SPINIFEX RIDGE PROJECT - EPA WAepa.wa.gov.au/sites/default/files/PER_documentation/Appendix M... · SPINIFEX RIDGE PROJECT GEOCHEMICAL CHARACTERISATION OF ... placed on waste-dumps

MOLY MINES LIMITED

SPINIFEX RIDGE PROJECT

GEOCHEMICAL CHARACTERISATION OF

REGOLITH, WASTE-BEDROCK AND

LOW-GRADE-ORE SAMPLES

Implications for Mine-Waste Management

GRAEME CAMPBELL AND ASSOCIATES PTY LTD

(ACN 061 827674) SEPTEMBER 2006

Job No. 0428

11578-RP-001-EV-0020_0

Graeme Campbell & Associates Pty Ltd

i

TABLE OF CONTENTS Page Nos. 1.0 INTRODUCTION……. .......................................................................................1 2.0 STUDY APPROACH….......................................................................................2 2.1 Testwork Programme..................................................................................2 2.1.1 Samples.........................................................................................2 2.1.2 Testwork .......................................................................................3 2.2 Calculated Parameters.................................................................................4 2.3 Classification Criteria .................................................................................4 2.4 Mine-Waste Weathering within the Australian Arid-Zone...........................8 3.0 GEOCHEMISTRY OF REGOLITH SAMPLES ..................................................11 3.1 Acid-Base Chemistry and Salinity...............................................................11 3.2 Multi-Element Composition........................................................................12 3.3 Mineralogy and Clay-Surface Chemistry.....................................................13 4.0 GEOCHEMISTRY OF WASTE-BEDROCK SAMPLES.....................................14 4.1 Acid-Base Chemistry and Salinity...............................................................14 4.2 Multi-Element Composition and Mineralogy ..............................................15 5.0 GEOCHEMISTRY OF LOW-GRADE-ORE SAMPLES .....................................16 6.0 MANAGEMENT IMPLICATIONS.....................................................................17 6.1 Regoliths……….. .......................................................................................17 6.2 Waste-Bedrocks.. ........................................................................................17 6.3 Low-Grade Ores.. .......................................................................................19 7.0 REFERENCES……….. .......................................................................................20

11578-RP-001-EV-0020_0


ii

TABLES, FIGURES AND APPENDICES (At Back of Report Text)

TABLES: Table 3.1: Acid-Base-Analysis, Salinity and Net-Acid-Generation Results

for Regolith Samples Table 3.2: Multi-Element-Analysis Results for Regolith Samples Table 3.3: Minerlogical and Clay-Surface-Chemistry Results for Regolith

Samples Table 4.1: Acid-Base-Analysis, Salinity and Net-Acid-Generation Results

for Waste-Bedrock Samples Table 4.2: Multi-Element-Analysis Results for Waste-Bedrock Samples

(Felsics) Table 4.3: Multi-Element-Analysis Results for Waste-Bedrock Samples

(Mafics) Table 4.4: Mineralogical Results for Waste-Bedrock Samples Table 5.1: Acid-Base-Analysis, Salinity and Net-Acid-Generation Results

for Low-Grade-Ore Samples Table 5.2: Multi-Element-Analysis Results for Low-Grade-Ore Samples Table 5.3: Mineralogical Results for Low-Grade-Ore Samples FIGURES: Figure 1: pH-Buffering Curves for Waste-Bedrock Samples Figure 2: pH-Buffering Curves for Low-Grade-Ore Samples APPENDICES: Appendix A: Details of Sampling Programme Appendix B: Testwork Methods Appendix C: Laboratory Reports

11578-RP-001-EV-0020_0

SUMMARY OF TECHNICAL TERMS EMPLOYED IN THIS REPORT

ACRONYM PARAMETER DEFINITION/DETERMINATION UNIT

AFP Acid-Formation Potential ARD Acid-Rock Drainage Total-S Total Sulphur Analysis Result % (w/w) Sulphide-S Sulphide Sulphur Testwork Result [i.e. Sulphide-S = Total-S - Sulphate-S] % (w/w) ANC Acid-Neutralisation Capacity Testwork Result kg H2SO4/tonne MPA Maximum-Potential Acidity Calculation kg H2SO4/tonne NAPP Net-Acid-Producing Potential Calculation kg H2SO4/tonne NAG Net-Acid Generation Testwork Result kg H2SO4/tonne NAF Non-Acid Forming Calculation: kg H2SO4/tonne

• Sulphide-S < 0.3 % • Sulphide-S ≥ 0.3 %, and negative-NAPP value with ANC/MPA ≥ 2.0

PAF Potentially-Acid Forming Calculation: kg H2SO4/tonne • Sulphide-S ≥ 0.3 %, and any positive-NAPP value • Sulphide-S ≥ 0.3 %, and a negative-NAPP value with ANC/MPA < 2.0

PAF-[SL] PAF-[Short-Lag] Estimation [e.g. inferred from 'kinetic' testing] PAF-[LL] PAF-[Long-Lag] Estimation [e.g. inferred from 'kinetic' testing] SOR Sulphide-Oxidation Rate Testwork Result [e.g. obtained from 'kinetic' testing] mg SO4/kg/week,

Notes:

The PAF-[SL] classification applies to PAF-materials (e.g. mine-wastes, and/or process-tailings) that are initially circum-neutral, but acidify (viz. pH less than 5) within weeks-to-months when exposed, and subjected to an "aggressive-weathering" regime typical of well-watered environments (e.g. where unsaturated-conditions prevail for at least a few days [via drainage/evaporation processes] between successive infiltration/flushing episodes that, in turn, occur regularly [e.g. monthly rainfall patterns comprising 1-2+ major-raindays of 10+ mm "on-average" during most of the annual hydrological-cycle]). The occurrence of thin, dilute films of pore-fluids on sulphide-grain surfaces which are regularly flushed constitutes an aeration/moisture regime that is near-optimal for sulphide-oxidation. In such well-watered settings, surface-zones of exposed mine-wastes/process-tailings seldom experience total-suctions in excess of 1+ bars (i.e. 0.1+ MPa). The PAF-[LL] classification applies to PAF-materials where exposure for years (even decades+) may be needed before acidification develops. Circum-neutral-pH during "lag-phase" weathering is chiefly due to "at-source" buffering by carbonate-minerals. Climate directly influences "lag-phase" duration, and a sulphide-gangue assemblage classified as PAF-[SL] in well-watered settings where the SOR is controlled by O2-supply, may instead be classified as PAF-[LL] in water-limited settings where the SOR is controlled by H2O-supply in terms of both total-suction, and infrequency of "flushing-episodes" (Campbell 2004, 2006). The formation of "secondary-oxidation-products" (e.g. Fe-oxyhydroxides) as indurated, and tightly adhering/cohering deposits, is typically enhanced during "lag-phase" weathering in water-limited settings, and is a further mechanism by with sulphide-oxidation is stifled under the ensuing "mild" weathering-regime. Surface-zones of exposed mine-wastes/process-tailings in such environments are typically characterised by total-suctions well in excess of 1 bar for most of the year. At high total-suctions, even the physical meaning of pore-fluid "films" becomes tenuous.

11578-RP-001-EV-0020_0


1

1.0 INTRODUCTION Moly Mines Limited is developing the Spinifex Ridge Project located c. 50 kms to the

north-east of Marble Bar, Western Australia.

Ore will be produced via open-pit mining, and the excavated waste-rock materials (viz.

regoliths and waste-bedrocks) placed on waste-dumps in the vicinity of the Pit.1

As part of the Pre-Feasibility Study (PFS) for the Project, Graeme Campbell &

Associates Pty Ltd (GCA) was previously commissioned to carry out a preliminary

programme of geochemical testwork on a range of regolith and waste-bedrock samples

derived from the Spinifex Ridge Deposit (GCA 2006).

As part of the Bankable-Feasibility Study (BFS), GCA was subsequently commissioned

to undertake follow-up testing of a range of additional regolith and waste-bedrock

samples, as well as testing of a range of low-grade-ore samples.

