EX-99.1

Exhibit 99.1

 

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BARRICK GOLD CORPORATION

 

TECHNICAL REPORT ON THE

CORTEZ JOINT VENTURE OPERATIONS,

LANDER AND EUREKA COUNTIES,

STATE OF NEVADA, U.S.A.

NI 43-101 Report

Qualified Persons:

R. Dennis Bergen, P.Eng.

Michael B. Gareau, P.Geo.

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 Cortez Joint Venture Operations, Lander and Eureka Counties, State of Nevada, U.S.A.
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 #1676    Status &

Issue No.

   FINAL

Version

   Rev 0
Issue Date    March 16, 2012   
Lead Author   

R. Dennis Bergen

Michael Gareau

Kathleen A. Altman

   (Signed)

(Signed)

(Signed)

Peer Reviewer    Graham Clow    (Signed)
Project Manager Approval    R. Dennis Bergen    (Signed)
Project Director Approval    Richard Lambert    (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

     1-5   

2 INTRODUCTION

     2-1   

3 RELIANCE ON OTHER EXPERTS

     3-1   

4 PROPERTY DESCRIPTION AND LOCATION

     4-1   

5 ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY

     5-1   

6 HISTORY

     6-1   

7 GEOLOGICAL SETTING AND MINERALIZATION

     7-1   

Regional Geology

     7-1   

Local Geology

     7-5   

Property (Deposit) Geology

     7-9   

Mineralization

     7-12   

8 DEPOSIT TYPES

     8-1   

9 EXPLORATION

     9-1   

10 DRILLING

     10-1   

11 SAMPLE PREPARATION, ANALYSES AND SECURITY

     11-1   

Sampling Method and Approach

     11-1   

Sample Preparation, Analysis and Security

     11-7   

Quality Assurance and Quality Control

     11-12   

12 DATA VERIFICATION

     12-1   

13 MINERAL PROCESSING AND METALLURGICAL TESTING

     13-1   

14 MINERAL RESOURCE ESTIMATE

     14-1   

Summary

     14-1   

Pipeline Complex

     14-3   

Gold Acres

     14-9   

Cortez Hills Complex

     14-15   

Cortez Pits (NW Deeps)

     14-23   

Cut-off Grades and Resource Reporting

     14-26   

Resource Classification

     14-27   

Mineral Resource Estimate December 31, 2011

     14-28   

RPA Review of Resource Estimates

     14-35   

15 MINERAL RESERVE ESTIMATE

     15-1   

Summary

     15-1   

Open Pit Mining

     15-10   

 

 

Barrick Gold Corporation – Cortez Joint Venture Operations    Rev. 0 Page i
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Cut-off Grade

     15-15   

Underground Mining

     15-20   

Reconciliation

     15-23   

16 MINING METHODS

     16-1   

Open Pit Mine

     16-2   

Underground Mine

     16-9   

Life of Mine Plan

     16-14   

17 RECOVERY METHODS

     17-1   

18 PROJECT INFRASTRUCTURE

     18-1   

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   

Social or Community Requirements

     20-4   

Mine Closure Requirements

     20-4   

21 CAPITAL AND OPERATING COSTS

     21-1   

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   

28 DATE AND SIGNATURE PAGE

     28-1   

29 CERTIFICATE OF QUALIFIED PERSON

     29-1   

LIST OF TABLES

 

          PAGE  

Table 1-1

   Mineral Resource Estimate – December 31, 2011      1-2   

Table 1-2

   Mineral Reserve Estimate – December 31, 2011      1-3   

Table 1-3

   LOM Capital Costs      1-13   

Table 1-4

   LOM Operating Costs      1-14   

Table 6-1

   History of Exploration and Mining at Cortez Site      6-2   

Table 6-2

   Cortez Project Annual Production, 1969–2011      6-6   

Table 11-1

   Amount of RC Sample Reduction      11-1   

Table 11-2

   Blast Hole Sample Reduction      11-4   

Table 11-3

   Chain of Custody Summary      11-12   

 

 

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Table 11-4

   Cortez Laboratory Standard and Blank Performance      11-18   

Table 13-1

   Mill Gold Recovery Equations      13-2   

Table 13-2

   Heap Leach Ultimate Gold Recovery Equations      13-2   

Table 13-3

   Refractory Ore Gold Recovery Equations      13-3   

Table 13-4

   Refractory Ore Gold Recovery Equations      13-4   

Table 13-5

   Heap Leach Production      13-5   

Table 14-1

   Mineral Resource Summary - December 31, 2011      14-1   

Table 14-2

   Cortez Mineral Resource Models      14-2   

Table 14-3

   Bulk Density – Pipeline Complex      14-3   

Table 14-4

   Pipeline Complex Block Model Parameters      14-4   

Table 14-5

   Search Ellipse Orientations by Domain – Pipeline Complex      14-6   

Table 14-6

   Interpolation Search Ellipse Parameters – Pipeline Complex      14-8   

Table 14-7

   Gold Acres Bulk Density      14-9   

Table 14-8

   Gold Acres Indicator Model Estimation Parameters      14-10   

Table 14-9

   ID3 Interpolation Passes Inside and Outside the Gold Acres 0.50 Indicator Model      14-12   

Table 14-10

   Gold Acres Untransformed Gold Statistics      14-14   

Table 14-11

   Bulk Density Cortez Hills Complex Mid-Year 2011      14-16   

Table 14-12

   Lower Zone Indicator Model Estimation Parameters      14-19   

Table 14-13

   ID3 Interpolation Passes Inside and Outside the Lower Zone 0.50 Indicator Model      14-21   

Table 14-14

   CHOP – Comparitive Statistics      14-23   

Table 14-15

   CHUG Middle Zone – Comparitive Statistics      14-23   

Table 14-16

   Lower Zone – Comparitive Statistics      14-23   

Table 14-17

   Cortez Pits Bulk Density      14-24   

Table 14-18

   ID3 Estimation Runs Cortez Pits Area      14-26   

Table 14-19

   Mineral Resource Cut-off Grades at $1,400/oz      14-27   

Table 14-20

   Total Measured & Indicated Mineral Resources – December 31, 2011      14-29   

Table 14-21

   Mill - Measured & Indicated Mineral Resources - December 31, 2011      14-30   

Table 14-22

   Heap Leach - Measured & Indicated Mineral Resources - December 31, 2011      14-31   

Table 14-23

   Refractory - Measured & Indicated Mineral Resources - December 31, 2011      14-32   

Table 14-24

   Total Inferred Mineral Resources – December 31, 2011      14-33   

Table 14-25

   Inferred Mineral Resources by Process Type – December 31, 2011      14-34   

Table 15-1

   Total Mineral Reserves – December 31, 2011      15-2   

Table 15-2

   Proportion of Reserves by Deposit      15-5   

Table 15-3

   Ore Process Proportion by Deposit      15-6   

Table 15-4

   Mill Mineral Reserves – December 31, 2011      15-7   

Table 15-5

   Heap Leach Mineral Reserves – December 31, 2011      15-8   

Table 15-6

   Refractory Mineral Reserves – December 31, 2011      15-9   

Table 15-7

   Leach Cut-off Grades      15-16   

Table 15-8

   Mill Cut-off Grade      15-16   

Table 15-9

   Refractory Cut-off Grade      15-17   

Table 15-10

   Mill Leach Inter-Process Cut-off      15-18   

Table 15-11

   Cortez Hills Whittle Pit Optimization Parameters      15-19   

Table 15-12

   Cortez Pits Whittle Pit Optimization Parameters      15-19   

Table 15-13

   Gold Acres Whittle Pit Optimization Parameters      15-20   

Table 15-14

   Pipeline Whittle Pit Optimization Parameters      15-20   

Table 15-15

   Underground Cut-off Grade Calculations      15-22   

Table 15-16

   Cortez Hills Open Pit Reconciliation      15-25   

 

 

Barrick Gold Corporation – Cortez Joint Venture Operations    Rev. 0 Page iii
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Table 15-17

   Underground Mineral Reserve Reconciliation      15-26   

Table 16-1

   Mine Operations      16-1   

Table 16-2

   Mill Production History      16-2   

Table 16-3

   Major Open Pit Equipment      16-8   

Table 16-4

   Underground Equipment Fleet      16-14   

Table 16-5

   Open Pit LOM Plan      16-15   

Table 16-6

   Underground LOM Plan      16-16   

Table 16-7

   Cortez Mill Processing Plan      16-17   

Table 16-8

   Cortez Heap Leach Processing Plan      16-18   

Table 16-9

   Cortez Refractory Processing Plan      16-18   

Table 16-10

   Total LOM Processing Plan      16-19   

Table 20-1

   Major Environmental Permits      20-3   

Table 20-2

   Surface Disturbance      20-4   

Table 21-1

   LOM Capital Plan      21-1   

Table 21-2

   LOM Operating Costs      21-2   

Table 21-3

   Manpower      21-3   

LIST OF FIGURES

 

          PAGE  

Figure 4-1

   Location Map      4-3   

Figure 4-2

   Land Ownership Map      4-4   

Figure 4-3

   Deposit Locations      4-5   

Figure 4-4

   Cortez Hills Infrastructure      4-6   

Figure 4-5

   Pipeline Complex Infrastructure      4-7   

Figure 7-1

   Regional Geology      7-4   

Figure 7-2

   Local Geology      7-7   

Figure 7-3

   Local Stratigraphy      7-8   

Figure 10-1

   Drill Hole Map      10-3   

Figure 10-2

   Pipeline Complex Drill Hole Plan      10-8   

Figure 10-3

   Pipeline Deposit – Cross Section 59200N      10-9   

Figure 10-4

   Crossroads Deposit - Cross Section 52700N      10-10   

Figure 10-5

   Gap Deposit – Cross Section 55400N      10-11   

Figure 10-6

   Gold Acres Drill Hole Plan      10-12   

Figure 10-7

   Gold Acres Deposit - Cross Section 59800N      10-13   

Figure 10-8

   Cortez Hills Drill Hole Plan      10-15   

Figure 10-9

   Cortez Hills – Cross Section 28600N (A-A’) Breccia, Middle and Lower Zones      10-16   

Figure 10-10

   Pediment - Long-Section B-B’      10-17   

Figure 10-11

   Lower Zone - Long-Section C-C’      10-18   

Figure 10-12

   Cortez Pits Area (NW Deeps) Drill Hole Plan      10-19   

Figure 10-13

   Cortez Pits Area – Cross Section 38200N      10-20   

Figure 13-1

   Historical Heap Leach Data      13-6   

Figure 14-1

   Resource Estimation Domains Pipeline Complex      14-5   

Figure 14-2

   Omnidirectional Correlogram – Pipeline Complex      14-7   

Figure 14-3

   Gold Acres Domains and Interpolation Search Ellipses      14-11   

Figure 14-4

   Omnidirectional Correlogram – Gold Acres      14-13   

Figure 14-5

   Gold Acres Vertical Section at 60,500 N      14-13   

Figure 14-6

   Gold Acres Vertical Section at 60,000 N      14-14   

 

 

Barrick Gold Corporation – Cortez Joint Venture Operations    Rev. 0 Page iv
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Figure 14-7

   Histogram Comparing Composites with Estimated Block Grades – Gold Acres      14-14   

Figure 14-8

   Cumulative Log Plot Comparing Composites with Estimated Block Grades – Gold Acres      14-15   

Figure 14-9

   Lower Zone Domains for Indicator Model      14-19   

Figure 15-1

   Deposit Locations      15-4   

Figure 15-2

   Cortez Hills Pits and Phases      15-12   

Figure 15-3

   Pipeline Pits and Phases      15-14   

Figure 15-4

   Schematic View of the Cortez Hills Underground      15-21   

Figure 16-1

   Cortez Hills Open Pit Phase 3 Pit Slope Design Sectors      16-5   

Figure 17-1

   Pipeline Mill Process Flow Sheet      17-5   

Figure 17-2

   Heap Leach Simplified Process Flow Sheet      17-6   

Figure 17-3

   Goldstrike Pressure Oxidation Flow Sheet      17-7   

Figure 17-4

   Goldstrike Roaster Flow Sheet      17-8   

Figure 18-1

   Pipeline Complex Infrastructure      18-2   

Figure 18-2

   Cortez Hills Complex Infrastructure      18-3   

Figure 20-1

   Barrick Cortez Permit Areas      20-2   

 

 

 

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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 Cortez Open Pit and Underground Mine (Cortez or the Project), in Eureka and Lander Counties, Nevada, USA. The purpose of this report is to support public disclosure of Mineral Resources and Mineral Reserves at Cortez as of December 31, 2011. This Technical Report conforms to NI 43-101 Standards of Disclosure for Mineral Projects. RPA visited the operations between November 14 and 17, 2011.

Barrick is a Canadian publicly traded mining company with a portfolio of operating mines and projects across five continents. The Cortez Operations are located in northeastern Nevada approximately 80 mi west and south of Elko.

The Cortez Mine is a joint venture between two wholly owned subsidiaries of Barrick, Barrick Cortez Inc. (60%) and Barrick Gold Finance Inc. (40%). The Cortez operations consist of the Pipeline, Gap, Cortez and Cortez Hills open pits, the Cortez Hills underground mine, an 11,000 stpd carbon-in-leach (CIL) gold plant, heap leach pads and heap leach processing plants, the planned Crossroads open pit, and the Mineral Resources in the Cortez Hills underground mine and at the Hilltop exploration project.

The open pit is a large scale operation utilizing a conventional truck and shovel fleet and mining approximately 300,000 stpd of ore and waste. Mining operations move between the various pits over the Life of Mine (LOM) plan. The underground mine is a 1,300 stpd mechanized mine. Ore from the mines is treated at an oxide mill at the site, on leach pads and refractory ore is shipped to Barrick’s Goldstrike operation for processing.

Table 1-1 summarizes the Cortez Mineral Resources as of December 31, 2011.

 

 

Barrick Gold Corporation – Cortez Joint Venture Operations    Rev. 0 Page 1-1
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TABLE 1-1 MINERAL RESOURCE ESTIMATE - DECEMBER 31, 2011

Barrick Gold Corporation – Cortez Operations

 

     Total Measured + Indicated      Total Inferred  

Mine &

Process Type

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

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

(000 oz)
 

Open Pit

                 

Mill

     5,128         0.058         296         1,740         0.058         101   

Heap Leach

     37,272         0.011         417         15,107         0.011         166   

Refractory

     5,516         0.107         589         1,836         0.148         271   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Sub-Total Open Pit

     47,916         0.027         1,302         18,684         0.029         537   

Underground

                 

Mill

     1,719         0.382         656         1,680         0.327         549   

Refractory

     4,757         0.378         1,800         1,517         0.349         529   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Sub-Total Underground

     6,476         0.379         2,456         3,197         0.337         1,078   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Totals

     54,391         0.069         3,758         21,881         0.074         1,615   

Notes:

  1. CIM definitions were followed for Mineral Resources.
  2. Mineral Resources are estimated at various cut-off grades depending on material type and processing stream.
  3. Mineral Resources are estimated using an average gold price of US$1,400 per ounce.
  4. A minimum mining width of 10 ft was used.
  5. Mineral Resources are additional to and exclusive of Mineral Reserves.
  6. Numbers may not add due to rounding.

Table 1-2 summarizes the Cortez Mineral Reserves as of December 31, 2011.

 

 

Barrick Gold Corporation – Cortez Joint Venture Operations    Rev. 0 Page 1-2
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TABLE 1-2 MINERAL RESERVE ESTIMATE – DECEMBER 31, 2011

Barrick Gold Corporation – Cortez Operations

 

     Total Proven      Total Probable      Total Proven + Probable  

Zone

   Tons      Grade      Au Oz      Tons      Grade      Au Oz      Tons      Grade      Au Oz  
   (000)      (oz/st)      (000)      (000)      (oz/st)      (000)      (000)      (oz/st)      (000)  

By Source

                          

Open Pit total

     24,887         0.039         973         270,418         0.037         9,881         295,306         0.037         10,854   

Underground total

     770         0.590         455         5,747         0.427         2,454         6,516         0.446         2,908   

Stockpiles Sub-total

     5,057         0.144         726                  5,057         0.144         726   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Cortez Total

     30,714         0.070         2,153         276,165         0.045         12,335         306,879         0.047         14,488   

By Process Stream

                          

Oxide Mill Reserves

     5,860         0.173         1,012         46,936         0.134         6,303         52,796         0.139         7,316   

Heap Leach Reserves

     19,576         0.013         252         215,711         0.013         2,715         235,287         0.013         2,967   

Refractory Reserves

     5,278         0.168         889         13,518         0.245         3,316         18,797         0.224         4,205   

Notes:

  1. CIM definitions were followed for Mineral Reserves.
  2. Mineral Reserves are estimated at a cut-off grade of 0.004 oz/st Au to 0.075 oz/st Au depending on process.
  3. Mineral Reserves are estimated using an average long-term gold price of US$1,200 per ounce.
  4. A minimum mining width of 15 ft was used.
  5.

Bulk density is 0.052 tons/ft3 to 0.091 tons/ft3 depending on material type.

  6. Numbers may not add due to rounding.

CONCLUSIONS

The Cortez Mine is currently in operation, with open pit and underground mining operations providing feed for onsite oxide mill and heap leach facilities and refractory ores for offsite processing. Based on RPA’s site visit, interviews with Cortez personnel and subsequent review of gathered information, RPA offers the following conclusions:

GEOLOGY AND MINERAL RESOURCES

 

   

Measured, Indicated, and Inferred Mineral Resources, excluding Mineral Reserves, have been estimated at Cortez as at December 31, 2011.

 

   

Measured and Indicated Mineral Resources total 54.4 million tons at a grade of 0.069 oz/st Au, containing 3.76 million ounces of gold.

 

   

Inferred Mineral Resources total 21.9 million tons at a grade of 0.074 oz/st Au, containing 1.62 million ounces of gold.

 

 

Barrick Gold Corporation – Cortez Joint Venture Operations    Rev. 0 Page 1-3
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The open pit and underground Mineral Resources as stated by Cortez management are estimated in a manner consistent with industry practices.

 

   

The Cortez Mineral Resource estimates meet the requirements of NI 43-101.

 

   

The drilling, data collection, sampling, analyses, geological interpretation, modelling, and resource estimation practices are considered to be satisfactory and generally appropriate for the deposit types, mineralization style, and planned mining methods.

MINING AND MINERAL RESERVES

 

   

The Proven and Probable Mineral Reserve are estimated as of December 31, 2011.

 

   

Proven and Probable Mineral Reserves total 306.9 million tons at a grade of 0.047 oz/st Au, containing 14.49 million ounces of gold.

 

   

The Mineral Reserves are contained within five open pit deposits, two underground deposits, and surface stockpiles.

 

   

Mining is underway at a rate of approximately 300,000 stpd in the open pit and at a rate of approximately 1,300 stpd underground. The stripping ratio averages 5:1 for the open pit. The ore delivery varies and the stockpiles are used to even the ore flow to the plant.

 

   

The mining methods and equipment are suitable for the deposits.

PROCESS

 

   

RPA is of the opinion that metallurgical test work completed for the Project has been appropriate to establish optimal processing routes for the different mineralization styles encountered in the deposits and that the gold recovery calculations for all of the processing options are currently appropriate to estimate the amount of gold that will be recovered over the LOM.

ECONOMIC ANALYSIS

 

   

The Project generates a positive cash flow and demonstrates robust economic results based upon the assumptions in this report.

RECOMMENDATIONS

RPA makes the following recommendations:

GEOLOGY AND MINERAL RESOURCES

 

   

Some sampled intervals in the database have been split into two or more smaller intervals that carry the duplicate sample numbers and the same assay results. This is a function of subdivision of original sample intervals, within the historical data, made by Cortez personnel to reflect observed geological contacts. RPA recommends, as a statistically preferable practice, that Cortez continue the

 

 

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stated process where the actual sampled intervals are set to reflect the logged geological breaks and contacts so as to reduce and eliminate the need for a later subdivision and repetition of assay values.

 

   

There should be explanatory notes attached to the database where any adjustments, corrections or additions are made to the database that do not correspond to the original or source data documents.

 

   

Exploration and resource definition should continue to upgrade the Inferred Mineral Resources.

 

   

Exploration drilling should continue to evaluate potential extensions of the Middle and Lower zones of the Cortez Hills Complex.

MINING AND MINERAL RESERVES

 

   

Cortez should consider alternative ore haul and processing options for the refractory ores to increase the annual processing capacity of these ores.

PROCESSING

 

   

More accurate short term estimates for gold production can be made if the leaching kinetics curves are included in the budget estimation process.

ECONOMICS

 

   

Preliminary economic assessments should continue for the various advanced exploration stage projects.

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 Cortez Mine is currently in production, and a material expansion is not being planned. RPA has performed an economic analysis of the Cortez Mine using the estimates presented in this report and confirms that the outcome is a positive cash flow that supports the statement of Mineral Reserves.

