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COWAL GOLD MINE EXTENSION MODIFICATION

APPENDIX CGEOCHEMISTRY ASSESSMENT

COWAL GOLD MINE EXTENSION

MODIFICATION

ENVIRONMENTAL GEOCHEMISTRY ASSESSMENT OF

WASTE ROCK AND TAILINGS

September 2013

Prepared For: Barrick Australia Limited PO Box 210 West Wyalong NSW 2671 Australia

Prepared By: Geo-Environmental Management Pty Ltd PO Box 6293 O’Connor ACT 2602 Australia ABN 21 486 702 686


Environmental Geochemistry Assessment of Waste Rock and Tailings Page...i

Geo-Environmental Management Pty Ltd

Contents

Page

1.0 INTRODUCTION ................................................................................................ 1

1.1 Cowal Gold Mine Background ................................................................. 1

1.2 Study Objectives ....................................................................................... 5

2.0 PREVIOUS GEOCHEMICAL INVESTIGATIONS .......................................... 6

2.1 pH, Salinity and Acid Forming Characteristics ........................................ 7

2.2 Metal Enrichment and Solubility .............................................................. 7

2.3 Tailings Liquor Chemistry ........................................................................ 8

2.4 Tailings Storage Facilities ........................................................................ 8

2.5 Pit Void Water Quality ............................................................................. 9

2.6 Previous Recommendations for Management .......................................... 9

3.0 GEOCHEMICAL ASSESSMENT PROGRAM ................................................ 10

3.1 Testing Methodology .............................................................................. 10

3.1.1 pH, Salinity and Sodicity Determination ....................................... 10

3.1.2 Acid Forming Characteristic Evaluation ....................................... 11

3.1.3 Multi-Element Analysis ................................................................. 14

3.2 Geochemical Classification .................................................................... 14

3.3 Sample Selection and Preparation .......................................................... 16

4.0 WASTE ROCK AND LOW GRADE ORE GEOCHEMISTRY ...................... 18

4.1 pH, Salinity and Sodicity ........................................................................ 19

4.2 Acid Forming Characteristics ................................................................. 20

4.3 Metal Enrichment and Solubility ............................................................ 23

5.0 TAILINGS GEOCHEMISTRY ......................................................................... 24

5.1 Acid Forming Characteristics ................................................................. 24

5.2 Element Composition ............................................................................. 26

6.0 CONCLUSIONS AND RECOMMENDATIONS ............................................. 27

6.1 Waste Rock Emplacements .................................................................... 27

6.2 Low Grade Ore Stockpiles...................................................................... 28

6.3 Tailings Storage Facilities ...................................................................... 29

6.4 Pit Void Water Quality ........................................................................... 30

6.5 Site Water Management ......................................................................... 30

7.0 REFERENCES ................................................................................................... 31


Environmental Geochemistry Assessment of Waste Rock and Tailings Page...ii


Tables Page

Table 1: Geochemical investigations conducted for the CGM to-date ..................... 6

Table 2: Electrical conductivity and corresponding salinity rankings for solid samples equilibrated in deionised water ................................................... 11

Table 3: ESP, sodicity and likely dispersion characteristics of samples ................. 11

Table 4: Sample quantities and intervals sampled for the different lithologies of the Modification Pit Extension ....................................................................... 17

Table 5: Summary of the pH and EC, and acid forming characteristics for the waste rock and low grade ore samples from the Modification Pit Extension. .... 18

Table 6: Average crustal abundances and concentration ranges for the significantly enriched elements in the waste rock and low grade ore samples from the Modification Pit Extension. ...................................................................... 23

Table 7: Summary of the acid-base account and NAG test results for the ore samples from the Modification Pit Extension. .......................................... 24

Figures Page

Figure 1: Regional Location ....................................................................................... 2

Figure 2: Modification General Arrangement ............................................................ 3

Figure 3: Typical acid-base account plot .................................................................. 13

Figure 4: Typical geochemical classification plot .................................................... 16

Figure 5: Salinity and sodicity ranking for selected waste rock samples from the Modification Pit Extension ....................................................................... 20

Figure 6: Acid-base account plot for the waste rock and low grade ore samples from the Modification Pit Extension ................................................................. 21

Figure 7: Geochemical classification plot for the waste rock and low grade ore samples from the Modification Pit Extension ........................................... 22

Figure 8: Acid-base account plot for the ore samples from the Modification Pit Extension. .................................................................................................. 25

Figure 9: Geochemical classification plot for the ore samples from the Modification Pit Extension. ............................................................................................ 25

Attachments Attachment A: Drill-Hole Locations and Sample Details

Attachment B: Waste Rock and Low Grade Ore Sample Test Results

Attachment C: Ore Sample Test Results


Environmental Geochemistry Assessment of Waste Rock and Tailings Page 1


1.0 Introduction Barrick (Cowal) Limited (Barrick), the owner and operator of the Cowal Gold Mine (CGM) in New South Wales (NSW), Australia, proposes to lodge an Environmental Assessment for a modification of the Development Consent in order to facilitate the approval of an extension to the mine. The Development Consent for the CGM has been modified on several occasions with the current modification known as the Cowal Gold Mine Extension Modification (the Modification). This proposed Modification involves an expansion of the current open pit resulting in the production of additional waste rock, gold-bearing ore and tailings, and the exposure of additional mine rock within the walls of the open pit. Geo-Environmental Management Pty Ltd (GEM) was commissioned by Barrick to conduct an assessment of the geochemical characteristics of the waste rock and tailings from the expanded pit area, and identify any potential geochemical impacts resulting from the proposed Modification. This report builds on previous investigations conducted for the existing CGM and provides the results and findings of detailed geochemical investigations conducted on drill-hole samples representing waste rock (including low grade ore) and ore samples as an indication of the tailings from the expanded pit area, identifies the potential geochemical implications for the proposed Modification, and provides recommendations for environmental management of the waste emplacements, low grade ore stockpiles, tailings storage facilities and the open pit. 1.1 Cowal Gold Mine Background The CGM is an open cut mining operation located approximately 38 kilometres (km) north-east of West Wyalong in central NSW (Figure 1). The general arrangement for the approved CGM and Modification is provided on Figure 2. Mining is currently approved to produce a total of approximately 99 million tonnes (Mt) of ore, 179 Mt of waste rock (including low grade ore) and 99 Mt of tailings over the 15 year life of mine. The waste rock is disposed within dedicated surface waste rock emplacements, including the Perimeter Waste Emplacement, the Northern Waste Emplacement and the Southern Waste Emplacement. The low grade ore is stockpiled within the Northern Waste Emplacement for future potential processing depending on market conditions. Gold is extracted from the ore on-site using a conventional carbon-in-leach (CIL) cyanide leaching circuit and the tailings are disposed within dedicated Tailings Storage Facilities (TSF), including the Northern TSF and the Southern TSF.


Environmental Geochemistry Assessment of Waste Rock and Tailings Page...4


The main activities associated with the Modification relevant to the waste rock and tailings geochemistry assessment would include:

• extension of the operational life of the CGM by an additional 5 years (i.e. until 2024);

• no change to Mining Lease (ML) 1535, and no requirement for additional ML tenement applications;

• continued development of open pit mining operations at the CGM including expansion of the extent and depth of the existing open pit (Figure 2);

• an increase in the total quantities of waste rock, ore and tailings produced over the life of the mine;

• an increase in total gold production from approximately 3.1 to 3.8 million ounces;

• no change to the existing process plant or its currently installed capacity to continue ore processing at a rate up to 7.5 million tonnes per annum;

• continued and expanded development of the existing northern and southern waste rock emplacements within ML 1535 for placement of mined waste rock over the life of the CGM, including (Figure 2):

− raising the maximum design height of the northern waste rock emplacement to 308 metres (m) Australian Height Datum (AHD);

− raising the maximum design height of the southern waster rock emplacement to 283 m AHD; and

− extension of the northern waste rock emplacement to the west with an additional disturbance footprint of approximately 39 hectares (ha);

• no change to the existing perimeter waste rock emplacement;

• continued and expanded development of soil stockpiles, the relation of existing soil stockpiles and stockpiling of mineralized material (i.e. potentially commercial ore) within ML 1535;

• continued use of the existing tailings storage facilities for the deposition of tailings produced over the life of the CGM, including raising the maximum design height of:

− the northern tailings storage facility to 248 m AHD; and

− the southern tailings storage facility to 225 m AHD;

• no change to the use of cyanide destruction in tailings prior to deposition in tailings storage facilities, with no change to the approved cyanide concentration limits in the aqueous component of the tailings slurry stream specified in the CGM Development Consent (DA 14/98);




• no change to the design objectives of the existing CGM water management system (i.e. up-catchment diversion system [UCDS], internal catchment diversion system [ICDS] and lake isolation system);

• no change to approved exploration activities;

• the treatment of some soil (e.g. with gypsum) in a dedicated stockpile to improve its characteristics as a plant growth medium prior to use in progressive rehabilitation; and

• a revised rehabilitation cover system to reflect the findings of ongoing rehabilitation trials at the CGM.

1.2 Study Objectives This study builds upon previous geochemical studies conducted for the existing CGM. The objectives of this study include:

• Assess the potential changes to the geochemical characteristics of the waste rock and low grade ore, including acid forming characteristics, element enrichment, solubility, salinity and sodicity (dispersion potential), based on the geochemical characteristics of representative drill-hole samples from the proposed extended pit area.

• Assess the potential changes to the geochemical characteristics of the tailings, including acid forming characteristics, and element enrichment and solubility, based on the geochemical characteristics of representative ore types within the proposed extended pit area.

• Identify any waste rock materials that are considered to be geochemically suitable for potential use as rehabilitation media based on the acid forming, salinity, sodicity, and element enrichment and solubility characteristics of these materials.

• Determine any predicted changes to the pit void water quality based on identified changes in the geochemical characteristics of the mine rock samples from the extended pit area.