The 'Static-Testwork' Programme focused on Acid-Formation Potential (AFP), Multi-

Element Composition, and Mineralogy.2

The testwork results from the GCA (2006) work, and the current study, are presented

and discussed in this report as one, and implications for mine-waste management

highlighted.3

This study supplements the environmental investigations undertaken by Outback Ecology Services Pty Ltd for the Spinifex Ridge Project.

1 The term "regolith", as employed herein, broadly applies to lithotypes (of varying parent-bedrock origins) that are variously weathered, and above the geological "Base-of-Oxidation". 2 A 'Static-Testwork' Programme comprises "whole-rock" analyses and tests. 3 This report supersedes the GCA (2006) report.

11578-RP-001-EV-0020_0


2

2.0 STUDY APPROACH Details of the sampling and testwork programmes, and the calculations and criteria

employed for classifying the regolith, waste-bedrock and low-grade-ore samples into

AFP categories, are presented and discussed in the following sections.

The dynamics of mine-waste weathering within the Australian arid-zone are also

discussed, since sulphide-oxidation rates are slowed appreciably in water-limited (c.f.

well-watered) settings: sulphide-oxidation in the arid-zone is restricted to transient "weathering-pulses", as governed by episodic wet-spells, and the locus of weathering confined to the surficial-zone which is wetted/flushed by rainfall (Campbell 2006, 2004;

Alarcon Leon 2005). Such "arid-zone-weathering" greatly reduces the risk for acid-

formation/solute-mobilisation, and affords options for management (e.g. placement

beneath reach of the [shallow] wetting-front) which are generally much simpler, and

less costly, to achieve than those required in well-watered settings where the seasonal

wetting-front penetrates deeply, and where it is also necessary to restrict the O2-supply.

2.1 Testwork Programme 2.1.1 Samples

Details of the samples submitted for testing by GCA are presented in Appendix A, and

correspond to those submitted for the GCA (2006) work, and the current programme of

follow-up testing.

The samples correspond to down-hole intervals of 2-3 m.

It is assumed that the samples submitted for testing are representative of the major lithotypes to be produced during open-pit mining, and so provide a meaningful picture of the generic mine-waste geochemistry, especially in terms of the relative abundances

11578-RP-001-EV-0020_0


3

of sulphide- and carbonate-minerals, and minor-element enrichments, at the "metre-scale".

2.1.2 Testwork

The samples were assigned GCA Sample-Numbers, and relevant details recorded in the

GCA Sample-Register. All samples were crushed (nominal 2 mm), and pulped

(nominal 75 µm), for specific tests.

The testwork methods employed in this study are based on recognised procedures for

the geochemical characterisation of soils and mine-wastes (e.g. AMIRA 2002; Morin

and Hutt 1997; Smith 1992; Higginson and Rayment 1992; Coastech Research 1991;

BC AMD Task Force 1989).

Part of the testwork was carried out by Genalysis Laboratory Services [GLS]

(Maddington), and SGS Environmental Service [SGS] (Welshpool). The analyses

performed by GLS and SGS have NATA endorsement.4 Specialised testing (viz. auto-

titrations and Net-Acid-Generation [NAG] Tests) was undertaken by Dr. Graeme

Campbell in the GCA Testing-Laboratory (Bridgetown).

The mineralogical investigation was carried out at CSIRO (Bentley) for the regolith

samples, and by Dr. Roger Townend of Roger Townend & Associates (Malaga) for the

waste-bedrock and low-grade-ore samples.

Details of the testwork methods are presented in Appendix B, and copies of the

laboratory and mineralogical reports are presented in Appendix C.

4 NATA = National Association of Testing Authorities.

11578-RP-001-EV-0020_0


4

2.2 Calculated Parameters

The Maximum-Potential-Acidity (MPA) values (in kg H2SO4/tonne) of the samples

were calculated by multiplying the Sulphide-S values (in %) by 30.6. The

multiplication-factor of 30.6 reflects both the reaction stoichiometry for the complete-

oxidation of pyrite, and/or pyrrhotite, by O2 to "Fe(OH)3" and H2SO4, and the different

weight-based units of % and kg H2SO4/tonne. The samples subjected to mineralogical

assessment in the present study had a sulphide-mineral suite comprising mainly pyrite,

and/or pyrrhotite. The stoichiometry of pyrite/pyrrhotite-oxidation is discussed further

in Appendix B.

The Net-Acid-Producing-Potential (NAPP) values (in kg H2SO4/tonne) were calculated

from the corresponding MPA and Acid-Neutralisation-Capacity (ANC) values (i.e.

NAPP = MPA - ANC). NAPP calculations were not performed for samples with

Sulphide-S values less than 0.1 %.

2.3 Classification Criteria In terms of AFP, mine-wastes may be classified into one of the following categories,

viz.

• Non-Acid Forming (NAF).

• Potentially-Acid Forming (PAF).

There are no unifying, "standard" criteria for classifying the AFP of mine-wastes (e.g.

Price 2005; Campbell 2002a,b; Smith 1992), and reflects the diversity of sulphide- and

gangue-mineral assemblages within (un)mineralised-lithotypes of varying weathering-

and alteration-status. Rather, criteria for classifying AFP may need to be tailored to

deposit-specific geochemistry, and mineralogy, and site-specific climate.

11578-RP-001-EV-0020_0


5

The AFP-classification criteria often employed at mining-operations worldwide are:

• NAF: Sulphide-S < 0.3 %. For Sulphide-S ≥ 0.3 %, both a negative NAPP

value, and an ANC/MPA ratio ≥ 2.0.

• PAF: For Sulphide-S ≥ 0.3 %, any positive-NAPP value; negative-NAPP

value with an ANC/MPA ratio < 2.0.

In assessing the AFP of mine-wastes, there is consensus that lithotypes with Sulphide-S

contents less than c. 0.3 % are unlikely to oxidise at rates fast enough to result in

acidification (e.g. pH less than 4-5). This position assumes that the groundmass hosting

such "trace-sulphides" is not simply quartz, and/or clays (Price 2005; Price et al. 1997),

and that for a carbonate-deficient gangue, the sulphide-minerals are not unusually

reactive (e.g. sulphide-oxidation rates [SORs] less than c. 20-40 mg SO4/kg/flush) [= c. 1-2 kg SO4/tonne/year for weekly flushing/drying-cycles].5 A "cut-off" of 0.3 % for

Sulphide-S also accords with the findings of kinetic-testing (viz. Weathering-Columns)

conducted, since the late-1980s, by Dr. Graeme Campbell for mine-wastes of diverse

mineralogy in terms of AFP. In all likelihood, a "cut-off" somewhat above a Sulphide-

S values of 0.3 % should validly apply for "screening" PAF- and NAF-lithotypes under

the "mild" weathering conditions of the Australian arid-zone (see below).

The ANC/MPA criteria for the NAF category reflects the need to compensate for less-

than-perfect availability of alkalinity-forms (e.g. carbonate-minerals) for neutralisation

of acid produced through sulphide-oxidation. A less-than-perfect availability of

alkalinity-forms may arise from:

(a) Restricted accessibility of acid to carbonate-grains;

5 Although 'steady-state' SORs (at circum-neutral-pH) for Sulphide-S contents less than 0.3 % may indeed exceed 1-2 kg SO4/tonne/year, such rates are generally restricted to either sedimentary forms (e.g. framboidal-pyrites, and marcasites), or hydrothermal-sulphides that are ultrafine-grained, and atypically reactive.