TECHNICAL SUMMARY

PROPERTY DESCRIPTION, LOCATION AND LAND TENURE

The Project is located 80 mi southwest of Elko, Nevada, USA. The Project is located in Eureka and Lander Counties. The Cortez property is surrounded by the Cortez Joint Venture Area of Interest (CJVAOI) that covers approximately 288.3 mi2 (100,561 ha). The property consists of 304.6 mi2 (78,890 ha) of unpatented mining claims and 83.7 mi2 (21,671 ha) of patented mining claims and fee mineral and surface land.

 

 

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The CJVAOI includes private land, patented and unpatented mineral claims and fee land and land controlled by competitors. The approximate co-ordinates of the Pipeline open pit are approximately 40°15’ North latitude and 116°43’ West longitude.

The 2012 holding costs for the Cortez property include $3.2 million in holding costs and $0.45 million in lease payments.

All Mineral Reserves and Mineral Resources, in addition to existing and future facilities to be used to exploit the Project deposits, are on public lands administered by the U.S. Department of Interior, Bureau of Land Management (BLM).

The Cortez operation is subject to a number of royalties including a 1.5% gross smelter return (GSR) on all production, a sliding scale, 0.40% to 5.0%, GSR royalty over the Pipeline/South Pipeline deposits, an additional sliding-scale GSR royalty on the undeveloped Crossroads deposit. GSR is defined as 100% of smelter revenue before deductions for refining and transportation. ECM Inc. (ECM) holds a net value royalty of 5.0% of gold sales from the South Pipeline deposit (which is approximately equivalent to a 3.9% GSR).

Rio Tinto is entitled to the payment of $50 million if and when an additional 12 million ounces of contained gold Mineral Resources are added to Barrick’s December 31, 2007 Mineral Reserve statement for Cortez. In addition Rio Tinto holds a sliding-scale royalty (of 0% at gold prices less than $400/oz to 3% at gold prices greater than $900/oz) on 40% of all Cortez production in excess of 15 million ounces on and after January 1, 2008.

INFRASTRUCTURE

There is extensive infrastructure in place to support the Cortez operations including:

 

   

The 11,000 stpd No. 2 Mill complete with run-of-mine (ROM) pad and crushing circuit

 

   

Pipeline leach pad areas (Area 28 and Area 30) and gold recovery plant

 

 

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Area 34 leach pad and gold recovery plant for Cortez Hills and Pediment

 

   

A tailings management facility which is being expanded

 

   

A gyratory crusher at the Cortez Hills open pit (CHOP) and an 11 mi long conveyor to the No. 2 Mill

 

   

Existing open pit mines at Cortez Hills open pit (CHOP), Cortez, Pipeline, and Gap

 

   

Pit dewatering wells and pumps for the open pits

 

   

Infiltration ponds for the disposal of water

 

   

An existing underground mine at Cortez Hills underground (CHUG)

 

   

Batch plant for shotcrete and cemented rock fill preparation

 

   

Stockpile areas for an assortment of ore types

 

   

Office complexes at the Mill No. 2, Mill No. 1, CHUG, and CHOP

 

   

Equipment maintenance shops at CHOP, CHUG, and adjacent to the Mill No. 2

 

   

Exploration offices, core handling and core storage warehouse

 

   

System of public and private roads connecting the facilities

 

   

Shared business support services from the business unit offices in Elko

HISTORY

Mining in the Cortez Mining District began with the discovery of silver ore in 1862. Underground silver mining was conducted in the area until the 1930s. Mineralization at Hilltop was also identified during the 1860s. Gold mineralization at Gold Acres was discovered in the late 1920s and mined by a small mining company from 1935 to 1960.

In 1959, American Exploration & Mining Co. (AMEX), a wholly-owned US subsidiary of Placer Development Ltd. (subsequently Placer Dome Inc.), entered into a lease-option agreement on the properties and started extensive exploration. In 1964, AMEX formed the Cortez Joint Venture (CJV).

The CJV initiated open pit mining in 1973, from the Gold Acres North and South pits. Leaching and milling of Gold Acres stockpiles and dumps continued until 1983. Mill-grade ores were mined from 1987 to 1996 and processed at the Cortez Mill No. 1. In 2003, the CJV commenced shipping Gold Acres refractory stockpiles for toll-processing at third-party facilities.

 

 

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The Horse Canyon deposits were discovered in early 1976. Three pits, North, South, and South Extension were mined in the period from 1984 to 1987. Exploration drilling campaigns at the Horse Creek deposit, originally discovered in the late 1960s, occurred in the mid-1980s and intermittently over the last ten years and are ongoing.

The Pipeline deposit was discovered by CJV geologists in March 1991 during drilling of deep condemnation holes. The Gap deposit was discovered in 1991 adjacent to the planned Stage 9 of the Pipeline pit.

In November 1991 CJV discovered the South Pipeline deposit. Construction of Mill No. 2 and pre-stripping of the first stage of the Pipeline pit began in 1996. Continued drilling resulted in the 1998 discovery of the Crossroads deposit beneath 550 ft of alluvium.

In 1996, CJV geologists began a program that led to the 1998 discovery of the Pediment deposit. The Cortez Hills deposit was discovered in October 2002. In 2004, the Cortez Hills Lower Zone was discovered. In November 2008 the Environmental Impact Statement (EIS) for the Cortez–Pediment development was approved. Production from underground began in late 2008, and the first ore production of Cortez Hills open pit (CHOP) occurred in late December 2009.

Barrick acquired an interest in Cortez through the 2006 acquisition of Placer Dome. In March 2008, Barrick acquired its 100% interest in the Project, purchasing the former Kennecott 40% interest, from Rio Tinto.

GEOLOGY AND MINERALIZATION

The Cortez gold district is in the eastern Great Basin of the Basin and Range Province. The Paleozoic basement rocks of northeastern Nevada are made up of a western deep-water, eugeoclinal siliclastic assemblage (Upper Plate) and an eastern shallow-water, miogeosynclinal carbonate assemblage (Lower Plate) of sedimentary strata. Cortez lies within the “Battle Mountain-Eureka Trend” (BMT), an alignment of gold mines and occurrences located in a northwest-southeast belt extending from the Marigold Mine some 50 miles northwest of Cortez, to Ruby Hill at Eureka 60 miles to the southeast. Paleozoic basement rocks have been folded and faulted, and cut by younger Jurassic and Tertiary aged intrusions.

 

 

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The Cortez deposits are “Carlin” style sedimentary rock-hosted and porphyry/epithermal deposits. Carlin deposits form as structurally and/or stratigraphically controlled replacement bodies consisting of strata-bound, tabular, disseminated gold mineralization occurring in Silurian-Devonian carbonate rocks. Deposits are localized at contacts between contrasting lithologies, metamorphosed to varying extents. They can also be discordant or breccia-related. The deposits are hydrothermal in origin, are usually structurally controlled and at Cortez are hosted in Lower Plate carbonate strata exposed by two erosional windows through allochthonous Upper Plate siliclastic units; the windows are on either side of Crescent Valley.

Mineralization consists primarily of submicron to micrometre-sized gold particles, very fine sulphide grains, and gold in solid solution in pyrite. Gold is disseminated throughout the host rock matrix in zones of silicified and decarbonatized, argillized, silty calcareous rocks and associated jasperoids. Gold may occur around limonite pseudomorphs of authigenic pyrite and arsenopyrite. Major ore minerals include native gold, pyrite, arsenopyrite, stibnite, realgar, orpiment, cinnabar, fluorite, barite, and rare thallium minerals. Gangue minerals typically comprise fine-grained quartz, barite, clay minerals, carbonaceous matter, and late-stage calcite veins.

In the Cortez district, the favoured host rocks for gold mineralization are the Wenban Limestone, followed by the Horse Canyon and Roberts Mountain formations. Mineralization reflects an interplay between structural and lithological ore controls in which hydrothermal solutions from intrusives moved to favourable porous decalcified limestone.

Mineralized host rocks are predominantly characterized as oxides, along with sulphidic and carbonaceous refractory material. Carbon content in the deposits is highly variable and occurs generally in the Wenban and Roberts Mountain Formations.

Supergene alteration extends up to 656 ft depth resulting in oxide ores which overlie the refractory sulphides. Alteration has liberated gold by the destruction of pyrite and resulted in the formation of oxide and secondary sulphate minerals which include goethite, hematite, jarosite, scorodite, alunite, and gypsum.

 

 

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EXPLORATION STATUS

Modern exploration commenced along the Battle Mountain–Eureka Trend in the 1960s, and has been nearly continuous since that time. Barrick funds ongoing multi-million dollar exploration programs each year in the Cortez district. Barrick has advanced stage exploration drilling projects in the area including the surface and underground drilling of the Cortez Hills Lower zones, and surface drilling and metallurgical test-work at Hilltop. Exploration crews are also working at the past producing Buckhorn gold-silver mine under an earn-in agreement.

MINERAL RESOURCES AND MINERAL RESERVES

RPA considers the December 31, 2011 Mineral Resource estimate completed by Barrick to be reasonable, acceptable, and NI 43-101 compliant. The Mineral Resources are exclusive of Mineral Reserves and are summarized in Table 1-1.

The resources are estimated from three dimensional block models created using Vulcan® software. Surfaces and solids representing topography, overburden, geological units and gold mineralization were incorporated into the resource block models. Resource estimates utilize drill hole, survey, geological, analytical and bulk density information entered, validated and maintained in a centralized acQuire® SQL Server database. Industry standard best practices were used to obtain the data; quality assurance and quality control protocols, as well as data validation procedures, were employed to insure the quality and quantity of data used for the resource estimates was appropriate and acceptable.

Twelve different gold deposits located in the Cortez operational district were modelled and estimated for contained mineral resources. Inverse distance weighted grade interpolation was used for a number of variables, including fire assay gold grades, cyanide leach gold grades and modelled fire assay to cyanide leach ratios. The latter is used to categorize mineral resources as mill, heap leach and refractory recovery processing materials.

 

 

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The Mineral Reserves for Cortez as of December 31, 2011 are summarized in Table 1-2. These Mineral Reserves are a combination of the open pit and underground operations and the stockpiles.

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

MINING METHOD

The LOM plan includes the mining and processing of the Mineral Reserves from 2012 to 2026.

OPEN PIT

The Cortez open pits are large scale operations utilizing a traditional truck and shovel fleet. There are five open pits within the Mineral Reserves. The Cortez Hills and Pediment pits are adjacent to one another and are located approximately 8.5 mi north of the Pipeline Complex that includes the Pipeline and South Pipeline, Gap and Crossroads pits. There are separate waste dump and stockpile locations for the two areas.

The open pit mining rate in 2012 is forecast to be 300,000 stpd and the rate is forecast increase to approximately 500,000 stpd in 2013. The LOM plan stripping ratio is 5:1. Ultimate pit limits were determined by generating Whittle pit shells based on the net cash generated and the recommended pit slopes. Haul ramps were designed to be 120 ft wide, including the safety berm for double lane traffic, and have a maximum grade of 10%. Mining thickness is 40 ft in waste and 20 ft to 40 ft in ore.

UNDERGROUND

The underground mine is a 1,300 stpd mechanized underground mine employing an underhand drift and fill stoping in the Breccia Zone with cemented rock fill to provide a safe working environment. The Middle Zone is planned to be mined by cut and fill.

 

 

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MINERAL PROCESSING

Ore from Cortez is either processed on site in the oxide processing facilities or transported to Barrick’s Goldstrike operation for refractory ore treatment.

Mill No. 2 or the Pipeline mill is a nominal 11,000 stpd oxide processing plant with crushing, a semi-autogenous grinding (SAG) mill, a ball mill, grind thickener, a carbon-in-column (CIC) circuit for the grind thickener overflow solution, a CIL circuit, tailings counter-current-decantation (CCD) wash thickener circuit, carbon stripping and reactivation circuits, and a refinery to produce gold doré. Plant throughput is currently estimated to be 11,500 stpd although it has consistently approached 14,000 stpd.

A primary gyratory crusher was installed adjacent to the Cortez Hills open pit together with a series of overland conveyors that transport the ore to the coarse ore stockpile at Mill No. 2. There is a primary jaw crusher at Mill No.2 that is used when processing ore from Pipeline, Gap and, in the future, Crossroads.

Tailings are stored in a zero-discharge tailings storage facility. A double liner covers the entire tailings area, extending completely under the dam embankment.

Low-grade oxide material is leached as ROM ore on three prepared double-lined leach pads. Pregnant solution from the leach pads is fed to CIC columns for gold recovery. The loaded carbon from the heap leach operation is transported to the mill for gold recovery.

Area 28 heap leach circuit has a water balance that is interlinked with the Pipeline mill circuit since it uses the tailings pond under-drain solution as leach solution and excess pad effluent is processed in the mill CIC circuit. Area 28 is at maximum capacity for ore stacking and is currently undergoing pad rinsing. Plans are to shut down the pad soon. Area 30 heap leach circuit is independent of the Pipeline mill. In the LOM plan ore delivery to the pad will recommence in 2012 and continue through 2022. Area 34 heap leach is a third pad that was designed to treat ore from CHOP. The first cells were placed under leach during March 2011 and ore deliveries are scheduled to continue through 2017 based on the LOM plan.

 

 

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Carbonaceous and sulphidic refractory ores are transported to Goldstrike for processing in either the pressure oxidation circuit or the roaster. Haulage of refractory ore to Goldstrike is currently limited by permit to 400,000 tons per year. The LOM plan includes the processing of approximately six million tons in each of the final two years of the LOM plan.

ENVIRONMENTAL, PERMITTING AND SOCIAL CONSIDERATIONS

The mine and the corporation have environmental groups and management systems to ensure that the necessary permits and licences are obtained and maintained. These groups also carry out the required monitoring and reporting required. Cortez has developed an environmental management system (EMS) to help manage the environmental requirements.

The BLM issued the original Environmental Impact Statement (EIS) and Record of Decision (RoD) in November 2008 and a supplemental EIS and RoD in March 2011. A number of permits are required to operate the Cortez Mine. Cortez adheres to permitting guidelines from the BLM, the Nevada Revised Statutes (NRS), the Nevada Administrative Statutes (NAS), and other federal government requirements.

CAPITAL AND OPERATING COST ESTIMATES

Current LOM capital costs for the Project are estimated to be $2.08 billion (Table 1-3).

TABLE 1-3 LOM CAPITAL COSTS

Barrick Gold Corporation—Cortez Operations

 

Item

   Cost ($ 000)  

Sustaining

     635,307   

Stripping

     776,212   

Underground Development

     52,161   

Drilling

     20,750   

Expansion

     460,427   

Closure

     150,000   

Total

     2,084,857   

The total operating cost has been estimated to be approximately $6 billion over the LOM. The average LOM operating cost per ton milled is estimated to be $19.50 (Table 1-4).

 

 

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TABLE 1-4 LOM OPERATING COSTS

Barrick Gold Corporation – Cortez Operations

 

Item

   Cost
($/st milled)
 

Mining

     11.77   

Process

     5.45   

General & Administration

     2.28   

Total

     19.50   

 

 

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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 Cortez Open Pit and Underground Mine (Cortez or the Project), in Eureka and Lander Counties, Nevada, USA. The purpose of this report is to support the public disclosure of the Mineral Resources and Mineral Reserves at Cortez as of December 31, 2011. This Technical Report conforms to NI 43-101 Standards of Disclosure for Mineral Projects. RPA visited the property from November 14 to 17, 2011.

Barrick is a Canadian publicly traded mining company with a portfolio of operating mines and projects across five continents. The Cortez Mine is a joint venture between two wholly owned subsidiaries of Barrick, Barrick Cortez Inc. (60%) and Barrick Gold Finance Inc. (40%). The Cortez Hills Project is 100% owned by Barrick Cortez Inc. The Cortez operations consist of the Pipeline, Gap, Cortez and Cortez Hills open pits, the Cortez Hills underground mine, an 11,000 stpd carbon-in-leach (CIL) gold plant, heap leach pads and heap leach processing plants, the planned Crossroads open pit and mineral resources in the Cortez Hills underground mine and at the Hilltop exploration project. Cortez is located in northeastern Nevada approximately 80 mi west and south of Elko.

SOURCES OF INFORMATION

Site visits were carried out by Dennis Bergen, P.Eng., Associate Principal Mining Engineer, Michael Gareau, P.Geo., Associate Senior Geologist, and Kathleen Ann Altman, Ph.D., P.E., Principal Metallurgist, from November 14 to 17, 2011.

Discussions were held with personnel from Barrick and Cortez:

 

   

Kitt Dale, Technical Services Director

 

   

Kevin Creel, District Manager, Exploration

 

   

Paul Richardson, Resource Geologist

 

   

Larry Snider, Senior Resource Geologist

 

   

Ken Ainsworth, Senior Mining Engineer, Ore Control

 

   

Erick Kennedy, Mine Engineer

 

   

Cal Cuisti, Database Administrator

 

   

Gene Kurz, Geologist

 

   

Clifford Krall, Chief Engineer Open Pit Operations

 

   

Dave Pearce, Chief Geologist – Surface

 

 

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Ian Squair, Senior Mining Engineer

 

   

Dan Richards, Senior Long Range Planning Engineer

 

   

Bob Brock, Senior Landman

 

   

Sam Ash, Chief Engineer, Underground

 

   

Andrew Collins, Metallurgist

 

   

Mark Bradley, Senior Geologist, Exploration

 

   

Cody Davis, Production Geologist, Underground

 

   

Beverley O’Malley, Cortez Hills Underground, Chief Geologist

 

   

Trent Weatherwax – Senior Planning Engineer, Underground

 

   

Sara Gilligan – Accounting Supervisor

 

   

Buddy Crill – Chief Electrical Engineer

 

   

Jon Kamensky, Chief Metallurgist

Mr. Bergen is responsible for the overall preparation of this report and reviewed the mining practices, reserve estimate, and economics of the open pit and underground operations and is responsible for Sections 2 through 6, 15, 16, 18, 19, 21, and 22. Mr. Gareau reviewed the geology, sampling, assaying, and resource estimates of the deposits and is responsible for Sections 7 to 12 and 14. Dr. Altman reviewed the metallurgical and environmental aspects of the operation and is responsible for Sections 13, 17, and 20. Mr. Bergen, Mr. Gareau, and Dr. Altman share responsibility for Sections 1, 2, 3, 25, and 26.

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

 

 

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LIST OF ABBREVIATIONS

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

 

µ

   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

asl

   above sea level    L/s    litres per second

bbl

   barrels    m    metre

Btu

   British thermal units    M    mega (million)

C$

   Canadian dollars    m2    square metre

cal

   calorie    m3    cubic metre

cfm

   cubic feet per minute    mi    mile

cm

   centimetre    mi2    square mile

cm2

   square centimetre    min    minute

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    oz/st    ounce per short ton

ft3

   cubic foot    oz    Troy ounce (31.1035g)

g

   gram    ppm    part per million

G

   giga (billion)    psia    pound per square inch absolute

Gal

   Imperial gallon    psig    pound per square inch gauge

g/L

   gram per litre    RL    relative elevation

g/t

   gram per tonne    s    second

gpm

   Imperial gallons per minute    st    short ton

gr/ft3

   grain per cubic foot    stpa    short ton per year

gr/m3

   grain per cubic metre    stpd    short ton per day

hr

   hour    t    metric tonne

ha

   hectare    tpa    metric tonne per year

hp

   horsepower    tpd    metric tonne per day

in

   inch    US$    United States dollar

in2

   square inch    USg    United States gallon

J

   joule    USgpm    US gallon per minute

k

   kilo (thousand)    V    volt

kcal

   kilocalorie    W    watt

kg

   kilogram    wmt    wet metric tonne

km

   kilometre    yd3    cubic yard

km/h

   kilometre per hour    yr    year

 

 

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3 RELIANCE ON OTHER EXPERTS

This report has been prepared by Roscoe Postle Associates Inc. (RPA) for Barrick Gold Corporation (Barrick). 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 Cortez 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 Cortez.

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

 

 

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4 PROPERTY DESCRIPTION AND LOCATION

The Cortez Gold Project is located 80 mi southwest of Elko, Nevada, USA. The Project is located in Eureka and Lander Counties (Figure 4-1). The Cortez property is surrounded by the Cortez Joint Venture Area of Interest (CJVAOI) that covers approximately 1,053 mi2 (Figure 4-2). The deposits and infrastructure are shown in Figures 4-3, 4-4, and 4-5.

The CJVAOI includes private land, patented, and unpatented mineral claims and fee land and land controlled by competitors. The approximate co-ordinates of the Pipeline open pit are approximately 40°15’ North latitude and 116°43’ West longitude.

LAND TENURE

At Cortez, Barrick directly controls approximately 198,265 acres of mineral rights with ownership of mining claims and fee lands. There are 9,587 claims consisting of:

 

   

8,767 unpatented lode claims

 

   

575 unpatented mill-site claims

 

   

93 patented lode claims

 

   

125 patented mill-site claim

 

   

27 unpatented placer claims and 185 patented mill-site claims

All lease agreements and claim holdings are current and in good standing.

The 2012 holding costs for the Cortez property include $3.2 million in holding costs and $0.45 million in lease payments.

Unpatented lode and mill-site claims are held under the 1872 mining law as amended, which requires the annual payment of $125 per claim on or before noon on the first of September each year. If the annual payment is not made for that specific claim, the claim will lapse and be subject to forfeiture. Patented ground or claims are surveyed by a certified mineral surveyor, and appropriate monuments placed in the ground. Each unpatented claim is marked on the ground, and does not require a mineral survey.