2.0 Previous Geochemical Investigations Detailed geochemical investigations were conducted by Environmental Geochemistry International Pty Ltd (EGi) prior to commencing mining operations at the approved CGM. These investigations were commissioned by the previous owners (North Limited) and reported in the Cowal Gold Project Environmental Impact Statement (EIS) (North Limited, 1998). Subsequent geochemical investigations conducted by EGi (EGi, 2004) were commissioned by Barrick to confirm the previous findings and expand the waste rock and tailings geochemical databases for mining operations, environmental management and closure planning. Further geochemical investigations have since been conducted by GEM for the E42 Modification (GEM, 2008). Table 1 provides an historical summary of the geochemical investigations carried out for the CGM to-date. Following is a review of the geochemical characteristics of the waste rock, low grade ore and tailings, and the implications for environmental management and closure planning at CGM from these investigations. Table 1: Geochemical investigations conducted for the CGM to-date

Geochemical Investigations Samples Analysed Test Work Conducted

Environmental Geochemical Assessment of Process Tailings, Mine Rock and Surface Zone Materials (EGi, 1995)

87 Mine Rock, Ore and Surface Materials

Salinity, ABA, NAG, Multi-Elements

2 Tailings Salinity, ABA, NAG, Multi-Elements, Leach Columns, CN Attenuation

Environmental Geochemical Assessment of Simulated Tailings (EGi, 1996)

1 Oxide Tailings ABA, NAG, Multi-Elements, CN Speciation and Decay

Environmental Geochemistry Assessment of Proposed Mining Activities (EGi, 1997) - Appendix C in the Cowal Gold Project EIS (North Limited, 1998)

4 Tailings ABA, NAG, Multi-Elements, CN Decay, Leach Columns

2 TSF Sub-Soils ABA, Soil Chemistry, Attenuation Characteristics

3 Construction Materials

ABA, Soil Chemistry

2 Waste Rock Composites

Salinity, ABA, Sequential Batch Extraction

Final Void Water Chemistry (EGi, 1998) 1 Groundwater Pit Water Chemistry Modelling

Geochemical Assessment of Waste Rock and Process Tailings (EGi, 2004)

100 Mine Rock and Ore

Salinity, ABA, NAG, Multi-Elements

8 Tailings ABA, NAG, Multi-Elements

Cowal Gold Mine E42 Modification, Tailings and Waste Rock Geochemical Assessment (GEM, 2008)

Review of existing data

Review of existing data

Review of Cowal Gold Mine Cyanide Destruction (CSIRO Minerals, 2010)

5 Tailings CN Speciation and Decay

ABA = Acid-Base Account, NAG = Net Acid Generation, ABCC = Acid Buffering Characteristic Curve




2.1 pH, Salinity and Acid Forming Characteristics The geochemical investigations carried out for the EIS indicated that reactive sulfides occur in the primary waste rock and combined primary tailings (i.e. combined flotation and CIL tailings). However, due to the presence of moderate to high acid neutralising capacity (ANC) in these materials they are expected to be non-acid forming (NAF). It was also reported that the oxide waste rock and tailings (i.e. CIL tailings from oxide ores) are expected to be NAF due to low reactive sulfide concentrations. These materials were also found to be moderately to highly saline. These findings were based on testing a total of 101 samples representing soil, waste rock, ore (including low grade ore) and tailings carried out by EGi (EGi, 1995; EGi, 1996; EGi, 1997). Subsequent confirmatory test work carried out by EGi in 2004 (100 waste rock and 8 tailings samples) confirmed the expected salinity and acid forming characteristics of these materials (EGi, 2004). 2.2 Metal Enrichment and Solubility Elemental analyses carried out on selected samples for the EIS and subsequent confirmation testing indicated that the majority of the waste rock and low grade ore was expected to have high concentrations of arsenic (As) and that some of these materials were also expected to have high concentrations of cadmium (Cd), lead (Pb), selenium (Se), antimony (Sb) and zinc (Zn), (EGi, 1997; EGi, 2004). These investigations also predicted high concentrations of As, Cd, Pb, molybdenum (Mo), Pb, Sb and Zn in the oxide and primary tailings (EGi, 1997; EGi, 2004). Silver (Ag) was not included in the analytical suite for these investigations. The potential for release of environmentally significant elements from waste rock and tailings was investigated by EGi in 1995 and 1997. Sequential batch water extractions indicated that leaching of environmentally important elements from waste rock at the CGM was unlikely to be of concern provided near neutral pH values were maintained. Column leach tests carried out on the tailings identified an initial flush of soluble copper (Cu) and Zn from the primary tailings (EGi, 1997). However, it was concluded that this release was most likely associated with the residual cyanide (CN) in the tailings liquor and did not represent a long-term concern (EGi, 1997).




2.3 Tailings Liquor Chemistry The results of test work conducted by EGi in 1996 and 1997 indicated that CN in the tailings liquor would decay rapidly in the ponded decant liquor (i.e. in the TSFs) and in the reclaim water (i.e. in the contained water storage) due primarily to the low metal content and high proportion of free CN (75% of the weak acid dissociable cyanide [CNWAD] is present as free CN) (EGi, 1997). Based on this test work it was reported that on-going CN decay in the tailings storage facilities would result in CNWAD concentrations in the reclaim water from 5 to 10 milligrams per litre (mg/L) when processing oxide ore and 10 to 15 mg/L when processing primary ore (EGi, 1997). Once discharge ceases it is expected that within 2 to 3 months the CNWAD complexes in the ponded decant would decay to very low concentrations. In April 2010 the INCO process replaced the previously used Caro’s Acid method for destruction of the cyanide in the tailings. CSIRO Minerals (2010) conducted a review of the changes in cyanide speciation within the deposited tailings and concluded that since the introduction of the INCO process at the CGM:

• the concentrations of CNWAD and the metal-cyanide species, including Cu, iron (Fe), nickel (Ni) and Zn, have remained relatively constant in the tailings; and

• thiocyanate concentrations in the tailings are generally consistent with concentrations resulting from the use of Caro’s acid since the middle of 2008.

The pH and electrical conductivity (EC) of the tailings decant liquor is monitored twice daily (day shift and night shift) at the central decant point of the TSF during tailings discharge. A review of the monitoring data collected from January 2012 to June 2012 at the Southern TSF and from March 2012 to June 2012 at the Northern TSF indicates a range in pH from 5.2 to 9.5 with an average (median) pH of 8.2, and a range in EC from 0.004 to 0.030 deciSiemens per metre (dS/m) with an average (mean) EC of 0.017 dS/m. These data confirm that the tailings decant liquor is typically non-saline and slightly alkaline, with one period of below neutral pH (pH 5.2 to 6.9) tailings decant from 8 to 10 October 2012. 2.4 Tailings Storage Facilities Sequential batch extraction tests using sub-soil materials from the tailings storage facilities and liquors from the primary and oxide tailings were carried out by EGi in 1997 to determine the attenuation capacity of the sub-soil materials. This test work indicated that CN is only poorly attenuated whereas Cu, Zn and As are generally strongly attenuated by the soils underlying the TSFs (EGi, 1997).




2.5 Pit Void Water Quality The geochemical test work carried out to-date indicates that the rock types that would be exposed within the pit walls would be NAF (EGi, 1995; EGi, 2004). These investigations also indicated that the primary rock types are likely to contain moderate reactive sulfides (0.5 to 1.0 %S) which have a risk of generating moderate sulfate loads when exposed to oxidation within the pit walls. However, given the regional groundwater has a total dissolved solids (TDS) count of around 40,000 to 45,000 mg/L, the contribution of sulfate salts from the pit walls to the overall TDS of pit water is expected to be negligible (EGi, 1997). 2.6 Previous Recommendations for Management Based on the findings of the previous geochemical investigations the following recommendations for environmental management of the CGM were provided (EGi, 2004):

• The results indicate a very low likelihood of acid rock drainage (ARD) from waste rock and tailings, therefore no special management requirements would be required for ARD control. However, operational monitoring and testing should be carried out on an occasional and as needed basis to confirm the low ARD potential of waste rock with particular focus on any unexpected waste rock types or alteration types which may be exposed during mining.

• The oxide waste rock has relatively high natural salinity and the primary waste rock has the potential to generate soluble salts (i.e. due to the presence of reactive sulfides, sulfate salts such as gypsum would be generated if these materials are left exposed to surficial weathering processes).

• The waste rock and tailings are expected to be enriched with As and some of these materials are also expected to be enriched with other elements including Cd, Mo, Sb, Pb and Zn. These elements should be included in the site water monitoring program on an occasional basis to confirm the expected low leaching potential of these elements.




3.0 Geochemical Assessment Program 3.1 Testing Methodology This assessment utilised a staged testing program. All of the samples were submitted for standard acid-base account test procedures, and based on these results a selection of the samples was submitted for additional testing. The following tests and procedures were carried out on all of the samples:

• pH and EC determination; • total S assay; • ANC determination; and • Net Acid Producing Potential (NAPP) calculation. The following tests were carried out on selected samples:

• exchangeable cation analysis; • sulfide S analysis; • single addition NAG test; and • multi-element scans on solids and water extracts. The acid-base account, sulfide S and exchangeable cation analysis, and NAG tests were performed by Australian Laboratory Services Pty Ltd in Brisbane and the multi-element analyses were performed by Genalysis Laboratories in Perth. Following is an overview of the test procedures used for this program. 3.1.1 pH, Salinity and Sodicity Determination pH and Electrical Conductivity Determination The pH and EC of a sample is determined by equilibrating a solid sample in deionised water for a minimum of 2 hours. Variations to this test include mixing the solids with water at a ratio of 1:2 or 1:5 by weight (w/w), or as a saturated paste. Typically a ratio of 1:2 is used for providing an indication of the inherent acidity and salinity of a material when it is initially exposed. The salinity rankings based on EC values from 1:5 extracts (EC1:5), 1:2 extracts (EC1:2) and saturation extracts (ECsat) are provided below in Table 2.




Table 2: Electrical conductivity and corresponding salinity rankings for solid samples equilibrated in deionised water

EC1:5 (dS/m) EC1:2 (dS/m) ECsat (dS/m) Salinity

< 0.2

0.2 to 0.3

0.3 to 0.4

> 0.4

< 0.5

0.5 to 1.5

1.5 to 2.5

> 2.5

< 2.0

2 to 4.0

3 to 8.0

> 8.0

Non-Saline

Slightly Saline

Moderately Saline

Highly Saline

Source: Rhoades et al. (1999)

Exchangeable Cation Analysis Exchangeable cation analyses are carried out to determine the sodicity of a sample. Sodicity occurs in materials that have high concentrations of exchangeable Sodium (Na) relative to the other major cations Calcium (Ca) and Magnesium (Mg), causing the material to be highly dispersive. The Exchangeable Sodium Percent (ESP) is used to determine the sodicity of a sample by comparing the amount of exchangeable Na to Ca and Mg concentrations. The ESP is used to rank materials according to sodicity and likely dispersion characteristics (Table 3). Table 3: ESP, sodicity and likely dispersion characteristics of samples

ESP Sodicity Dispersion

< 6

6 to 15

15 to 30

> 30

Non-Sodic

Slightly Sodic

Moderately Sodic

Highly Sodic

Not Dispersive

Slightly Dispersive

Moderately Dispersive

Highly Dispersive

3.1.2 Acid Forming Characteristic Evaluation A number of test procedures are used to assess the acid forming characteristics of mine waste materials. The most widely used assessment methods are the ABA and the NAG test. These methods are referred to as static procedures because each involves a single measurement in time. Acid-Base Account The acid-base account involves laboratory procedures that evaluate the balance between acid generation processes (oxidation of sulfide minerals) and acid neutralising processes (dissolution of alkaline carbonates, displacement of exchangeable bases, and weathering of silicates). The values arising from the acid-base account are referred to as the maximum potential acidity (MPA) and the ANC, respectively. The difference between the MPA and ANC value is referred to as the NAPP.