11578-RP-001-EV-0020_0


6

(b) Rate-limiting dissolution of carbonates-grains near pH=6-7; and,

(c) Depletion of carbonate-minerals through rainfall-fed leaching within

waste-dumps.6

In terms of (a), restricted accessibility of acid to the surfaces of carbonate-grains may

occur at different spatial-scales (viz. at the "whole-rock-scale" where rapid flows of

Acid-Rock Drainage [ARD] by-pass the calcareous-matrix of rock-fragments [e.g.

limestones] via preferential-flow pathways within a waste-dump, and at the "pore/grain-

scale" in which the surfaces of carbonate-grains are "blinded/rimmed" by precipitates of

Fe(III)-oxyhydroxides [e.g. ferrihydrite-type phases]). As shown by Li (1997), Fe-rich

varieties of ferroan-carbonates are especially prone to "surface-armouring" effects (e.g.

kinetic-testing of pyritic tailings-solids containing pyrite, ankerites and siderites resulted

in acidic leachates when less than one-third of the carbonate-grains had dissolved). The

effectiveness, or otherwise, of circum-neutral buffering is closely tied to inter alia the

residence-time of pore-fluids in contact with carbonate-grain surfaces, and therefore a

function of mine-site climate. In water-limited settings where flushing from infiltration

is infrequent, and where moisture dynamics mainly involve slow unsaturated-flow

below "field-capacity" (c.f. regular, rapid flow rates near saturation in well-watered

settings), longer residence-times favour diffusion of soluble-alkalinity forms across

armoured carbonate-grains, and thereby favour neutralisation reactions.

To compensate for the effects of (a) to (c) above, some practitioners advocate that, for a

mine-waste sample to be classified as NAF, it must have an ANC/MPA ratio of at least

3.0 (see review of earlier literature by Smith [1992]). In recent years, fundamental-

research (especially estimation of reaction-rates for diverse sulphide/gangue-mineral

assemblages), and field-experience at mining operations world-wide, have shown that

the potential for ARD production is very low for mine-waste materials with ANC/MPA

6 Depletion of carbonate-minerals through dissolution in meteoric-waters is generally minimal in water-limited settings, especially within the "hydrologically-active-zone" (e.g. top 2-3 m) of a waste-dump, since re-precipitation occurs during evapo-concentration when strongly-desiccating conditions return after major wet-spells.

11578-RP-001-EV-0020_0


7

ratios greater than 2.0 (AMIRA 2002; Price et al. 1997, Currey et al. 1997, and Murray

et al. 1995).7 This ANC/MPA ratio is employed in the present work.8

The risk posed by handling PAF-lithotypes during the active-lifetime of a deposit is

governed primarily by the duration of the lag-phase (i.e. the period during which

sulphide-oxidation occurs, but acidification does not develop, due to circum-neutral

buffering by gangue-phases [chiefly carbonate-minerals]).9 Although the duration of

the lag-phase for mine-wastes at field-scale cannot be accurately predicted a priori, estimates (albeit approximate) may still be needed to identify threshold exposure-times

for the safe handling of PAF-lithotypes, and so reduce ARD risk. Estimates of SORs,

and lag-phase duration, may be obtained through programmes of kinetic-testing (viz.

Weathering-Columns), and consideration of inter alia the moisture/aeration-regimes of

exposed (i.e. uncovered) mine-wastes under the climatic conditions of the mine-site

(especially rainfall distribution in relation to Potential-Evapotranspiration [PET] rates,

as dicussed further below). In the absence of results from kinetic-testing, experience

permits "first-pass" estimates of SORs and lag-phase duration to be made from the

results of static-testing, and thereby used to further classify PAF-lithotypes into PAF-[Short-Lag] and PAF-[Long-Lag] sub-categories (see further below). Such "first-

pass" estimations are necessarily provisional, and subject to revision, in the light of the

outcomes of kinetic-testing, and field observations.

7 Such ANC/MPA ratios are consistent with those indicated from SORs, and carbonate-depletion rates, as reported in the International-Kinetic Database for mine-waste materials from around the world (Morin and Hutt 1997). 8 It should be noted that mining-regulators in Nevada (USA) classify a mine-waste sample as NAF, if it is characterised by an ANC/MPA ratio greater than 1.2 (US EPA 1994). This lower ANC/MPA ratio reflects the semi-arid conditions typically encountered at mine-sites in Nevada. Although utilised in the early-1990s, it is understood that an ANC/MPA ratio of 1.2 is still entertained by regulators in Nevada for "screening" PAF and NAF varieties of mine-wastes in semi-arid settings. 9 SO4 is still produced by sulphide-oxidation during the lag-phase, and appreciable amounts of soluble-forms of certain minor-elements (e.g. Ni and As) may be released at circum-neutral-pH during lag-phase weathering. However, in the latter case, the mine-wastes would need to be at least appreciably enriched in Total-Ni and Total-As to begin with.

11578-RP-001-EV-0020_0


8

2.4 Mine-Waste Weathering within the Australian Arid-Zone Sulphide-oxidation is promoted by moisture regimes where suphide-grain surfaces are

covered by thin films of (dilute) pore-fluids which favour exchange of reactants (e.g.

O2) and oxidation-products (e.g. SO4). Moist conditions, corresponding to total-

suctions within the near-bar range, are the norm at mine-sites in well-watered settings

where flushing by rainfall is frequent, and evaporative-drying is modest (e.g. west coast

of Tasmania, and New Zealand). Under these conditions, the rate of sulphide-oxidation

is limited by the supply of O2 (via either diffusion, or advection), so that controlling the

O2 supply is central to strategies for the longer-term containment of PAF mine-wastes

(e.g. isolation beneath earthen, barrier-cover systems where a compacted soil-layer of

fine-texture is permanently maintained near saturation to restrict O2-diffusive ingress).

An example of this approach is the multi-layered, barrier-cover system on the waste-

dumps at the Martha Mine in the north island of New Zealand (Miller and Brodie 2000).

At mine-sites in the Australian arid-zone, moist conditions seldom occur, and reflects

infrequent, transient wet-spells followed by rapid evaporative-drying, especially during

the summer months when diurnal, soil-thermal gradients within the top few decimetres

are marked (e.g. approaching 10 oC/cm [Rose 1968]), corresponding to PET rates of 10-

20+ mm/day. Dry and dusty conditions are therefore the norm where the residual-

moisture (viz. total-suctions well in excess of 10 bars) stifles sulphide-oxidation which

is no longer controlled by the O2 supply. Instead, sulphide-oxidation rates depend on

the frequency of episodic, major rain-days (e.g. 5-10+ mm/day) effective in flushing

sulphide-grains within the "hydrologically-active-surface-zone" of waste-rock dumps,

and low-grade-ore stockpiles (Campbell 2006). Furthermore, the rapid drying-out

following episodic flushing, and the extended period (e.g. ranging up to several months)

before the next flushing-event, promotes the formation of insoluble oxidation-products

(e.g. colloidal ferrihydrite-type phases) which tightly adhere/cohere to the reactive-sites

on sulphide-grain surfaces, and thereby retards subsequent reaction. This mechanism is

favoured during lag-phase (i.e. circum-neutral) weathering, since under strongly-acidic

(e.g. pH less than 2-3) conditions, sulphide-oxidation may continue at appreciable rates

11578-RP-001-EV-0020_0


9

without flushing, due to high osmotic-suctions that cause condensation of water-vapour

from the air, as well as precipitation and "swelling" of hygroscopic acidic-salts in

sulphide-grain-boundaries which exposes new reactive-sites (Jerz and Rimstidt 2004).

Numerous mechanisms therefore ensure that sulphide-oxidation within the arid-zone is

restricted to "weathering-windows" which are rainfall-driven and short-lived, and

closely parallels the "rainfall-pulse" dynamics characteristic of biological responses,

and energy-resource flows, in water-limited ecosystems generally (e.g. Schwinning et

al. 2004; Noy-Meir 1974).

Although difficult to project accurately, the indications are that, for a given assemblage

of sulphide- and carbonate-minerals, sulphide-oxidation rates in mine-wastes under

arid-zone-weathering conditions are 5-10+ times slower than those in well-watered

settings (Campbell, unpublished results). Accordingly, within the arid-zone, a PAF-

[Short-Lag] classification, corresponding to the onset of acidic conditions within

months-to-years, would generally apply to mine-wastes which:

(a) contain at least traces of sulphide-minerals which are ultra-reactive (e.g.

framboidal-pyrites and marcasites which invariably reflect sedimentary

origins); and,

(b) have a groundmass deficient in reactive carbonate-minerals (e.g. calcites,

dolomites and ankerites).

