Update - Custom Probiotics

Amulsar Project Geochemical Characterization and Prediction Report -Update

Prepared for

Lydian International

Dated 31 August 2014

Prepared by Global Resource Engineering, Ltd

Amulsar Project Geochemical Characterization and Prediction Report --Update Lydian International

Page i

Table of Contents 1.0

INTRODUCTION .................................................................................................................................. 1

2.0

BACKGROUND AND REPORT OBJECTIVES .......................................................................................... 1

3.0

GEOLOGY ............................................................................................................................................ 2

4.0

SUMMARY OF GEOCHEMICAL CHARACTERIZATION PROGRAM ........................................................ 4

5.0

ACID BASE ACCOUNTING AND NET ACID GENERATION ..................................................................... 7

5.1

Tigranes/Artavasdes/Arshak Barren Rock ................................................................................ 7

5.2

Erato Barren Rock ................................................................................................................... 11

5.3

ABA Statistical Analysis ........................................................................................................... 15

5.4

Spent Ore ................................................................................................................................ 16

5.5

Borrow Materials .................................................................................................................... 17

5.6

ABA Interpretation and Sample Classification ........................................................................ 18

5.6.1

Barren Rock ............................................................................................................................. 18

5.6.2

Spent Ore ................................................................................................................................ 21

5.6.3


6.0

SOLID PHASE COMPOSITION ............................................................................................................ 23

6.1

Elemental Chemistry ............................................................................................................... 23

6.1.1

Barren Rock ............................................................................................................................. 24

6.1.2


6.2 7.0

Mineralogy .............................................................................................................................. 26 SHORT-TERM LEACH TESTING .......................................................................................................... 27

7.1

Barren Rock ............................................................................................................................. 28

7.2

Spent Ore ................................................................................................................................ 29

7.3


8.0

KINETIC TESTING ............................................................................................................................... 33

8.1

ARD Geochemical Reaction Kinetics ....................................................................................... 33

8.2

Humidity Cell Results: Reaction Products .............................................................................. 34

8.2.1

Oxidized LV Samples ............................................................................................................... 38

8.2.2

Sample ARD-74C ..................................................................................................................... 39

8.2.3

LV Samples Resistant to Ferric Iron Oxidation ........................................................................ 39

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8.3

Humidity Cell Results: Metals Leaching ................................................................................. 39

8.4

Observed Geochemical Kinetics At Amulsar ........................................................................... 41

9.0

CONCLUSIONS OF CHARACTERIZATION TESTING............................................................................. 45

9.1

Barren Rock ............................................................................................................................. 45

9.1.1

UV Barren Rock ....................................................................................................................... 45

9.1.2

LV Barren Rock ........................................................................................................................ 45

9.1.3

Spatial Variation in Barren Rock Geochemical Properties. ..................................................... 45

9.2

Spent Heap Leach Material ..................................................................................................... 46

9.3


9.4

The Role of Alunite .................................................................................................................. 46

10.0

ARD MANAGEMENT AND MITIGATION PLAN: OPERATIONS PHASE ..................................... 46

10.1

ARD Management Plan During Operations ............................................................................ 47

10.1.1

BRSF ARD Management Plan .................................................................................................. 48

10.1.2

ARD Management Downstream from Site 27 ........................................................................ 48

10.2 10.2.1

BRSF ARD Mitigation ............................................................................................................... 49 BRSF Seepage .......................................................................................................................... 49

10.2.1.1

Encapsulation .................................................................................................................. 49

10.2.1.2

Evapotranspiration Cover ............................................................................................... 50

10.2.1.3

Seeps and Springs ........................................................................................................... 51

10.2.1.4

BRSF Seepage Volume..................................................................................................... 51

10.2.1.5

BRSF Seepage Water Quality .......................................................................................... 52

10.2.2

BRSF Runoff ............................................................................................................................. 54

10.2.2.1

BRSF Development .......................................................................................................... 54

10.2.2.2

BRSF Runoff Volume ....................................................................................................... 55

10.2.2.3

BRSF Runoff Quality ........................................................................................................ 56

10.3

Pit ARD Management Plan ...................................................................................................... 56

10.4

Pit Dewatering ARD Mitigation ............................................................................................... 58

10.4.1

Pit Dewatering Prediction ....................................................................................................... 58

10.4.2

Pit Dewatering Quantity ......................................................................................................... 59

10.4.3

Pit Dewatering Quality ............................................................................................................ 61

10.5

Pit Backfill ARD Management and Mitigation......................................................................... 62

10.6

Summary of ARD Mitigation and Management Measures: Operations Phase...................... 62


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11.0

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ARD MANAGEMENT AND MITIGATION PLAN, CLOSURE PHASE ............................................ 64

11.1

Runoff from Reclaimed Surfaces............................................................................................. 64

11.2

BRSF Seepage Post-Closure..................................................................................................... 65