The MPA is calculated using the total sulfur content of the sample. This calculation assumes that all of the sulfur measured in the sample occurs as pyrite (FeS2) and that the pyrite reacts under oxidising conditions to generate acid according to the following reaction:

FeS2 + 15/4 O2 + 7/2 H2O => Fe(OH)3 + 2 H2SO4 According to this reaction, the MPA of a sample containing 1 %S as pyrite would be 30.6 kilograms of H2SO4 per tonne of material (i.e. kg H2SO4/t). Hence the MPA of a sample is calculated from the total sulfur content using the following formula:

MPA (kg H2SO4/t) = (Total %S) x 30.6 The use of the total sulfur assay to estimate the MPA is a conservative approach because some sulfur may occur in forms other than pyrite. Sulfate sulfur and native sulfur, for example, are non-acid generating sulfur forms. Also, some sulfur may occur as other metal sulfides (e.g. covellite, chalcocite, sphalerite, galena) that yield less acidity than pyrite when oxidised. The acid formed from pyrite oxidation would to some extent react with acid neutralising minerals contained within the sample. This inherent acid neutralisation is quantified in terms of the ANC and is determined using the Modified Sobek method. This method involves the addition of a known amount of standardised hydrochloric acid (HCl) to an accurately weighed sample, allowing the sample time to react (with heating), then back titrating the mixture with standardised sodium hydroxide (NaOH) to determine the amount of unreacted HCl. The amount of acid consumed by reaction with the sample is then calculated giving the ANC expressed in the same units as the MPA, which is kg H2SO4/t. Determination of the ANC using the Modified Sobek provides an indication of the total neutralisation capacity of a material. However, in some materials not all mineral phases would be readily available to neutralise sulfide generated acidity. For these material types acid buffering characteristic curves (ABCCs) can be used to determine the amount of ANC that is available to neutralise any sulfide generated acidity under more natural weathering conditions. The ABCCs are obtained by slow titration of a sample with acid while continuously monitoring pH and plotting the amount of acid added against pH. Careful evaluation of the plot provides an indication of the portion of ANC within a sample that is readily available for acid neutralisation.




The NAPP is a theoretical calculation commonly used to indicate if a material has the potential to produce acid. It represents the balance between the capacity of a sample to generate acid (MPA) and its capacity to neutralise acid (ANC). The NAPP is also expressed in units of kg H2SO4/t and is calculated as follows:

NAPP = MPA - ANC If the MPA is less than the ANC then the NAPP is negative, which indicates that the sample may have sufficient ANC to prevent acid generation. Conversely, if the MPA exceeds the ANC then the NAPP is positive, which indicates that the material may be acid generating. The ANC/MPA ratio is used as a means of assessing the risk of acid generation from mine waste materials. A positive NAPP is equivalent to an ANC/MPA ratio less than 1, and a negative NAPP is equivalent to an ANC/MPA ratio greater than 1. Generally, an ANC/MPA ratio of 3 or more signifies that there is a high probability that the material is not acid generating. Figure 3 is an acid-base account plot which is commonly used to provide a graphical representation of the distribution of sulfur and ANC in a sample set. The plotted line shows where the NAPP = 0 (i.e. ANC = MPA or ANC/MPA=1) (Figure 3). Samples that plot to the lower-right of this line have a positive NAPP and samples that plot to the upper right of it have a negative NAPP. Figure 3 also shows the plotted lines corresponding to ANC/MPA ratios of 2 and 3.

0

50

100

150

0 1 2 3 4 5

Total S (%)

ANC/MPA=3 ANC/MPA=2

+ve NAPP

-ve NAPP

NAPP=0

Figure 3: Typical acid-base account plot




Net Acid Generation Test The NAG test involves the addition of hydrogen peroxide to a sample to oxidise the contained reactive sulfide, then measurement of pH and titration of any net acidity produced. A NAGpH < 4.5 indicates that acid conditions remain after all acid generating and acid neutralising reactions have taken place and a NAGpH > 4.5 indicates that any generated acidity has been neutralised. Therefore, the NAG test provides a direct assessment of the potential for a material to produce acid after a period of exposure and weathering and is used to complement the results of the theoretical NAPP predictions. 3.1.3 Multi-Element Analysis Multi-element scans are primarily carried out on solid samples to identify any elements that are present at concentrations that may be of environmental concern with respect to water quality and revegetation. The assay results from the solid samples are compared to the average crustal abundance for each element to provide a measure of the extent of element enrichment. The extent of enrichment is reported as the Geochemical Abundance Index (GAI). However, identified element enrichment does not necessarily mean that an element would be a concern for revegetation, water quality, or public health and this technique is used to identify any significant element enrichments that warrant further examination. Multi-element scans also are performed on liquor samples to determine the chemical composition of the solution and identify any elemental concerns for water quality. 3.2 Geochemical Classification The acid forming potential of a sample is classified on the basis of the acid-base account and NAG test results into one of the following categories:

• Barren

• Non-Acid Forming (NAF)

• Potentially Acid Forming (PAF)

• Acid Forming (AF)

• Uncertain (UC)




Barren A sample classified as barren essentially has no acid generating capacity and no acid buffering capacity. This category is most likely to apply to highly weathered materials. In essence, it represents an ‘inert’ material with respect to acid generation. The criteria used to classify a sample as barren may vary between sites, but it generally applies to materials with a total sulfur content ≤ 0.1 %S and an ANC ≤ 5 kg H2SO4/t. Non-Acid Forming A sample classified as NAF may or may not have a significant sulfur content but the availability of ANC within the sample is more than adequate to neutralise all the acid that theoretically could be produced by any contained sulfide minerals. As such, material classified as NAF is considered unlikely to be a source of acidic drainage. A sample is usually defined as NAF when it has a negative NAPP and a final NAGpH ≥ 4.5. Potentially Acid Forming A sample classified as PAF always has a significant sulfur content, the acid generating potential of which exceeds the inherent acid neutralising capacity of the material. This means there is a high risk that such a material, even if pH circum-neutral when freshly mined or processed, could oxidise and generate acidic drainage if exposed to atmospheric conditions. A sample is usually defined as PAF when it has a positive NAPP and a final NAGpH < 4.5. Acid Forming A sample classified as AF has the same characteristics as the PAF samples however these samples also have an existing pH of less than 4.5. This indicates that acid conditions have already been developed, confirming the acid forming nature of the sample. Uncertain An uncertain classification is used when there is an apparent conflict between the NAPP and NAG results (i.e. when the NAPP is positive and NAGpH > 4.5, or when the NAPP is negative and NAGpH ≤ 4.5).




Figure 4 shows a typical geochemical classification plot for mine waste materials where the NAPP values are plotted against the NAGpH values. Samples that plot in the upper left quadrate, with negative NAPP values and NAGpH values greater than 4.5, are classified as NAF. Those that plot on the lower right quadrate, with positive NAPP values and NAGpH values of 4.5 or less, are classified as PAF. Samples that plot in the upper right or lower left quadrates of this plot have an uncertain geochemical classification (UC) due to a contradiction in the acid-base and NAG test results, and further testing is required to determine the geochemical classification of these material types.

1

2

3

4

5

6

7

8

9

10

11

12

-200 -150 -100 -50 0 50 100 150 200

NAPP kg H2SO4/t

NAF

PAFUC

UC

Figure 4: Typical geochemical classification plot

3.3 Sample Selection and Preparation For this assessment selected 1 m interval drill-hole pulp samples from the extended pit area were provided by Barrick. Two drill holes (E42D1632 and E42D1634) intersecting a representative profile of the stratigraphic sequence through the proposed pit extension area for the Modification were selected for sampling. From these drill-holes continuous sampling intervals were selected based on the material type (waste rock or low grade ore) and lithology, where each interval represented materials of discrete material type and lithology. Composite samples, representing the different material types and lithologies, were made-up using equal portions of each pulp sample within the selected intervals. Using this technique, a total of 65 composite samples, including 54 waste rock and 11 low grade ore samples, were prepared (Attachment A [Tables A1 and A2]).




This technique allowed continuous representative sampling of each identified statigraphic unit with the sampling frequency for the different units based on its prevalence through the sequence. However, due to the strataform nature of the deposit (i.e. interbedded low grade ore and ore), continuous sampling was not possible for some intervals and for these intervals the pulps containing interbedded low grade ore or ore units were either sampled separately or not sampled. The different lithologies sampled include Alluvium, Saprolite, Saprock, Diorite, and Dyke, Shear Zone and Fault Zone material. The location of these drill-holes within the Modification area and detailed sample information, including material type, lithology and sample interval, for each drill hole are provided in Attachment A. A summary of the material types and total interval sampled is provided in Table 4. Table 4: Sample quantities and intervals sampled for the different lithologies of the Modification Pit Extension

Lithology Material Type Sample Count

Interval Sampled (m)

Alluvium Waste 2 27

Saprolite Waste 2 30

Saprock Waste 6 92

Diorite Waste 40 623

Low Grade Ore 9 278

Dyke Waste 2 28

Shear Zone Waste 2 8

Low Grade Ore 1 3

Fault Zone Low Grade Ore 1 1




4.0 Waste Rock and Low Grade Ore Geochemistry The geochemical test results for the waste rock and low grade ore samples are provided in Attachment B. All of the waste rock and low grade ore samples were submitted for pH1:2 and EC1:2, and acid-base analysis (total sulfur assay and ANC determination) and a summary of these results is provided in Table 5. Table 5: Summary of the pH and EC, and acid forming characteristics for the waste rock and low grade ore samples from the Modification Pit Extension

Waste Type pH1:2 EC1:2 Total S MPA ANC NAPP

(dS/m) (%S) (kg H2SO4/t)

Alluvium Min 6.2 2.245 0.02 1 2 -2

Max 6.7 3.275 0.03 1 2 -1

(2 samples) Aver 6.5 2.760 0.03 1 2 -1

Saprolite Min 6.3 3.875 0.02 1 3 -64

Max 7.9 4.620 0.04 1 64 -2

(2 samples) Aver 7.1 4.248 0.03 1 34 -33

Saprock Min 7.1 1.485 0.01 0 3 -10

Max 7.6 6.616 0.05 2 10 -2

(6 samples) Aver 7.3 3.490 0.03 1 8 -7

Diorite Min 8.1 0.298 0.02 1 57 -130

Max 8.6 0.518 0.60 18 138 -53

(40 samples) Aver 8.4 0.403 0.27 8 90 -82

Dyke Min 8.2 0.381 0.25 8 101 -104

Max 8.3 0.394 0.59 18 122 -93

(2 samples) Aver 8.3 0.388 0.42 13 112 -99

Shear Zone Min 8.3 0.508 0.79 24 152 -162

Max 8.4 0.523 0.90 28 186 -124

(2 samples) Aver 8.4 0.516 0.85 26 169 -143

All Waste Min 6.2 0.298 0.01 0 2 -162

Max 8.6 6.616 0.90 28 186 -1

(54 samples) Aver 8.4 0.979 0.26 8 79 -72

Low Grade Ore Min 8.1 0.329 0.58 18 70 -278

Max 8.5 0.493 1.08 33 299 -45

(11 samples) Aver 8.2 0.428 0.80 24 114 -90

NOTE: Because the pH is a log-scale the average pH values presented are median (geometric mean) values.