Mine-wastes containing traces of ultra-reactive-sulphides may be classified as PAF-

[Long-Lag], provided that reactive-carbonates (e.g. calcites) also occur. Where ultra-

reactive-sulphides are limited (e.g. medium/coarse-grained pyrite of volcanic origin), a

PAF-[Long-Lag] classification, corresponding to a lag-phase of decades, may still apply

in the arid-zone, even where the groundmass is deficient in reactive-carbonates.

11578-RP-001-EV-0020_0


10

An important consequent of arid-zone-weathering for mine-waste management is that

PAF mine-wastes may be securely isolated and contained in the longer-term by simply

placing them beneath the reach of the (shallow) seasonal wetting-front. Since the

distribution of rainfall and PET in the Outback is such that infiltration into medium-

textured soils is seldom deeper than c. 1-2 m, except in localised water-gaining areas

(i.e. topographic depressions), it is generally a straight forward exercise to isolate PAF

lithotypes in the construction, and closure, of waste-dumps.

In brief, the fundamental reaction-mechanisms of sulphide-oxidation are identical in well-watered and water-limited settings. However, due to both direct and indirect effects from water, arid-zone weathering is characterised by suppressed reaction rates, so that restricting the water-supply (c.f. O2-supply) is the first-order control strategy for the secure, longer-term containment of PAF-mine-wastes. That isolation of PAF-mine-wastes from water is straight forward to achieve within the Australian arid-zone, is self-evident.

11578-RP-001-EV-0020_0


11

3.0 GEOCHEMISTRY OF REGOLITH SAMPLES The testwork results on the geochemistry of the regolith samples are presented in Tables

3.1-3.3.

3.1 Acid-Base Chemistry and Salinity

Collectively, the samples were characterised by (Table 3.1):

• pH-(1:2) values of 7.7-10.0, and EC-(1:2) values of 0.051-0.30 mS/cm;10

• Sulphide-S values that ranged from less than 0.01 %, to 0.08 %; and,

• ANC values of 0.9-23 kg H2SO4/tonne.

The testwork results indicate that the Felsic- and Mafic-regoliths should not pose concerns for acid-formation through sulphide-oxidation (i.e. these regoliths are NAF with a negligible capacity to both produce, and consume, acid). The Felsic- and Mafic-regoliths are heavily leached with low contents of soluble-salts,

and so pose no salinity concerns for runoff-water quality, and plant growth (where they are employed as rooting-zone media in revegetation programmes). If the Felsic-, and/or Mafic-regoliths, are employed to sheet the upper/side-surfaces of the waste-dumps at decommissioning, then the vegetation communities will need to contend with alkaline conditions within their root-zones.

10 EC= Electrical-Conductivity. The pH-(1:2) and EC-(1:2) Tests (and other testwork) are described in Appendix B.

11578-RP-001-EV-0020_0


12

3.2 Multi-Element Composition The multi-element composition of selected regolith samples is indicated by the data

presented in Table 3.2.11 The corresponding element-enrichments, as indicated by the

values of the Geochemical-Abundance Index (GAI), are also presented in these

Tables.12 It should be noted that these element-enrichments are relative enrichments,

based on the element contents typically recorded for unmineralised soils, regoliths and

bedrocks (Bowen 1979).

The assayed samples generally had contents of major- and minor-elements below, or

close to, those typically recorded for unmineralised soils, regoliths, and bedrocks (Table

3.2).

One of the Felsic-regolith samples was variously enriched in Ag, As, Bi, Sb, and Mo.

However, the contents of these minor-elements were well within the range recorded for

mine-wastes produced at hard-rock mines in Western Australia.13 These enriched

minor-elements should correspond to stable forms sorbed to clays, sesquioxides, and

primary-silicates, and/or incorporated into the crystal-lattices of such minerals.14

The analysis results indicate that, geochemically, the Felsic- and Mafic-regoliths should be relatively "clean" (viz. low contents of environmentally-significant elements). Where minor-element enrichments occur, they should not be marked, and should not pose concerns for water-quality, and/or revegetation. A low "tenor" of minor-elements would generally be expected for regoliths derived from parent-bedrocks associated with low-grade Mo mineralisation.

11 The suite of elements listed in Table 3.2 is grouped into (a) the major-elements (viz. Na, K, Mg, Ca, Al and Fe) making-up the lattices of primary-silicates, clays, sesquioxides and carbonate-minerals, and (b) minor-elements. A distinction is made between minor-elements which, under neutral-to-alkaline conditions, occur (i) as cationic-hydrolysis forms (e.g. Cu), and (ii) as anions/oxyanions (e.g. Mo, and As). Anionic forms may exhibit moderate solubility under neutral-to-alkaline conditions. 12 The GAI is defined in Appendix B. 13 This statement is based on the experience of Dr. Graeme Campbell, since the late-1980s, in related testing of mine-waste samples derived from local iron-ore-, gold-, nickel-, and base-metal-mines. 14 Sorption reactions correspond to adsorption and precipitation reactions (Sposito 1984).

11578-RP-001-EV-0020_0


13

3.3 Mineralogy and Clay-Surface Chemistry The mineralogical results recorded for the selected regolith samples are presented in

Table 3.3. The values of the Cation-Exchange Capacities (CECs), and proportions of

major-cations making up the clay-exchange complex, are also indicated in this Table.15

The clay-mineral suite mainly comprised kaolinites with sub-ordinate illites and

montmorillonites (i.e. smectites).

The CEC values of the samples were 0.26-10 cmol (p+)/kg. The near-negligible CEC

value of 0.26 cmol (p+)/kg for sample GCA6179 reflects this sample being essentially

quartz. The occupancy of Na+ ions on the clay-exchange complex was less than 1-2 %

of the CEC, so the clays were non-sodic. Accordingly, clay-dispersion tendency, if any,

should be slight (ACMER 2004).

The testwork results indicate that the Felsic- and Mafic-regoliths should exhibit stability against clay-dispersion effects. In addition, deep-cracking behaviour, due to shrink-swell cycling by expansive-clays (e.g. smectites), should not be an issue.

15 The CEC values correspond to the use of 1 M-NH4-acetate (pH=7) [Higginson and Rayment 1992]. Where the clay-mineral suite is dominated by 'low-activity' clays (e.g. kaolinites), the CEC values determined herein are likely biased somewhat "on-the-high-side" (Rengasamy and Churchman 1999).

11578-RP-001-EV-0020_0


14

4.0 GEOCHEMISTRY OF WASTE-BEDROCK SAMPLES The testwork results on the geochemistry of the waste-bedrock samples are presented in

Tables 4.1-4.4, and shown on Figure 1.

4.1 Acid-Base Chemistry and Salinity Collectively, the samples were characterised by (Table 4.1):

• pH-(1:2) values of 8.8-10.0, and EC-(1:2) values of 0.11-0.64 mS/cm;

• Sulphide-S values that ranged from less than 0.01%, to 1.2 %;

• ANC values of 3.8-74 kg H2SO4/tonne;

• NAPP values that ranged from -58 kg H2SO4/tonne, to 29 kg

H2SO4/tonne; and,

• NAG-pH values of 2.8-10.3, and NAG values that ranged from less than

0.5 kg H2SO4/tonne, to 18 kg H2SO4/tonne.

As a group, the Mafic-waste-bedrock samples tended to have higher Sulphide-S values,

and ANC values. Of the 10 samples tested, 3 samples had Sulphide-S values above 0.3

%.

The 7 samples of Felsic-waste-bedrocks all had Sulphide-S values less than 0.3 %.

The shapes of the pH-buffering curves for selected waste-bedrock samples show a well-

defined "inflection-point" near pH=7, associated with acid-consumption by reactive-

carbonates. Calcites were identifed as trace/accessory components in the samples

subjected to mineralogical assessment (Table 4.4).

11578-RP-001-EV-0020_0


15

Although the number of samples tested was by no means marked, the indications are that the Felsic- and Mafic-waste-bedrocks should typically be classified as NAF, and reflects "minute/trace-sulphides" in a groundmass typically containing minute-to-trace

amounts of calcites, and locally, accessory amounts of calcites. Two of the Mafic-waste-bedrock samples were classified as PAF, and together represent a 6-m interval within drillhole SRD078 characterised by "trace-sulphides" in a "gutless-groundmass" in terms of circum-neutral buffering. 4.2 Multi-Element Composition and Mineralogy The assayed samples of waste-bedrocks were variously enriched in Ag, Cu, Cd, As, Bi,

Sb, Se, and Mo (Tables 4.2 and 4.3). However, the degree of enrichment in these

minor-elements was not marked, and there was no systematic difference between the

multi-element composition of the Mafic- and Felsic-waste-bedrock samples. The Cu

contents ranging up to 2,100 mg/kg reflect traces of chalcopyrite (Table 4.4).