11.3

Tigranes/Artavasdes Backfill Seepage .................................................................................... 66

11.4

Erato Seepage ......................................................................................................................... 68

11.5

HLF Seepage ............................................................................................................................ 71

12.0

CONCLUSIONS ......................................................................................................................... 74

13.0

WORKS CITED .......................................................................................................................... 75

List of Tables Table 4-1 - Sample Numbers and Characterization Tests ............................................................................. 6 Table 5-1 - ABA Summary - Tigranes/Artavasdes Barren Rock ..................................................................... 8 Table 5-2 - ABA Summary - Erato Barren Rock ........................................................................................... 12 Table 5-3 - ABA Results - Tigranes/Artavasdes Spent Ore (includes one Erato sample) ............................ 16 Table 5-4 - ABA Results - Erato Spent Ore .................................................................................................. 16 Table 5-5 - ABA Results - Borrow Materials ................................................................................................ 17 Table 5-6 - Screening Guidelines for Acid Generation Potential Prediction ............................................... 18 Table 5-7 - NNP and NPR Summary for Tigranes/Artavasdes and Erato Barren Rock................................ 19 Table 7-1 - SPLP Summary - Tigranes/Artavasdes and Erato Barren Rock ................................................. 28 Table 7-2 - NAG Effluent Summary - Tigranes/Artavasdes and Erato Barren Rock .................................... 29 Table 7-3 - SPLP Results - Tigranes/Artavasdes and Erato Spent Ore ........................................................ 30 Table 7-4 - SPLP Results - Amulsar Borrow Materials ................................................................................. 32 Table 8-1 - Site 13 and 27 Mine Waste ABA Compared with Amulsar Pits ................................................ 42 Table 8-2 - Site 13 and 27 Mine Waste Leachate, May 2014 ..................................................................... 43 Table 10-1 - Average BRSF Toe Discharge Water Quality Upon Closure (at Site 27 Pond) ........................ 53 Table 10-2 - Runoff Areas for the Site 27 BRSF ........................................................................................... 55 Table 10-3 - Runoff Areas of Amulsar Pits .................................................................................................. 58 Table 10-4 - Pit Dewatering Water Quality Prediction: Year 9 (Worst Case)............................................. 61 Table 10-5 - Detention Pond Water Quality During Operations (Worst Conditions in Mine Life) ............. 62 Table 11-1 - Average BRSF Toe Discharge Water Quality Upon Closure (at Site 27 Pond) ........................ 65 Table 11-2 - Average Tigranes/Artavasdes Pit Backfill Seepage Water Quality Upon Closure................... 68 Table 11-3 - Estimated Erato Pit Seepage Water Quality (Average Scenario) ............................................ 70 Table 11-4 - Estimated Erato Seepage Metal Concentrations over Time (Average Scenario) ................... 71 Table 11-5 - HLF Drain-Down Water Quality After Detoxification .............................................................. 73 Table 4-1 - Sample Numbers and Characterization Tests ............................................................................. 6 Table 5-1 - ABA Summary - Tigranes/Artavasdes Barren Rock ..................................................................... 8 Table 5-2 - ABA Summary - Erato Barren Rock ........................................................................................... 12 Global Resource Engineering C:\Users\Larry\Documents\Lydian Int\Reports\Geochem Char. and Prediction Update\Geochemistry Report_8-30-14.docx