 

 

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All Mineral Reserves and Mineral Resources, in addition to existing and future facilities to be used to exploit the Project deposits, are on public lands administered by the Battle Mountain or Elko Field Offices of the U.S. Department of Interior, Bureau of Land Management (BLM).

ROYALTIES

The Cortez operation is subject to a number of royalties. All production at Cortez is subject to a 1.5% gross smelter return (GSR) royalty payable to the former shareholders of Idaho Mining Corporation. This was originally a 2.5% GSR royalty covered by a cap of ounces produced; the production cap has been met and the royalty reduced to a 1.5%. GSR is defined as 100% of smelter revenue before deductions for refining and transportation. The Idaho Mining Corporation royalty pertains to any production from the Pipeline, South Pipeline, Crossroads, Gap, Gold Acres, Cortez NW Deep, Cortez Hills, Pediment, and Hilltop deposits.

Royal Gold Inc. holds a sliding-scale GSR royalty over the Pipeline/South Pipeline deposits ranging from 0.40% to 5.0%. An additional sliding-scale GSR royalty is held over the undeveloped Crossroads deposit.

ECM Inc. (ECM) holds a net value royalty of 5.0% of gold sales from the South Pipeline deposit (which is approximately equivalent to a 3.9% GSR).

Rio Tinto is entitled to the payment of $50 million payable if and when an additional 12 million ounces of contained gold Mineral Resources are added to Barrick’s December 31, 2007 Mineral Reserve statement for Cortez. In addition, Rio Tinto holds a sliding-scale royalty (of 0% at gold prices less than $400/oz to 3% at gold prices greater than $900/oz) on 40% of all Cortez production in excess of 15 million ounces on and after January 1, 2008.

 

 

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4-3


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4-4


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4-5


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4-6


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4-7


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5 ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY

ACCESSIBILITY

The Project is reached by travelling approximately 32 mi east from Battle Mountain, Nevada, on US Interstate 80. Alternative access is from Elko, Nevada, approximately 45 mi west to the Beowawe exit, then approximately 35 mi south on Nevada State Route 306 which extends southward from US Interstate 80. Both US Interstate 80 and Nevada State Route 306 are paved roads.

The mining district is also crossed by a network of gravel roads, providing easy access to various portions of the Project. All roads are suitable for all weather conditions; however, in extreme winter conditions, roads may be closed for short periods for snow removal.

The Union Pacific Rail line runs parallel to US Interstate 80 to the north of the Project. Elko, the closest large city to the Project, is serviced by daily commercial airline flights to Salt Lake City, Utah.

The property is located at elevations between 4,500 ft and 5,500 ft on the valley floor and up the side of Mount Tenabo. The valley floor is sparsely vegetated while the mountain slopes have small pinion pine and juniper trees.

CLIMATE

The Project is located in the high desert region of the Basin and Range physiographic province. There are warm summers and generally mild winters, however, overnight freezing conditions are common during winter. The mean annual temperature is 51°F. Precipitation averages six inches per year, primarily derived from snow and summer thunderstorms. Typically, the months with the greatest precipitation are March, May, and November. During the winter months at elevations above about 5,500 ft asl, precipitation generally occurs as snow. Evaporation is estimated at 42 in. to 44 in. per year.

 

 

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Operations continue on site year-round and are not materially impacted by weather.

LOCAL RESOURCES

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

Electric power is carried to the Cortez Pipeline area via the Nevada Energy 50 mi long, 120 kV transmission line. A 9.5 mi extension of the power line was constructed from Pipeline to serve the Cortez Hills development.

Water for process use at Cortez Mill No. 2 is supplied from the Pipeline open pit dewatering system. Approximately 1,450 gallons per minute of the pit dewatering volume is diverted for plant use. Additional water can be sourced as needed from wells at Mill No. 1.

Process water supply for Cortez Hills will be drawn in whole or in part from dewatering operations. If sufficient volume cannot be produced by dewatering, process water will be supplied by existing production wells at the Pipeline and/or Cortez facilities.

Water from the Cortez Hills underground is pumped across Crescent Valley to an existing surface re-infiltration area.

INFRASTRUCTURE

There is an extensive infrastructure in place to support the Cortez operations including:

 

   

The 11,000 stpd No. 2 Mill complete with run-of-mine (ROM) pad and crushing circuit (including a primary jaw crusher)

 

   

Pipeline leach pad and gold recovery plant

 

   

Area 34 leach pad and gold recovery plant for Cortez Hills and Pediment

 

   

A tailings management facility which is being expanded

 

   

A gyratory crusher at the Cortez Hills open pit (CHOP) and an 11 mi long conveyor to the No. 2 Mill

 

 

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Existing active open pit mines at CHOP, Cortez, Pipeline, and Gap

 

   

Pit dewatering wells and pumps for the open pits

 

   

Infiltration ponds for the disposal of water

 

   

An existing underground mine at Cortez Hills Underground (CHUG)

 

   

Batch plant for shotcrete and cemented rock fill preparation

 

   

Stockpile areas for an assortment of ore types

 

   

Office complexes at the Mill No. 2, Mill No. 1, CHUG, and CHOP

 

   

Equipment maintenance shops at CHOP, CHUG, and adjacent to the Mill No. 2

 

   

Exploration offices, core handling and core storage warehouse

 

   

System of public and private roads connecting the facilities

 

   

Shared business support services from the business unit offices in Elko

PHYSIOGRAPHY

The Pipeline mine and Mill No. 2 are located at the southern end of the Crescent Valley in Lander County, Nevada. The Cortez Hills deposits and operations are at the northern end of Eureka County. The Crescent Valley is a structural and topographic basin between the Northern Shoshone Range on the west and the Cortez Range on the east. Most mine facilities are on the west side of the valley at an elevation of approximately 5,000 ft. This includes the original workings of the Gold Acres mine, now inactive, the Pipeline pit, the Gap pit and the proposed Crossroads pit.

The Cortez Mine and Mill No. 1 (both inactive) are located along the northern edge of the Cortez Range seven miles southeast of the Pipeline pit. The Cortez Hills and Pediment deposits are located in the Cortez Hills approximately three miles south of the Cortez pit and at an elevation of approximately 6,000 ft.

The vegetation consists primarily of shrubs and grasses, such as sagebrush, rabbitbrush, cheatgrass, and grama. Juniper trees, pinion pine, mountain mahogany, and a variety of grasses are also present. In general, vegetation is relatively sparse. No endangered or threatened species, BLM-sensitive species, or plants proposed for listing have been identified in the Project area.

 

 

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Fauna that have been observed in the Project area are typical of those of the Great Basin area, and include jackrabbits, cottontail rabbits, mule deer, antelope, coyotes, various rodents, and reptiles. No proposed threatened, or endangered species are considered to exist within the Project area.

 

 

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6 HISTORY

Mining in the Cortez Mining District began with the discovery of silver mineralization in 1862 along the quartzite outcroppings at the western base of Mount Tenabo, some four miles to the southeast of the Cortez Mill No. 1 complex. Underground silver mining was conducted in the area until the 1930s. Mineralization at Hilltop was also identified during the 1860s. The majority of production occurred between 1915 and 1951 from underground sources, with approximate production of 18,000 ounces of gold, 360,000 ounces of silver and subordinate amounts of lead, copper, and antimony. Gold mineralization at Gold Acres was discovered in the late 1920s and mined by a small mining company from 1935 to 1960. The mine was one of the few gold operations to remain open during World War II.

In 1959, American Exploration & Mining Co. (AMEX), a wholly-owned US subsidiary of Placer Development Ltd. (subsequently Placer Dome Inc.), entered into a lease-option agreement on the properties of the Cortez Metals Co. and started extensive exploration of the mine workings and surrounding area. In 1963 AMEX entered into an exploration agreement with Idaho Mining Corp., which had acquired large areas of mineralized ground adjoining the AMEX holdings. In 1964, AMEX formed the Cortez Joint Venture (CJV) with the added participation of the Bunker Hill Co., Vernon F. Taylor, Jr., and Webb Resources Inc.

The US Geological Survey found anomalous gold in altered outcrops at the base of the Cortez Range in 1966. The CJV shortly afterwards discovered the Cortez deposit. Production at Cortez began in 1969 and continued until 1972, and then resumed from 1988 to 1993. Production was from the F-Canyon, Cortez and Ada 52 pits. Waste dumps from the operations were reclaimed during the 1990s. The Cortez process facilities include three inactive heap leach pads, West, East and 91-C leach pads, constructed in 1972, 1984 and 1990 respectively. The leach pads have been inactive since 1994. Seven tailings storage areas are situated in the Cortez area, TA 1 to TA 7, inclusive.

 

 

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TABLE 6-1 HISTORY OF EXPLORATION AND MINING AT CORTEZ SITE

Barrick Gold Corporation – Cortez Operations

 

Period

  

Activity

1862–1932    Cortez Silver mine in operation
1912–1921    Mining of gold, lead, copper and antimony at Hilltop
Late 1920s    Gold Acres deposit discovered
1935–1960    Gold mined from the Gold Acres deposit by other companies. Gold Acres mined as an open pit operation
1964    CJV formed
1966    Cortez deposit discovered
1968    Horse Creek (formerly Red Hill) discovered by Homestake Mining Co.
1969–1972; 1988–1993    Cortez deposit mined
1973–1976    New southern extension of the Gold Acres deposit mined and Horse Canyon deposit discovered
1976–1983    Low-grade oxide ores from Cortez and Gold Acres heap leached
1983–1987    Horse Canyon deposit mined
1987–1996    Mining resumed in the Cortez and Gold Acres deposits
1989    Acquisition of Hilltop deposit
1991    Pipeline, South Pipeline, Crescent and Gap deposits discovered
1994    Commenced mining the Crescent pit within the north western portion of the South Pipeline deposit
1996    Mining commenced on the Pipeline deposit
1997    Production at Mill No. 2 commenced. Total development and capital costs were $250 million.
1998    Crossroads and Pediment deposits discovered.
1999    Mill No. 1 was placed on care and maintenance.
2001    Plan of Operations was submitted for Pipeline expansion and Pediment
2002    South Area heap leach facility was commissioned
2003    Cortez Hills deposit discovery announced
2004–2009    Infill drilling continued at Cortez Hills and Pediment deposits Discovery of Lower Zone at Cortez Hills
2005    Completion of positive internal feasibility study on Cortez Hills
2006    Barrick acquires Placer Dome; commencement of mining at the South Gap deposit
2008    Acquisition of remaining 40% interest in Project through Barrick purchase of Kennecott interest. Positive Record of Decision received for Cortez Hills development

2009

   Development of open pit commences at Cortez Hills

The CJV initiated exploration drilling around the pre-existing Gold Acres deposit in 1969, and obtained exploration rights to the former mining area in 1969. Open pit mining began in 1973, from the North and South pits. Low-grade ores from Gold Acres were

 

 

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mined and processed by heap leaching until 1976. Leaching and milling of Gold Acres stockpiles and dumps continued until 1983. The Gold Acres heap leach facility is associated with the deposits. Drilling resumed, resulting in the discovery of refractory gold mineralization in the vicinity of the North pit. Mill-grade ores were mined from 1987 to 1996 and processed at the Cortez Mill No. 1. Total production from this deposit (historic and recent) is estimated to exceed 500,000 ounces of gold. In 2003, the CJV commenced shipping Gold Acres refractory stockpiles for toll-processing at third-party facilities.

The Horse Canyon deposits were discovered in early 1976. Three pits, North, South, and South Extension were mined in the period from 1984 to 1987. Approximately 3.5 million tons were mined with approximately 385,000 ounces of gold recovered.

The Pipeline, South Pipeline, and Crossroads gold deposits occur in sequence from northwest to southeast and were entirely concealed beneath pediment gravels up to 300 ft thick. The Pipeline deposit was discovered by CJV geologists in March 1991 during drilling of deep condemnation holes on the pediment east of Gold Acres. The Gap deposit was discovered in 1991 adjacent to the planned Stage 9 of the Pipeline pit.

The Pipeline South area was initially controlled by association placer claims under the control of the CJV since the early 1970s. Only scattered sub-ore grade gold has been identified. The area was over-staked with lode claims by ECM in early 1987. By May 1987, Royal Gold had leased this property, known as the GAS claims, from ECM. The claim conflict was resolved by the formation of the Royal/Cortez Joint Venture between Royal Gold and the CJV later that year.

Royal Gold completed geophysical surveys and drilling programs between 1987 and 1989 that led to the identification of additional sub-economic gold grades, primarily in an anomaly known as GAS 2. Although a mineral resource was estimated no further work was undertaken by Royal Gold or by CJV due to the limited amount of drill data available. No further drilling by Royal Gold occurred due to lack of funding.

In August 1991, the Royal/Cortez Joint Venture was terminated and the CJV leased the property directly from ECM. A later dispute between Royal and the CJV concerning termination of the Royal/Cortez Joint Venture led to the formation of the South Pipeline Project and the royalty structure.

 

 

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In November 1991 CJV discovered the South Pipeline deposit. Additional gold was identified in August 1992. Step-out and in-fill drilling continued through July 1994. This drilling confirmed the presence of a relatively shallow gold occurrence above the water table, the Crescent deposit. Mining of the Crescent pit (northwest part of the South Pipeline deposit) commenced in May 1994 and was completed in 1997. The Crescent pit has since been subsumed by the Pipeline pit.

An internal Feasibility Study covering the Pipeline and South Pipeline deposits was completed by Placer Dome Technical Services in 1995. Construction of Mill No. 2 and pre-stripping of the first stage of the Pipeline pit began in 1996. The Pipeline pit has estimated Mineral Reserves and is included in Barrick’s current LOM plan. Two waste dumps are permitted (Gap and Pipeline). Associated infrastructure includes the integrated Pipeline heap leach and tailings facility, South Area heap leach facility, and Mill No. 2.

Continued drilling along northwest-southeast structural trends at Pipeline in 1998 resulted in discovery of the Crossroads deposit southeast of the South Pipeline deposit. Crossroads is concealed beneath 550 ft of alluvium. It represents a continuation of mineralization from South Pipeline.

In 1996, CJV geologists began a program to test for concealed mineralization south of the Cortez Mine. Geochemical and geophysical surveys were used to guide deep reverse circulation (RC) drilling, initially focusing on an area immediately west of the Cortez Fault. In 1998, the Pediment deposit was discovered in a deep RC drilling program designed to test potential for bedrock mineralization in the central and western portions of the alluvium-covered Cortez Fault Corridor. Subsequent RC and core drilling programs through 2002 defined the Pediment deposit.

The Cortez Hills deposit was discovered in October 2002 as part of an RC drilling exploration program investigating a steep gravity gradient anomaly near the projected intersection of north–northwest-trending Cortez Fault Corridor structures and west–northwest-trending faults beneath alluvial cover immediately to the north of the Pediment deposit. In 2004, the Cortez Hills Lower Zone was discovered as part of the step-out drilling to the west of the Cortez Hills deposit.

 

 

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In November 2008 the Environmental Impact Statement (EIS) for the Cortez–Pediment development was approved. The project is being developed as two open pits and a concurrent underground development of a high-grade portion underlying the pits. Production from underground began in late 2008, and the first ore production of CHOP phases one through three occurred in late December 2009.

In March 2008, Barrick acquired a 100% interest in the Project, purchasing the former Kennecott 40% interest for a consideration of $1.695 billion in cash, an additional $50 million payable if and when an additional 12 million ounces of contained gold Mineral Resources are added to Barrick’s December 31, 2007 Mineral Reserve statement for Cortez, and a sliding-scale royalty payable to Rio Tinto on 40% of all Cortez production in excess of 15 million ounces on and after January 1, 2008.

Production from the Project in the period 1969 to 2011 is summarized in Table 6-2.

 

 

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TABLE 6-2 CORTEZ PROJECT ANNUAL PRODUCTION, 1969–2011

Barrick Gold Corporation – Cortez Operations

 

Year

Ended

   Gold
(000 oz)

1969

   166

1970

   209

1971

   120

1972

   190

1973

   76

1974

   104

1975

   74

1976

   28

1977

   2

1978

   2

1979

   2

1980

   8

1981

   21

1982

   25

1983

   47

1984

   49

1985

   56

1986

   62

1987

   51

1988

   42

1989

   40

1990

   54

1991

   58

1992

   77

1993

   67

1994

   70

1995

   111

1996

   161

1997

   407

1998

   1,138

1999

   1,328

2000

   1,010

2001

   1,188

2002

   1,082

2003

   1,065

2004

   1,052

2005

   904

2006

   427

2007

   323

2008

   428

2009

   518

2010

   1,140

2011

   1,421

Total

   15,403

Note: Production from 1969 to 2005 is total production, reported on a 100% basis, sourced from corporate annual reports. Production from April to December 2006, 2007, and January to February 2008 is the Barrick interest only, at 60% of production. Barrick production at 100% is included from March 2008 onwards.

 

 

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7 GEOLOGICAL SETTING AND MINERALIZATION

REGIONAL GEOLOGY

This section on Regional Geology has been extracted and modified from the Scott Wilson RPA July 2010 Cortez audit report.

The Project is located in the eastern Great Basin (Basin and Range Province) at the southern closure of Crescent Valley, a northeast trending structural and topographic basin between the Northern Shoshone Range on the west and the Cortez Range on the east. The Project lies within the “Battle Mountain-Eureka Trend” (BMT), an alignment of gold mines and occurrences located in a northwest-southeast belt extending from the Marigold Mine some 50 mi northwest of Cortez, to Ruby Hill at Eureka 60 mi to the southeast.

Two regionally recognized Paleozoic assemblages comprise the basement sedimentary strata of northeastern Nevada. These assemblages were deposited on the western continental margin of North America. The western assemblage is a deep water marine package of siliciclastic rocks consisting of mudstone, chert, siltstone, sandstone, and minor limestone. The eastern shallow water sedimentary assemblage consists predominantly carbonate rocks including limestone, dolomite and some quartzite units. The eastern assemblage underlies all other stratigraphic units in eastern and central Nevada.

Jurassic to Cretaceous intrusive rocks of granitic composition intrude the Paleozoic sedimentary rock and are locally exposed as stocks, sills and dikes. Tertiary extrusive rocks unconformably overlie the older packages and are dominated by a bimodal suite of rhyolite and basaltic flows with associated felsic tuffs and lesser amounts of intermediate volcanic rocks. Post-mineralization Eocene to Oligocene quartz porphyry dikes and sills have been emplaced along low angle thrust faults as well as high angle structures, in some cases intruding the gold deposits. Late Tertiary and Quaternary erosional products have partially filled the valley basins with coalescing alluvial fan deposits marginal to the mountains and finer-grained alluvium in the valley centres.

 

 

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The Antler orogeny extensively deformed Paleozoic rocks of the Great Basin in Nevada and western Utah during Late Devonian and Early Mississippian time. In the late Devonian about 350 million years ago, the Antler volcanic island arc terrane collided with what was then the west coast of North America and the North American Plate. The collision zone is marked by the Roberts Mountains Thrust, a system of low-angle thrust faults along which the Upper Plate clastic rocks were thrust some 90 miles eastward over the Lower Plate carbonates. Mesozoic compressional deformation was also important regionally as indicated by various east and west as well as north-northeast and south-southwest verging thrusts. Tertiary faulting developed basins and ranges with the former subsequently filled with volcanic and sedimentary rocks during Tertiary time. Gold mineralization occurred at the onset of Tertiary volcanism, approximately 39 million years ago.

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

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

 

   

the thinned western margin of the North American craton in early Paleozoic times,

 

   

the west-central portion of the Lower Devonian Antler foreland basin,

 

   

the east edge of deformation related to the late Paleozoic Humboldt orogeny,

 

   

an area of Jurassic plutonism, metamorphism and deformation,

 

   

the hinterland of the early Tertiary Sevier orogenic belt, and

 

   

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

The collision between the Antler terrane and the North America Plate induced higher crustal temperatures and pressures, which produced numerous hot springs along the

 

 

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suture zone. Several episodes of subsurface magmatism are known to have occurred subsequent to the collision. During these episodes, and particularly during the Eocene epoch, hot springs brought dissolved minerals toward the surface, precipitating them out along fissures. Among these minerals were gold and silver. Most of the largest gold deposits lie within approximately 300 ft of the Roberts Mountain Thrust at the base of the Upper Plate allochthon. Geochronologic study indicates that most of the gold in the BMT was emplaced over a short interval of time between approximately 42 Ma and 36 Ma. Analyses of the sulphosalt galkhaite from the Rodeo deposit at Barrick’s Goldstrike Mine (Carlin Trend) have yielded a mineralization age of 39.8 ± 0.6 Ma.

The regional geology is shown in Figure 7-1.