The samples subjected to mineralogical assessment comprised mainly quartz,

plagioclases, amphiboles, and chlorites. The sulphide-mineral suite was co-dominated

by pyrite and pyrrhotite with sub-ordinate chalcopyrite (Table 4.4). Trace-to-accessory

amounts of calcites also occurred.

The analysis results indicate that, geochemically, the Felsic- and Mafic-waste-bedrocks should be relatively "clean" (viz. low contents of environmentally-significant elements). Where minor-element enrichments occur, they should not be marked, and should not pose concerns for water-quality, and/or revegetation. This situation parallels that for the regoliths (Section 3.2).

11578-RP-001-EV-0020_0


16

5.0 GEOCHEMISTRY OF LOW-GRADE-ORE SAMPLES The low-grade-ore samples were characterised by (Table 5.1):

• pH-(1:2) values of 9.5-10.1, and EC-(1:2) values of 0.075-0.28 mS/cm;

• Sulphide-S values that ranged from less than 0.05 %, to 0.72 %;

• ANC values of 5.3-55 kg H2SO4/tonne;

• NAPP values that ranged from -45 kg H2SO4/tonne, to 3.9 kg

H2SO4/tonne; and,

• NAG-pH values of 6.3-9.8, and NAG values less than 0.5 kg

H2SO4/tonne.

The shapes of the pH-buffering curves for selected low-grade-ore samples show a well-

defined "inflection-point" near pH=7, associated with acid-consumption by reactive-

carbonates. Calcites were identifed as trace/accessory components in the samples

subjected to mineralogical assessment, except for the lone sample of the Quartz-Zone-

low-grade-ore (Table 5.3).

The low-grade-ore samples assayed for multi-element composition were variously

enriched in Ag, Cu, Cd, Bi, Sb, Se, and Mo, although the degree of enrichment was not

marked (Table 5.2). The Cu contents ranged up to 1,800 mg/kg, associated with traces

of chalcopyrite, and the Mo contents ranged up to 540 mg/kg, associated chiefly with

molbdenite.

The samples subjected to mineralogical assessment comprised mainly quartz,

plagioclases, amphiboles, and chlorites. The sulphide-mineral suite was co-dominated

11578-RP-001-EV-0020_0


17

by pyrite, pyrrhotite and chalcopyrite (Table 4.4). Trace-to-accessory amounts of

calcites also occurred.

The testwork results indicate that all low-grade-ore samples, but one, were classified as NAF, and reflects "minute/trace-sulphides" in a groundmass with "trace-accessory-carbonates". The lone Mafic-low-grade-ore classified as PAF reflects "trace-sulphides" in a grounmass essentially devoid of carbonate-minerals. Since Mo solubility (chiefly as molybdate [MoO4] which behaves hydrogeochemically similar to that of SO4) is favoured under neutral-to-alkaline conditions (Smith et al. 1997), soluble-Mo forms should be produced during ageing of the low-grade-ores on the stockpiles which may remain for some years. Intutitively, under the arid-zone-weathering regime at the mine-site, the Total-Mo contents of several hundred mg/kg in the low-grade-ores is not expected to result in water-quality concerns. However, this projection would need to be confirmed through kinetic-testing (viz. Weathering-Columns) to assess the solubility behaviour of Mo associated with the weathering of "trace-molybdenite".16

16 Any kinetic-testing should employ rock-chips/fines of both low-grade-ores, and high-grade-ores, where the latter corresponds to an upper-limit in the amount of molybdenite undergoing weathering. In addition, the kinetic-testing should assess Mo-solubility behaviour under moisture/aeration-regimes which are near-optimal for sulphide-oxidation (e.g. AMIRA 2002), and the "flushing-frequency-dependence" of sulphide-oxidation which is more pertinent to the stockpiles in situ.

11578-RP-001-EV-0020_0


18

6.0 MANAGEMENT IMPLICATIONS In the present study, samples of regoliths, waste-bedrocks and low-grade ores derived

from the Spinifex Ridge Deposit, have been geochemically characterised.

Details of the sampling programme, testwork methods employed, and approach to

classifying the samples into AFP categories, are presented in Section 2, and Appendices

A and B. All testwork results are presented, and interpreted, in Sections 3 to 5.

The testing undertaken in this study provides a useful working-model of the

geochemical character of the major types of regoliths and waste-bedrocks to be

produced through open-pit mining. This working-model will necessarily need to be

confirmed (or refined) as the geological- and mining-models progressively evolve,

especially in relation to the nature of the 'as-produced' streams of mine-wastes.

Based on the testwork results obtained herein, implications for mine-waste management

are outlined in the following sections.

6.1 Regoliths

No geochemical concerns are foreseen for the Felsic- and Mafic-regoliths, and no

physical concerns are foreseen in terms of deep-cracking behaviour, and tendency for

clay-dispersion. However, the regoliths may still be prone to erosion on side-slopes

where fine-earth (viz. -2-mm) fractions are clay-poor (i.e. silt/sand-enriched), and so

weakly-cohesive [ACMER 2004]. These aspects need to be assessed by others.

6.2 Waste-Bedrocks The indications are that PAF-waste-bedrocks should be the exception to the rule, due to

a generic assemblage of "minute/trace-sulphides" in a groundmass that contains calcite,

albeit seldom more than a trace component. In the first instance, use of a Total-S value

11578-RP-001-EV-0020_0


19

of 0.30 % to distinguish between NAF- and PAF-waste-bedrocks is recommended for

the proposed waste-zone modelling, viz.

• NAF category for Total-S values less than, or equal to, 0.30 %; and,

• PAF category for Total-S values greater than 0.30 %.

It is understood that the Total-S values correspond to samples of down-hole intervals of

c. 2-3 m.

Since calcites are seldom present as more than a "trace-component", there is little point

in incorporating some measure of ANC in the criteria for "screening" PAF and NAF

varieties (e.g. use of Total-C [or some fraction of this] to estimate ANC).

Given the arid-zone-weathering regime at the mine-site, a "cut-off" of 0.30 % for Total-

S is deemed geochemically conservative, since ultra-reactive-sulphides in the Felsic-

and Mafic-waste-bedrocks are anticipated to be limited. However, a programme of

kinetic-testing would be needed to confirm (or refine) this projection.

6.3 Low-Grade Ores

The low-grade-ore stockpiles should not pose concerns for acid-formation. However, as

outlined above, further information (e.g. kinetic-testing) would be needed to allow

assessment of Mo-solubility behaviour during ageing on the stockpiles. Given the arid-

zone-weathering regime, any formation of soluble-Mo form should be restricted to the

surficial-zone subjected to infrequent infiltration/flushing, and so the loads of soluble-

Mo forms should be modest.

11578-RP-001-EV-0020_0


20

7.0 REFERENCES ACMER, 2004, "Identification and Management of Dispersive Mine Spoils", Final

Report, June 2004, Australian Centre for Mining Environmental Research.

Alarcon Leon E, 2005, "Pyrite Oxidation at Circum-Neutral-pH: Influence of Water

Content and Implications for Mine-Waste Management in Semi-Arid/Arid

Environments", Chapter 4 in "Pyrite Weathering and Lithium (Li+) Transport

Under Unsaturated Flow Conditions in Model and Mine-Tailing Systems",

Ph.D. Thesis, School of Earth and Geographical Sciences, The University of

Western Australia, Crawley.

AMIRA International Ltd, 2002, "ARD Test Handbook", Prepared by Ian Wark

Research Institute, and Environmental Geochemistry International Pty Ltd.