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Table 5-3 - ABA Results - Tigranes/Artavasdes Spent Ore (includes one Erato sample) ............................ 16 Table 5-4 - ABA Results - Erato Spent Ore .................................................................................................. 16 Table 5-5 - ABA Results - Borrow Materials ................................................................................................ 17 Table 5-6 - Screening Guidelines for Acid Generation Potential Prediction ............................................... 18 Table 5-7 - NNP and NPR Summary for Tigranes/Artavasdes and Erato Barren Rock................................ 19 Table 7-1 - SPLP Summary - Tigranes/Artavasdes and Erato Barren Rock ................................................. 28 Table 7-2 - NAG Effluent Summary - Tigranes/Artavasdes and Erato Barren Rock .................................... 29 Table 7-3 - SPLP Results - Tigranes/Artavasdes and Erato Spent Ore ........................................................ 30 Table 7-4 - SPLP Results - Amulsar Borrow Materials ................................................................................. 32 Table 8-1 - Site 13 and 27 Mine Waste ABA Compared with Amulsar Pits ................................................ 42 Table 8-2 - Site 13 and 27 Mine Waste Leachate, May 2014 ..................................................................... 43 Table 10-1 - Average BRSF Toe Discharge Water Quality Upon Closure (at Site 27 Pond) ........................ 53 Table 10-2 - Runoff Areas for the Site 27 BRSF ........................................................................................... 55 Table 10-3 - Runoff Areas of Amulsar Pits .................................................................................................. 58 Table 10-4 - Pit Dewatering Water Quality Prediction: Year 9 (Worst Case)............................................. 61 Table 10-5 - Detention Pond Water Quality During Operations (Worst Conditions in Mine Life) ............. 62 Table 11-1 - Average BRSF Toe Discharge Water Quality Upon Closure (at Site 27 Pond) ........................ 65 Table 11-2 - Average Tigranes/Artavasdes Pit Backfill Seepage Water Quality Upon Closure................... 68 Table 11-3 - Estimated Erato Pit Seepage Water Quality (Average Scenario) ............................................ 70 Table 11-4 - Estimated Erato Seepage Metal Concentrations over Time (Average Scenario) ................... 71 Table 11-5 - HLF Drain-Down Water Quality After Detoxification .............................................................. 73 List of Figures Figure 3-1 - Regional Context of the Amulsar Deposit (White and Walters, 2010) ...................................... 3 Figure 4-1 - Tigranes/Artavasdes Sample Locations ..................................................................................... 5 Figure 4-2 - Erato Sample Locations ............................................................................................................. 6 Figure 5-1 - Paste pH vs. Sulfide Sulfur for TigArt Barren Rock .................................................................... 9 Figure 5-2 - Total Sulfur vs. Sulfide Sulfur for Tigranes/Artavasdes Barren Rock ....................................... 10 Figure 5-3 - Sulfur Speciation for Tigranes/Artavasdes Barren Rock .......................................................... 11 Figure 5-4 - Paste pH vs. Sulfide Sulfur for Erato Barren Rock.................................................................... 13 Figure 5-5 - Total Sulfur vs. Sulfide Sulfur for Erato Barren Rock ............................................................... 14 Figure 5-6 - Sulfur Speciation for Erato Barren Rock .................................................................................. 15 Figure 5-7 - Paste pH vs. NAG pH for Amulsar Borrow Materials ............................................................... 18 Figure 5-8 - NNP vs. NPR for Tigranes/Artavasdes and Erato Barren Rock ................................................ 20 Figure 5-9 - NPR vs. NAG pH for Erato Barren Rock.................................................................................... 21 Figure 5-10 - NNP vs. NPR – Amulsar Spent Ore ......................................................................................... 22 Figure 5-11 - NNP vs. NPR – Amulsar Borrow Materials ............................................................................. 23 Figure 6-1 - Comparison of Average Tigranes/Artavasdes Barren Rock Trace Metal Abundances to Average Crustal Abundances ...................................................................................................................... 24 Figure 6-2 - Comparison of Average Erato Barren Rock Trace Metal Abundances to Average Crustal Abundances................................................................................................................................................. 25 Global Resource Engineering C:\Users\Larry\Documents\Lydian Int\Reports\Geochem Char. and Prediction Update\Geochemistry Report_8-30-14.docx

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Figure 6-3 - Comparison of Average Amulsar Borrow Material Trace Metal Abundances to Average Crustal Abundances .................................................................................................................................... 26 Figure 8-1 - pH vs. Time in Kinetic Cell Tests .............................................................................................. 35 Figure 8-2 - Cumulative Acidity in Kinetic Cell Tests ................................................................................... 36 Figure 8-3 - Sulfate vs. Time in Kinetic Cell Tests ........................................................................................ 37 Figure 8-4 - Iron vs. Time in Kinetic Cell Tests ............................................................................................ 38 Figure 8-5 - Copper Trends in Tigranes/Artavasdes Barren Rock Humidity Cells ....................................... 39 Figure 8-6 - Selenium Trends in Tigranes/Artavasdes Barren Rock Humidity Cells .................................... 40 Figure 8-7 - Manganese Trends in Tigranes/Artavasdes Barren Rock Humidity Cells ................................ 41 Figure 8-8 - Oxidation Rind in Historic Mine Waste Piles ........................................................................... 44 Figure 10-1 - ARD Management Plan.......................................................................................................... 47 Figure 10-2 - Encapsulation at Site 27 with Waste and Low-Grade Stockpile ............................................ 49 Figure 10-3 - Close-up, Moisture Content Distribution, Year 8 .................................................................. 50 Figure 10-4 - BRSF Leachate During Time ................................................................................................... 52 Figure 10-5 - Oxygen Concentration in Covered Barren Rock .................................................................... 53 Figure 10-6 - Runoff Rates for BRSF Through Mine Life ............................................................................. 56 Figure 10-7 - Pit Conceptual Model: Early Operations ............................................................................... 57 Figure 10-8 - Pit Conceptual Model: Tigranes-Artavasdes Backfill Period.................................................. 57 Figure 10-9 - Dewatering Rates for Amulsar Pits ........................................................................................ 59 Figure 10-10 - Dewatering Rates for the Tigranes, Artavasdes, and Arshak Pits........................................ 60 Figure 10-11 - Dewatering Rates for the Erato Pit ...................................................................................... 60 Figure 11-1 - Closure-Phase ARD Management Plan .................................................................................. 64 Figure 11-2 - Closure-Phase ARD Seepage from Tigranes/Artavasdes Pits ................................................ 67 Figure 11-3 - Closure-Phase ARD Seepage from Erato Pit .......................................................................... 69 Figure 11-4 - Toe Discharge at the Base of the HLF .................................................................................... 72 List of Appendices Appendix A