 

 

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Local Geology

Both the western and eastern Paleozoic assemblages are present in the Cortez area. At Cortez the western assemblage, termed the Upper Plate, includes:

 

   

Devonian Slaven Formation cherts and argillites

 

   

Silurian Elder Formation sandstone and Fourmile Canyon Formation

 

   

Ordovician Vinini and Valmy Formations siliclastic rocks

The eastern assemblage, or Lower Plate, consists of:

 

   

Devonian Horse Canyon Formation laminated calcareous siltstone, mudstones with interbedded chert and silicified siltstones

 

   

Early Devonian Wenban Formation carbonate turbidites, debris flows, micrites and silty limestones

 

   

Silurian-Devonian Roberts Mountains Formation laminated silty limestones

 

   

Ordovician Eureka Formation quartzites and Hanson Creek Formation sandy dolomites

 

   

Cambrian Hamburg dolomite

Two erosional windows of Lower Plate rocks are mapped in the Cortez area both located at the southern end of Crescent Valley (Figure 7-2). The Gold Acres window on the eastern flank of the Shoshone Range, is buried to the east beneath the alluvial fill of Crescent Valley, and presumably is offset by the Crescent fault located on the south side of the valley near the Cortez Mine. South of the Crescent fault is the Cortez window which appears to be a continuation of the Gold Acres window. The Cortez window is a two to three mile-wide, north–south trending zone that extends from the margin of Crescent Valley near the existing Cortez Mine south through the Cortez Hills area and into the northern Grass Valley area.

Aeromagnetic studies indicate that intrusive rocks underlie most of the Cortez Mountains. Outcrops of igneous intrusions in the Cortez district are granodiorite of Jurassic-cretaceous age (104 Ma to 150 Ma) and the Jurassic-age quartz monzonite Mill Canyon Stock. Felsic and mafic and dikes of similar age occur primarily in north to northwest striking faults. Contact metamorphism affects the sedimentary rocks adjacent to the larger igneous bodies and is evident in the formation of marble, calc-silicates, hornfels, and skarn. Post-mineral porphyry dacite and rhyodacite dikes and sills of Tertiary age are present and notable where they cross-cut mineralized zones.

 

 

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The local geology and stratigraphy of the Cortez Project area is shown in Figures 7-2 and 7-3, respectively.

The Gold Acres, Pipeline, Gap and Crossroads gold deposits are at the south end of the Shoshone Range located on the west side of Crescent Valley within the Gold Acre Lower Plate window. Gold Acres mineralization is hosted within the Roberts Mountains thrust fault which is up to 400 feet thick in the mine. The Pipeline, South Pipeline, Gap and Crossroads deposits occur within Lower Plate Horse Canyon, Wenban and Roberts Mountains formations.

The Hilltop gold deposit, located approximately 10 mi north of Gold Acres is hosted by an Eocene porphyry and surrounding brecciated, Upper Plate siliciclastic sedimentary rocks of the Ordovician Valmy Formation along a northwest-trending belt of similar aged intrusions. Hilltop is an epithermal intrusive related deposit.

The Cortez Pits, Cortez Hills, and Pediment gold deposits are on the south side of Crescent Valley associated with the Cortez Lower Plate window. The Cortez Hills mineralized breccia, thrust fault related Middle and Lower zones are within Horse Canyon, Wenban, and Roberts Mountains units. The Pediment deposit appears to be contained within Miocene-age conglomeratic sediments located immediately southwest of the Cortez Hills deposit. The Horse Canyon deposit is in Pine valley and is in lower plate formation.

The Buckhorn gold mine, approximately seven miles east of Cortez. It is a past producer that shut down in 1991 with historical production of 250,000 ounces of gold. It is a low-sulphidation epithermal vein and replacement mineralization localized by structures and permeable horizons mainly hosted in the Tertiary basalts.

 

 

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PROPERTY (DEPOSIT) GEOLOGY

Deposit descriptions for the Pipeline Complex, Gold Acres, Pediment, and Cortez Pits deposits were extracted in whole or in part from the Scott Wilson RPA Cortez 2010 Audit Report and modified where required for this Report to reflect the current geological understanding of these areas.

PIPELINE COMPLEX

PIPELINE/SOUTH PIPELINE/CROSSROADS

The Pipeline, South Pipeline and Crossroads deposits are separate zones of one gold-mineralized system which strikes approximately N20W, is over 8,000 ft long and 5,000 ft wide. Economic gold grades do not occur over the full expanse of this system, but variable degrees of hydrothermal alteration are evident throughout. Alteration types include oxidation, decalcification, weak contact metamorphism, argillization, silicification, and carbonization. Mineralization at the Pipeline Complex occurs just outboard of the metamorphic aureole associated with the Gold Acres intrusive. Alluvium cover is absent in the northwest but thickens up to 450 ft in the eastern Pipeline pit area and ranges from 315 ft to 770 ft over the Crossroads deposit to the south.

The area is characterized by folded and low-angle faulted Paleozoic carbonates. The primary host rocks are variably altered, thin- to thick-bedded, carbonate turbidites, debris flows, micrites and silty limestones of the Devonian Wenban Formation and thin-bedded, planar-laminated calcareous siltstones, mudstones, with inter-bedded chert and silicified siltstones of the Devonian Horse Canyon formation overlying. At depth, planar laminated, silty limestones of the Silurian Roberts Mountains Formation also host mineralization.

Initial porosities in the turbidites, siltstones and silty limestones were enhanced through argillization and decarbonitization along structural and stratigraphic controls. Thrust and normal faulting have shattered the more brittle cherty and silicified beds creating a secondary porosity. The highest and most continuous gold grades occur in the inter-bedded cherts and silicified turbidites of the Horse Canyon formation and in the Wenban Formation either where capped by the Horse Canyon formation or in areas of more intense decarbonitization. Host formations have been thickened and repeated by low-angle thrusting largely associated with the Late Devonian Antler Orogeny.

 

 

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GAP

The Gap deposit is hosted in Devonian Wenban Limestone and lies west of the Pipeline Deposit. Mineralization occurs where north-northwest and northeast, high-angle faults intersect thermally altered Wenban Formation in the axis of the Gold Acres antiform. Bedding in the Wenban Limestone is sub-horizontal to gently east-dipping. Portions of the limestone host-rocks of the deposit that lie within the metamorphic aureole of the Gold Acres Stock have been altered to calc-silicate marble, hornfels, skarn, and gossan. Skarn within the Gap pit can be correlated with the upper skarn in the Gold Acres deposit.

GOLD ACRES

The Gold Acres pit is centered on the long axis of a low-amplitude, north-northwest trending antiform. The primary host rocks to the mineralization are sheared Upper Plate siliciclastics and greenstones of the Ordovician Valmy Formation and cherts and quartz siltstone of the Devonian Slaven Formation, sheared Lower Plate silty limestone with discontinuous thin phosphatic black lenses of the Silurian Roberts Mountains Formation and micrite to silty micrite of the Devonian Wenban Formation. The intensity of metamorphism associated with the Gold Acres Stock varies depending on original lithology and ranges from hornfels to calc-silicate marble to skarn. Drill hole intercepts indicate that the pluton is 400 ft to 600 ft below the current Gold Acres pits.

Two discrete horizons, referred to as “Upper Skarn” and “Lower Skarn,” have been mapped at Gold Acres. The Upper Skarn unit is a bleached felsic sill-like body with endoskarn development and is presumed to be associated with the granodioritic Gold Acres Stock of Jurassic-Cretaceous (104 Ma to 150 Ma) age. The “Lower Skarn” is a garnet–diopside skarn believed to be lower Wenban Formation. The two skarn horizons are separated by an 80 ft to 200 ft thick zone comprising slices of Upper and Lower plate rocks known as the Imbricate Thrust Zone (ITZ).

CORTEZ HILLS COMPLEX

The Cortez Hills Complex includes the Cortez Hills Breccia, Middle and Lower zones, and the Pediment deposit.

BRECCIA, MIDDLE AND LOWER ZONES

The upper levels of mineralization in the Cortez Hills deposit are hosted in the Horse Canyon Formation. The bulk of the deposit is hosted in the Wenban limestone. At depth, mineralization is also hosted by Roberts Mountains Formation as well as Hanson Creek Dolomite. The range-bounding Cortez Fault is located just east of the deposit.

 

 

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The location of Breccia gold mineralization appears to have been emplaced on hydrothermal brecciated and fractured rocks that are centred on a northwest striking and moderately southwest dipping fault and its attendant structures, named the Voodoo Fault. At depth the stratigraphy has been deformed by thrust faulting leading to both folding and fracturing. Gold mineralization at depth occurs as tabular, sub-horizontal to shallow dipping zones associated with calcareous rocks subject to preparation by alteration and deformation; this deeper mineralization forms the Middle and Lower zones at Cortez Hills. Post-mineral quartz porphyry dikes and sills intrude the Cortez Hills deposits. A northwest trending swarm of steely dipping dikes defines the limits between the Middle and Lower zones.

PEDIMENT

The Cortez Pediment deposit is located in a Tertiary gravel-filled canyon immediately south of Cortez Hills and appears to have originated from material and gold eroded from the top of the Cortez Hills deposit. In contrast to rock formations, the gravels at Pediment display inverted stratigraphy in that the deepest unit is a 50 ft to 200 ft thick siltstone-dominated gravel sourced from the gold mineralized Horse Canyon Formation and it underlies a limestone-dominated gravel (100 ft to 800 ft thick) derived from the erosion of uplifted, barren Wenban Limestone. The gravels are covered by thin, unconsolidated fanglomerate composed of Eureka Quartzite fragments, the quartzite having been exposed by later uplift east of the Cortez Fault. There are no obvious structural controls, although the Pediment deposit is strongly elongated north–northeast.

CORTEZ PITS (NW DEEPS)

The Cortez NW Deeps deposit is hosted by strongly altered, thin- to medium-bedded silty limestone of the Roberts Mountains Formation and by sheared and altered interbedded dolomite and limestones of the underlying Ordovician Hanson Creek Formation. Wenban Limestone caps most ridges and hills around the NW Deeps deposit and locally appears to have acted as a cap rock over alteration systems in the underlying Roberts Mountains Formation. Prior to mining, Quaternary alluvium formed a thin veneer of cover over the deposit. Alluvium thickens abruptly to the north across the Cortez range-front normal fault.

 

 

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Quartz monzonites of the Jurassic Mill Canyon Stock are present east of the deposit on the uplifted side of a north–northwest-trending normal fault. Numerous Oligocene quartz porphyry dikes and sills intrude the deposit. These dikes are considered to be post-mineralization.

A series of north–northwest-trending and northeast-trending faults cut the Roberts Mountains Formation at the deposit. Mineralization occurs where these faults intersect shallow east-dipping thrust breccia zones (thrust duplexes) within the Roberts Mountains Formation.

MINERALIZATION

With the exception of Cortez Hills, the description of Mineralization for this section is taken largely from the July 2010 Scott Wilson RPA Cortez audit report with modifications as required for this Report.

Gold mineralization is reported as mineral resources for the following nine deposits in the Cortez area:

 

   

Pipeline Complex (3 deposits) – Pipeline, Gap and Crossroads

 

   

Gold Acres

 

   

Cortez Hills Complex (4 zones) – Breccia, Middle, Lower and Pediment

 

   

Cortez Pits (NW Deeps)

Mineralization consists primarily of submicron to micrometre-sized gold particles, very fine sulphide grains, and gold in solid solution in pyrite. Mineralization occurs disseminated throughout the host rock matrix in zones of silicified and decarbonatized, argillized, silty calcareous rocks and associated jasperoids. Gold may occur around limonite pseudomorphs of authigenic pyrite and arsenopyrite. Major ore minerals include native gold, pyrite, arsenopyrite, stibnite, realgar, orpiment, cinnabar, fluorite, barite, and rare thallium minerals. Gangue minerals typically comprise fine-grained quartz, barite, clay minerals, carbonaceous matter, and late-stage calcite veins.

Argillization is characterized by removal of kaolinite and growth of illite in proximity to controlling faults. Arsenic, antimony, iron, and copper accompany gold in north–northwest oriented fault structures and silver, arsenic, manganese, and lead in northeast trending faults.

 

 

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In the Cortez district, the favoured host rocks for gold mineralization are the Wenban Limestone, followed by the Horse Canyon and Roberts Mountain formations. Mineralization reflects an interplay between structural and lithological ore controls in which hydrothermal solutions from intrusives moved to favourable porous decalcified limestone.

Mineralization is predominantly characterized by oxides, and sulphidic and carbonaceous refractory material. Carbon content in the deposits is highly variable and occurs generally in the Wenban and Roberts Mountain Formations.

Supergene alteration extends up to 656 ft depth resulting in oxide ores which overlie the refractory sulphides. Alteration has liberated gold by the destruction of pyrite and resulted in the formation of oxide and secondary sulphate minerals which include goethite, hematite, jarosite, scorodite, alunite, and gypsum.

PIPELINE COMPLEX

Mineralization at Pipeline occurs where the east-dipping thrust duplex crosses a deep-seated 305° striking fracture system. The majority of the mineralization is tabular and stratiform with a shallow easterly dip.

The main Pipeline deposit is 50 ft to 300 ft thick, tabular zone at 500 ft to 600 ft beneath the surface; it dips at a low angle to the east and extends 750 ft north-south by 1500 ft east-west. South Pipeline consists of two zones 1) a shallow zone starting at 65 ft to 150 ft depth and 2) a deep zone starting at 1,000 ft. The shallow zone occupies an area of approximately 1,800 ft by 2,000 ft, north and east respectively, and exhibits both low-angle and high-angle structural controls on gold distribution. The deep zone occupies an area 200 ft north-south by 600+ ft east-west, is up to 250 ft thick and is more closely associated with high-angle structures. Drill depths average 1,000 ft although drill holes up to 1,400 ft are not uncommon in the center of the deposit where mineralization ranges from 400 ft to over 1,000 ft in thickness.

 

 

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Crossroads lies at the south end of the Pipeline trend and is deeper varying in thickness from less than 10 ft to greater than 300 ft with a primary control of low-angle structures sub-parallel to bedding and an overall 20o easterly dip. The zone is intensely sheared, shattered, and/or brecciated, with minor offsets along the high-angle faults. Oxidation extends to depths in excess of 1,300 ft. Crossroads consists of two mineralized zones: an upper stratiform zone along the Horse Canyon–Wenban contact and a deeper zone controlled by an east-northeast striking, west dipping (20° to 25°) structural zone which cuts across stratigraphy.

At Gap mineralization occurs where north-northwest and northeast, high-angle faults intersect thermally altered Wenban Formation in the axis of the Gold Acres antiform. A northern zone of mineralization is primarily hosted within gossan horizons cut by high-angle faults in thermally altered Devonian Wenban Limestone. The southern zone is outside the metamorphic aureole; mineralization occurs within a 1,000 ft wide corridor of strong fracturing bounded on the northeast side by a high-angle, N45W northeast-dipping fault. Gold mineralization is post-metamorphic and strongly oxidized. Carbon alteration is prevalent and increases with depth.

GOLD ACRES

At Gold Acres the mineralized area is approximately 6,000 ft long by 2,500 ft wide with an average thickness ranging from 80 ft to 200 ft. Mineralization is mainly refractory; high gold grades (greater than 0.10 oz/st Au) are associated with secondary carbon and/or fine-grained sooty sulfide minerals. Minor oxide gold mineralization is hosted within the Upper Plate rocks overlying the Imbricate Thrust Zone (ITZ). The Lower Skarn is largely barren of gold, although it does host minor polymetallic mineralization (Zn–Mo–Cu) presumed to be coeval with intrusive emplacement and skarn formation.

The Gold Acres deposit was developed in two lobes, the north (London Extension Pit) and the south (Old Gold Acres Pit, or OGA). The London Extension Pit is bounded on the north by the northeast striking, moderately westward dipping (50° to 60°) Gold Acres Fault. The Gold Acres Fault down drops the ITZ and Gold Acres Stock approximately 200 ft to the northwest. The Island Fault separates the London Extension and OGA pits and strikes approximately to the north–northeast, dipping at 50° to the northwest. The Island Fault apparently down-drops mineralization in the London Extension Pit relative to the OGA Pit. Multiple northeast-trending faults between the Gold Acres and Island

 

 

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Faults incrementally down-drop mineralized stratigraphy to the north in a stair-step pattern. Both pits have been inactive since 1995 except for a small program in the London Extension Pit in 2000–2001 when refractory ore was mined to supply a third-party for processing.

CORTEZ HILLS COMPLEX

BRECCIA, MIDDLE AND LOWER ZONES

Breccia gold mineralization is hosted in hydrothermally brecciated and fractured rocks that are spatially associated with the Voodoo Fault and its attendant structures. Altered, matrix supported breccia bodies contain the highest gold grades and are surrounded by ‘crackle’ breccias and highly fractured rock with moderate gold grades continuing outwards to less fractured rocks with lower grades. Most of the Breccia mineralization dips moderately southwest enveloping the Voodoo Fault. The upper portion has a northeast dip that possibly reflects control by an antithetic structure. Breccia Zone mineralization extends from a near surface elevation of 5,850 ft to 4,070 ft, terminating just east of the Middle Zone. It is approximately 1,000 ft wide with a northwest trend, and varies in width from 250 ft to 1,900 ft

Mineralization of the Middle and Lower zones lie at depth to the west and southwest of the Breccia zone. These sub-horizontal, tabular zones are associated with alteration localized along a complex zone of thrust faulting and back thrusts in the Roberts Mountain Formation that has also incorporated slices of Wenban limestone. A swarm of northwest trending post mineral quartz porphyry dikes separates the Middle from the Lower Zone. The Lower Zone has a distinct northwest-southeast trend in the Roberts Mountain and Hanson Creek Formations that is interpreted as the crest of a plunging antiform. The Middle zone occurs between elevations 4,235 ft and 3,825 ft, is approximately 1,800 ft wide northwest-southeast by 1,300 ft long northeast-southwest and ranges in thickness from 10 ft to 270 ft. The Lower Zone lies at an elevation of 4,260 ft to the northwest and 3,060 ft to the southeast, extends 4,300 ft northwest-southeast, varies in width from 1,450 ft in the north to 500 ft in the south and ranges in thickness from 60 ft to 270 ft. Both the Middle and Lower zones are open to both the northwest and southeast.

Post-mineral dikes and sills are significant in that they are estimated to account for up to 10% of the waste rock volume within portions the Cortez Hills deposits.

 

 

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Gold mineralization is often spatially associated with decalcification and to a lesser degree silicification. Deep oxidation at Cortez Hills is inferred to be related to deep, convection-driven circulation of mixed meteoric and spent hydrothermal fluids during the waning stages of the mineralizing event. The enhanced weathering phenomenon resulted in significant carbonate dissolution and clay formation as well as extremely deep oxidation of gold-bearing iron sulphide minerals. Arsenates of copper and zinc have been noted in, and adjacent to, oxidized mineralization.

PEDIMENT

Most of the gold in the Pediment deposit is present within the lower of the two gravel/ conglomerate units draped over a paleobasement of thermally altered limestone and marble. Two mineralized zones have been delineated 1) a shallow zone along the southern extent of the deposit, with a depth to the top of the zone ranging from 150 ft to 300 ft, and 2) a deeper zone at the northern part of the deposit, which begins at a depth of approximately 500 ft. Both mineralized zones exhibit a tabular geometry and occupy a general area of 3,000 ft north-south by 600 ft east–west. Gold mineralization is associated with clasts of strongly altered carbonate rocks that have been oxidized and are similar to mineralization found in situ in the near-surface portion of the Cortez Hills Complex.

CORTEZ PITS (NW DEEPS)

The Cortez NW Deep deposit is a continuation of the mined-out main Cortez deposit. The deposit consists of remnants of oxide mineralization in the east wall of the Bass Pond pit and deeper, sulphide and carbonaceous mineralization. A series of north–northwest trending and northeast trending faults cut the Roberts Mountains Formation at the deposit. Gold mineralization is localized where these faults intersect shallow east dipping thrust breccia zones (thrust duplexes). Most of the Cortez NW Deep higher-grade gold mineralization (less than 0.1 oz/st Au) occurs in two zones lying between the 4,200 ft and 4,500 ft elevations beneath the old Cortez open pit floor. Present surface elevations are between 4,800 ft and 5,300 ft. One zone consists of an oxidized and strongly altered thrust zone within the Roberts Mountains Formation and the other is an unoxidized, sulphide-bearing thrust zone at the top of the Hanson Creek Formation. Post mineral quartz porphyry dikes have been emplaced along thrust faults.

 

 

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Locally, silica overprints all lithologies but does not show a strong correlation with gold at a local scale. Silicification occurs as massive fault fill, bedding replacements after decalcification and as micro-veinlets. Massive silicification fills both north–northwest and northeast trending faults. Bedding replacement by silica occurs along beds that were originally carbonate-rich.

Oxidation is pervasive at 4,700 ft elevation. Mineralization becomes dominantly refractory at 4,200 ft to 4,350 ft elevation.

 

 

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8 DEPOSIT TYPES

The Cortez deposits are “Carlin” style sedimentary rock-hosted and porphyry/epithermal deposits. Carlin deposits form as structurally and/or stratigraphically controlled replacement bodies consisting of stratabound, tabular, disseminated gold mineralization occurring in Silurian-Devonian carbonate rocks. Deposits are localized at contacts between contrasting lithologies, metamorphosed to varying extents. They can also be discordant or breccia-related.