Berigari MS and Al-Any FMS, 1994, "Gypsum Determination in Soils by Conversion

to Water-Soluble Sodium Sulfate", Soil Science Society of America Journal, 58:1624-1627

Belzile N, Chen Y-W, Cai M-F and Li Y, 2004, "A Review on Pyrrhotite Oxidation",

Journal of Geochemical Exploration, 84:65-76.

Bowen HJM, 1979, "Environmental Chemistry of the Elements", Academic Press, New

York.

British Columbia Acid Mine Drainage Task Force Report, 1989, "Draft Acid Rock

Drainage Technical Guide. Volume 1".

Campbell GD, 2002a, "Geochemistry and Management of Pyritic Mine-Wastes: I.

Characterisation", in Proceedings of Workshop on "Soil Technology -

11578-RP-001-EV-0020_0


21

Contaminated Land", February 2002, Centre for Land Rehabilitation, University

of Western Australia.

Campbell GD, 2002b, "Geochemistry and Management of Pyritic Mine-Wastes: II.

Weathering Behaviour and Arsenic Solubility", in Proceedings of Workshop on

"Soil Technology - Contaminated Land", February 2002, Centre for Land

Rehabilitation, University of Western Australia.

Campbell GD, 2004, "Store/Release Covers in the Australian Outback: A Review",

Section 13 in the Proceedings from the Australian Centre for Geomechanics

seminar on "Mine Closure – Towards Sustainable Outcomes", 5-6 August,

Perth.

Campbell GD, 2006, "Acid-Formation Potential of Mine-Wastes: Sampling, Testwork

and Interpretation Approaches for the WA Goldfields", in the Goldfields

Environmental Management Groups "2006 Workshop on Environmental

Management", 24-26 May 2006, Kalgoorlie-Boulder. In addition, power-point

presentation titled: "Geochemistry of Mine-Wastes and Process-Tailings at Gold

and Nickel Mines in WA Goldfields: Manner and Rates of Weathering in

Water-Limited Environments". A copy of this presentation is available upon

request. ([email protected]).

Coastech Research Inc., 1991, "Acid Rock Drainage Prediction Manual".

Currey NA, Ritchie PJ and Murray GSC, 1997, "Management Strategies for Acid Rock

Drainage at Kidston Gold Mine, North Queensland", pp. 93-102 in McLean RW

and Bell LC (eds), "Third Australian Workshop on Acid Mine Drainage

Proceedings", Australian Centre for Minesite Rehabilitation Research.

Förstner U, Ahlf W and Calmano W, 1993, "Sediment Quality Objectives and Criteria

Development in Germany", Water Science & Technology, 28:307-316.

11578-RP-001-EV-0020_0


22

Graeme Campbell & Associates Pty Ltd, "Spinifex Ridge Project: Preliminary Testing

of Regolith and Waste-Bedrock Samples ['Static-Testwork'], Unpublished report

prepared for Moly Mines Limited.

Jambor JL, Dutrizac JE and Chen TT, 2000, "Contribution of Specific Minerals to the

Neutralization Potential in Static Tests", pp. 551-565 in "Proceedings from the

Fifth International Conference on Acid Rock Drainage", Volume I, Denver.

Jambor JL, Dutrizac JE, Groat LA and Raudsepp M, 2002, "Static Tests of

Neutralization Potentials of Silicate and Aluminosilicate Minerals",

Environmental Geology, 43:1-17.

Janzen MP, Nicholson RV and Scharer JM, 2000, "Pyrrhotite Reaction Kinetics:

Reaction Rates for Oxidation by Oxygen, Ferric Iron, and for Nonoxidative

Dissolution", Geochimica et Cosmochimica Acta, 64:1511-1522.

Jerz JK and Rimstidt JD, 2004, "Pyrite Oxidation in Moist Air", Geochimica et Cosmochimica Acta, 68:701-714.

Lenahan WC and Murray-Smith R de L, 1986, "Assay and Analytical Practice in the

South African Mining Industry", The South African Institute of Mining and

Metallurgy Monograph Series M6, Johannesburg.

Li MG, 1997, "Neutralization Potential Versus Observed Mineral Dissolution in

Humidity Cell Tests for Louvicourt Tailings", pp. 149-164 in "Proceedings of

the Fourth International Conference on Acid Rock Drainage", Volume I,

Vancouver.

Miller S and Brodie K, 2000, "Cover Performance for the Control of Sulfide Oxidation

and Acid Drainage from Waste Rock at the Martha Mine, New Zealand", pp. 99-

108 in Grundon NJ and Bell LC (eds), "Proceedings of the Fourth Australian

11578-RP-001-EV-0020_0


23

Workshop on Acid Mine Drainage", Australian Centre for Mining

Environmental Research.

Miller SD, Jeffery JJ and Donohue TA, 1994, "Developments in Predicting and

Management of Acid Forming Mine Wastes in Australia and Southeast Asia",

pp. 177-184 in "Proceedings of the International Land Reclamation and Mine

Drainage Conference and Third International Conference on the Abatement of

Acidic Drainage", Pittsburgh.

Miller S, Robertson A and Donohue T, 1997, "Advances in Acid Drainage Prediction

Using the Net Acid Generation (NAG) Test", pp. 535-547 in "Proceedings of the

Fourth International Conference on Acid Rock Drainage", Vancouver.

Morin KA and Hutt NM, 1997, "Environmental Geochemistry of Minesite Drainage:

Practical Theory and Case Studies", MDAG Publishing, Vancouver.

Murray GSC, Robertson JD and Ferguson KD, 1995, "Defining the AMD Problem. I.

A Corporate Perspective", pp. 3-15 in Grundon NJ and Bell LC (eds), "Second

Australian Acid Mine Drainage Workshop Proceedings", Australian Centre for

Minesite Rehabilitation Research.

Nicholson RV and Scharer JM, 1994, "Laboratory Studies of Pyrrhotite Oxidation

Kinetics", pp. 14-30 in Alpers CN and Blowes DW (eds), "Environmental

Geochemistry of Sulfide Oxidation", ACS Symposium Series 550, American

Chemical Society, Washington DC.

Noy-Meir I, 1974, "Desert Ecosystems: Higher Trophic Levels", Annual Review of Ecology and Systematics, 5:195-214.

11578-RP-001-EV-0020_0


24

O'Shay T, Hossner LR and Dixon JB, 1990, "A Modified Hydrogen Peroxide Method

for Determination of Potential Acidity in Pyritic Overburden", Journal of Environmental Quality, 19:778-782.

Price W, 2005, "Criteria Used in Material Characterization and the Prediction of

Drainage Chemistry: "Screaming Criteria"", Presentation B.1 in "Proceedings

of the 12th Annual British Columbia – MEND ML/ARD Workshop on

"Challenges in the Prediction of Drainage Chemistry", November 30 to

December 1, 2005, Vancouver, British Columbia.

Price WA, Morin K and Hutt N, 1997, "Guidelines for the Prediction of Acid Rock

Drainage and Metal Leaching for Mines in British Columbia: Part II.

Recommended Procedures for Static and Kinetic Testing", pp. 15-30 in

"Proceedings of the Fourth International Conference on Acid Rock Drainage",

Volume I, Vancouver.

Rayment GE and Higginson FR, 1992, "Australian Laboratory Handbook of Soil and

Water Chemical Methods", Inkata Press, Melbourne.

Rengasamy P and Churchman GJ, 1999, "Cation Exchange Capacity, Exchangeable

Cations and Sodicity", Chapter 9 in Peverill KI, Sparrow LA, and Reuter DJ

(eds), "Soil Analysis: An Interpretation Manual", CSIRO Publishing,

Collingwood.

Rimstidt JD and Newcomb WD, 1993, "Measurement and Analysis of Rate Data: The

Rate of Reaction of Ferric Iron With Pyrite", Geochimica et Cosmochimica Acta, 57:1919-1934.

Rimstidt JD and Vaughan DJ, 2003, "Pyrite Oxidation: A State-of-the-Art Assessment

of Reaction Mechanism", Geochimica et Cosmochimica Acta, 67:873-880.

11578-RP-001-EV-0020_0


25

Rose CW, 1968, "Water Transport in Soil With a Daily Temperature Wave. I. Theory

and Experiment", Australian Journal of Soil Research, 6:31-34.