4.1 pH, Salinity and Sodicity The pH1:2 values for the waste rock samples range from 6.2 to 8.6 with an average (median) of 8.4 (Table 5). The materials from the oxidised zone (i.e. oxide waste rock), including Alluvium, Saprolite and Saprock, typically have a lower pH1:2 value with average values ranging from 6.5 to 7.3, whereas those for the other lithologies from the fresh zone (i.e. primary waste rock), including the Diorite, and Dyke, Shear Zone and Fault Zone material, range from 8.3 to 8.4. The pH1:2 values for the low grade ore samples are similar to those of the primary waste rock ranging from 8.1 to 8.5 with average (median) value of 8.2. The EC1:2 values for the waste rock samples range widely from 0.298 to 6.616 dS/m. However, the samples with high EC1:2 values (i.e. > 0.5 dS/m) are restricted to the oxide waste rock samples, including Alluvium, Saprolite and Saprock. The oxide waste rock samples typically have a moderate to high salinity ranking with EC1:2 values ranging from 1.485 to 6.616 dS/m, while the primary waste rock samples, including the Diorite, and Dyke, Shear Zone and Fault Zone material, typically have a non-saline ranking with EC1:2 values ranging from 0.298 to 0.523 dS/m. The low grade ore samples all have a non-saline ranking with EC1:2 values ranging from 0.329 to 0.493 dS/m. Twenty of the waste rock samples representing the different lithologies with a range of EC1:2 values were selected for exchangeable cation analysis, including the cation exchange capacity and ESP, to evaluate the sodicity risk presented by waste rock from the proposed pit extension area. The results from these analyses are provided in Attachment B, and the ESP and EC1:2 values, plotted on Figure 5, provide the salinity and sodicity rankings of these samples. This plot shows that the selected samples range from non-saline to highly saline and from non-sodic to highly sodic. However, the oxide waste rock samples are generally ranked as moderately to highly sodic, with ESP values ranging from 7.8 to 47.8 %, and the primary waste rock types are ranked as non-sodic, with ESP values ranging from 0.6 to 1.5 %. This plot also shows that all of the non-saline samples are non-sodic, while all of the saline samples (slightly to highly saline) are sodic (slightly to highly sodic).




0.0

1.0

2.0

3.0

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5.0

6.0

7.0

0 10 20 30 40 50

Ele

ctri

cal C

on

du

ctiv

ity

(dS

/m)

Exchangeable Sodium Percent (%)

Alluvium

Saprolite

Saprock

Diorite

Dyke

Shear Zone

Non-Saline

SlightlySodic

Slightly Saline

Moderately Saline

Non-Sodic Highly SodicModerately Sodic

Highly Saline

Figure 5: Salinity and sodicity ranking for selected waste rock samples from the Modification Pit Extension 4.2 Acid Forming Characteristics The acid-base analysis results for the waste rock and low grade ore from the proposed pit extension area are provided in Attachment B and summarised for the different lithologies in Table 5. The total sulfur content ranges from <0.01 to 0.90 %S in the waste rock samples and from 0.58 to 1.08 %S in the low grade ore samples. The oxide waste rock samples typically have lower sulfur contents with average values of 0.03 %S, while the primary waste rock samples typically have higher contents with average values from 0.27 to 0.85 %S. Sulfide sulfur analyses were performed on 35 selected samples with a range in total sulfur contents (see Attachment B [Tables B1 and B2]). The sulfide sulfur content of these samples ranges from <0.005 to 0.98 %S. All of the selected oxide waste rock samples have sulfide sulfur contents of <0.005 %S indicating that the sulfur in these samples most likely occurs as sulfate, while that for the primary waste rock and low grade ore samples typically accounts for 90 to 100% of the total sulfur indicating that these materials only contain a small proportion of non-sulfide sulfur. The ANC values for the waste rock samples range widely from 2 to 186 kg H2SO4/t with an average of 79 kg H2SO4/t. However, the oxide waste samples typically have a relatively low ANC with average values ranging from 2 to 34 kg H2SO4/t, while the primary waste samples typically have a moderate to high ANC with average values ranging from 90 to 169 kg H2SO4/t. The low grade ore samples also have a moderate to high ANC with values ranging from 70 to 299 kg H2SO4/t and an average value of 114 kg H2SO4/t.




Figure 6 is a plot of the total sulfur content against the ANC value for the different waste rock types and low grade ore. Samples that plot above the NAPP=0 (ANC/MPA=1) line are NAPP negative indicating an excess in acid buffering capacity over potential acidity. Samples that plot above the ANC/MPA=2 line have at least a two-fold excess in acid buffering over acid potential and those that plot above the ANC/MPA=3 line have a three-fold excess. This plot shows that, apart from one sample with a moderate ANC, the oxide waste rock samples have low sulfur contents (≤ 0.1 %S) and ANC values (≤ 10 kg H2SO4/t), and are considered to be geochemically barren. The primary waste rock samples are NAPP negative with ANC/MPA ratios greater than 3, and the low grade ore samples are NAPP negative with ANC/MPA ratios greater than 2 indicating that these materials have a significant excess in acid buffering over inherent acid potential. The resulting NAPP values for these samples are all negative. Those for the waste rock samples range from minus 1 to minus 162 kg H2SO4/t, while those for the low grade ore range from minus 45 to minus 278 kg H2SO4/t.

0

50

100

150

200

250

300

0.0 0.5 1.0 1.5 2.0 2.5 3.0

AN

C (

kg H

2SO

4/t)

Total S (%)

Alluvium

Saprolite

Saprock

Diorite

Dyke

Shear Zone

Low Grade Ore

+ve NAPP

-ve NAPPNAPP=0

ANC/MPA=2

ANC/MPA=3

Figure 6: Acid-base account plot for the waste rock and low grade ore samples from the Modification Pit Extension To further investigate the acid forming characteristics and confirm the geochemical classification of these materials 30 of the samples (19 waste rock and 11 low grade ore) and the results of these tests are provided in Attachment B (Tables B1 and B2). Figure 7 is a plot of the NAPP values compared to the NAGpH of the selected waste rock and low grade ore samples. This plot shows that all of the samples have NAGpH values above 4.5 confirming that the samples are NAF.




2

3

4

5

6

7

8

9

10

11

12

-300 -200 -100 0 100 200

NA

G p

H

NAPP (kg H2SO4/t)

Alluvium

Saprolite

Saprock

Diorite

Dyke

Shear Zone

Low Grade Ore

NAF

PAFUC

UC

Figure 7: Geochemical classification plot for the waste rock and low grade ore samples from the Modification Pit Extension

Based on these results it is expected that the waste rock and low grade ore from the extended pit area would be NAF and that some of these materials are likely to be relatively acid consuming due to moderate to high ANC values resulting in NAPP values of less than minus 100 kg H2SO4/t. However, the primary waste rock and low grade ore materials are expected to contain moderate sulfides and, although NAF, these materials are likely to develop saline conditions, similar to the oxide waste rock, if allowed to oxidise when exposed during mining. As the waste rock is expected to be typically non-saline and NAF the majority of this material is considered to be geochemically suitable for use as a rehabilitation material (rock armour). However, materials with higher reactive sulfide contents (greater than 0.5 %S) are likely to present a risk of developing saline conditions when oxidised and these materials should either be excluded from use as rehabilitation material or blended with lower sulfur material in order to produce a low sulfide material. Materials with reactive sulfur contents greater than 0.5 %S are expected to contain visible sulfides which are identifiable in the field and therefore a visual assessment program could be implemented to identify the higher sulfur material to be excluded from use as rehabilitation material. If materials with higher reactive sulfide contents are blended with the lower sulfur material to produce a geochemically suitable rehabilitation material, a quality control program would need to be implemented involving the geochemical sampling and testing of the blended material to confirm its suitability prior to it being used for rehabilitation.




4.3 Metal Enrichment and Solubility

Fifteen samples, including 11 waste rock and 4 low grade ore samples were selected for multi-element analysis. Selection of these samples was based on the stratigraphy, lithology and geochemical characteristics of the samples. The results from these analyses and the geochemical abundances indices for the selected samples are provided in Attachment B (Tables B4 and B5). These results indicate that As and Sb are significantly enriched in the majority of the waste rock samples and that Ag, As and Sb are significantly enriched in all of the low grade ore samples (Attachment B [Table B5]). Additional to these, Ag is significantly enriched in one of the waste rock samples. The average crustal abundance and concentration ranges of these elements in the waste rock and low grade ore samples are provided in Table 6. Table 6: Average crustal abundances and concentration ranges for the significantly enriched elements in the waste rock and low grade ore samples from the Modification Pit Extension

Element Average Crustal

Abundance (mg/kg)

Concentration Range (mg/kg)

Waste Rock Low Grade Ore

Ag 0.07 0.14 - 0.75 0.62 - 1.03

As 1.5 8.9 - 106.0 27.0 - 111.5

Sb 0.2 1.48 - 11.08 3.25 - 5.08 Previous investigations identified the significant enrichment of these elements in the waste rock and low grade ore from the current mine pit along with a number of other elements including Cd, Pb, Se and Zn (EGi, 1995; EGi, 2004). Multi-element scans were performed on water extracts (1 part sample/2 parts deionised water) from these samples in order to identify any elements that are likely to be readily soluble in the waste rock and low grade ore. The results from these scans are presented in Attachment B (Table B6) and indicate that the high salinity in the oxide waste rock is due to a combination of chloride and sulfate salts (e.g. NaCl and CaSO4). Consistent with the previous investigations (EGi, 1995; EGi, 2004), these results indicate that the contained metals are expected to be relatively insoluble under the prevailing near neutral pH conditions of the waste rock. However, these results also indicate that the contained As in some of the low grade ore may be readily soluble.