Host rocks are most commonly thinly bedded silty or argillaceous carbonaceous limestone or dolomite, commonly with carbonaceous shale. Although less mineralized, non-carbonate siliciclastic and rare metavolcanic rocks can locally host gold that reaches economic grades. Felsic plutons and dikes may also be mineralized at some deposits.

The deposits are hydrothermal in origin and are usually structurally controlled. The carbonate host rocks are part of an autochthonous miogeoclinal carbonate sequence (Lower Plate) exposed as tectonic windows beneath the Roberts Mountain allochthon. The lower Paleozoic allochthonous (Upper Plate) rocks are siliciclastic eugeoclinal rocks that were displaced eastward along the Roberts Mountain Thrust over younger units during the upper Paleozoic Antler Orogeny. Carlin deposits are localized along the thrust.

Current models attribute the genesis of the deposits to:

 

   

epizonal plutons that contributed heat and possibly fluids and metals;

 

   

meteoric fluid circulation resulting from crustal extension and widespread magmatism;

 

   

metamorphic fluids, possibly with a magmatic contribution, from deep or mid-crustal levels;

 

   

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

The past-producing Buckhorn gold-silver mine and the Hilltop gold project, are examples of a different and younger style of mineralization in the Cortez District. Both deposits are

 

 

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epithermal. Buckhorn is a more typical example of a low-sulphidation epithermal system while Hilltop is more closely intrusive related. Both are thought to be Miocene in age and deposited during Tertiary faulting, volcanism, and Basin and Range development. Hilltop is epithermal intrusive-related gold mineralization with minor copper.

 

 

 

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9 EXPLORATION

Modern exploration commenced along the Battle Mountain–Eureka Trend in the 1960s, and has been nearly continuous since that time. Exploration in the Cortez District has been undertaken by Barrick and its predecessor companies such as the CJV and has included mapping, various geochemical and geophysical surveys, pitting, trenching, petrographic and mineralogy studies, and various types of drilling.

Barrick funds a multi-million dollar exploration budget each year for the Cortez area. Barrick has advanced stage exploration drilling projects at the mine.

1) Continued surface and underground drilling of the Cortez Hills Middle and Lower zones.

2) Surface drilling and metallurgical test-work at Hilltop.

Exploration crews are also working at the past producing Buckhorn gold-silver mine under an earn-in agreement.

Many of the targets being investigated are partially or totally concealed by younger overburden and Tertiary rock cover or by allochthonous Upper Plate Paleozoic siliclastic rocks. Geophysical surveys are being used to help map buried bedrock features. At Buckhorn, prospect mapping and geochemical studies are part of the exploration activities.

EXPLORATION POTENTIAL

Exploration drilling at Cortez Hills has identified sufficient potentially economic gold mineralization to report Mineral Resources (see Section 14). There is room for further significant increases in Mineral Resources and there is potential for multi-million ounce gold deposits. Near-term exploration opportunities also exist to expand current resources on the western edge of the Pipeline pit and at Crossroads.

Barrick has completed 49 holes for 19,000 ft of drilling at Hilltop and have outlined a body of epithermal, intrusive-related gold mineralization with a preliminary potential of 1.0 million to 1.5 million ounces of gold. There is still potential to expand this target as it remains open in several directions. The next steps are to complete fill-in drilling for

 

 

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grade continuity, metallurgical test-work for recovery process options and extension drilling to expand the mineralization. The objective is to establish a reportable Mineral Resource at Hilltop.

Longer-term exploration potential remains for deep underground targets in the Gold Acres Window, as well as for potential open-pit and underground-mineable targets in the southern and eastern Cortez Window.

 

 

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10 DRILLING

Exploration and drilling activities for resource development in the Cortez district span a period of more than 40 years and include a variety of drilling techniques and the use of numerous different drill contractors. Approximately 17,819 drill holes are currently in the Barrick Cortez Project database. This number is known to be incomplete, as a significant portion of the drilling completed by companies other than Barrick and the CJV have not been incorporated in the Project digital database. The drill hole types included in the Project database include:

 

   

Reverse circulation (79% of total drilling)

 

   

Core (18%)

 

   

Other (3.0%)

Figure 10-1 illustrates the distribution of drill holes contained in the Project database for the Cortez district. Drill hole collars included in this figure are not representative of the total drilling within the Project. Many of the drill holes external to the Cortez and Gold Acre Windows were completed for reconnaissance purposes.

REVERSE CIRCULATION (RC) DRILLING METHODS

RC drilling is currently used during the initial phases of exploration, condemnation drilling and to pre-collar diamond coring holes through intervals of overburden and unaltered cap rocks. RC holes range in diameter from 4.5 in. to 7 in. Diameters of 6.5 in. and 6.75 in. are currently used for exploration.

Current practice is for RC holes encountering mineralization to be bracketed on four sides by core holes increasing the density of core holes in mineralized zones. RC pre-collar holes are cased with 4.5 in. casing and core drilling is continued through mineralization and footwall rocks. The depth to which RC drilling is used depends on the water table depth which is in turn dependent on mining dewatering activity in the area. Since 1980, RC has been typically used for 600 ft to 3,500 ft holes. RC pneumatic hammers are used up to 1,800 ft. Auxiliary compressors are used to increase the effectiveness of the down-hole hammers. Tri-cone rock bits are used at depths below the working depth of hammer bits. Centre-return hammers and bits were used for RC drilling at Pipeline. The deepest RC hole at Pipeline reached a depth of 3,280 ft; the deepest at Cortez Hills has been 3,500 ft.

 

 

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CORE DRILLING METHODS

Core sizes for wire-line diamond drilling are typically HQ (2.5 in. diameter) for resource development drilling. Occasionally, core holes are reduced from HQ size to NQ (1.9 in. diameter) size in difficult drilling conditions. Surface metallurgical core includes HQ and PQ-3 (3.27 in. diameter) sizes.

Conventional core handling methods and wax impregnated cardboard core boxes are used by the contractors who deliver the core to the logging facility on site. Core runs of 5 ft are typical in waste rock zones, but the shattered and broken nature of the Pipeline shear zone usually results in shorter runs. The drill crew inserts wooden blocks to mark the end of each core run. Manual versus natural breaks in the core are clearly marked with a wax crayon. Core is delivered to the logging shed by technicians or the drilling foreman at least once per shift.

CONVENTIONAL AND MUD DRILLING METHODS

These drilling method use air to pull the sample from the bit to the hole collar up the outside of the drill stem. Typically conventional air holes were short, and terminated at the water table. The drill diameter range was from 5.5 in. to 6.5 in. Conventional mud drilling used a similar sampling technique, with drill water-based bentonite clay/inorganic polymer muds employed facilitating drill sample return. Mud rotary drill holes range in diameter from 6 in. to 9 in. Mud-rotary drills have been used to drill relatively thick sections of alluvium over the Crossroads deposit or in areas being condemned for waste dumps and processing facilities. Core tools were used to complete the bedrock sections of these holes. Limited information remains on the drilling, logging, and sampling methodology for hole-types that were drilled prior to the mid-1990s.

 

 

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COLLAR SURVEYS

Collar coordinates from the 1960s to the 1980s drilling were determined by optical surveys, field estimates, Brunton compass and pacing, or compass-and-string distance. Recent campaigns have hole collars surveyed with either Total Station electronic distance measurement (EDM) or geodetic-grade, global positioning system (GPS) instruments. Two separate reference grids (Pipeline Mine grid and Cortez grid) are maintained. Survey Data in remote areas is collected in TUTM (Truncated Universal Transverse Mercator) Coordinates and then converted to the appropriate mine grid.

DOWN-HOLE SURVEYS

Down-hole surveying began in 1991 at the Pipeline deposit. Significant deviations were shown in RC drilling and down-hole surveying has been carried out since then. Most holes were surveyed with a recording gyroscope by a commercial contractor. Readings are taken every 50 ft down-hole and digitally transferred to the Project database. Boyles Brothers Drilling used a multi-shot recording gyroscope (MSRG) tool until April 1993. Silver State Surveying later performed all MSRG surveys and currently contractors WelNav and International Directional Services LLC (IDS) provide the surveys. Mahoney et al. (2009) reports that significant work has been carried out by Cortez to determine the accuracy of the instruments of each contractor.

Underground core holes drilled prior to May 2008 were surveyed down-hole by IDS. Since then surveying has been done by Cortez personnel using Reflex® magnetic instrumentation. Geotechnical holes have been drilled in each discovery to date using oriented tools. These normally use a plasticine, triple scribe, and down-hole camera system.

Down-hole surveys for a limited number of holes are incomplete where ground conditions such as caving restrict access for the survey instrument.

SAMPLE RECOVERY

In general, core-drilling practices at Pipeline, Crossroads, Gap, the Cortez Pits (NW Deeps), Cortez Hills and Pediment ensure a relatively high core recovery. Core recovery is sufficient to provide representative samples of a sedimentary rock-hosted gold deposit. Prior to 1991, core recovery values and RC sample weights were not

 

 

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routinely digitized or added to the general drill hole database. Wet drilling conditions for RC holes prohibit measurements of sample weights as a result recovery of RC materials cannot be calculated.

Core recoveries are maximized by use of triple-tube core barrels, face-discharge bits, and special drilling mud. Core recovery averaged 93% for 314 holes used in the Pipeline and South Pipeline Feasibility Study (Placer Dome Technical Services, 1995). The median core recovery for the Cortez Hills deposit was 96%. Only four core holes in the Cortez Hills deposit had less than 80% core recovery and were located in an approximate 150 ft by 150 ft geographic area in the upper extreme eastern portion of the lower-grade mineralized area near the intersection of four faults.

GEOTECHNICAL AND HYDROLOGICAL DRILLING

Geotechnical and hydrological holes have been drilled to provide raw data for the hydrological and geotechnical portions of the Pre-Feasibility and Feasibility Studies on the Pipeline and Cortez Hills deposits, and subsequently to support mining operations. Twelve underground core holes have been drilled for geotechnical purposes. These holes were designed parallel to planned drifts and served to predict the character of the rock mass to be developed.

GRADE CONTROL DRILLING

OPEN PIT

Blast-holes in rock on 20 ft benches are drilled on a square pattern of 20 ft by 20 ft with an 87/8 in. bit. This spacing has been decreased to 16 ft by 16 ft in carbonaceous ore. On 40 ft benches, blast-hole (97/8 in. bit) spacing ranges from 24 ft by 24 ft up to 28 ft by 28 ft. Blast-holes in alluvium employ a 105/8 in. bit and are spaced from 33 ft to 37 ft apart on a square grid. All blast-holes have a 4 ft sub-drill.

UNDERGROUND

Initial core drilling for the breccia zone was completed with flat fans of HQ core-holes drilled to nominal 50 ft spacing across the body of the projected mineralization at Cortez Hills. These fans are drilled approximately every 60 ft to 75 ft on the vertical axis of the body. Additional Cubex RC fan drilling using a 4 in. bit is carried out on working levels at a nominal 25 ft to 50 ft spacing. Down-hole surveys for Cubex are conducted by the drill contractor, Connors Drilling LLC, which uses Reflex instrumentation run within PVC tubing placed in the hole.

 

 

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Subsequent core drilling has been from drill platforms that drill perpendicular (shower heads) to mineralization. Breccia zone holes were drilled from the hangingwall side of the deposit. Middle and Lower Zones holes are drilled from development drifts located directly above the mineralization. Cubex (underground RC drills) drilling is used for grade control and can be drilled from active mining levels or dedicated drill bays

MINERAL RESOURCE DELINEATION DRILLING

Surface drilling is initially carried out on a 400 ft square pattern, closing in the next stage to a 200 ft grid. In-fill drilling is done on a five-spot pattern, resulting in an average hole spacing of 141 ft. At Pipeline, ‘X-shaped’ patterns of more closely spaced holes have been drilled to provide information for gold grade variography; this may locally decrease the hole spacing to approximately 70 ft.

Underground mineralization is drilled to a nominal 200 ft spacing from surface, then underground drilling is conducted to reduce spacing to 100 ft or less for Mineral Resource to Mineral Reserve transition. Prior to production additional underground drilling is completed to close up the spacing to between 25 and 50 ft for final mine design.

Drill holes are generally vertical. Inclined core holes were drilled at Cortez Hills to confirm the orientation of relatively high-grade gold-mineralized zones and to obtain geotechnical information for the planned Cortez Hills pit. Several angle core holes were drilled at the Cortez Pits (NW Deep) and Pipeline to provide geotechnical data and further delineate areas of mineralization.

PIPELINE COMPLEX AND GOLD ACRES

Drilling in the area of the Pipeline Complex including the Pipeline, Crossroads, Gap and Gold Acres deposits comprises 5,419 drill holes for approximately five million feet. Drilling dates from the 1960s to 2008, and comprises conventional, RC and core drilling. Almost all of the conventional drilling was in upper portions of the deposits, and has subsequently been mined out. Approximately 20 conventional holes were drilled after 2006, for approximately 60,000 ft. The resource estimation database contains 3,266 holes totalling 2,908,456.8 ft of which 2,973 are core holes for 2,704,949 ft and 293 are RC holes for 203,508 ft, including pre-drilling for core holes.

 

 

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Figure 10-2 shows a drill hole location plan for the Pipeline Complex including the Pipeline, Crossroads and Gap deposits.

Figures 10-3, 10-4 and 10-5 show representative cross sections through the Pipeline, Crossroads and Gaps deposits, respectively.

GOLD ACRES

The resource drilling database for Gold Acres consists of 1,725 surface drill holes for 461,363 ft and includes over 68,700 assays. Figure 10-6 shows a surface plan with drill hole locations (white dots) for the Gold Acres deposit and Figure 10-7 provides a representative cross section through the deposit.

 

 

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CORTEZ HILLS AND PEDIMENT

Figure 10-8 shows a drill hole location plan for the Cortez Hills Complex including the Breccia, Middle and Lower zones of Cortez Hills and the Pediment deposit. Drilling in the area of the Pediment and Cortez Hills deposits totals over two million feet in 1,894 holes completed from 1964 to 2011. Drill holes at the Pediment and Cortez Hills deposits are nominally spaced at 100 ft by 100 ft. All the gold assaying was done at one laboratory. All holes are down-hole surveyed. Of the 1,109 surface holes, 21% are diamond drill holes (372,896 ft) and 79% (1,429,314 ft) are RC including pre-drill for coring.

Surface drilling above the underground portion of the Cortez Hills Breccia, Middle and Lower Zones from 2005 to 2008 consisted of a total of 1,109 holes. Beginning in 2008, drilling has been primarily from underground platforms. The mid-year 2011 resource database for the Breccia, Middle and Lower Zones comprises 785 underground based holes totalling 337,903 ft, of which core drilling accounts for 273,457 ft in 482 holes and RC drilling accounts for 64,446 ft in 303 holes. Approximately 37,000 gold assays were performed, all at one laboratory. Drill spacing at the Cortez Hills Lower Zone deposit is nominally spaced at 200 ft by 250 ft. Underground drill hole spacing at Middle Zone varies from 100 ft by 100 ft to 50 ft by 50 ft. Underground drilling of the Breccia Zone varies from 50 ft by 50 ft or less in areas of active mining to 150 ft by 150 ft within the “Indicated” portion of the Mineral Resources.

Figures 10-9 to 10-11 show cross sections and longitudinal sections illustrating the geology, gold mineralization limits, and typical drill hole density for the various Cortez Hills zones.

CORTEZ PITS (NW DEEP)

Drilling in the Cortez Pits area dates back to before 1967 but only validated holes from 1986 to 2011 are included in the drill database used for resource work. The Mineral Resource Estimate is supported by approximately 280,860 ft of drilling in 450 holes and 37,415 assays. This includes 245,951 ft of RC drilling in 396 holes and 34,952 ft of core drilling in 54 holes.

Figure 10-12 presents the drilling for the Cortez Pits area and Figure 10-13 is a typical cross section.

 

 

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COMMENTS ON DRILLING

In RPA’s opinion the quantity and quality of the lithological, geotechnical, collar, and down-hole survey data collected in the exploration, delineation, and grade control drill programs are sufficient to support Mineral Resource and Mineral Reserve estimation, and:

 

   

Drill hole orientations are appropriate with respect to the orientation of the mineralization.

 

   

Drilling is normally perpendicular to the strike of the mineralization, but depending on the dip of the drill hole and the dip of the mineralization drill intercept widths are typically greater than true widths.

 

   

Drill hole intercepts adequately reflect the nature of the gold mineralization. Down hole composite data indicate areas of higher-grade and lower-grade mineralization, and waste material within the deposits.

 

   

The deposits have been well drilled.

 

   

Through interpretation and aggregation of the drill hole data, the sections provide a representative estimation of the true thickness of the mineralization for the various deposits in relation to planned pit and underground mining boundaries that are used to constrain the Mineral Resources and Mineral Reserves.

 

   

Collar surveys have been performed using industry-standard instrumentation.

 

   

Down-hole surveys have been performed using industry-standard instrumentation.

RPA identified no factors with respect to the data collection from the drill programs that could adversely affect Mineral Resource or Mineral Reserve estimation. Historic drilling, primarily conventional techniques, are known to have been affected by down-hole contamination, however, these holes are either in mined-out areas or data from the suspect holes have been excluded from Mineral Resource or Mineral Reserve estimation.

 

 

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11 SAMPLE PREPARATION, ANALYSES AND SECURITY

A large portion of Section 11 was extracted from the Scott Wilson RPA 2010 Cortez audit report with only modifications and additions where required. The sub-sections on sample security and on quality assurance and quality control (QA/QC) in particular have been significantly modified and updated.

SAMPLING METHOD AND APPROACH

RC SAMPLING

Drillers carry out the sampling on the RC drill rig. After material discharge from the hydraulic, revolving wet sample splitter on the cyclone, the fraction to be sampled was subdivided by a Y-shaped joint in a 5 in. sample discharge pipe and each split collected in a five-gallon plastic bucket lined with 19 in. by 22 in. Micro-Pore® sample bags. Bags are pre-numbered and tagged by Cortez. Recently, collection has been modified to Micro-Pore® bags placed in one-gallon metal sleeves hung beneath each arm of the Y pipe splitter. Samples are allowed to air dry in the field and are then picked up at the drill sites by geological technicians. Where areas are relatively open to the public, this loss of chain of command may compromise sample security.

RC chip samples (typically -1/2 in.) were collected by drillers in 5 ft intervals for Gold Acres drilling and in the initial 1991 drilling at Pipeline. By late 1991, RC samples at Pipeline were collected on 10 ft intervals as was done at Cortez Hills. The 10 ft samples weigh from 10 lb to 15 lb and represent a mass reduction to a small percent of the original.

TABLE 11-1 AMOUNT OF RC SAMPLE REDUCTION

Barrick Gold Corporation – Cortez Operations

 

RC Hole    10 ft Length  

    Diameter    

       10 lb              15 lb      

7”

     2%         4%   

4.5”

     6%         9%   

7”

     41x         27x   

4.5”

     17x         11x   

 

 

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RC sampling procedures were modified for drilling at the Pediment deposit in accordance with recommendations by consultant Francis Pitard in 1999. Samples weighing from 35 lb to 40 lb are now collected from development RC holes at Pediment.

Footage intervals were recorded by a technician on a separate shipment record from the corresponding sample numbers. Commercially prepared standards and blank samples of landscaping marble are inserted by the drillers randomly into the numbering sequence prior to sample pickup.

Chip samples of each RC interval are collected and stored in plastic chip trays for geologic logging. Each chip tray represents about 200 ft of drilling. Chips are logged by project geologists or geological contractors. The logging form is set up to record stratigraphic formation, rock type, rock textural characteristics, veining, significant minerals, alteration, and estimated sulphide, carbonate and carbon content. Completed logs are entered into a master database. Chip trays are stored in a central warehouse facility on site. Until the 1970s, representative RC chips were glued to boards as hole records; however, none have survived. Digital backup copies of the geologic logs are stored offsite. All hardcopy logs that were used prior to the inception of digital logging are archived in files, labelled, and stored in the exploration or mine geology offices.

Drilling is almost always carried out with water injection. Drilling below elevations ranging from 5,000 ft to 5,700 ft at Cortez Hills is below the water table. Total sample weight cannot be measured because of wet drilling conditions; therefore RC recovery cannot be calculated.

CORE LOGGING AND SAMPLING

Drill core was washed and photographed prior to logging. Core is digitally photographed wet, except in cases of exceptionally poor rock quality. Older film photographs have been scanned and electronically archived. Step-out exploratory drill holes are summary-logged and representative chip samples are collected at one foot intervals, making up a composite sample over 20 ft. The chip samples are analyzed for gold as well as multi-element geochemistry. Chip samples are excluded from grade estimations. If the core was later cut, the cut core values are used for grade estimation, if the core was not cut, because of low grade assay results than the chip grades are set 0.0001 opt and treated as waste during grade estimation. Retained core character samples are stored on site at the Pipeline and Cortez core storage facilities.

 

 

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Once the assays are returned for the exploratory hole, detailed geologic logging is carried over the mineralized interval, bracketed by 100 ft of core above and below. The interval is then cut and resubmitted for gold assay. In-fill and development drill holes are subjected to detailed geologic and geotechnical logging.