Schwinning S, Sala OE, Loik ME and Ehleringer, 2004, "Thresholds, Memory and

Seasonality: Understanding Pulse Dynamics in Arid/Semi-Arid Ecosystems",

Oecologia, 141:191-193.

Shaw S, 2005, "Case Studies and Subsequent Guidelines for the Use of the Static NAG

Procedure", Presenttaion A.4 in "Proceedings of the 12th Annual British

Columbia – MEND ML/ARD Workshop on "Challenges in the Prediction of

Drainage Chemistry", November 30 to December 1, 2005, Vancouver, British

Columbia.

Smith A, 1992, "Prediction of Acid Generation Potential", in Hutchison IPG and Ellison

RD (eds), "Mine Waste Management", Lewis Publishers, Michigan.

Smith KS, Balistrieri LS, Smith SM and Severson RC, 1997, "Distribution and Mobility

of Molybdenum in the Terrestial Environment", pp. 23-46 in Gupta UC (ed.),

"Molybdenum in Agriculture", Cambridge University Press, Cambridge.

Sobek AA, Schuller WA, Freeman JR and Smith RM, 1978, "Field and Laboratory

Methods Applicable to Overburdens and Minesoils", EPA-600/2-78-054.

Sposito G, 1984, "The Surface Chemistry of Soils", Oxford University Press, Oxford.

Stevens RE and Carron MK, 1948, "Simple Field Test for Distinguishing Minerals by

Abrasion pH", American Mineralogist, 33:31-49.

U.S. Environmental Protection Agency, 1994, "Technical Document: Acid Mine

Drainage Prediction", EPA530-R-94-036, NTIS PB94-201829.

11578-RP-001-EV-0020_0


26

White AF and Brantley SL (eds.), 1995, "Chemical Weathering Rates of Silicate

Minerals", Reviews in Mineralogy, Volume 31, Mineralogical Society of

America, Washington, D.C.

11578-RP-001-EV-0020_0


TABLES

11578-RP-001-EV-0020_0

Table 3.1: Acid-Base-Analysis, Salinity and Net-Acid-Generation Results for Regolith Samples

GCA- DRILLHOLE & EC-(1:2) TOTAL-S TOTAL-C ANC NAPP NAG AFP SAMPLE LITHOTYPE DOWN-HOLE pH-(1:2) [mS/cm] (%) (%) kg H2SO4/tonne NAG-pH CATEGORY

NO. INTERVAL (m) GCA6061 Felsic SRD071, 46-50 7.7 (8.2) 0.051 (0.050) 0.03 (0.03) 0.07 0.9 (0.9) nc <0.5 6.6 NAF GCA6175 Felsic SRD054, 8-10 10.0 0.10 <0.01 0.09 11 nc nm nm NAF GCA6176 Felsic SRD080, 42-45 9.2 0.16 <0.01 0.05 6.8 nc nm nm NAF GCA6177 Felsic SRC123, 33-36 9.3 0.079 <0.01 0.06 4.7 nc nm nm NAF GCA6178 Felsic SRD073, 28-30 9.0 0.056 <0.01 0.02 3.9 nc nm nm NAF GCA6179 Felsic SRC133, 27-30 9.2 0.060 <0.01 0.04 1.5 nc nm nm NAF GCA6180 Felsic SRD066, 8-10 9.6 0.091 <0.01 0.05 7.4 nc nm nm NAF GCA6181 Felsic SRD055, 4-6 9.9 0.13 0.08 0.08 9.6 nc nm nm NAF GCA6182 Felsic SRC120, 3-6 9.8 0.13 <0.01 0.08 12 nc nm nm NAF

GCA6183 Mafic SRC100, 6-9 9.7 0.18 <0.01 0.04 21 nc nm nm NAF GCA6184 Mafic SRC118, 9-12 9.7 0.19 <0.01 0.05 23 nc nm nm NAF GCA6185 Mafic SRD059, 12-13 9.8 0.30 <0.01 0.13 16 nc nm nm NAF GCA6186 Mafic SRC118, 18-21 9.7 0.15 <0.01 0.11 18 nc nm nm NAF

Notes: EC = Electrical Conductivity; ANC = Acid-Neutralisation Capacity; NAPP = Net-Acid-Producing Potential; NAG = Net-Acid Generation; AFP = Acid-Formation Potential; NAF = Non-Acid Forming; nm = not measured; nc = not calculated. pH-(1:2) and EC-(1:2) values correspond to pH and EC measured on sample slurries prepared with deionised-water, and a solid:solution ratio of c. 1:2 (w/w). All results expressed on a dry-weight basis, except for pH-(1:2), EC-(1:2), and NAG-pH. Values in parentheses represent duplicates.

11578-RP-001-EV-0020_0

Table 3.2: Multi-Element-Analysis Results for Regolith Samples Note: Refer Appendix B for the definition of the Geochemical-Abundance-Index (GAI) indicated in this table. TOTAL-ELEMENT CONTENT (mg/kg or %) AV.-CRUSTAL- GEOCHEMICAL-ABUNDANCE INDEX (GAI) ELEMENT Felsic Felsic Felsic Mafic ABUNDANCE Felsic Felsic Felsic Mafic

(GCA6061) (GCA6175) (GCA6180) (GCA6184) (mg/kg or %) (GCA6061) (GCA6175) (GCA6180) (GCA6184) Al 0.77% 6.8% 4.7% 8.4% 8.2% 0 0 0 0 Fe 0.42% 0.55% 0.67% 6.6% 4.1% 0 0 0 0 Na 0.027% 1.3% 0.98% 1.3% 2.3% 0 0 0 0 K 0.32% 3.7% 1.2% 1.4% 2.1% 0 0 0 0

Mg 0.13% 0.58% 1.3% 3.2% 2.3% 0 0 0 0 Ca 0.023% 1.3% 0.21% 3.8% 4.1% 0 0 0 0 Ag 1.4 <0.1 2.7 0.3 0.07 4 0 5 2 Cu 360 19 230 280 50 2 0 2 2 Zn 23 15 34 88 75 0 0 0 0 Cd 0.2 <0.1 <0.1 <0.1 0.11 0 0 0 0 Pb 3 8 <2 3 14 0 0 0 0 Cr 24 10 13 340 100 0 0 0 1 Ni 28 18 17 150 80 0 0 0 0 Co 5.1 2.4 2.3 41 20 0 0 0 0 Mn 35 130 130 1,200 950 0 0 0 0 Hg 0.01 <0.01 0.01 <0.01 0.05 0 0 0 0 Sn 0.7 0.8 1.2 2.0 2.2 0 0 0 0 Sr 4.4 32 35 67 370 0 0 0 0 Ba 17 280 42 55 500 0 0 0 0 Th 0.59 6.2 2.8 0.31 12 0 0 0 0 U 0.30 2.0 0.82 0.12 2.4 0 0 0 0 Tl 0.24 1.1 0.56 1.40 0.6 0 0 0 1 V 15 12 19 280 160 0 0 0 0 As 37 <1 <1 <1 1.5 4 0 0 0 Bi 1.4 0.07 0.12 0.23 0.048 4 0 1 2 Sb 5.7 0.30 0.54 0.41 0.2 4 0 1 0 Se 0.18 0.01 <0.01 0.05 0.05 1 0 0 0 Mo 47 9.1 2.5 3.2 1.5 4 2 0 1 B <50 <50 <50 <50 10 0 0 0 0 P 66 210 250 280 1,000 0 0 0 0 F 210 460 890 1,000 950 0 0 0 0

Note: Average-crustal abundance of elements based on Bowen (1979).