Complete ABA Results and Figures – Tigranes/Artavasdes and Erato Waste Rock

Appendix A1 Complete ABA Results and Figures – Tigranes/Artavasdes and Erato Waste Rock – Tigranes/Artavasdes Figures Appendix A2 Complete ABA Results and Figures – Tigranes/Artavasdes and Erato Waste Rock – Erato Waste Rock Figures Appendix B Materials

Bulk Chemistry Data (ICP) – Tigranes/Artavasdes and Erato Waste Rock; Site Borrow

Appendix C

Mineralogy Data (XRD and Petrography) – Tigranes/Artavasdes and Erato Waste Rock

Appendix D

Complete Short-Term Leach Results for All Waste Materials

Appendix E

Complete Humidity Cell Test Results and Figures for Tigranes/Artavasdes Waste Rock

Appendix E1

HCT Figures


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Appendix E2

Page vi

pH Comparison Figures and Tables

Appendix F

Testing of Historic Mine Waste Samples

Appendix G

Geochemistry Modelling

Appendix H

BRSF Seepage Model

Appendix I

Pit Dewatering Model


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1.0

Page 1

INTRODUCTION

Lydian International Ltd. (Lydian) is evaluating the feasibility of mining the Amulsar gold deposit (the Project). Global Resource Engineering (GRE) was given the task of continuing an assessment of the longterm geochemical and environmental behavior of various waste types, and assessing the impact of associated site facilities. The initial sampling and analysis was conducted by Golder Associates (Golder, 2013). The work is being carried out to support completion of a Feasibility Study (FS) and an Environmental and Social Impact Assessment (ESIA). It includes baseline geochemical characterization of barren rock for two planned open pits, the Tigranes/Artavasdes/Arshak combined pit (hereafter referred to as the TigArt pit), and the Erato pit. This is being done to assess the potential of the pits to produce acid rock drainage (ARD), and to assess the metal leaching potential of the barren rock. Also included is a baseline characterization of TigArt and Erato spent ore, and of potential mine haul road and access road construction material ("borrow material"). The report also outlines the ARD management plan as well as proposed mitigation measures to minimize the potential water quality impacts from ARD on a local and regional scale. All potential sources of ARD are considered in this report including: pit dewatering water, runoff from the Barren Rock Storage Facility (BRSF), leachate through the BRSF, runoff from the TigArt pit backfill, leachate through the TigArt backfill, seepage into the Erato backfill and various minor sources around the Project. With mitigation measures considered, long-term water quality predictions are developed for all sources of potential ARD on site. During the operations phase, geochemical predictions define the influent water chemistry for the Process Water Conditioning Plant (PWCP) that is the ultimate destination of mine contact water. During closure, the predictions are used as influent concentrations for the design of Passive Treatment Systems (PTS) or as the source concentrations for local and regional water quality impact models.

2.0

BACKGROUND AND REPORT OBJECTIVES

This report builds on, and supersedes all prior studies of geochemistry at the Amulsar project. Many conclusions of the prior study (Golder, 2013), have been revised in this study based on the expanded testing and analysis program performed in 2014. It is accepted that the residual sulfides present in portions of the mineralized areas to be mined have a potential of oxidizing, and the resulting oxidation products would result in an acidic leachate and elevated salt and dissolved metal values. Naturally occurring acid rock drainage exists in and around the mine area, in acidic seeps and springs and from historic exploration disturbances. The objectives of this report are as follows: • •

to present the results of the up-to-date geochemical characterization program; to draw conclusions about the generalized ARD behavior of Amulsar barren rock;


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• • •

Page 2

to apply reasonable and appropriate mitigation measures to minimize ARD; to predict the water quality around the site during the mining closure and post closure periods; and to support the site-wide management of ARD in order to protect local and regional water quality.

The report supplies information critical to the ARD management plan and the closure plan. Those documents include the details of the ARD management and treatment plan, and the short-term and long-term protection program for water in the receiving environment. A primary objective of the ARD management plan is the capture and consumption of mine contact water in a zero-discharge flow circuit. Mine contact water is defined as water in contact with mining activities or areas that has the potential for water quality degradation for all constituents apart from total suspended solids. This includes ARD-impacted water, process water (in the Heap Leach Facility – HLF), and water from the truck shop. It does not include runoff from haul roads, access, roads, and conveyor corridors. This “non-contact water” is managed in the Surface Water Management Plan (SWMP) (GRE, 2014), and is not part of the scope of this report. Another primary objective of the ARD management plan is the passive treatment of mine facility discharge upon closure. The ARD mitigation measures are designed to minimize the speed and intensity of ARD reactions to produce a post-closure discharge within the acceptable range of current passive treatment technology.