5.0 Tailings Geochemistry It is understood that the alteration and mineralisation of the proposed pit extension area is continuous with that of the current pit and that the same ore types are present. Based on this it is expected that the tailings from the proposed extension area would be geochemically similar to the tailings from the current pit. To confirm this, the geochemical characteristics of ore samples from the proposed pit extension area were compared to those from the previous investigations. The geochemical test results for five selected drill-hole samples representing the ore from the region of the pit extension area are provided in Attachment C (Table C1). These samples include the primary diorite, upper volcaniclastics (UVC) and lower volcaniclastics (LVC) ore types. The test results for these samples, including the acid-base account, NAG testing and elemental analysis, were provided by Barrick. 5.1 Acid Forming Characteristics A summary of the test results for the ore samples, representing the primary ore from the Modification pit extension, is provided in Table 7 and the acid-base account and geochemical classification plots for these samples are provided on Figures 8 and 9, respectively. These samples have a moderate sulfur content of approximately 1.0 %S and moderate ANC of approximately 100 kg H2SO4/t. The resulting NAPP values are all negative ranging from minus 6 to minus 105 kg H2SO4/t. The NAGpH values ranging from 7.0 to 9.1 confirm that these samples are all NAF. Based on these results it is expected that the tailings produced from the primary ore represented by these samples is expected to be NAF. However, due to the moderate sulfur content these tailings may become saline if allowed to oxidise. These results are consistent with those of the primary tailings and ore type samples from the previous investigations (EGi, 1995; EGi, 2004). Table 7: Summary of the acid-base account and NAG test results for the ore samples from the Modification Pit Extension

Ore Type Total S MPA ANC NAPP ANC/

MPA NAGpH

(%S) (kg H2SO4/t)

Primary Diorite 1.02 31 111 -80 3.6 8.1

Primary UVC 1.34 41 79 -38 1.7 8.1

Primary LVC 0.97 30 134 -104 4.7 9.0




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0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50

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C (

kg H

2SO

4/t)

Total S (%)

Primary Diorite

Primary UVC

Primary LVC

+ve NAPP

-ve NAPP

NA

PP

=0A

NC

/MP

A=2

ANC/MPA=3

Figure 8: Acid-base account plot for the ore samples from the Modification Pit Extension

1

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4

5

6

7

8

9

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11

-200 -150 -100 -50 0 50 100 150 200

NA

G p

H

NAPP (kg H2SO4/t)

Primary Diorite

Primary UVC

Primary LVC

NAF

PAFUC

UC

Figure 9: Geochemical classification plot for the ore samples from the Modification Pit Extension




5.2 Element Composition The results of the multi-element scans and the geochemical abundance indices for the ore samples are provided in Attachment C (Table C2). These results indicate that Cd and Se are significantly enriched in all of the samples and that Pb, Sb and Zn are significantly enriched in some of the samples. Although Ag and As have been identified as significantly enriched in the ore samples from previous investigations (EGi, 2004), these elements were not included in the analytical suite for these samples. The results from the previous investigations indicate an enriched element suite for the ore and tailings from the current pit which is the same as that for the ore samples from the Modification pit extension, including Ag, As, Cd, Pb, Sb, Se and Zn (EGi, 1995; EGi, 2004). Based on this, it is expected that the tailings associated with ore from the Modification pit extension area would be geochemically similar to those from the current pit and are expected to be enriched in Ag, As, Cd, Pb, Sb, Se and Zn.




6.0 Conclusions and Recommendation For this assessment 70 drill-hole samples representing the waste rock, low grade ore and ore from the proposed Modification pit extension area were characterised in order to identify any geochemical implications for management of the waste rock emplacements, low grade ore stockpiles, TSFs and the mine pit. Following is a summary of the findings from the previous investigations and the management strategy developed for these materials. These findings are compared to those for the Modification pit extension, identifying any potential modifications that would be required for the management of the waste rock emplacements, low grade ore stockpiles, TSFs, mine pit and the site water quality monitoring programs if this Modification is to proceed. 6.1 Waste Rock Emplacements The previous investigations indicated that the waste rock from the current pit was expected to be NAF and that the oxide waste rock was expected to be naturally saline. Although the primary waste rock was expected to be non-saline, due to the relatively high reactive sulfide content it was reported that this material had a risk of becoming saline if allowed to oxidise. The waste rock was also found to be significantly enriched with As, Cd, Pb, Se, Sb and Zn. However, it was predicted that, under the near neutral pH condition of the exposed waste rock, these and any other environmentally important elements would remain insoluble. Based on these findings the following recommendations were provided: • Due to the low ARD risk no special management requirements would be required

for ARD control of the waste rock. However, operational monitoring and testing would need to be carried out on an occasional and as needed basis to confirm the low ARD potential of waste rock with particular focus on any unexpected waste rock types or alteration types which may be exposed during mining.

• Due to the salinity of the oxide waste rock and the potential of the primary waste rock to become saline, release of sulfate salts, such as gypsum, may occur if these materials are left exposed to surficial weathering processes.

• Due to the significant enrichment of As, Cd, Pb, Se, Sb and Zn, it was recommended that these elements be included in the site water monitoring program on an occasional basis to confirm the expected low leaching potential of these elements.




The results of the geochemical assessment of the waste rock from the Modification pit extension indicate that:

• the oxide waste rock is generally expected to have a near-neutral pH and to be moderately to highly saline and moderately to highly sodic, and the primary waste rock is generally expected to be slightly alkaline, and non-saline and non-sodic;

• all waste rock types are expected to be NAF with the oxide waste rock being geochemically barren (i.e. low sulfur and low ANC) and the primary waste rock being relatively reactive (i.e. moderate to high sulfur and ANC); and

• the majority of the waste rock is expected to be significantly enriched with As and Sb, and some of the waste rock may be significantly enriched with Ag.

These results confirm that the waste rock from the current pit and Modification pit extension are geochemically comparable, indicating that the management strategies currently employed for the waste rock emplacements would not need to be modified to accommodate the Modification. Because the waste rock from the Modification pit extension is geochemically comparable to the current pit, the same controls (i.e. the exclusion of materials with higher reactive sulfide contents) on the use of waste rock for rehabilitation (rock amouring) would apply to avoid the development of saline conditions. Although the results of this assessment indicate a reduced suite of enriched elements in the waste rock from the Modification pit extension, Ag has also been identified as potentially being enriched which was not previously identified. 6.2 Low Grade Ore Stockpiles The previous investigations reported that the low grade ore from the current pit was expected to be NAF. This material was found to have a high reactive sulfide content and moderate to high ANC, and therefore, the material was identified to be at risk of becoming highly saline if allowed to oxidise. The low grade ore was also expected to be significantly enriched with As, Cd, Pb, Se, Sb and Zn, however, it was found that under the predicted near neutral pH conditions, the contained environmentally important elements would most likely remain insoluble. Because of the predicted NAF nature and low ARD risk of the low grade ore no special management was required for ARD control of the low grade ore stockpile. However, due to the enrichment of As, Cd, Pb, Se, Sb and Zn it was recommended that these elements be included in the water monitoring program for the stockpile.




This geochemical assessment indicates that the low grade ore from the Modification pit extension is expected to have a moderate sulfur content, with a moderate to high ANC and this material classified as NAF. As with the low grade ore from the current pit, this material has a risk of becoming saline if the contained sulfides are allowed to oxidise. Similar to the waste rock from the Modification pit extension, the low grade ore has the potential to be of significantly enriched elements including Ag, As and Sb (i.e. a reduced suite compared to previous assessment). However, differing from the low grade ore from the current pit, As was found to be readily soluble in one of the samples from the Modification pit extension. Based on these findings no changes to the current management strategy for the low grade ore stockpile would be required for the Modification. 6.3 Tailings Storage Facilities Previous analysis of the tailings from the current operations included static geochemical characterisation, multi-element analysis, CN speciation, decay analysis, leach column testing of flotation tailings and primary CIL residues produced from oxide and primary ores. These analyses found that the oxide tailings had a low reactive sulfide content and that the primary tailings had a relatively high reactive sulfide content. However, both tailings types had a moderate to high ANC and were classified as NAF. The oxide tailings were also found to be potentially saline and although the primary tailings were non-saline, the risk of this material developing saline conditions was reported due to the relatively high reactive sulfide content. The oxide and primary tailings were found to be significantly enriched with As, Cd, Mo, Pb, Sb and Zn, however, under the near neutral pH conditions, none of the contained elements were found to be soluble. Due to the salinity concerns for the oxide and primary tailings it was recommended that the TSF design include a cover in order to avoid development of a salt-pan. Review of recent monitoring data indicates that the tailings decant liquor is typically non-saline and slightly alkaline. Representative samples of the tailings from the proposed Modification pit extension area were not available for this assessment and therefore a comparison between the geochemical characteristics of the ore materials from the current operations and proposed Modification pit extension was used to predict the likely geochemical characteristics of the tailings. The analysis of ore samples from the current pit indicated that the ore had a relatively high reactive sulfide content, and due to a moderately high ANC it was classified as NAF. The ore was also found to be enriched with Ag, As, Cd, Pb, Sb, Se and Zn. Due to the consistency in alteration and mineralisation between the current pit and the Modification extension area it was expected that the ore and therefore the tailings would be geochemically similar.




The results of the analysis of ore samples from the Modification pit extension confirmed the NAF classification of the ore and indicated the enrichment of Cd, Pb, Sb, Se and Zn (NOTE: Ag and As were not included in the analytical suite), confirming the geochemical consistency between the ore of the current pit and the Modification pit extension Based on these findings it is expected that the tailings from the proposed Modification pit extension would be geochemically similar to the current tailings and the adopted management strategy for the existing TSFs would not need to be modified for the Modification. 6.4 Pit Void Water Quality The results of this assessment indicate that the oxide and primary waste rock types from the proposed Modification extended pit are geochemically similar to those assessed during the previous investigations. Based on these findings it is expected that the rock to be exposed in the pit walls would be NAF. However the oxide wall rock is expected to be moderately to highly saline and the primary wall is expected to become saline when oxidised. Due to these characteristics the wall rocks that would be exposed in the proposed Modification extended pit are expected to generate a significant sulfate salt load within the pit void water. However, as noted in previous investigations for the CGM (EGi, 1997), given the regional groundwater has a TDS of around 40,000 to 45,000 mg/L, the contribution of sulfate salts from the pit walls to the overall TDS of pit water is expected to be negligible. 6.5 Site Water Management The findings of the previous geochemical investigations at the CGM have been used to help develop the site water quality monitoring programs for the pit, waste rock emplacements, low grade ore stockpile, ROM ore stockpile, and tailings storage facilities. The parameters include: • EC, pH, turbidity, dissolved oxygen, temperature, biological oxygen demand,

faecal indicators, total hardness, total suspended solids, TDS. Ca, Mg, K, Na, chloride, sulphate, Ag, As, Cd, Mo, Pb, Sb, Se and Zn.

Because the waste rock, pit wall rock, low grade ore, ROM ore and tailings are expected to be relatively geochemically similar to those from the current pit configuration no changes to the site water quality monitoring programs for the pit, waste rock emplacements, low grade ore stockpile, ROM ore stockpile, and tailings storage facilities are expected to be necessary. However, it is recommended that these programs be reviewed on an annual basis, and modified as necessary, in order to maintain and rationalise these programs.




7.0 References Bowen H.J.M. (1979) Environmental Chemistry of the Elements. Academic Press, London. Commonwealth Scientific and Industrial Research Organisation Minerals (2010) Review of Cowal Gold Mine Cyanide Destruction. Report prepared for Barrick Australia Limited. Environmental Geochemistry International Pty Ltd (1995) Cowal Gold Project Environmental Geochemical Assessment of Process Tailings, Mine Rock and Surface Zone Materials. Report prepared for North Limited. Environmental Geochemistry International Pty Ltd (1996) Cowal Gold Project Environmental Geochemical Assessment of Simulated Tailings. Report prepared for North Limited. Environmental Geochemistry International Pty Ltd (1997) Cowal Gold Project Environmental Geochemistry Assessment of Proposed Mining Activities for Cowal Gold Project. Report prepared for North Limited. Environmental Geochemistry International Pty Ltd (1998) Cowal Gold Project Final Void Water Chemistry. Report prepared for North Limited. Environmental Geochemistry International Pty Ltd (2004) Geochemical Assessment of Waste Rock and Process Tailings. Report prepared for Barrick Australia Limited. Geo-Environmental Management Pty Ltd (2008) Cowal Gold Mine E42 Modification, Tailings and Waste Rock Geochemical Assessment. Report prepared for Barrick Australia Limited. North Limited (1998) Cowal Gold Project Environmental Impact Statement. Rhoades J.D., Chanduvi F. and Lesch S.M. (1999) Soil Salinity Assessment: Methods and Interpretation of Electrical Conductivity Measurements. FAO Irrigation and Drainage Paper No. 57, Food and Agriculture Orginisation of the United Nations, Rome, Italy.