The core is logged by a geologist for geological and geotechnical elements. Prior to 2004, logging was either done on paper and then entered into a computer or entered directly into a computer and was verified by Placer Dome software with text and graphics capability. After review by geologists, corrected logs were reprinted and electronically merged into the master database by a computer administrator. After the implementation of an acQuire® SQL Server database in 2004, logging was changed to an acQuire® data input form. This requires selection of attributes from a prescribed list, avoiding entry of non-standard symbols or qualifiers. The computerized geological logging format allows for recording mineralogy, structure, texture, alteration, rock type, colour, brightness, lightness, grain size, sorting, sphericity, shape, degree of decalcification, and carbon content.

Point load tests of selected intervals and other geotechnical data were collected by staff technicians and the geology department. After mid-2006, Golder Associates Ltd. (Golder) carried out this task but only on core drilled for geotechnical purposes or upon request.

Most drill-core from Pipeline and Cortez Hills was sampled and assayed at 10 ft intervals, though several holes were assayed at 5 ft or variable geological intervals early in the drilling programs. Since 2004 exploration core holes have been sampled on 10 ft intervals in barren rock and on geologically defined intervals up to five feet in mineralization.

Almost all core was sawn in half by a Cortez technician. A hydraulic splitter has been used for extremely hard rock to maintain acceptable production rates. Any fragmented core less than one inch diameter was split through a riffle splitter. One-half of the core or a riffle split was placed back in the original core box and the other half in 10 in. by 22 in.

 

 

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Micro-Pore® cloth sample bags with a numbered paper sample tag. Sample numbers are assigned using sample ticket books. The sample number was also handwritten on the exterior of the bag with a permanent marking pen, along with the drill hole number. Including drill hole numbers with sample labels is not considered best practice. A technician recorded footage intervals on a separate shipment record form with the corresponding sample number. Metallurgical core was quartered, with one quarter retained as a character sample and the remaining assayed and consumed for metallurgical testing.

The retained core is stored on site. Barrick exploration has a core storage facility, which contains drilling for the site, located near the Pipeline administration office. Other sample storage areas include the East Pit at Cortez Pits and the Gold Acres Pit.

CONVENTIONAL AIR-ROTARY AND MUD-ROTARY SAMPLING

Sampling was carried out at 5 ft to 10 ft intervals. Early (mid-1980s) rotary air sampling may have been accomplished in dry conditions using non-porous plastic bags. Sample numbers were assigned using sample ticket books.

BLASTHOLE SAMPLING

The practice is to double sample the 40 ft blast holes on ore bearing levels. One sample represents the bottom 20 ft, while the other represents the upper 20ft of the hole. Any 40 ft trim shots are single sampled as are 20 ft holes on a 20 ft bench. A representative sample of blast-hole drill cuttings is collected by placing a 6 in. diameter, 12 in. tall vertical cylinder near the drill hole and inside the rig dust rubber curtain. Approximately 7 lb to 8 lb of material is collected. The sample number records the location and uses a bar-coded tag. Samples are assayed at the Cortez Mine assay laboratory. Analytical data are incorporated electronically into the blast-hole database.

TABLE 11-2 BLAST HOLE SAMPLE REDUCTION

Barrick Gold Corporation – Cortez Operations

 

    Diameter        Sample Reduction to:      Including Sub-Drill  

(in.)

       7 lb.              8 lb.              7 lb.              8 lb.      

9.875

     0.22%         0.25%         0.20%         0.22%   

8.875

     0.53%         0.61%         0.44%         0.51%   

9.875

     465x           407x           511x           447x     

8.875

     188x           164x           225x           197x     

 

 

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Blast-hole sample results are used for open-pit mine grade control, but are not used for Mineral Resource and Reserve estimates.

UNDERGROUND MUCK SAMPLING (CORTEZ HILLS)

Muck sampling is the only means of grade control currently used at Cortez Hills underground. Grab samples are collected by shovel from the bucket of the 6 yard scoop tram load-haul-dump (LHD). At the truck bay, the LHD operator takes a sample of every 1st, 5th, 10th, and 15th LHD load from the muck pile of a given round.

The muck sample is placed in 12 in. by 18 in. bar coded bags and represents approximately 20 lb of material. Screen tests and Pierre Gy developed analysis determined that samples of one inch to two inch fragments plus fines are representative. Samples are assayed at the Cortez Mine assay laboratory. Analytical data are incorporated electronically into a muck database within the acQuire® database and there is a plan to use the muck sample results and the exploration drilling results in a Vulcan software grade control module to create mini-block models. No quality QA/QC samples were being inserted into the muck sample stream at the time of RPA’s visit.

Underground muck sample results are used for mine grade control (material routing on a round by round basis), but are not used for mineral resource and reserve estimates.

BULK DENSITY DETERMINATION

Whole core sampling for bulk density measurement was initiated in April 1992 at the Pipeline deposit and density was determined for a total of 467 ore and waste samples. Standard practice since 1999 has been to collect samples at 35 ft to 40 ft intervals in mineralized rock and less frequently in the hanging wall and footwall. Currently, there are 4,646 density determinations for rock types at Pipeline and Cortez Hills.

Core is prepared by the Cortez geology staff and the mine metallurgical laboratory carries out the density measurements. The primary method of measuring core density is by wax immersion. Competent core is coated in wax and then immersed in water. There are five other methods which have been used in the past and may be used on occasion depending on the situation. Those other methods are:

 

  1. Fragment displacement (lacquer coated fragments are immersed in water)

 

 

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  2. Core displacement (lacquer coated core is immersed in water)

 

  3. Core axis length and diameter is measured and applied to dry weight of sample

 

  4. Plastic sleeve (poor quality core in PVC pipe is wrapped and immersed in water)

 

  5. Buoyancy (competent core is wrapped in cellophane and immersed in water)

Cortez has compiled bulk densities for the various rocks and overburden for each deposit. Values range from 11.7 ft3/st to 16.6 ft3/st for rocks and 16.2 ft3/st to 19.1 ft3/st for alluvium and the Pediment deposit.

LOGGING, SAMPLING AND SAMPLE STORAGE FACILITIES

Cortez has permanent facilities for core logging and sampling, as well as storage warehouses. RPA visited the exploration core facility located near the Pipeline Mill and found the layout to be clean, organized and in line with industry standards for layout, facilities and procedures. Drill core, RC chips, retained character core, pulp, and pulp duplicate samples are stored onsite in the Cortez and Pipeline storage warehouses. Older core for mined-out portions of the deposits has been skeletonized to reduce storage. Samples rejects are retained but stored outside where they degrade after two to three years at which time they are no longer useful. Prior to 2006, core could be stored in open air core yards, but this practice has been discontinued.

RPA COMMENTS ON SAMPLING METHOD AND APPROACH

Cortez identified bias issues in historic drill programs. However, the reserves affected have been mined out, whereas the affected drill holes are marked in the Project database such that they cannot be used for Mineral Resource or Mineral Reserve grade estimation.

Other than the housekeeping issues mentioned, in RPA’s opinion the core handling, logging and sampling protocols conform to industry-standard practice, are being carried out to a reasonable standard and are acceptable for Mineral Resource and Mineral Reserve estimation.

 

 

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SAMPLE PREPARATION, ANALYSIS AND SECURITY

Prior to 2008, mine personnel were involved with or responsible for:

 

   

Sample collection

 

   

Core splitting

 

   

Sample preparation of geochemical, pit, trench, RC, conventional-mud, conventional-rotary, and core samples

 

   

Delivery of samples to the analytical laboratory

 

   

Analysis of gold and pathfinder elements for exploration purposes

 

   

Analysis of gold and contaminant elements for production and grade control purposes

 

   

Specific gravity determinations

 

   

Sample storage

 

   

Sample security

Since 2008, Barrick staff have been involved with or responsible for:

 

   

Sample collection

 

   

Core splitting

 

   

Analysis of gold and contaminant elements for production and grade control purposes

 

   

Specific gravity determinations

 

   

Sample storage

 

   

Sample security

Analytical procedures that support Mineral Resource estimation, including sample preparation and sample analysis, were performed by independent analytical laboratories without company involvement from 2005 to the present. Samples prior to that date were primarily prepared and analyzed by the Cortez laboratory.

 

 

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ANALYTICAL LABORATORIES

Prior to 2000, the mine laboratories at Mill No. 1 (Laboratory No. 1) and Mill No. 2 (Laboratory No. 2) assayed a majority of exploration samples, principally those for Pipeline, Crossroads, Gap, and Cortez NW Deep (Cortez Pits). Laboratory No. 1 was located at the old Cortez Mine facility and closed in 1997. Laboratory No. 2 was constructed in 1997 and currently is operating at the Pipeline process facility.

A number of commercial mineral laboratories were used for assaying or check assaying since 1991, including Rocky Mountain Geochemical Laboratory, American Assay Laboratory, ALS Chemex, Barringer Laboratories (now Inspectorate), the Placer Dome Research Centre, and Monitor Geochemical Laboratory.

ALS Chemex has been the primary independent commercial laboratory used. A majority of core and RC samples for Cortez Hills and Pediment deposits were prepared by ALS Chemex’s sample preparation facility in Reno, Nevada, and assayed in Vancouver, B.C.

From 2005, all exploration assaying as well as underground assaying for development drilling at Cortez Hills and supplementary drilling at Pipeline, Gap and Crossroads, has been performed by ALS Chemex. The mine laboratory has been principally used for mine related “ore” control analysis and processing analysis.

The mineral laboratories used are ISO registered except for the Inspectorate (Barringer), Rocky Mountain Geochemical Laboratory, Monitor Geochemical Laboratory, and the Cortez Mine laboratories.

SAMPLE PREPARATION

Sample preparation protocols for the commercial and mine laboratories were similar. The initial sample preparation for Pipeline drilling in 1991 to 1992 was:

 

   

Sample bags were dried at 350°F for six to 12 hours.

 

   

Samples were weighed on a triple beam balance to an accuracy of 0.1 kg.

 

   

Samples were fed through a TM Engineering Ltd.’s (TM) Rhino Jaw Crusher set at 1/8”.

 

   

Entire sample was screened to minus 10 mesh. Oversize was run through a Bico disc pulverizer to reduce the oversize to minus 10 mesh.

 

 

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Entire samples were split to 500 g with a Jones-type splitter. The 500 g split was dried a second time.

 

   

A 500 g aliquot was pulverized to 100% passing 150 mesh in a TM vibratory ring pulverizer. Pulverized sample was homogenized on a roll mat. Ring pulverizer was cleaned by pulverizing a crushed crucible between each sample.

 

   

Reject was retained and stored.

The coarse-crush protocol was changed to 80% passing 10 mesh in late 1992, and between 1992 and 1997 it was changed to 95% passing 6 mesh. By 1998, the crushing protocol was changed to:

 

   

Entire sample crushed to minus  1/4 in. using a jaw crusher.

 

   

Entire sample crushed to 95% passing 8 mesh in a rolls crusher.

 

   

500 g aliquot split for pulverizing to minus 200 mesh in an automated pulverizer.

This protocol was maintained until about 2000 when new crushing and grinding equipment was acquired by mine Laboratory No. 2. The mine laboratory now uses a RockLabs crusher and rotary splitter and a TM automated ring-and-puck pulverizer for exploration samples. The RockLabs splitter uses a two-stage process to crush the entire exploration sample to 95% passing 10 mesh and produce a 500 g sample aliquot. The 500 g is pulverized for 75 seconds in the automated pulverizer, producing a product of 95% passing 175 mesh. Gravel is pulverized between each run of the 24-compartment pulverizer to clean the unit. Crush and pulverizer specifications are checked once weekly. Balances are calibrated every six months.

Blast-hole samples from 3 lb to 20 lb are crushed to 95% passing 6 mesh in a TM Rhino jaw crusher. A 250 g to 300 g aliquot is split with a Jones-type riffle splitter. No reject is retained. The 250 g to 300 g aliquot is then pulverized for 150 seconds in a manual ring-and-puck pulverizer or for 75 seconds in the TM automated pulverizer.

ALS Chemex uses the following sample preparation procedures for Cortez samples:

   

High temperature drying of samples (DRY-21 procedure).

 

   

Weigh, dry, fine crush entire sample to better than 70% minus 2 mm, split off up to 250 g and pulverize split to greater than 85% passing 75 µm (PREP-31 procedure).

 

 

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Compositing procedure, homogenize the composite pulp, gravimetric procedure (CMP-22).

 

   

Gold analyses: Gold assay (0.005 ppm to 10 ppm) by 30 g fire assay – atomic absorption (AA) analysis (Au-AA23 procedure).

 

   

Au (0.03 ppm to 50 ppm by cyanide leach – AAS, 30 g nominal weight (Au-AA13 procedure).

 

   

Au by fire assay and gravimetric finish, 30 g nominal weight, range 0.05 ppm to 1,000 ppm Au (Au-GRA21 procedure).

 

   

Multi-element analyses by aqua regia digestion/ICP-AES/ICP-MS, 50 elements (ME-MS41 procedure).

ANALYSIS

A standard fire assay with gravimetric finish is performed on one-assay ton (29.18 g) pulp aliquots for all core and RC samples analyzed by the mine laboratory. If the initial fire assay is greater than 0.1 oz/st Au, an additional fire assay is performed. If the initial fire assay is greater than 0.2 oz/st Au, two additional fire assays are performed. The mean value of the two or three assays was used for resource estimation in the Pipeline Feasibility Study resource model.

In 2004 ALS Chemex assayed Cortez Hills and Pediment samples by fire assay and AA finish, using a 30 g pulp aliquot. All samples reporting greater than 0.1 oz/st Au on the initial assay were re-assayed by fire assay with gravimetric finish. Cyanide leach gold assays were performed for initial FA assays higher than 0.008 oz/st Au. A cold cyanide shake leach, analyzed by AA, is performed if the initial fire assay is higher than 0.015 oz/st Au. If the initial fire assay is higher than 0.04 oz/st Au and lower than 0.15 oz/st Au, a “preg-rob” test is performed. This is performed by combining 10 g of pulp with 20 mL of a 0.05 oz/st Au cyanide solution and agitating for eight to ten minutes, then analyzing by AA. Samples with a cyanide AA/fire assay ratio of less than 0.3 are routinely assayed for sulphur and total carbon in a LECO furnace.

The current practice is to fire assay, AA, and preg rob on all intervals within pre-selected zones. More selective triggers apply in unmineralized zones.

 

 

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A Laboratory Information Management System (LIMS) was implemented at mine Laboratory No. 2 in 1998. Laboratory No. 2 uses a sample bar code system and transfers all information to the mine database electronically via the LIMS. ALS Chemex assay certificates are downloaded from the ALS Chemex website and loaded directly into the mine database using acQuire®.

Twenty foot composites made from core and RC samples are routinely analyzed for a 49 element suite by ALS Chemex. For the underground development holes, multi-element analysis is performed on every sample (~5 ft intervals). The trace-element suite is obtained by inductively coupled plasma–arc atomic absorption spectroscopy (ICP) following an aqua regia digestion of the sample pulp. Trace elements include As, Sb, Hg, Tl, Fe, and Ca, which in association with Au, show positive or negative correlations with mineralized areas. High Hg analyses from the partial-digestion ICP data have been checked against cold-vapour hydride analyses, also run at ALS Chemex, and have shown generally close correlation (±5%) with the cold-vapour values. The multi-element ICP suite has changed in composition and detection limits several times in the last 15 to 20 years as analytical techniques have improved.

Additional assay methods, as recorded in the database of the 1960s, were typically used for exploration or other specialized purposes such as gas sampling, and were not consistently carried out. They include gravimetric, sulphuric acid digest, total copper, neutron activation analysis, X-ray diffraction, and X-ray fluorescence methods.

SAMPLE SECURITY

Table 11-3 summarizes the chain-of-custody of the various sample materials as it makes its way from the point where material is originally collected to the analytical laboratory. Grade control samples from operations are managed by employees of the Cortez mining operation (wholly owned by Barrick) and its drill contractors; while exploration samples are managed by Barrick exploration personnel and its contractors. Prior to 2008 the chain-of-custody was managed by CJV staff and their contractors.

Blast-holes samples are delivered directly from the pits to the Cortez laboratory. Underground muck samples are delivered initially to the Portal and then to the sample room at the F-Canyon Office block. Underground RC samples are taken directly to the F-Canyon sample room. Underground drill core boxes are taken directly to F-Canyon lay-down area. Exploration samples, after leaving the drill rigs, are taken by Company personnel to the secure Exploration Complex.

 

 

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Sample security relies on the samples being either always attended to by Company personnel or stored in the locked on-site preparation facility or stored in a secure area prior to pick-up by ALS Laboratory personnel or delivery to the on-site Cortez laboratory. For the most part, a unique and independent sample number is used for each sample with dispatch-submittal sheets and database entries used to track the progress of samples and to ensure that all samples are received by the laboratory.

TABLE 11-3 CHAIN OF CUSTODY SUMMARY

Barrick Gold Corporation – Cortez Operations

 

Sample Source

Grade Control

   Exploration Drilling

Blast-holes (o/p)

   Muck (u/g)    Core (u/g)    RC (u/g)    RC    Core

Material collection at source

           

Cortez drillers

   Cortez loader operator    Cortez Geotechnician    Drill Contractor    Drill Contractor    Barrick employees

Transportation from source, handling, sample delivery to lab

     

Cortez drill & blast personnel

   Cortez Supervisor    Drill Contractor    Drill Contractor    Barrick employees    Barrick employees
   Cortez employees    Cortez employees    Cortez employees    Barrick Geotechnician   
      ALS employees    ALS employees    ALS employees    ALS employees

Sample Preparation and Analysis

           

Cortez lab

   Cortez lab    ALS lab    ALS lab    ALS lab    ALS lab

Sample numbering and tracking

           

 

   

A unique and independent sample number and sample number tags are used in all cases except underground muck samples that are identified by location (e.g. heading & footage).

 

   

Sample dispatch and submittal sheets are used to check and track samples through the system

 

   

Sample information is entered into the computer database to help tracking and for receipt of results

RPA’S COMMENTS ON SAMPLE PREPARATION, ANALYSIS AND SECURITY

In RPA’s opinion the sample preparation, analytical procedures and sample security used at Cortez for mining operations and exploration projects are appropriate and are being carried out in a reasonable fashion.

QUALITY ASSURANCE AND QUALITY CONTROL

Since 2006, Barrick corporate geochemists have visited the laboratories that undertake analysis and sample preparation for the Cortez Project. QA/QC for sampling, sample preparation, and assaying has evolved at Cortez since 1991. Procedures include insertion of blanks and mine-derived or commercial standards into sample streams to the mine and commercial laboratories, check assays of pulp duplicates by commercial laboratories, and assaying of coarse reject duplicates. Starting with the Pipeline deposit, the mine submitted one blank and one standard sample with every ten core and RC samples. A check sequence typically consisted of a standard followed by a blank.

 

 

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Barrick’s QA/QC practices at Cortez exploration comprise a minimum of one standard, one blank and one duplicate introduced to the sample stream resulting in 10% quality control samples. Underground grade control drilling involves insertion of one standard and one control blank for every 30 samples, but because whole core is often sampled there is no opportunity for duplicate samples.

Monthly QA/QC reporting for Cortez was started in 2009 and is prepared by the Database Administrator. The report evaluates the performance of standards, blanks and duplicate samples inserted into the sample streams. It also identifies any QAQC failures, tracks their investigation and resolution including any assay reruns.

STANDARD SAMPLES

Standards are materials of known values used to check and quantify the analytical accuracy of laboratories.

At Cortez standards were originally made from stockpile materials at the mine. Accepted values for each standard were determined by having the mine laboratory assay splits from the samples several times (ranging from twice to 40 times) following homogenization of the sample in a cement mixer. The average grade from the first six 50 gallon barrels of standard collected for the Pipeline drilling campaign was 0.175 oz/st Au with a standard deviation of 0.0135. When the material was consumed, six additional 50 gallon barrels of standard materials were collected. The average grade was 0.120 oz/st Au with a standard deviation of 0.014. Blanks were typically below the mine laboratory detection limit (less than 0.002 oz/st Au). Leach material grading 0.012 oz/st Au was later used for blanks. At least 48 mine standards were developed with this method. When barrels of standard material were consumed, new samples were collected from the mine stockpiles. Since 2006, commercially available core and RC drill standards and blanks have been used as detailed in the following subsection.

Routine quality assurance is limited to pass/fail checking of the reference standard assays against their accepted values. Assay batches are rejected if the assay of a standard is outside the range of assay values originally returned by the mine laboratory

 

 

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during initially assaying of the standard. The pass/fail criterion for Cortez-derived standards was approximately equivalent to one standard deviation from the mean. Generally accepted practice is to set acceptable limits at two standard deviations from the mean for homogenous pulp standards. However, the mine standards were not developed in a rigorous manner because of the need for a significant volume of reference material. The more stringent fail limits were more appropriate given a large standard deviation in assays on the standards.

Since the adoption of commercial standards in 2006, the pass/fail criterion has reverted to two standard deviations from the mean.