3.0

GEOLOGY

The Amulsar ore bodies in central Armenia represent a high-sulfidation gold deposit hosted in a northwest-trending mid- to late-Paleogene calc-alkaline magmatic arc system that extends from southern Georgia (to the northwest) to Turkey and Iran (to the southeast). The near-shore, subductionrelated continental arc system is composed of mixed marine and terrigenous volcanic to volcanosedimentary rocks, and hosts a series of genetically related porphyry Cu-Mo and Au-sulfidation deposits. The location of the Amulsar deposit within the group is shown in Figure 3-1 (map from White and Walters, 2010). In the figure, blue circles indicate Cu-Mo deposits, and yellow circles indicate Au deposits.


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Figure 3-1 - Regional Context of the Amulsar Deposit (White and Walters, 2010)

Locally, upper Paleocene volcaniclastic marine conglomerates are overlain by tuffs exhibiting base metal mineralization. Both units are unconformably overlain by extensive, upper Eocene, basalt-andesite volcano-sedimentary breccias and extrusives. This entire mid-Paleogene assembly was subsequently intruded by a hypabyssal andesite porphyry pluton, with associated bedding-parallel extrusives to the north and west. The Amulsar high-sulfidation deposit is hosted at the base of a silicified lithocap, which reflects strongly acid-leached Eocene-Oligocene andesitic and volcaniclastic protoliths (referred to as the Upper Volcanics lithologic group in this study, abbreviated "UV") whose original textures and mineralogy have been obliterated. These rocks overlie the Paleogene assemblage described above, and were Global Resource Engineering C:\Users\Larry\Documents\Lydian Int\Reports\Geochem Char. and Prediction Update\Geochemistry Report_8-30-14.docx

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subsequently intruded by a sill-shaped feldspar-augite porphyritic andesite (referred to as the Lower Volcanics lithologic group in this study, abbreviated "LV"). Emplacement of the andesite occurred postsilicification, but pre-mineralization. The periodic intrusive/extrusive events and associated tectonism resulted in formation of multi-stage phreatic and hydrothermal breccias throughout the deposit. The majority of breccias appear to be either syngenetic with lithocap formation, or with the subsequent mineralization event. Steeply dipping silica-alunite alteration at Amulsar suggests the deposit is located in the deeper parts of a high sulfidation system. Argillic alteration can be seen in the porphyritic andesite, with kaolinite replacing feldspar phenocrysts, pyrite replacing feldspar phenocrysts, and secondary silica flooding the groundmass. The argillic alteration formed an impermeable barrier to gold-bearing fluids. Supergene oxides blanket the deposit, reflecting sulfide oxidation to hematite and jarosite. Most vuggy quartz is not a result of primary (hydrothermal) silicate leaching, but rather supergene removal of pyrite. Gold mineralization occurs in faults and fractures, and in high-permeability host rock units that extend laterally from the primary fluid conduits.

4.0

SUMMARY OF GEOCHEMICAL CHARACTERIZATION PROGRAM

Geochemical characterization programs are typically phased, beginning with initial static testing. The static tests may be followed by longer-term kinetic testing, depending on the results. The aim of static testing is to establish the geochemical characteristics of the material being tested, specifically with respect to its ARD and metal leaching potential. If the static testing indicates the potential for ARD production and metal leaching, or if the tests are inconclusive, kinetic testing may be conducted to help resolve uncertainty, indicate the rates of potential ARD generation and metal leaching, and support prediction of the water quality of long-term mine discharges. The geochemical characterization program at Amulsar has involved the conduct of both static and kinetic tests. The initial sampling and testing program carried out by Golder was divided into three phases. Phase I static testing consisted of acid base accounting (ABA). Phase II static testing consisted of follow-up bulk chemical, mineralogical, and short-term leach testing on a subset of samples that were selected based on the ABA results. Phase III consisted of kinetic testing. At the time Golder selected samples for geochemical characterization and carried out the testing, the mine plan called for mining the Erato pit and the combined Tigranes/Artavasdes pit. More recent mine planning resulted in the expansion of the combined pit and adding of the Arshak pit area to Tigranes and Artavasdes. After that change in the mine plan, a review was made of the distribution of the original samples to provide that the existing sample set was adequately representative of the barren rock and of the pit walls that would be generated under the new pit layout. In addition to assessing whether all affected pit regions were adequately represented in the sample set, GRE also checked the assignment of samples to rock categories, and reassigned the units as necessary. Based on the review and reassignment, it was concluded that some samples were not representative of the barren rock (either because they were from regions outside of those that would be affected by the Global Resource Engineering C:\Users\Larry\Documents\Lydian Int\Reports\Geochem Char. and Prediction Update\Geochemistry Report_8-30-14.docx

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pits, or because they were actually ore instead of barren rock). Test results associated with these samples were removed from the data set. After the surviving geochemical data set was reviewed, the conclusion was reached that the existing geochemical samples did not adequately represent barren rock associated with the expanded TigArt pit, and also that additional samples were required to represent the Erato pit zone. Therefore, additional samples were selected for analysis. A total of 89 additional samples were taken representing the TigArt pit, and 30 additional Erato pit samples were taken. These samples were subjected to ABA testing and bulk chemical analysis. Figure 4-1 shows the distribution of geochemical samples included in the characterization program in the Tigranes/Artavasdes/Arshak pit. Figure 4-2 provides the same information for the Erato pit. The density and distribution of samples shown in these figures is considered to be representative for the geochemical characterization of the barren rock that will be generated by the project.