Environmental Geochemistry Assessment of Waste Rock and Tailings


ATTACHMENT A

Drill-Hole Locations and Sample Details

Figure A1: Drill-hole locations for the geochemistry assessment program of the Modification Pit Extension.

Table A1: Sample detail for drill-hole E42D1632, Modification Pit Extension.

Table A2: Sample detail for drill-hole E42D1632, Modification Pit Extension.

!.!.

!.!.

!.

!?

!?

!?

!?E42D1634

E42D1632

E42D1162

E42D1119E42D1082

E42D1064E42D1007

1535DD066

1535DD051

532500

5325

00

535000

5350

00

537500

5375

00

540000

5400

00

6277500 6277500

6280000 6280000

HAL-12-40_CGM Ext Mod_PEA_Geochem_201C

Drill-Hole Locations for theGeochemistry Assessment Programof the Modification Pit Extension

FIGURE A-1

LAKE COWAL

LEGENDMining Lease Boundary (ML 1535)Approximate Extent of Existing/Approved Surface DisturbanceModification ComponentsApproximate Extent of Additional Modification Surface DisturbanceModification Open Pit ExtentDrill Hole SamplesOreWaste Rock and Low Grade Ore

RAILWAY

Road

Bonehams Lane

WEST WYALONG BURCHER

Travelling Stock Reserve

Travelling Stock Reserve

ML 1535

COWAL GOLD MINE EXTENSION MODIFICATIONSource: Barrick (2010, 2013); Date of Orthophoto: April 2013

0 1000

MetresGRID DATUM MGA94 ZONE 55

Lake Cowal

!.

!?

From To Interval

CGM32/1 Alluvium Waste 0 14 14

CGM32/2 Alluvium Waste 14 27 13

CGM32/3 Saprolite Waste 27 42 15

CGM32/4 Saprolite Waste 42 57 15

CGM32/5 Saprock Waste 57 73 16




CGM32/9 Diorite Waste 121 138 17


CGM32/11 Dyke Waste 157 163 6

CGM32/12 Diorite Low Grade Ore 163 173 10






















Depth (m)Sample ID Lithology Material Type

Table A1: Sample detail for drill-hole E42D1632, Cowal Open Pit Extension Project.

From To Interval







CGM34/7 Shear Zone Waste 116 121 5


CGM34/9 Dyke Waste 136 158 22















CGM34/24 Fault Zone Low Grade Ore 352 353 1







CGM34/31 Shear Zone Waste 451 454 3

CGM34/32 Shear Zone Low Grade Ore 452 455 3

Depth (m)Sample ID Lithology Material Type

Table A2: Sample detail for drill-hole E42D1634, Cowal Open Pit Extension Project.




ATTACHMENT B

Waste Rock and Low Grade Ore Sample Test Results

Table B1: Acid forming characteristics of drill-hole E42D1632 samples, Modification Pit Extension.

Table B2: Acid forming characteristics of drill-hole E42D1634 samples, Modification Pit Extension.

Table B3: pH and EC, exchangeable cations, cation exchange capacity and exchangeable sodium percent for the selected drill-hole samples from the Modification Pit Extension.

Table B4: Multi-element composition of selected drill-hole samples, Modification Pit Extension.

Table B5: Geochemical abundance indices for selected drill-hole samples, Modification Pit Extension.

Table B6: Chemical composition of water extracts from selected drill-hole samples, Modification Pit Extension..

Total %SSulfide

%SMPA ANC

NAPP (Tot S)

NAPP (sulfide)

ANC/ MPA

NAGpH NAG(pH4.5) NAG(pH7.0)

CGM32/1 Waste Alluvium 6.7 2.245 0.02 1 2 -2 3.6 7.3 0 0 NAFCGM32/2 Waste Alluvium 6.2 3.275 0.03 <0.005 1 2 -1 -2 2.4 7.0 0 0 NAFCGM32/3 Waste Saprolite 6.3 4.620 0.04 <0.005 1 3 -2 -3 2.5 6.9 0 0 NAFCGM32/4 Waste Saprolite 7.9 3.875 0.02 1 64 -64 105.1 NAFCGM32/5 Waste Saprock 7.2 6.616 0.04 <0.005 1 3 -2 -3 2.4 7.5 0 0 NAFCGM32/6 Waste Saprock 7.1 5.238 0.04 1 5 -4 4.3 8.4 0 0 NAFCGM32/7 Waste Saprock 7.2 3.370 0.05 2 8 -7 5.4 8.4 0 0 NAFCGM32/8 Waste Saprock 7.3 2.129 0.02 1 9 -9 15.4 8.4 0 0 NAFCGM32/9 Waste Diorite 8.4 0.518 0.06 0.061 2 122 -120 -120 66.4 NAFCGM32/10 Waste Diorite 8.5 0.307 0.02 1 71 -70 116.2 NAFCGM32/11 Waste Dyke 8.2 0.394 0.59 0.560 18 122 -104 -105 6.8 10.9 0 0 NAFCGM32/12 Low Grade Ore Diorite 8.2 0.329 0.93 0.863 28 127 -99 -101 4.5 11.0 0 0 NAFCGM32/13 Waste Diorite 8.3 0.394 0.29 9 119 -110 13.4 NAFCGM32/14 Waste Diorite 8.6 0.298 0.26 8 138 -130 17.3 NAFCGM32/15 Waste Diorite 8.4 0.358 0.04 1 105 -104 85.8 NAFCGM32/16 Waste Diorite 8.4 0.418 0.08 2 112 -110 45.8 NAFCGM32/17 Waste Diorite 8.3 0.499 0.28 0.244 9 119 -110 -112 13.9 NAFCGM32/18 Waste Diorite 8.4 0.437 0.22 0.236 7 116 -109 -109 17.2 NAFCGM32/19 Waste Diorite 8.3 0.393 0.30 0.306 9 134 -125 -125 14.6 NAFCGM32/20 Waste Diorite 8.5 0.508 0.13 0.117 4 89 -85 -85 22.3 NAFCGM32/21 Low Grade Ore Diorite 8.2 0.455 0.58 0.527 18 77 -59 -61 4.3 11.1 0 0 NAFCGM32/22 Waste Diorite 8.6 0.422 0.18 0.184 6 79 -73 -73 14.3 NAFCGM32/23 Waste Diorite 8.6 0.488 0.18 6 72 -67 13.1 NAFCGM32/24 Waste Diorite 8.5 0.377 0.18 0.154 6 63 -57 -58 11.4 NAFCGM32/25 Low Grade Ore Diorite 8.5 0.493 0.58 18 76 -58 4.3 10.7 0 0 NAFCGM32/26 Waste Diorite 8.3 0.446 0.44 0.403 13 77 -63 -64 5.7 10.9 0 0 NAFCGM32/27 Waste Diorite 8.6 0.390 0.30 9 103 -94 11.2 NAFCGM32/28 Waste Diorite 8.3 0.332 0.24 0.230 7 68 -61 -61 9.3 NAFCGM32/29 Waste Diorite 8.2 0.506 0.33 10 71 -61 7.1 NAFCGM32/30 Low Grade Ore Diorite 8.1 0.483 0.81 0.774 25 70 -45 -46 2.8 10.8 0 0 NAFCGM32/31 Waste Diorite 8.3 0.444 0.25 0.232 8 70 -63 -63 9.2 NAFCGM32/32 Waste Diorite 8.3 0.436 0.26 8 67 -59 8.4 NAFCGM32/33 Waste Diorite 8.4 0.349 0.11 0.108 3 57 -54 -54 17.0 NAFKEY ARD Classification KeypH1:2 = pH of 1:2 extract NAPP = Net Acid Producing Potential (kgH2SO4/t) NAF = Non-Acid FormingEC1:2 = Electrical Conductivity of 1:2 extract (dS/m) NAGpH = pH of NAG liquor PAF = Potentially Acid FormingMPA = Maximum Potential Acidity (kgH2SO4/t) NAG(pH4.5) = Net Acid Generation capacity to pH 4.5 (kgH2SO4/t) UC = Uncertain () show expected class.ANC = Acid Neutralising Capacity (kgH2SO4/t) NAG(pH7.0) = Net Acid Generation capacity to pH 7.0 (kgH2SO4/t)

Table B1: Acid forming characteristics of drill-hole E42D1632 samples, Cowal Open Pit Extension Project.

ARD Classification

Sample ID pH1:2 EC1:2

NAG TESTACID-BASE ANALYSISLithologyMaterial Type

Total %SSulfide

%SMPA ANC

NAPP (Tot S)

NAPP (sulfide)

ANC/ MPA

NAGpH NAG(pH4.5) NAG(pH7.0)