Until 2006, reference material was obtained from working benches in Pipeline where blasthole assays showed consistent grades between multiple holes. This material was scooped out with a front-end loader, placed at a storage area, then cone and quartered as needed. At least 20 samples were collected from each pile, and then the remaining material was placed in a 55 gal drum. The drum was sent to the mine laboratory where the ore was crushed to minus quarter inch and an additional 20 samples were collected for assay. Crushed material was put back in the drums and moved to the geology department. The material was very similar in appearance to RC drill cuttings of material.

In 2006, it was determined that since Pipeline mining had progressed to the lower grade portions of the deposit, it was no longer feasible to create reference material from working benches as the variability in the low-grade material was too great.

Exploration and development drilling is currently making use of a set of commercial standards purchased from RockLabs Ltd. of Auckland, New Zealand. A set of low- and high-grade refractory material standards was also created from blended bench material in the Gold Acres pit in 2008 and is currently in use.

BLANK SAMPLES

A blank control sample is material with a zero gold value. Blanks are inserted to assess sample preparation, specifically to identify “grade smearing” or sample carryover in subsequent samples caused by improper sample preparation and contamination, and to evaluate analytical “background noise”. Since 2006 landscape marble has been the material used to make blank samples for QA/QC at Cortez. Prior to 2006, blank material was made from:

 

 

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Unmineralized drill core from gold Acres

 

   

Waste rock from the Cortez pit

 

   

Alluvial gravel taken from a pit near the Gold Acres haul road

The following criteria are used to evaluate analytical results received for blank samples.

 

i Assay result less than 0.002 oz/st                                                                                       Pass

 

ii Pass limit is extended by 1% carry-over from surrounding samples

 

iii Assay result equal to or greater than 0.0002 oz/st                                                            Failure

Laboratory procedures include cleaning of the sample preparation circuit after sample batches and not after each sample; the reason for this is a cost and time issue. The 1% allowance of carry-over grade from surrounding samples makes some allowance for potential contamination from high grade samples processed within a sample batch. Occasionally there is a failure with the blanks. A failure triggers an investigation to determine if there has been a sample labeling problem; if not then all the samples associated with the failed blank are reassayed.

DUPLICATE SAMPLES

Duplicate samples of coarse rejects provide information on sample preparation and assay precision, while duplicate pulp samples may be used to quantify analytical precision. The pass/fail criteria used by Barrick for duplicate pulp samples is +/- 20%. Duplicate reject samples are not routinely taken at Cortez and hence there are no specific pass/fail criteria.

OUTSIDE CHECK SAMPLES

Recent practices at Cortez for independent check assays are to have the primary laboratory, ALS Chemex, randomly select every 20th pulp and forward these to American Assay Laboratory for a second check assay. This represents a 5% check ratio. Prior to the third quarter of 2011 the check assays were done on coarse rejects at 3.5% ratio. Pass/fail criteria used is +/-20% of the original value. Samples with a variance of more than 20% were reviewed individually when check assays were being performed on coarse rejects.

 

 

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In the past results of check assaying on pulps and coarse rejects were not routinely evaluated. Check assays, however, were used intermittently to evaluate biases between the mine laboratories and commercial laboratories.

For the period 1992 to 1996, a large number of commercial laboratories were used to check assays by Laboratory No. 1. No record was kept of the source laboratories for each check in all cases; therefore, some of the data cannot be differentiated by laboratory. A detailed review of check and duplicate assay records in 2003 reduced the number of unidentified laboratory assays to approximately 4%. No significant bias was detected between the mine and the commercial laboratories.

Check assay plots show a relatively high variability between the mine laboratory and commercial laboratories for 1997 through 1999 assaying. For grades greater than 0.01 oz/st Au, a majority of check assays are within ±20% to ±30% of the original value which is somewhat higher than the expected ±10%.

Check assays on samples primarily from the Pediment and Cortez Hills deposits by Rocky Mountain Geochemical and American Analytical laboratories in 2000 to 2003 show less variability, with most checks within ±10% of the original value. In 2003, Cortez investigated these biases in detail and adjusted historical assays for the Pipeline, South Pipeline, Crossroads, and Gap deposits for laboratory biases and sampling biases. The practice of adjusting assays has been discontinued.

Checks of the mine laboratory (Laboratory No. 1) assays were made for the 1995 feasibility study. A pulp duplicate was prepared for one in every five Pipeline core sample and one in every ten South Pipeline core sample. A pulp duplicate was prepared for one in every ten RC sample for Pipeline and one every twenty RC sample for South Pipeline. These were assayed by Monitor Geochemical Laboratory and the Placer Dome Research Centre. Since 1995, this procedure of checking the mine laboratory assays has continued using Rocky Mountain Geochemical Laboratory, American Assay Laboratory, Barringer Laboratories (now Inspectorate), and Monitor Geochemical Laboratory.

 

 

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SCREEN CHECKS

Screen check assaying is not done at Cortez. Previous test work determined that coarse gold has not been an analytical issue to date, given the disseminated distribution and very fine grained character of the gold mineralization.

CORTEZ LABORATORY

The on-site Cortez laboratory runs its own internal QA/QC program. They use commercial prepared and purchased standards of various grades. Current frequency of control samples is as follows:

 

   

Production samples (FA-GRAV and CNL-AA)

 

  - 21 samples per set

 

  - 1 standard, 1 blank and 1 duplicate per set

 

   

Mill shift samples (solutions & solids)

 

  - 1 standard for each solution set of 23 samples and each solid set of 12 samples

 

   

XRF – Carbon analysis

  - 1 standard for each set of 20 samples

 

   

Leco – Carbon and sulfur analyses

 

  - 1 standard and 1 blank for each set of 22 samples

 

   

Exploration samples (FA-GRAV and CNL-AA)

 

  - 21 samples per set

 

  - 1 standard, 1 blank and 1 duplicate per set

The laboratory is organized such that quality control samples are inserted automatically. Different grades of standards are used and run with underground, open pit and mill process samples.

A monthly QA/QC compliance report details investigative findings regarding samples that fail the control criteria. With respect to gold analysis by both fire assay with a gravity finish (FA-GRAV) and cyanide leach and AA finish (CNL-AA) the following pass/fail criteria are applied by the Cortez laboratory. The pass criterion for standards is two standard deviations; standard variance between two and three standard deviations is taken as a warning; action is required when variance exceeds three standard deviations. The pass criterion for blanks is gold values less than 0.002 oz/st gold.

 

 

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Table 11-4 is the summary table on the performance of the Cortez laboratory standards and blanks in September 2011. Investigations were undertaken on the standards and blanks to assess the reason for the failure and determination of corrective actions and re-assaying where required.

 

TABLE 11-4 CORTEZ LABORATORY STANDARD AND BLANK PERFORMANCE

Barrick Gold Corporation – Cortez Operations

 

     Total
Number of
Results
     Number
Passed
     Percent
Passed (%)
     Number
Failed
     Percent
Failed (%)
 

Fire Assay Standard

     696         691         99.28         5         0.72   

Cyanide Leach Standard

     696         691         99.28         5         0.72   

Fire Assay Blank

     696         696         100.00         0         0.00   

Cyanide Leach Blank

     696         689         98.99         7         1.01   

RPA’S COMMENTS ON QA/QC

RPA examined two QA/QC reports from September 2011. One is prepared and issued by the Database Administrator who monitors both the performance of the mine and the external independent laboratories. There were no problems with the standards in September but three of 156 blanks, four of 95 duplicates and one of 70 check assays were identified for investigation. The second report is an internal report prepared by the Cortez laboratory on their internal QA/QC protocol. Ten of 1,392 standards and seven of 1,392 blanks failed and were investigated. These reports each identified a small number of standard, blank and duplicate control samples that failed the established pass criteria. Investigations of these “failures” are presented in the reports. Where investigations were unable to provide valid explanations for the variances, assay reruns of the affected sample batches were made. RPA approves of the regular monthly QA/QC reporting; a positive response to an RPA housekeeping recommendation made in its 2010 Audit Report.

RPA noted that a number of the mine prepared standards show a statistical bias more often high but some show a low bias, even while staying within the established pass criteria. This is likely a problem with either insufficient analysis of the mine prepared standard to establish its expected value or possibly a problem of homogeneity of the standard. Barrick’s geochemists are aware of this issue and are investigating it. The commercially purchased standards do not appear to have this issue.

 

 

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A housekeeping issue with respect to QA/QC practices identified in RPA’s 2010 audit that remains to be addressed is that sample recovery data are not recorded for RC drilling, e.g. the weight of material over any given drilled interval is not recorded. Weighing the samples for recovery is a QA/QC function, the review of which could serve to point out sample bias. This point is somewhat mitigated by the restricted use of RC drilling for step-out exploration only and follow-up being undertaken with core drilling.

RPA notes and approves of the corrective action at Cortez to deal with a housekeeping issues identified in the 2010 Audit Report. Specifically that QA/QC samples for the RC drilling are now inserted into the sample stream by company personnel at a secure location and no longer by the contract drillers at the rig site and that QA/QC samples are now added to the underground muck samples prior to submission to the Cortez laboratory.

In RPA’s opinion the QA/QC protocols and reports meet industry-standard practice and provide the necessary control to identify potential analytical problems and allow for corrective follow-up and re-analysis when required. RPA agrees with the recent increase to 5% independent check assays from the previous 3.5%. RPA recommends that it would be preferable to use commercially purchased standards rather than mine prepared standards.

 

 

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12 DATA VERIFICATION

DATABASES

The Cortez technical database is being managed by the acQuire® system implemented in 2004 replacing an earlier database system. Exploration data from a variety of sources are imported into acQuire® using a variety of techniques and procedures to check the integrity of the data entered. Data that were collected prior to the introduction of digital logging have been subject to validation, using built-in program triggers that automatically checked data upon upload to the database. Since the mid-1990s, geological data have been validated by software routines and uploaded directly into the database. Analytical data are uploaded from digital sources. Survey data is uploaded by the project geologist from digital survey files. Verification is performed on all digitally collected data upon upload to the main database, and includes checks on surveys, collar co-ordinates, lithology data, and assay data. Since 2009, Cortez Hills and Pipeline Complex blast-hole data and Cortez Hills underground Cubex drilling data are also imported into acQuire®.

The acQuire® database is sourced for the information needed to complete Mineral Resource and Reserve estimates; commercial software packages are used for these estimates.

Database security and integrity is accomplished by restricting access and user level permissions that are set by the Database Manager. Once data entry and validation are completed for a drill hole, access is locked. There are procedures for updates that retain all the original information and prioritize use of the updates.

REVIEW OF ASSAY BIASES

In 2003, an in-house study was carried out to determine the causes of historical biases between resource estimates based on exploration drilling, mine production based on blast-hole models, and mill production. Results indicated that:

 

   

Blasthole assays performed by atomic absorption were biased low.

 

   

Blasthole and exploration hole fire assays performed by the mine laboratories were biased low relative to fire assays by commercial laboratories.

 

 

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There are sampling losses in exploration holes which result in an occasional low bias, even though core recovery is very high.

 

   

There are smoothing effects in resource estimation procedures that result in lower average grades in RC holes.

 

   

Small scale higher grade zones may exist between holes and are missed by drilling.

The relative low bias of fire assays by mine laboratories relative to commercial laboratories was readily apparent from the large number of check assays performed since 1997. Adjustment factors were developed by Cortez during 2004 for the apparent low bias of exploration fire assays relative to fire assays of adjacent blastholes. These “sampling bias” adjustments account for an as-yet-not-understood loss of gold in assays of exploration core. Core drilling methods were highly professional and core recovery was generally high (greater than 90%); therefore sampling losses in the core drilling were surprising. However, a 10% loss of gold might occur in a 5% or less loss of core if the most altered and mineralized material is preferentially susceptible to loss. Assays for the Pipeline, South Pipeline, Crossroads, and Gap deposits were then modified using a series of regression formulae dependent on the sample type (blasthole or core), geological domain (Pipeline shear or non-shear), and source laboratory. Assays for Cortez NW Deep, Pediment, and Cortez Hills were not adjusted.

Mahoney et al. (2009) report that, after further review of assay bias in 2006, Cortez noted that the majority of the areas with problematic assay data had been mined out. Remaining data were evaluated on a hole by hole basis and where a down-hole contamination or bias issue occurred it was noted. The drill hole in question was flagged and was not used to support Mineral Resource or Mineral Reserve estimates. No bias adjustment factors for assay data have been used since 2007.

CORE VERSUS RC DRILL COMPARISON, CORTEZ HILLS

An in-house study, triggered by down-hole contamination noted in at least three RC drill holes, was undertaken in July 2004 to compare results from RC and core holes used in the Cortez Hills resource estimate. Core versus RC twin data were reviewed and resources were estimated separately based on only RC data and on only core data for comparison. Preliminary results suggested that core holes on average were of higher grade than RC holes, depending on the grade range. The core averages were

 

 

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considered to be biased high because core holes were more common in the high-grade centre of the deposit. Individual RC/core twin holes compared reasonably well, showing less of a high bias in the core holes. Additional core drilling at Cortez Hills since 2004 has replaced the contaminated RC holes.

BLASTHOLE SAMPLING REVIEW

Cortez reviewed the use of a pie sampler versus the cylinder sampler and found no significant difference in assays between the methods for 1,900 blastholes. The cylinder sampler has been retained.

EXTERNAL REVIEWS

Sampling reviews were undertaken in 1992 and 1999 by Francis Pitard, checking elements of the sample preparation procedures. Modifications were made to RC sample collection for the Pediment deposit drilling.

AMEC reviewed the Cortez Hills and Pediment drill database in 2004 and 2005, checking lithological and analytical data and database integrity. Data were found to be suitable to support Mineral Resource estimation.

INTERNAL REVIEWS

The Pipeline, Crossroads, Gap, and Gold Acres databases were audited by internal Placer Dome corporate audit teams in 1996, 1998, 2001, and 2002. These reviews indicated a low error rate.

RPA DATABASE REVIEW

RPA undertook reviews of the database as part of an audit review report in July 2010 and again in the preparation of this Technical Report.

JULY 2010 REVIEW

RPA received drill hole and block model databases in Vulcan/ISIS formats. Files were reformatted to ASCII and imported into Gemcom GEMS 6.2.2 software for review. GEMS is employed to validate the drill hole database using software routines that trap errors and potential problems such as:

 

 

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Intervals exceeding the hole length (from-to problem).

 

   

Negative length intervals (from-to problem).

 

   

Zero length intervals (from-to problem).

 

   

Inconsistent down hole survey records or lack of zero depth entry at collar needed by GEMS.

 

   

Out-of-sequence and overlapping intervals (from-to problem; additional sampling/check sampling included in table).

 

   

No interval defined within analyzed sequences (not sampled or missing samples/results).

GEMS validation routines found some down-hole survey records lacking collar zeros (fourth bullet above) and several cases of zero intervals, most at the end of lithology files/tables. None of these minor errors impact on resource estimation. Otherwise the drill hole databases were clean and readily imported.

JANUARY 2012 REVIEW

Drill hole and block model databases for each of the resources reported by Cortez for mid-2011 were received from Barrick in Vulcan/ISIS formats. The validation review focused on the databases supporting the June 30, 2011 Mineral Resource and Reserve estimates for the following models that presently represent more than 76% of the Mineral Reserve gold ounces reported as at June 30, 2011 and more than 59% of the gold ounces reported for Mineral Resources that are additional to the Mineral Reserves.

 

   

Cortez Hills complex open pit model that includes part the Breccia zone and the Pediment deposit

 

   

Cortez Hills complex underground model that includes the Breccia and Middle zones

 

   

Lower zone model of the Cortez Hills Complex

The above checks were made specifically because the databases for the Cortez Hills complexes have been changing over the past two years with the addition of a significant amount of new drilling. The Pipeline complex and Gold Acres databases have not changed since the RPA audit review reported in July 2010 and summarized above.

 

 

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The resource databases for the above listed models were imported into Vulcan 3D Version 8.0.3 software for review. Vulcan database validity routines found no errors with out of range values, or from-to intervals, and that sample lengths and assays values are within reasonable limits. Drill hole collars were found to be within the area limits of the model, with the following exceptions.

 

   

Hole T1-1 from 1964 is outside the Cortez Hills area but poses no problems as it has no valid assays and hence not used for the resource estimate.

 

   

Red Hill database contains two pairs of RC holes, one pair from 1976 and one pair from 1987, located outside the model limits; all four holes were flagged so as not to be used for resource estimation.

 

   

There were no twinned holes located in the checked databases.

 

   

Wedged holes are present in the Cortez Hills database and the duplicate portions of the wedged holes were set to a null value so that they are not double counted during grade estimation.

All the data appears to be consistently presented and organized; all units within the database are consistent. Prior to resource estimation the Cortez or Barrick resource geologist reviews each new drill hole in the database and any holes and assays identified to have problems are flagged as rejected so that they will not be used. RPA approves of this practice.

RPA notes that some sampled intervals in the database have been split into two or more smaller “from-to” intervals that carry the duplicate sample numbers and the same assay results: this has been noted even in holes drilled as recently as 2010. This is a function of subdivision of original sample intervals made by Cortez personnel to reflect observed geological contacts. RPA recommends, as a statistically preferable practice, that the actual sampled intervals should themselves be set to reflect the logged geological breaks and contacts so as to reduce and eliminate the need for a later subdivision and repetition of assay values.

RPA also undertook a spot check comparison of the supplied resource databases against original documents for collar surveys, down-hole surveys and laboratory assay certificates. The 35 holes checked for collar surveys were all found to be correctly entered. Two of the 16 holes reviewed for down hole surveys, specifically holes HC04-07 and HC04-13, were to have a variance of 0.27 degrees from the original azimuth for

 

 

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every one of the measurements. Given that the variance is less than one degree it is not deemed to be material and is presumed to be a deliberate adjustment. An additional down hole survey entry was found in hole NWD10-08 at a depth of 75 ft for which there was no corresponding original data point. Consultation with the Database Administrator confirms that absence of support for this entry and it was immediately removed from the database.

The azimuth and inclination measurements for the remainder of the database entries were found to correspond with the original down hole survey measurements.

The gold fire assay (“fa1”) and cyanide leach assay (“aa1”) values for 16 holes were checked against the original laboratory assay certificates. The fire assay values corresponded to the original certificates for all 16 holes. In drill hole DC-189, three of 289 cyanide leach values did not correspond with any of the laboratory certificates provided for checks; and in hole NWD10-08, 39 of 123 cyanide leach values did not correspond with the laboratory certificates. Cyanide leach values in the database for the remaining 14 holes corresponded to the laboratory certificates. RPA notes that the resource estimates are made from assay data columns (“fa1res” and “aa1res”) in the database that have received certain checks and validations prior to use for grade interpolations. For example the cyanide leach values for holes DC-189 and NWD10-08 which there is no corresponding assay certificate were reset to a below detection limit value and hence do not impact the grade interpolations or determination of leach and mill material versus refractory material.

If not already in place, then RPA recommends as a housekeeping item that there should be explanatory notes attached to the database where any adjustments, corrections or additions are made to the database that do not correspond to the original or source data documents. As another housekeeping issue, RPA notes that the assay and analytical data in the database can at times be derived from more than one source or laboratory certificate. In the database there is however only one sample identification field or column (“sampid”) and that spot check of the database was made more difficult because only one of the data sources is reflected in the “sampid” field. RPA recommends including multiple columns to record and track the multiple sources of data used to construct the database; this should make database validation simpler and more efficient.

 

 

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It is RPA’s opinion that the Cortez database is well prepared, adequate and suitable for mineral resource estimation.

 

 

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13 MINERAL PROCESSING AND METALLURGICAL TESTING

During the nearly 40 year history of the Cortez Mine, a significant number of metallurgical studies including laboratory scale and/or pilot plant test work have been completed and historical operating data is available. The Cortez Mine has utilized numerous processes including carbon-in-leach (CIL) for higher grade oxide ore, heap leaching for lower grade oxide ore, roasting for carbonaceous refractory ore and pressure oxidation for higher grade sulphidic ore. Mill No. 1, which included CIL and a roaster, was placed on care and maintenance at the end of October 1999. The roaster has been inactive since 1995 and is currently being demolished.

Metallurgical testing of new ore types has confirmed the choices for processing unit operations and provided data to estimate capital and operating costs and gold recovery for the various ore types. Test data also been generated to determine the expected performance in Mill No. 2 as new resources have been identified and included in the life-of-mine plans.

GOLD RECOVERY

The recovery of gold is a function of the processing method (CIL, heap leaching, roasting, and pressure oxidation) and the lithology of the mineralization being processed. The recoveries used to support Mineral Resource and Mineral Reserve estimations are based on recovery equations that are derived from feasibility studies, metallurgical laboratory test work and historic production data, as summarized in Tables 13-1 to 13-3. These figures are incorporated in the Lerchs–Grossman pit shells that constrain the Mineral Resources and Mineral Reserves to be extracted by open pit mining methods.

Test work reports and plant operating results were reviewed to verify the reported recoveries used in the Mineral Resources and Mineral Reserves estimates.

For leach ore, the estimated recovery figure for Pipeline oxide is based on actual heap performance values.