Figure 4-1 - Tigranes/Artavasdes Sample Locations


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Figure 4-2 - Erato Sample Locations

Table 4-1 shows the number of tests conducted, including both the surviving Golder samples and the 2014 GRE samples, broken down by material type and test category. GRE's 2014 test work did not involve any samples of spent ore from either pit, or of borrow materials. All of the data from samples used by Golder for these categories has been retained in the database.

Table 4-1 - Sample Numbers and Characterization Tests Material Type

ABA

NAG pH Testing

Bulk Chemistry

Mineralogy

SPLP Effluent Testing

NAG Effluent Testing

Humidity Cell Testing

Barren Rock - Tigranes/ Artavasdes

154

-

97

8

8

8

8

Barren Rock - Erato

80

50

42

12

9

12

-

Spent ore Tigranes/ Artavasdes

6

-

-

-

6

-

-

Spent ore Erato

7

7

7

-

7

7

-

Borrow materials

5

5

5

-

5

5

-


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Test work carried out under Golder's supervision was performed by a number of certified laboratories. Mineralogical testing was conducted by DCM Science Laboratory (DCM) in Denver, Colorado, USA. The Tigranes/Artavasdes spent ore ABA and short-term leach tests were carried out by Wardell Armstrong International (Wardell). Kinetic testing for the Tigranes/Artavasdes waste characterization program was carried out by Chemac Environmental Services of Centennial, Colorado, USA. All other test work was done by SVL Analytical, Inc. (SVL) in Kellogg, Idaho, USA. All testing carried out under GRE supervision was done by SGS in Vancouver, B.C., Canada. This work consisted of ABA analysis, whole rock analysis, and metals by aqua regia digestion with ICP-MS finish.

5.0

ACID BASE ACCOUNTING AND NET ACID GENERATION

ABA tests provide a screening-level evaluation of the bulk acid-generating characteristics of a material. ABA testing was conducted using the Modified Sobek Method (Sobek et al., 1978, with modifications based on Lawrence and Wang, 1996). The ABA testing consisted of the following tests: • • •

Paste pH; Sulfur speciation; Acid Neutralization Potential (NP);

In addition, pH measurements of leachates generated from the net acid generation (NAG) procedure (AMIRA, 2002) was performed. Complete ABA/NAG results for the Tigranes/Artavasdes barren rock and spent ore, the Erato barren rock and spent ore, and the Amulsar borrow materials characterization programs are given in Appendix A, and are summarized in the sections that follow.

5.1 Tigranes/Artavasdes/Arshak Barren Rock

Summary results for TigArt ABA testing are given in Table 5-1. The TigArt data set includes 10 colluvium samples, 83 LV samples, 54 UV samples, and 7 samples designated LV/UV. The LV/UV designation was given to samples for which the proper rock unit assignment was not obvious. For the purpose of generating the statistics of the table, LV/UV samples have been included in the LV group, and results reported as below the detection level were counted as zero. Table 5-1 shows that the barren rocks have little to no acid neutralization potential. This is not unusual for a high sulfidation epithermal deposit, where extensive acid leaching during deposit formation frequently removes any original carbonate or aluminosilicate minerals that might have provided neutralization potential.


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Table 5-1 - ABA Summary - Tigranes/Artavasdes Barren Rock Barren Rock

Statistics

Mean Std. Dev. Mean Upper Volcanics Std. Dev. Mean Colluvium Std. Dev. Lower Volcanics

AP NP Total S Paste pH TCaCO3/kT TCaCO3/kT percent 4.86 40.94 0.26 2.51 1.07 60.00 1.67 2.57 5.54 4.30 0.14 0.76 0.70 21.39 0.85 1.40 5.79 0.87 0.20 1.07 0.84 1.02 0.41 1.27