CGM34/1 Waste Saprock 7.6 2.100 0.01 0 10 -9 32.0 9.0 0 0 NAFCGM34/2 Waste Saprock 7.5 1.485 <0.01 0 10 -10 33.3 9.0 0 0 NAFCGM34/3 Waste Diorite 8.2 0.407 0.22 7 69 -62 10.2 NAFCGM34/4 Waste Diorite 8.2 0.335 0.20 6 100 -94 16.3 NAFCGM34/5 Waste Diorite 8.2 0.298 0.08 2 89 -86 36.2 NAFCGM34/6 Waste Diorite 8.1 0.326 0.08 0.074 2 108 -106 -106 44.1 NAFCGM34/7 Waste Shear Zone 8.3 0.523 0.79 0.748 24 186 -162 -163 7.7 10.4 0 0 NAFCGM34/8 Waste Diorite 8.3 0.385 0.58 0.542 18 113 -95 -96 6.4 10.7 0 0 NAFCGM34/9 Waste Dyke 8.3 0.381 0.25 8 101 -93 13.2 NAFCGM34/10 Waste Diorite 8.4 0.300 0.14 4 81 -77 18.9 NAFCGM34/11 Waste Diorite 8.4 0.383 0.33 0.343 10 92 -82 -82 9.1 NAFCGM34/12 Low Grade Ore Diorite 8.2 0.418 1.08 0.980 33 92 -58 -62 2.8 11.0 0 0 NAFCGM34/13 Waste Diorite 8.4 0.371 0.35 0.302 11 74 -63 -64 6.9 NAFCGM34/14 Waste Diorite 8.4 0.380 0.58 18 101 -83 5.7 11.1 0 0 NAFCGM34/15 Low Grade Ore Diorite 8.5 0.482 0.97 0.909 30 88 -59 -61 3.0 11.0 0 0 NAFCGM34/16 Waste Diorite 8.5 0.365 0.12 4 71 -67 19.3 NAFCGM34/17 Waste Diorite 8.4 0.445 0.42 13 98 -85 7.6 NAFCGM34/18 Waste Diorite 8.4 0.489 0.32 10 100 -90 10.2 NAFCGM34/19 Waste Diorite 8.4 0.441 0.33 0.290 10 82 -72 -73 8.1 NAFCGM34/20 Waste Diorite 8.3 0.420 0.33 10 88 -77 8.7 NAFCGM34/21 Waste Diorite 8.4 0.369 0.26 0.256 8 72 -64 -65 9.1 NAFCGM34/22 Waste Diorite 8.5 0.355 0.30 0.322 9 62 -53 -52 6.7 NAFCGM34/23 Low Grade Ore Diorite 8.2 0.342 0.67 0.623 21 299 -278 -280 14.6 10.8 0 0 NAFCGM34/24 Low Grade Ore Fault Zone 8.4 0.402 0.61 0.559 19 85 -66 -67 4.5 11.0 0 0 NAFCGM34/25 Waste Diorite 8.4 0.399 0.54 17 72 -56 4.4 10.8 0 0 NAFCGM34/26 Waste Diorite 8.4 0.417 0.51 16 75 -59 4.8 11.0 0 0 NAFCGM34/27 Low Grade Ore Diorite 8.3 0.439 0.88 0.810 27 72 -45 -47 2.7 11.0 0 0 NAFCGM34/28 Waste Diorite 8.4 0.435 0.53 0.502 16 106 -90 -91 6.5 10.8 0 0 NAFCGM34/29 Low Grade Ore Diorite 8.4 0.447 1.04 0.974 32 102 -70 -72 3.2 10.6 0 0 NAFCGM34/30 Waste Diorite 8.4 0.488 0.60 0.546 18 108 -90 -91 5.9 10.6 0 0 NAFCGM34/31 Waste Shear Zone 8.4 0.508 0.90 0.845 28 152 -124 -126 5.5 10.1 0 0 NAFCGM34/32 Low Grade Ore Shear Zone 8.2 0.419 0.60 18 170 -152 9.3 10.3 0 0 NAFKEY ARD Classification KeypH1:2 = pH of 1:2 extract NAPP = Net Acid Producing Potential (kgH2SO4/t) NAF = Non-Acid FormingEC1:2 = Electrical Conductivity of 1:2 extract (dS/m) NAGpH = pH of NAG liquor PAF = Potentially Acid FormingMPA = Maximum Potential Acidity (kgH2SO4/t) NAG(pH4.5) = Net Acid Generation capacity to pH 4.5 (kgH2SO4/t) UC = Uncertain () show expected class.ANC = Acid Neutralising Capacity (kgH2SO4/t) NAG(pH7.0) = Net Acid Generation capacity to pH 7.0 (kgH2SO4/t)

Table B2: Acid forming characteristics of drill-hole E42D1634 samples, Cowal Open Pit Extension Project.

Sample ID Ore/ Waste Lithology pH1:2 EC1:2

ACID-BASE ANALYSIS NAG TESTARD

Classification

Ca Mg K Na

CGM32/1 Alluvium 6.7 2.245 1.0 2.4 0.5 0.9 4.8 18.0

CGM32/2 Alluvium 6.2 3.275 1.4 3.4 0.4 1.0 6.2 16.2

CGM32/3 Saprolite 6.3 4.620 2.8 6.8 0.6 3.8 13.9 27.3

CGM32/4 Saprolite 7.9 3.875 19.3 6.0 0.6 2.2 28.1 7.8

CGM32/5 Saprock 7.2 6.616 2.3 4.2 0.4 1.5 8.4 18.2

CGM32/6 Saprock 7.1 5.238 3.4 6.9 0.5 4.7 15.5 30.3

CGM32/7 Saprock 7.2 3.370 2.8 4.9 0.2 4.3 12.3 35.2

CGM32/8 Saprock 7.3 2.129 2.1 3.2 0.4 1.6 7.4 21.9

CGM34/1 Saprock 7.6 2.100 2.5 4.0 0.4 4.2 11.0 37.9

CGM34/2 Saprock 7.5 1.485 3.2 4.8 0.3 7.6 15.9 47.8

CGM32/10 Diorite 8.5 0.307 23.4 2.2 0.5 0.4 26.6 1.5

CGM32/20 Diorite 8.5 0.508 23.8 2.4 1.2 0.4 27.8 1.5

CGM32/27 Diorite 8.6 0.390 22.3 1.5 1.5 0.3 25.6 1.2

CGM32/28 Diorite 8.3 0.332 24.0 2.0 0.9 0.4 27.4 1.4

CGM34/17 Diorite 8.4 0.445 23.1 2.2 1.6 0.3 27.2 1.2

CGM34/30 Diorite 8.4 0.488 22.8 2.0 1.7 0.4 27.0 1.5

CGM32/11 Dyke 8.2 0.394 22.6 1.3 0.7 0.2 24.8 0.7

CGM34/9 Dyke 8.3 0.381 21.8 1.5 0.9 0.3 24.6 1.4

CGM34/7 Shear Zone 8.3 0.523 21.6 3.2 1.7 0.3 26.8 1.0

CGM34/31 Shear Zone 8.4 0.508 21.3 2.0 2.4 0.2 25.9 0.6

KEYpH1:2 = pH of 1:2 extract CEC = Cation Exchange Capacity (meq/100g)

EC1:2 = Electrical Conductivity of 1:2 extract (dS/m) ESP = Exchangeable Sodium Percent (%)

Table B3: pH and EC, exchangeable cations, cation exchange capacity and exchangeable sodium percent for the selected drill-hole samples from the Cowal Open Pit Extension Project.

CEC ESPSample CodeSample

DescriptionpH1:2 EC1:2

Exch. Cations (meq/100g)

CGM32/2 CGM32/3 CGM32/5 CGM34/2 CGM32/10 CGM32/14 CGM32/33 CGM34/25 CGM34/30 CGM32/11 CGM34/31 CGM34/12 CGM34/23 CGM34/24 CGM34/32

Alluvium Saprolite DykeShear Zone

Fault Zone

Shear Zone

Ag mg/kg 0.01 0.14 0.18 0.33 0.22 0.25 0.2 0.31 0.35 0.46 0.45 0.75 0.7 0.62 0.67 1.03

Al % 0.005% 4.075% 4.559% 12.281% 8.769% 8.575% 8.407% 9.435% 9.585% 9.246% 7.571% 9.132% 8.875% 9.622% 9.368% 7.785%

As mg/kg 0.5 22.8 59.5 60.3 106.0 35.8 11.0 16.7 20.1 8.9 44.0 91.4 111.5 91.3 27.0 38.6

B mg/kg 50 < < < 57 80 < < < < < 124 < < < <

Ba mg/kg 0.1 144.1 114.6 790.8 256.8 401.3 349.3 344.9 400.7 719.1 366.2 724.6 195.6 413.8 300.3 330.1

Be mg/kg 0.05 1.37 0.61 1.54 0.58 0.84 0.91 0.81 0.81 0.75 0.94 1.29 0.63 0.78 0.83 0.82

Ca % 0.005% 0.051% 0.044% 0.095% 1.967% 4.195% 5.928% 4.593% 4.204% 3.938% 4.496% 4.759% 3.496% 3.767% 4.021% 5.828%

Cd mg/kg 0.02 0.03 0.08 0.53 0.45 0.09 0.07 0.06 0.06 0.16 0.07 0.32 0.13 0.04 0.08 0.19

Co mg/kg 0.1 3.0 1.7 46.6 26.8 25.0 22.5 22.1 16.7 14.7 21.5 13.6 20.2 17.0 17.5 17.9

Cr mg/kg 5 35 14 19 22 31 25 < 9 < 12 7 23 9 9 5

Cu mg/kg 1 42 45 272 186 152 92 209 114 151 296 166 87 102 206 420

Fe % 0.01% 5.62% 7.30% 10.11% 7.16% 7.71% 6.49% 6.80% 5.61% 5.28% 7.68% 4.46% 5.87% 5.66% 5.61% 5.53%

Hg mg/kg 0.001 0.007 0.010 0.017 0.007 0.002 < < 0.003 0.008 0.002 0.050 0.053 0.008 0.007 0.025

K % 0.002% 0.598% 0.280% 1.666% 1.231% 1.616% 2.424% 1.326% 2.147% 1.951% 1.877% 4.446% 2.385% 2.351% 2.852% 3.250%

Mg % 0.002% 0.186% 0.127% 0.402% 1.333% 2.489% 1.794% 1.842% 1.666% 1.425% 2.125% 1.377% 2.514% 1.387% 1.516% 1.277%

Mn mg/kg 1 108 54 3080 1330 1322 1375 1330 1339 1249 1476 1387 1396 1105 1327 1620

Mo mg/kg 0.1 0.5 0.9 1.1 0.8 1.0 0.7 0.7 0.6 0.3 0.8 2.9 0.6 0.6 0.5 0.9

Na % 0.002% 0.247% 0.191% 0.396% 3.304% 3.478% 1.838% 3.703% 3.583% 3.863% 1.994% 0.249% 2.425% 3.749% 2.624% 1.017%

Ni mg/kg 1 7 5 10 15 21 17 8 8 6 11 8 15 9 8 9

P mg/kg 50 94 72 751 1065 1144 983 1760 1151 1191 1567 1297 920 1103 1081 1041

Pb mg/kg 0.5 25.3 16.7 25.2 7.0 8.1 6.0 4.6 5.5 4.6 7.7 14.2 10.6 6.5 6.1 10.2

Sb mg/kg 0.05 2.07 3.33 8.09 4.99 1.66 1.93 1.48 2.68 2.41 2.63 11.08 4.09 3.25 3.77 5.08

Se mg/kg 0.01 0.05 0.15 0.06 0.07 0.08 0.07 0.11 0.11 0.15 0.22 0.15 0.18 0.14 0.17 0.39

Si % 0.1% 37.3% 29.4% 23.7% 25.5% 26.7% 22.3% 24.2% 23.5% 23.6% 25.8% 21.9% 22.6% 24.4% 23.6% 22.4%

Sn mg/kg 0.1 2.1 1.0 1.0 0.6 0.6 0.5 0.7 0.6 0.7 1.0 0.8 0.5 0.6 0.5 0.5

Th mg/kg 0.01 10.12 3.24 2.67 1.51 1.60 1.29 1.50 1.52 1.51 2.84 1.63 1.13 1.48 1.42 1.40

U mg/kg 0.01 2.11 1.46 1.77 0.71 1.07 0.83 1.03 1.02 0.99 1.95 0.92 0.87 1.02 0.95 0.84

V mg/kg 1 120 95 409 329 297 290 310 245 210 248 239 251 237 232 212

Zn mg/kg 1 42 12 112 126 100 92 94 112 122 125 113 134 99 121 103

< element at or below analytical detection limit.

Table B4: Multi-element composition of selected drill-hole samples, Cowal Open Pit Extension Project.