 

 

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TABLE 13-1 MILL GOLD RECOVERY EQUATIONS

Barrick Gold Corporation – Cortez Operations

 

Ore Type

  

Recovery Equations

Cortez Hills HG £ 0.15 oz/st

   % Recovery = (18 x HG) + 86.4 – 2.4

Cortez Hills HG > 0.15 oz/st

   % Recovery = {[(100 x HG) – 1.3 x Ln(HG)) – 4.1]/HG} – 2.4

Cortez Hills Middle Zone

   % Recovery = 113.81 (AA/FA)3 – 289.17 (AA/FA)2 + 264.08 (AA/FA) + 1.77

Pipeline (Stage 3)

   % Recovery = 94.2 – (0.29/HG) – 2

Pipeline/South Pipeline (Stages 8, 9, 10)

   % Recovery = (85.11 x exp(0.36xHG) – 3.6 (Cap Recovery at 88.1%)

Crossroads

   % Recovery = 88%

Silica

   % Recovery = 3.85 x Ln(HG) + 94.16

GAP

   Use Pipeline/South Pipeline Equation

 

Notes:    

  

HG = gold head grade in oz/st

AA/FA = cyanide soluble gold assay: fire assay gold ratio

Ln = natural log function

Exp = exponent

TABLE 13-2 HEAP LEACH ULTIMATE GOLD RECOVERY EQUATIONS

Barrick Gold Corporation – Cortez Operations

 

Ore Type

  

Recovery Equations

Cortez Hills    % Recovery = 65%
Pediment    % Recovery = 68%
Pipeline (Stage 3)    %Recovery = 68%
Pipeline/South Pipeline    % Recovery = 62%
Pipeline Phase 9    % Recovery = (0.0358 x Ln(HG) + 0.8122) x 100
Pipeline Phase 10    % Recovery = (0.0248 x Ln(HG) + 0.7742) x 100
Crossroads    % Recovery = (0.030 x Ln(HG) + 0.7739) x 100
Silica    % Recovery = 60%
GAP – gossan    % Recovery = 50%
GAP – marble    % Recovery = 56%
Gold Acres    % Recovery = 68%

 

Notes:

  

HG = gold head grade in oz/st

Ln = natural log function

 

 

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TABLE 13-3 REFRACTORY ORE GOLD RECOVERY EQUATIONS

Barrick Gold Corporation – Cortez Operations

 

Process

   AA/FA    %CO3  

Head Grade (HG)

oz/st

  

Gold Recovery Equations

Roaster

   £0.50    >8%   > 1.15    % Recovery = 93.0 - 0.6
        0.35 < HG £ 1.15    % Recovery = 3.1719Ln(HG) + 92.592 - 0.6
        0.125 < HG £ 0.35   

% Recovery = -95.006(HG)2 + 67.038(HG)

+ 77.446 - 0.6

        0.055 < HG £ 0.125   

% Recovery = -1017.2(HG)2 + 377.14(HG)

+ 53.439 - 0.6

       

Arsenic Effect (As > 1,200 ppm):

-0.0000004(As ppm)2 – 0.0005(As ppm) + 1.176

     

 

  

 

 

 

  

 

Roaster

Middle

Zone

   £0.50         89.5 – 0.0029 (As)
     

 

  

 

 

 

  

 

Alkali

Autoclave

+

Cyanide

   £0.50    >10%   > 1.3    % Recovery = 95.0 – 6.86
        0.28 < HG < 1.3    % Recovery = 6.4334(HG)3 – 23.02(HG)2 + 28.56(HG) + 82.247 – 6.86
        0.065 < HG < 0.28    % Recovery = 661.36(HG)3 – 628.01(HG)2 + 208.23(HG) + 65.114 – 6.86
     

 

  

 

 

 

  

 

Alkali

Autoclave

+ CaTS

   £0.50      > 1.3    % Recovery = 95.0 + 1.23 – 8.09 + 2.35 – 1.5
        0.28 < HG < 1.3    % Recovery = 6.4334(HG)3 – 23.02(HG)2 + 28.56(HG) + 82.247 + 1.23 – 8.09 + 2.35 – 1.5
        0.065 < HG < 0.28    % Recovery = 661.36(HG)3 – 628.01(HG)2 + 208.23(HG) + 65.114 + 1.23 – 8.09 + 2.35 – 1.5
     

 

  

 

 

 

  

 

Acid

Autoclave

+

Cyanide

   £0.50    £10%   > 1.3    %Recovery = 95.0 + 1.23
        0.28 < HG < 1.3    % Recovery = 6.4334(HG)3 – 23.02(HG)2 + 28.56(HG) + 82.247 + 1.23
        0.065 < HG < 0.28    % Recovery = 661.36(HG)3 – 628.01(HG)2 + 208.23(HG) + 65.114 – 1.23
     

 

  

 

 

 

  

 

Acid

Autoclave

+ CaTS

   £0.50    £10%   > 1.3    %Recovery = 95.0 + 1.23 + 2.35 – 1.5
        0.28 < HG < 1.3    % Recovery = 6.4334(HG)3 – 23.02(HG)2 + 28.56(HG) + 82.247 + 1.23 + 2.35 – 1.5
        0.065 < HG < 0.28   

% Recovery = 661.36(HG)3 – 628.91(HG)2 + 208.23(HG) + 65.114 + 1.23 + 2.35 – 1.5

     

 

  

 

 

 

  

 

Notes:   

HG = gold head grade in oz/st

Ln = natural log function

CaTS = calcium thiosulphate

CO3 = carbonate

Table 13-4 summarizes the results of the budgeted versus actual data taken from the Cortez Flash Reports which was evaluated to verify the recovery estimates.

 

 

Barrick Gold Corporation – Cortez Joint Venture Operations    Rev. 0 Page 13-3
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TABLE 13-4 REFRACTORY ORE GOLD RECOVERY EQUATIONS

Barrick Gold Corporation – Cortez Operations

 

           2009                 2010           2011 September YTD  
     Actual     Budget     Actual/
Budget
    Actual     Budget     Actual/
Budget
    Actual     Budget     Actual/
Budget
 

Open Pit Mill

                  

Grade Processed

     0.074        0.078        95     0.211        0.185        114     0.295        0.287        103

Recovery Rate

     76.9     84.4     91     88.8     89.1     100     92.7     91.4     101

Tons Per Day

     9,852        8,724        113     9,303        8,791        106     10,063        10,340        97

Open Pit Leach

                  

Grade Processed

     0.014        0.012        122     0.016        0.012        136     0.019        0.013        145

Recovery Rate

     91.7     76.2     120     496.9     110.4     450     82.3     161.4     51

Tons Per Day

     33,057        46,110        72     1,964        12,116        16     17,766        11,915        149

Open Pit Refractory

                  

Grade Processed

           0.340        0.300        113     0.399        0.395        101

Recovery Rate

           86.9     88.2     99     87.1     89.3     98

Tons Per Day

           910        939        97     841        737        114

Open Pit Other

                  

Grade Processed

     0.188        0.154        123            

Recovery Rate

     85.7     85.0     101            

Tons Per Day

     482        616        78            

Open Pit Total

                  

Grade Processed

     0.030        0.024        125     0.189        0.094        201     0.127        0.149        86

Recovery Rate

     83.0     81.0     102     94.3     90.5     104     91.2     94.3     97

Tons Per Day

     43,391        55,451        78     12,177        25,292        48     28,671        22,992        125

Underground Mill

                  

Grade Processed

     0.635        0.684        93     0.930        0.909        102     0.761        0.876        87

Recovery Rate

     90.0     92.1     98     90.6     90.0     101     89.1     90.0     99

Tons Per Day

     405        627        65     1,096        1,209        91     1,052        1,160        91

Underground Refractory

                  

Grade Processed

           0.757        1.100        69     0.666        0.891        75

Recovery Rate

           91.2     95.0     96     91.4     90.3     101

Tons Per Day

           43        157        28     217        354        61

Underground Other

                  

Grade Processed

     0.722        0.381        190            

Recovery Rate

     89.0     89.1     100            

Tons Per Day

     173        41        421            

Underground Total

                  

Grade Processed

     0.661        0.665        99     0.924        0.931        99     0.745        0.879        85

Recovery Rate

     89.7     92.0     98     90.6     90.7     100     89.4     90.1     99

Tons Per Day

     577        668        86     86.4     91.5     94     1,366        1,067        128

 

 

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The estimated and actual gold recoveries correlate well for the mill and the refractory ore processing, however, they are significantly different for heap leach recoveries in 2010 and 2011. RPA notes that the budgeted leach recovery is calculated based on the ounces that are forecast to be recovered in a given period and the number of ounces placed on the pad during the same time period. This methodology does not take into account the leaching kinetics and time required to recover gold from a heap leaching operation. Therefore, the historic heap leach production data was analyzed as an additional check of the recovery calculations used by Cortez.

Table 13-5 compares the contained, estimated recoverable, and actual recovered gold ounces for the life of the Cortez heap leach pads (i.e. Areas 28, 30, and 34). Figure 13-1 provides the same data graphically.

TABLE 13-5 HEAP LEACH PRODUCTION

Barrick Gold Corporation – Cortez Operations

 

     Contained      Estimated
Recoverable
    Actual
Produced
 

1997

     55,283         37,593        28,233   

1998

     227,543         154,729        123,954   

1999

     327,236         222,521        210,900   

2000

     569,580         387,314        282,865   

2001

     1,080,428         734,691        525,535   

2002

     1,434,327         965,890        805,058   

2003

     1,977,765         1,295,223        1,132,603   

2004

     2,772,711         1,780,253        1,626,014   

2005

     3,205,513         2,050,826        2,003,862   

2006

     3,509,395         2,239,609        2,206,856   

2007

     4,020,000         2,540,263        2,490,603   

2008

     4,477,028         2,767,618        2,706,451   

2009

     4,651,153         2,867,336        2,866,109   

2010

     4,725,476         2,920,335        2,924,864   

2011

     4,763,047         2,948,137        3,009,332   

Recovery

        61.9     63.2

 

 

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FIGURE 13-1 HISTORICAL HEAP LEACH DATA

 

LOGO

The data clearly shows that the estimated gold production from the heap leach pads and the actual gold production correlate well. In evaluating the individual leach pads, it appears that the estimated gold production and actual gold production from the A30 leach pad is very close but the estimates for the A28 and A34 pads are not as good. Based on this observation, RPA recommends that Cortez should continue to monitor the actual heap leach recovery results and modify the equations used to estimate the gold recovery as needed.

SUMMARY AND CONCLUSIONS

Based on these analyses RPA is of the opinion that metallurgical test work completed for the Project has been appropriate to establish optimal processing routes for the different mineralization styles encountered in the deposits and that the gold recovery calculations for all of the processing options are currently appropriate to estimate the amount of gold that will be recovered over the LOM, however, more accurate short term estimates can be made if the leaching kinetics are included in the budget estimation process.

 

 

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14 MINERAL RESOURCE ESTIMATE

SUMMARY

A summary of the Mineral Resources, excluding Mineral Reserves, for Cortez as of December 31, 2011, is shown in Table 14-1. The Mineral Resources are presented by the most likely mine extraction method and gold recovery process. Cut-off grades for the Mineral Resources were established using a gold price of $1,400 per ounce.

TABLE 14-1 MINERAL RESOURCE SUMMARY - DECEMBER 31, 2011

Barrick Gold Corporation – Cortez Operations

 

Mine & Process Type

   Total Measured + Indicated      Total Inferred  
   Tons      Grade      Contained
Gold
     Tons      Grade      Contained
Gold
 
   (000 t)      (oz/st Au)      (000 oz)      (000 t)      (oz/st Au)      (000 oz)  

Open Pit

                 

Mill

     5,128         0.058         296         1,740         0.058         101   

Heap Leach

     37,272         0.011         417         15,107         0.011         166   

Refractory

     5,516         0.107         589         1,836         0.148         271   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Sub-Total Open Pit

     47,916         0.027         1,302         18,684         0.029         537   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Underground

                 

Mill

     1,719         0.382         656         1,680         0.327         549   

Refractory

     4,757         0.378         1,800         1,517         0.349         529   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Sub-Total Underground

     6,476         0.379         2,456         3,197         0.337         1,078   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Totals

     54,391         0.069         3,757         21,881         0.074         1,615   
  

 

 

    

 

 

    

 

 

    

 

 

    

 

 

    

 

 

 

Notes:

 

  1. CIM definitions were followed for Mineral Resources.
  2. Mineral Resources are estimated at the cut-off grades given in Table 14-20.
  3. Mineral Resources are estimated using an average gold price of US$1,400 per ounce,
  4. A minimum mining width of 10 ft was used.
  5. Mineral Resources are additional to and exclusive of Mineral Reserves.
  6. Numbers may not add due to rounding.

Mineral resources decreased with the conversion of some Mineral Resources to Mineral Reserves with the most significant change affecting the Crossroads deposit at the Pipeline Complex. There are also some minor changes resulting from depletion by mining of some Inferred Resource blocks in the Cortez Hills open pit and from model adjustments at Cortez Hills, both open pit and underground.

 

 

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The Cortez site-based Technical Services Group is responsible for Mineral Resource estimation for projects managed by the Cortez Operations Group.

Cortez is currently reporting Mineral Resource estimates for four principal areas in the district. These include the Pipeline Complex and Gold Acres deposit on the west side of Crescent Valley and the Cortez Hills Complex, Cortez Pits area on the east side of the valley. Each of the mentioned complexes includes several gold deposits or zones. Table 14-2 identifies the principal areas, their included deposits or zones, when the resources were most recently updated and which group is responsible for the reported Mineral Resource estimate.

TABLE 14-2 CORTEZ MINERAL RESOURCE MODELS

Barrick Gold Corporation – Cortez Operations

 

Area

  

Deposits or Zones

included

   Last Update   

Responsible Group

Pipeline Complex

   Pipeline Gap Crossroads    EOY 2010    Mine Technical Group

Gold Acres

      2008    Mine Technical Group

Cortez Hills Complex

   Open Pit    EOY 2010    Mine Technical Group
   Pediment    EOY 2010    Mine Technical Group
   Breccia    Mid-2011    Mine Technical Group
   Middle    EOY 2010    Mine Technical Group
   Lower    Mid-2011    Tucson Technical Group

Cortez Pits

   NW Deeps    Mid-2011    Mine Technical Group

At the deposit scale, the Cortez geologists recognize the interplay of structural preparation, favourable lithologies and various alteration styles on the control of gold grade distribution; however, at the drill hole scale it is often difficult to visually define the limits of mineralization. Consequently, gold grade is the principal indicator of gold distribution at the drill hole scale for most of the deposits at Cortez with the exception of the visually recognizable hydrothermal breccia body at Cortez Hills. All solids and surfaces are snapped to drill holes where applicable to construct these features. Both the Tucson Technical Group and Cortez use Vulcan ® software for all of their mineral resource estimation work.

 

 

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PIPELINE COMPLEX

DATA

For resource estimation, the drill hole data were limited to holes within or immediately adjacent to the various block model boundaries. A total of 3,266 drill holes for 2,908,457 ft and 194,507 assays are in the database.

GRADE CAPPING AND COMPOSITING

Raw gold assays were capped for outliers within the modelled high-grade gold indicator based on examination of cumulative probability plots and histograms. Gold assays at Pipeline were capped at 1.2 oz/st, at Gap at 0.4 oz/st and at Crossroads at 0.7 oz/st. The capped assays were composited using down-hole 20 ft lengths, equivalent to expected minimum mining height for an open pit bench. Compositing honours domain boundaries.

BULK DENSITY

Bulk density values (tons/ft3), as provided by Cortez Exploration, were assigned to the rock unit wireframes on formation and alteration type and the bulk density data is populated into the block model using scripts. Table 14-3 lists the bulk density values used for the deposits in the Pipeline Complex.

TABLE 14-3 BULK DENSITY – PIPELINE COMPLEX

Barrick Gold Corporation – Cortez Mine

 

Formation

   Density  

Dw

     0.07645   

Srm

     0.0746   

OHC

     0.0837   

Abyss

     0.0798   

Marble

     0.0779   

Srm Marble

     0.08554   

Skarn

     0.0789   

Srm Skarn

     0.0910   

Gossan

     0.0737   

Srm Gossan

     0.0655   

shear

     0.0680   

silica

     0.07399   

QAL

     0.06169   

Dump

     0.05714   

 

 

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BLOCK MODEL AND MINERALIZED DOMAINS

Three-dimensional (3D) surfaces or wireframe solids were constructed by Cortez Exploration for topography, alluvium-bedrock contact, rock formations, alteration, and mineralization boundaries. These solids were used in block model creation to provide a numeric value for each associated variable, e.g., formation, alteration, silica.

Three domains were established corresponding to the main deposits (Pipeline, Crossroads and Gap), with each domain conforming to the dominant orientation and continuity of mineralization (Figure 14-1). A three-dimensional 40 ft by 40 ft by 20 ft block model was developed based on the three generalized domains. Resources in the Pipeline and Crossroads domains were estimated using 20 ft composites and 40 ft by 40 ft by 20 ft blocks, but the Gap domain was further estimated using 10 ft composite lengths and 20 ft by 20 ft by 10 ft blocks, and subsequently “regularized” up to the 40 ft by 40 ft by 20 ft blocks. The block model parameters are listed in Table 14-4.

TABLE 14-4 PIPELINE COMPLEX BLOCK MODEL PARAMETERS

Barrick Gold Corporation – Cortez Operations

 

Easting (ft)      Northing (ft)      Elevation (ft)  

Min

   Max      Min      Max      Min      Max  

97000

     109120         49500         61980         2880         5540   

97000

     101240         53500         59420         4180         5540   
Block Size (ft)      Number of Blocks  

Easting

   Northing      Elev.      Easting      Northing      Elev.  

40

     40         20         303         312         133   

20

     20         10         212         296         136   

 

 

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LOGO

FIGURE 14-1 RESOURCE ESTIMATION DOMAINS PIPELINE COMPLEX

(Figure 3-3 from 2010 Cortez Audit report – Eric to insert and clean up – will need to label domains)

 

14-5


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INDICATOR BLOCK MODEL

Three indicators were estimated to provide a probability “flag” for gold values. The low-grade indicator was assigned for Au greater than or equal to 0.002 oz/st, the mid-grade indicator for Au greater than or equal to 0.015 oz/st, and the high-grade indicator was assigned for Au greater than or equal to 0.15 oz/st at Pipeline and Crossroads and Au greater than or equal to 0.05 oz/st at Gap. Each deposit/domain utilized the estimated gold indicators somewhat differently for gold estimation.

Table 14-5 shows the general orientations of the search ellipses for each domain.

TABLE 14-5 SEARCH ELLIPSE ORIENTATIONS BY DOMAIN – PIPELINE

COMPLEX

Barrick Gold Corporation – Cortez Operations

 

Domain

   Azimuth     Plunge     Dip  

Gap

     315 °      0 °      5 ° 

Pipeline

     330 °      0 °      -15 ° 

Crossroads

     300 °      0 °      15 ° 

A fourth orientation, at 340° azimuth and -8° northeast dip, was used at Crossroads to represent the “IB” unit of the host Devonian Wenban Formation. A silica solid was used to constrain this orientation for estimation.

Inverse Distance (ID) estimation of the indicators used search radii of 400 ft by 400 ft by 60 ft (easting, northing, elevation), but constraint was applied by the requirement of a minimum of five samples and the number of samples per hole limited to two. In addition, composites from a minimum of three drill holes were required for the indicator to be estimated.

The estimated gold indicator values as well as the modelled formation and alteration codes were back-flagged to the drill hole composites to accommodate data selection for grade interpolation. Gold estimation at Pipeline and Gap used two indicators, whereas Crossroads estimation used all three indicators.

GRADE INTERPOLATION

The block model includes 31 estimated model parameters, input data and block flags including inverse distance to the third power (ID3) estimated gold grade, nearest

 

 

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neighbour (NN) estimated gold grade, density, gold indicators, cyanide leach to fire assay (AA/FA) ratios and refractory flags, resource classification, alteration types, grade estimation parameters, distance, number of holes, and various other topographical flags.

Block estimation of gold grade utilized nested ID3 passes with search ellipse strategy based on omnidirectional variography (correlogram) for composites. The search distances are taken as 80% and 90% of the sill, respectively. The correlogram and interpolation search parameters are shown in Figure 14-2 and Table 14-6.

At Crossroads, the mid-grade indicator uses the same distances and sample criteria as the high-grade indicator above, and is estimated after the high-grade and before the low-grade indicators.

FIGURE 14-2 OMNIDIRECTIONAL CORRELOGRAM – PIPELINE COMPLEX

 

LOGO

 

 

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TABLE 14-6 INTERPOLATION SEARCH ELLIPSE PARAMETERS – PIPELINE COMPLEX

Barrick Gold Corporation – Cortez Operations

 

 

Estimation Pass

   Distance (ft)      Min. #
Sample
     Max. #
Sample
     Max. per
Hole
 
   Major
Axis
     Semi-
Major
Axis
     Minor
Axis
          

au_box

     20         20         10         1         99         1   
     180         180         20         2         3         1   

Inside HG indicator

     70         70         20         1         3         1   
     240         240         40         1         7         2   
     180         180