Sulfide S percent 1.31 1.92 0.14 0.68 0.03 0.03

Sulfate S percent 0.36 0.55 0.11 0.20 0.13 0.11

The LV barren rock samples have insignificant NP, they do possess significant AP. Mean sulfide sulfur concentrations are approximately 1.31 percent in Lower Volcanics. The high sulfide sulfur concentrations of Lower Volcanics porphyry andesite samples reflect pervasive pyritization of feldspar phenocrysts by hydrothermal fluids. The upper volcanics group has trace sulfide sulfur. This residual sulfide remains after the near-complete oxidation of the formation. The sulfide content of colluvium samples is low. Weathering of the sediment has resulted in destruction by oxidation of the majority of the sulfide mineral content that had initially been present. Figure 5-1 is a graph of paste pH vs. sulfide sulfur for 154 barren rock samples from the TigArt pit. The most obvious trend is a strong inverse correlation between paste pH and sulfide sulfur for samples of the Lower Volcanics (LV) group. The Lower Volcanics samples display a wide range of sulfide values, and a correspondence between sulfide levels and acidity is shown. A second observation is that samples of Upper Volcanics (UV) cluster close to the low-sulfide edge of the graph. While these samples show a considerable range in pH, the range is less acidic than that of the Lower Volcanics samples. A single, anomalous sample that was classified as Upper Volcanics has a sulfide sulfur level of approximately 5 percent, with a correspondingly low pH. Most of the UV samples plot to the left of the 0.1 percent sulfide sulfur line.


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Figure 5-1 - Paste pH vs. Sulfide Sulfur for TigArt Barren Rock

Figure 5-2 is a graph of total sulfur vs. sulfide sulfur for TigArt barren rock samples. The graph shows a pronounced bimodal distribution. One group of points consisting almost entirely of LV samples forms a linear trend that diverges only slightly from the diagonal line representing a 1:1 ratio of sulfide sulfur to total sulfur. In these samples, sulfide is the dominant sulfur species. Samples making up the other group have only a modest proportion of their sulfur content present as sulfide. This group contains most of the UV samples and many LV samples. Thus a substantial fraction of the sulfur in those samples is not in a form that would be associated with acid formation.


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Figure 5-2 - Total Sulfur vs. Sulfide Sulfur for Tigranes/Artavasdes Barren Rock

Figure 5-3 is a ternary diagram, which differentiates sulfur into sulfate sulfur, sulfide sulfur, and nonextractable sulfur for the same TigArt barren rock samples considered in the preceding two graphs. A large proportion of the LV samples plot toward the lower right corner of the diagram, showing again that sulfur is dominantly present in the sulfide form in many of the Lower Volcanics samples. However, sulfide sulfur is not the dominant sulfur component for most samples in the other groups (UV, UV/LV, and colluvium), and also for a large number of the LV samples. This is important because the non-sulfide sulfur species do not contribute to formation of ARD. The previous interpretation of the data (Golder, 2013) had included the assumption that alunite (a hydrated aluminum sulfate, which is abundant in some of the the volcanics of the deposit), under some circumstances could be responsible for production of ARD. This issue is considered in more detail in Section 9.4. Non-extractable sulfur is the dominant sulfur species in many of the samples, including most of the UV samples, most colluvium samples, and many LV samples. Sulfate is the dominant species for a smaller number of UV and LV samples. The conclusion to be drawn from the diagram is that acid-generating sulfide sulfur is not the dominant sulfur species in TigArt UV samples, and sulfide is subordinate in many of the LV samples.


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Figure 5-3 - Sulfur Speciation for Tigranes/Artavasdes Barren Rock

5.2 Erato Barren Rock

The geochemical database includes ABA results for samples of barren rock representing the Erato pit. This includes 6 colluvium samples, 29 LV samples, 43 UV samples, and 2 LV/UV samples. Table 5-2 is a summary of Erato pit ABA results broken down by barren rock category. The LV/UV samples have been included in the LV group for the purpose of calculating statistics, and values reported as below a detection limit are counted as zero. The results closely resemble those seen for the TigArt pit. The samples display a similar lack of neutralization potential, again showing that neutralizing minerals that may have existed in the rocks of the deposit area before the mineralizing event have been consumed. Values for acid potential are similar to those seen at the TigArt pit for the individual barren rock categories, with the highest average level shown for the LV samples, and substantially lower levels for the UV and colluvium categories.


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Table 5-2 - ABA Summary - Erato Barren Rock Barren Rock Lower Volcanics

Upper Volcanics

Colluvium

Paste Statistics pH Mean Std. Dev. Mean Std. Dev. Mean Std. Dev.

5.00 1.04 5.30 0.60 5.75 0.19

AP

NP

TCaCO3/kT TCaCO3/kT 27.44 0.38 49.26 0.96 5.48 0.27 24.62 0.85 5.33 1.08 11.19 0.86

NAG pH 4.28 1.12 4.72 0.50 4.92 0.15

Total S percent 2.16 2.23 0.83 1.43 1.69 2.42

Sulfide S percent 0.88 1.58 0.18 0.79 0.17 0.36

Sulfate S percent 0.38 0.60 0.11 0.15 0.20 0.28

Average sulfide sulfur values for Erato LV samples (0.88 percent) are about a half percent lower than TigArt LV samples (1.31 percent). However, the two sample populations closely resemble one another in that AP greatly outweighs NP, and that the most significant ARD (and likely metal-leaching) potential exists in the LV lithologic group. As with the TigArt barren rock, the UV formation and colluvium contain trace sulfides. NAG pH values are available for 50 Erato barren rock samples. As expected, NAG pH values are consistently lower than paste pH values. The results indicate that complete sulfide oxidation would result in all lithologies being net acid-generating, with LV samples generating an effluent pH slightly above 4 and UV samples an effluent pH slightly below 5.