Element UnitDetect. Limit

Sample Description/Code

Waste Low Grade Ore

Saprock Diorite Diorite



Fault Zone

Shear Zone

Ag 0.07 - 1 2 1 1 1 2 2 2 2 3 3 3 3 3Al 8.2% - - - - - - - - - - - - - - -As 1.5 3 5 5 6 4 2 3 3 2 4 5 6 5 4 4B 10 <2 <2 <2 2 2 <2 <2 <2 <2 <2 3 <2 <2 <2 <2

Ba 500 - - - - - - - - - - - - - - -Be 2.6 - - - - - - - - - - - - - - -Ca 4.0% - - - - - - - - - - - - - - -Cd 0.11 - - 2 1 - - - - - - 1 - - - -Co 20 - - 1 - - - - - - - - - - - -Cr 100 - - - - - - - - - - - - - - -Cu 50 - - 2 1 1 - 1 1 1 2 1 - - 1 2Fe 4.1% - - 1 - - - - - - - - - - - -Hg 0.05 - - - - - - - - - - - - - - -K 2.1% - - - - - - - - - - - - - - -

Mg 2.3% - - - - - - - - - - - - - - -Mn 950 - - 1 - - - - - - - - - - - -Mo 1.5 - - - - - - - - - - - - - - -Na 2.3% - - - - - - - - - - - - - - -Ni 80 - - - - - - - - - - - - - - -P 1000 - - - - - - - - - - - - - - -

Pb 14 - - - - - - - - - - - - - - -Sb 0.2 3 3 5 4 2 3 2 3 3 3 5 4 3 4 4Se 0.05 - 1 - - - - 1 1 1 2 1 1 1 1 2Si 27.7% - - - - - - - - - - - - - - -Sn 2.2 - - - - - - - - - - - - - - -Th 12 - - - - - - - - - - - - - - -U 2.4 - - - - - - - - - - - - - - -V 160 - - 1 - - - - - - - - - - - -Zn 75 - - - - - - - - - - - - - - -

*Bowen H.J.M.(1979) Environmental Chemistry of the Elements.

Table B5: Geochemical abundance indices for selected drill-hole samples, Cowal Open Pit Extension Project.

*Mean Crustal

Abundance


ElementWaste Low Grade Ore




Fault Zone

Shear Zone

pH 0.1 6.2 6.3 7.2 7.5 8.5 8.6 8.4 8.4 8.4 8.2 8.4 8.2 8.2 8.4 8.2EC dS/m 0.001 3.275 4.620 6.616 1.485 0.307 0.298 0.349 0.399 0.488 0.394 0.508 0.418 0.342 0.402 0.419

SO4 mg/l 0.3 260.4 132.4 177.7 89.7 10.1 25.6 47.5 108.1 178.1 53.8 98.5 122.5 78.5 41.9 92.1Cl mg/l 5.0 1300 675 1050 445 39 23 35 31 36 32 35 25 27 31 40

Al mg/l 0.01 < < < < 0.15 0.2 0.3 0.2 0.3 0.13 0.19 0.12 0.36 0.37 0.24B mg/l 0.01 0.1 0.09 0.05 < 0.04 0.03 0.04 0.06 0.04 0.02 0.04 0.03 0.02 0.04 0.03

Ca mg/l 0.01 38.39 16.18 39.13 1.74 7.98 8.74 10.52 12.14 25.76 12.61 14.66 16.79 10.02 7.81 14.35Cr mg/l 0.01 < < < < < < < < < < < < < < <Cu mg/l 0.01 < < < < < < < < < < < < < < <Fe mg/l 0.01 0.1 < < 0.02 < 0.06 < 0.03 0.27 < 0.02 0.01 0.04 0.04 <K mg/l 0.1 22 7 11.4 1.8 19.2 50.5 17.5 63.2 57 57 35.7 56.9 51 43.2 30.9

Mg mg/l 0.01 74.96 28.8 58.62 2.18 3.54 1.77 5.42 3.4 9.77 3.47 7.02 3.98 2.85 2.71 7.96Mn mg/l 0.01 0.91 0.04 0.23 < < < < 0.01 0.03 < < 0.01 < < 0.01Na mg/l 0.1 750.5 451.2 612.7 353.4 81.7 43.8 80.4 85.4 88 59.4 100.9 61.1 75.9 86.4 97Ni mg/l 0.01 < < < < < < < < < < < < < < <P mg/l 0.1 < < < < < < < < < < < < < < <Si mg/l 0.05 7.11 6.55 3.9 7.76 2.27 2.46 1.64 2.06 1.95 2.15 1.69 2.25 1.91 1.86 1.54V mg/l 0.01 0.01 < < 0.02 < 0.01 < < < < < < < < <Zn mg/l 0.01 0.02 < < < < < < < < < < < < < <

Ag ug/l 0.01 < < < < < < < < 0.02 < < < < 0.03 <As ug/l 0.1 1.1 6.6 0.4 25.9 5.9 2.9 0.9 2.4 0.9 5.3 0.9 47.3 4.7 2.2 2.8Ba ug/l 0.05 66.39 20.92 33.37 2.3 15.32 45.83 7.62 49.7 53.61 89.17 49.21 31.32 7.77 49.58 33.47Be ug/l 0.1 < < < < < < < < < < < < < < <Cd ug/l 0.02 0.2 0.12 0.3 0.08 0.06 0.06 0.03 0.04 0.06 0.02 0.05 < < 0.17 0.04Co ug/l 0.1 4.8 0.3 2.3 0.1 < < < < 0.8 < < < < 0.2 <Hg ug/l 0.1 0.2 0.2 0.3 < 0.1 < < < < 0.1 0.2 < < < <Mo ug/l 0.05 0.17 0.06 0.14 4.02 4.73 3.49 3.8 12.83 8.73 47.25 10.9 16.19 9.68 11.71 4.7Pb ug/l 0.5 0.8 < < < 1.3 < < < < < < < < < <Sb ug/l 0.01 0.06 0.15 0.56 1.89 1.48 2.69 0.93 4.11 1.68 2.25 1.45 6.69 3.02 2.85 1.47Se ug/l 0.5 4.8 3.1 3.2 2.5 < < 0.5 0.9 1.1 1.2 0.9 < < 1 0.7Sn ug/l 0.1 < < < < < < < < < < < < 0.2 < <Th ug/l 0.005 < < < < < < < < 0.006 < < < < < <U ug/l 0.005 0.03 0.021 0.015 0.013 0.038 0.062 0.03 0.18 0.12 0.14 0.057 0.171 0.063 0.06 0.056

< element at or below analytical detection limit.

Table B6: Chemical composition of water extracts from selected drill-hole samples, Cowal Open Pit Extension Project.

Detection Limit


Parameter UnitWaste Low Grade Ore





ATTACHMENT C

Ore Sample Test Results

Table C1: Acid forming characteristics of selected drill-hole samples representing ore from the Modification Pit Extension.

Table C2: Multi-element composition and geochemical abundance indices for selected drill-hole samples representing ore from the Modification Pit Extension.

ACID-BASE ANALYSIS NAG TEST

From To Inter. Total %S

MPA ANC NAPP ANC/ MPA

NAGpH NAG(pH4.5)

GRVPD05 E42D1007 342 354 12 Primary Diorite 8.1 0.847 1.02 31 111 -80 3.6 8.1 0 NAF

GRVLV01 E42D1064 367 377 10 Primary LVC 9.1 0.846 1.18 36 140 -104 3.9 9.1 0 NAF

GRVUV02 E42D1082 220 231 11 Primary UVC 7.0 0.601 0.66 20 26 -6 1.3 7.0 0 NAF

GRVLV03 E42D1119 360 371 11 Primary LVC 8.8 0.578 0.76 23 128 -105 5.5 8.8 0 NAF

GRVUV05 E42D1162 216 226 10 Primary UVC 9.1 0.971 2.02 62 131 -69 2.1 9.1 0 NAF

KEY ARD Classification KeypH1:2 = pH of 1:2 extract NAPP = Net Acid Producing Potential (kgH2SO4/t) NAF = Non-Acid FormingEC1:2 = Electrical Conductivity of 1:2 extract (dS/m) NAGpH = pH of NAG liquor PAF = Potentially Acid FormingMPA = Maximum Potential Acidity (kgH2SO4/t) NAG(pH4.5) = NAG capacity to pH 4.5 (kgH2SO4/t) PAF/LC = PAF Low CapacityANC = Acid Neutralising Capacity (kgH2SO4/t)

Table C1: Acid forming characteristics of selected drill-hole samples representing ore from the Cowal Open Pit Extension Project.

Sample IDDrill-Hole

ID

Depth (m)Lithology pH1:2 EC1:2

Geochem. Class.

Primary Diorite

Primary Diorite

GRVPD05 GRVUV02 GRVUV05 GRVLV01 GRVLV03 GRVPD05 GRVUV02 GRVUV05 GRVLV01 GRVLV03

Ag mg/kg na na na na na 0.07 na na na na naAl % na na na na na 8.2% na na na na naAs mg/kg na na na na na 1.5 na na na na naB mg/kg <10 <10 <10 <10 <10 10 - - - - -

Ba mg/kg 20 20 30 20 60 500 - - - - -Be mg/kg 0.19 0.3 0.41 0.35 0.46 2.6 - - - - -Ca % 2.10% 0.92% 4.27% 3.36% 3.32% 4.0% - - - - -Cd mg/kg 2.26 2.17 4.18 0.99 2.27 0.11 4 4 5 3 4Co mg/kg 14.3 4.9 13.2 16.6 13.6 20 - - - - -Cr mg/kg 9 5 7 21 16 100 - - - - -Cu mg/kg 173 34.4 134.5 102 105.5 50 1 - 1 - -Fe % 3.98% 3.14% 4.49% 5.27% 4.66% 4.1% - - - - -Hg mg/kg 0.04 0.02 0.04 0.01 0.02 0.05 - - - - -K % 0.10% 0.14% 0.17% 0.13% 0.21% 2.1% - - - - -

Mg % 1.38% 0.57% 0.61% 1.52% 1.00% 2.3% - - - - -Mn mg/kg 1060 1480 1510 1300 1820 950 - - - - -Mo mg/kg 1.28 1.3 2.37 1.27 0.74 1.5 - - - - -Na % 0.03% 0.02% 0.01% 0.03% 0.02% 2.3% - - - - -Ni mg/kg 5.3 0.5 4.3 10 5 80 - - - - -P mg/kg 1230 810 1410 1170 1370 1000 - - - - -Pb mg/kg 5.1 147 121 6.1 41 14 - 3 3 - 1Sb mg/kg 0.55 0.45 1.56 0.48 0.88 0.2 1 1 2 1 2Se mg/kg 0.7 0.5 1.1 1.4 0.9 0.05 3 3 4 4 4Sn mg/kg 0.2 <0.1 <0.1 0.2 <0.1 2.2 - - - - -Th mg/kg 0.8 0.6 0.8 0.7 1.1 12 - - - - -U mg/kg 0.29 0.14 0.22 0.27 0.4 2.4 - - - - -V mg/kg 67 7 18 92 38 160 - - - - -Zn mg/kg 412 392 742 256 408 75 2 2 3 1 2

< element at or below analytical detection limit. *Bowen H.J.M.(1979) Environmental Chemistry of the Elements.

Table C2: Multi-element composition and geochemical abundance indices for selected drill-hole samples representing ore from the Cowal Open Pit Extension Project.

Primary UVC Primary LVC *Mean Crustal

AbundanceElement Unit

Primary UVC Primary LVC

appendix c geochemistry assessment - evolution mining · environmental geochemistry assessment of...

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