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Figure 5-4 is a graph of paste pH versus sulfide sulfur for Erato barren rock samples. This graph should be compared with Figure 5-1. The two graphs show the similar behavior of the two sample sets. LV samples show a much greater range of sulfide sulfur values than UV samples, which are consistently low in sulfide sulfur. The relationship between LV sulfide sulfur and paste pH is similar, with increasing levels of sulfide corresponding with lower pH. The most obvious difference between the graphs is that there are fewer LV samples with sulfide values between 1 percent and 4 percent in Figure 5-4, so that the linear relationship is less obvious. UV samples from the Erato pit occupy essentially the same range of paste pH values as samples from the TigArt pit.

Figure 5-4 - Paste pH vs. Sulfide Sulfur for Erato Barren Rock


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Figure 5-5 is a graph of total sulfur vs. sulfide sulfur for Erato barren rock samples, and should be compared with Figure 5-2. In some respects the two graphs are similar, with one group of LV samples following a trend that is parallel to and offset from the line representing a 1:1 ratio between sulfide sulfur and total sulfur, and a second group of LV, UV and colluvium samples that stays close to the Yaxis. A larger proportion of the Erato barren rock samples have relatively low sulfide sulfur levels.

Figure 5-5 - Total Sulfur vs. Sulfide Sulfur for Erato Barren Rock


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Figure 5-6 is a ternary diagram showing the relative proportions of sulfate sulfur, sulfide sulfur, and nonextractable sulfur in the Erato barren rock samples. Comparison with Figure 5-3 indicates that the Erato samples show a similar distribution, but that sulfide sulfur is the dominant sulfur form in a somewhat smaller proportion of the Erato samples. Those samples are most often LV samples, but a few UV samples also plot close to the diagram's high-sulfide apex. Most samples, representing all waste rock categories, are dominated by non-extractable sulfur.

Figure 5-6 - Sulfur Speciation for Erato Barren Rock

5.3 ABA Statistical Analysis

In order to determine whether or not significant differences exist between the pit populations, student t-tests were performed to compare the three pits: Erato, Tigranes-Artavasdes and Arshak. Populations were defined by the pit and rock type, resulting in 9 populations. The t-tests show that the three pit sample populations are compatible with each other, with a 95 percent confidence interval for each rock type. Therefore, generalizations based on results from TigArt samples are applicable to the Erato pit.


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5.4 Spent Ore

Seven spent heap leach residue samples from a pilot-scale leaching test were evaluated by Wardell in 2011. The seven samples included three composites, one each from the Tigranes, Artavasdes, and Erato deposits. The remaining four samples represented specific mineralization types, and included gossan material, fault gouge, siliceous breccia and pervasive siliceous iron-oxide in-fill material. ABA results are given in Table 5-3.

Table 5-3 - ABA Results - Tigranes/Artavasdes Spent Ore (includes one Erato sample) Total Sulfur

Acid-Soluble Sulfate

Sulfide Sulfur

percent

percent

percent

MPF

0.04

0.02

GSN

0.58

FG

0.37

Sample

SB

0.02

AP T CaCO3/kT 0.63

NP T CaCO3/kT 3.06

0.05

0.53

16.5

4.31

0.06

0.31

9.59

2.69

0.38

0.04

0.34

10.66

2.31

1,2

1.15

0.03

1.13

35.16

1.37

1

0.7

0.05

0.65

20.22

2.5

1

0.38

0.01

0.37

11.63

0.69

MC068

MC070 MC071

Notes: 1. Composite sample 2. Erato sample

Sulfide sulfur values range from below 0.1 percent to 1.1 percent, with a mean value close to 0.5 percent. The highest sulfide sulfur values are found in the Erato composite sample (MC068). In general, the sulfide sulfur concentrations are very close to the total sulfur concentrations, indicating that there are no significant non-sulfide sulfur forms, which is unlike the barren rock sample populations. All samples display a general lack of neutralizing carbonate and silicate minerals. Six Erato spent ore samples from laboratory-scale column leach testing were evaluated by Golder in 2013. ABA results for this group of samples are given in Table 5-4.

Table 5-4 - ABA Results - Erato Spent Ore

Sample

Total Sulfur

Acid-Soluble Sulfate

Sulfide Sulfur

AP

NP

percent

percent

percent

T CaCO3/kT

T CaCO3/kT

DDA-030

0.95

0.24