11578-RP-001-EV-0020_0

Table 3.3: Mineralogical and Clay-Surface-Chemistry Results for Regolith Samples

Felsic (GCA6175) Felsic (GCA6176) Felsic (GCA6179) Felsic (GCA6182)

quartz dominant quartz dominant quartz dominant plagioclase dominant quartz major

plagioclase minor plagioclase minor muscovite muscovite kaolinite accessory kaolinite accessory kaolinite accessory chlorite illite rutile montmorillonite

chlorite trace chlorite trace illite trace montmorillonite chlorite muscovite

CEC %-Proportion of CEC CEC %-Proportion of CEC CEC %-Proportion of CEC CEC %-Proportion of CEC [cmol Na K Mg Ca [cmol Na K Mg Ca [cmol Na K Mg Ca [cmol Na K Mg Ca

(p+)/kg] (p+)/kg] (p+)/kg] (p+)/kg]

7.8 <1 2 2 96 6.3 1 3 49 46 0.26 <1 9 29 62 10 <1 <1 15 85

Mafic (GCA6183) Mafic (GCA6184) Mafic (GCA6185)

quartz dominant quartz major quartz major

hornblende plagioclase plagioclase minor muscovite minor

kaolinite accessory kaolinite accessory kaolinite accessory chlorite chlorite muscovite

biotite chlorite plagioclase montmorillonite trace montmorillonite trace biotite trace

rutile rutile

CEC %-Proportion of CEC CEC %-Proportion of CEC CEC %-Proportion of CEC [cmol Na K Mg Ca [cmol Na K Mg Ca [cmol Na K Mg Ca

(p+)/kg] (p+)/kg] (p+)/kg]

7.5 1 <1 28 70 10 2 2 35 60 9.6 1 <1 8 90

Notes: CEC = Cation-Exchange Capacity. dominant = greater than 50 %; major = 20-50 %; minor = 10-20 %; accessory = 2-10 %; and, trace = less than 2 %.

11578-RP-001-EV-0020_0

Table 4.1: Acid-Base-Analysis, Salinity and Net-Acid-Generation Results for Waste-Bedrock Samples

GCA- DRILLHOLE & EC-(1:2) TOTAL-S SO4-S SULPHIDE- TOTAL-C CO3-C ANC NAPP NAG AFP SAMPLE LITHOTYPE DOWN-HOLE pH-(1:2) [mS/cm] (%) (%) S (%) (%) kg H2SO4/tonne NAG-pH CATEGORY

NO. INTERVAL (m) (%) GCA6062 Felsic SRD075, 300-303 9.9 0.13 0.22 0.01 0.21 0.40 nm 31 -24 <0.5 6.3 NAF GCA6063 Felsic SRD075, 303-306 9.9 0.13 0.11 0.01 0.10 0.26 nm 30 -26 <0.5 6.7 NAF GCA6064 Felsic SRD079, 144-147 10.0 0.11 <0.01 nm <0.01 0.09 nm 16 nc <0.5 7.6 NAF GCA6065 Felsic SRD079, 147-150 9.9 0.14 0.14 0.02 0.12 0.08 nm 17 -13 <0.5 7.3 NAF GCA6187 Felsic SRD054, 52-54 9.8 0.16 <0.01 nm <0.01 0.15 0.12 24 nc <0.5 10.3 NAF GCA6188 Felsic SRD077, 78-81 9.6 0.12 0.13 0.03 0.10 0.87 nm 74 (70) -66 <0.5 9.9 NAF GCA6189 Felsic SRD065, 18-20 8.8 0.64 0.31 0.04 0.27 0.74 nm 33 -24 <0.5 9.8 NAF

GCA6066 Mafic SRD056, 78-81 10.0 0.12 0.68 0.03 0.65 0.32 nm 43 -23 <0.5 6.4 NAF GCA6067 Mafic SRD055, 234-237 9.7 0.14 0.15 0.02 0.13 0.19 nm 29 -25 <0.5 6.7 NAF GCA6068 Mafic SRD055, 237-240 9.7 0.15 0.18 0.02 0.16 0.39 nm 63 -58 <0.5 7.1 NAF GCA6069 Mafic SRD078, 111-114 9.9 0.13 0.43 0.02 0.41 0.03 nm 3.8 8.8 <0.5 7.2 [3.6] PAF GCA6070 Mafic SRD078, 114-117 9.9 0.16 1.2 0.02 1.2 0.02 nm 7.9 29 18 (17) 2.9 (2.8) PAF

GCA6190A Mafic SRC132, 33-36 9.6 0.13 <0.01 nm <0.01 0.33 0.27 33 nc <0.5 9.9 NAF GCA6190B Mafic SRC132, 33-36 9.7 0.12 <0.01 nm <0.01 0.16 0.13 31 nc <0.5 9.8 NAF GCA6191 Mafic SRC113, 117-120 9.6 0.16 0.03 nm 0.03 0.49 0.40 72 nc <0.5 10.2 NAF GCA6192 Mafic SRC100, 96-99 9.4 0.15 0.26 0.03 0.23 0.24 0.12 43 -35 <0.5 (<0.5) 9.8 (9.9) NAF GCA6193 Mafic SRD137, 96-99 9.6 0.13 0.20 0.02 0.18 0.18 nm 42 -36 <0.5 9.3 NAF

Notes: EC = Electrical Conductivity; ANC = Acid-Neutralisation Capacity; NAPP = Net-Acid-Producing Potential; NAG = Net-Acid Generation; AFP = Acid-Formation Potential; NAF = Non-Acid Forming; PAF = Potentially-Acid Forming; nm = not measured; nc = not calculated. pH-(1:2) and EC-(1:2) values correspond to pH and EC measured on sample slurries prepared with deionised-water, and a solid:solution ratio of c. 1:2 (w/w). All results expressed on a dry-weight basis, except for pH-(1:2), EC-(1:2), and NAG-pH. Values in (parentheses) represent duplicates. The NAG-pH value of 3.6 in [parentheses] for sample GCA6069 represents the pH value prior to the boiling-step to decomposed any unreacted-H2O2.

11578-RP-001-EV-0020_0

Table 4.2: Multi-Element-Analysis Results for Waste-Bedrock Samples (Felsics) Note: Refer Appendix B for the definition of the Geochemical-Abundance-Index (GAI) indicated in this table. TOTAL-ELEMENT CONTENT (mg/kg or %) AV.-CRUSTAL- GEOCHEMICAL-ABUNDANCE INDEX (GAI) ELEMENT Felsic Felsic Felsic ABUNDANCE Felsic Felsic Felsic

(GCA6062) (GCA6064) (GCA6188) (mg/kg or %) (GCA6062) (GCA6064) (GCA6188) Al 4.7% 6.6% 0.94% 8.2% 0 0 0 Fe 1.8% 0.89% 1.4% 4.1% 0 0 0 Na 1.1% 0.83% 0.023% 2.3% 0 0 0 K 2.9% 5.4% 0.20% 2.1% 0 1 0

Mg 1.4% 0.81% 0.99% 2.3% 0 0 0 Ca 1.8% 1.4% 2.2% 4.1% 0 0 0 Ag 1.5 <0.1 2.6 0.07 4 0 5 Cu 1,300 10 1,800 50 4 0 5 Zn 72 19 59 75 0 0 0 Cd 1.1 <0.1 0.7 0.11 3 0 2 Pb 13 9 4 14 0 0 0 Cr 55 <2 22 100 0 0 0 Ni 9 <1 130 80 0 0 0 Co 8.2 2.2 33 20 0 0 0 Mn 380 200 440 950 0 0 0 Hg 0.03 <0.01 0.05 0.05 0 0 0 Sn 2.4 0.8 1.6 2.2 0 0 0 Sr 50 45 15 370 0 0 0 Ba 230 230 5.2 500 0 0 0 Th 4.8 6.4 0.72 12 0 0 0 U 1.8 1.8 0.26 2.4 0 0 0 Tl 1.4 1.5 0.25 0.6 1 1 0 V 32 12 16 160 0 0 0 As 5 <1 41 1.5 1 0 4 Bi 11 0.06 2.1 0.048 6 0 5 Sb 2.5 0.30 11 0.2 3 0 5 Se 0.70 0.03 1.0 0.05 3 0 4 Mo 370 65 20 1.5 6 5 3 B <50 <50 <50 10 0 0 0 P 250 270 85 1,000 0 0 0 F 760 490 440 950 0 0 0


11578-RP-001-EV-0020_0

Table 4.3: Multi-Element-Analysis Results for Waste-Bedrock Samples (Mafics) Note: Refer Appendix B for the definition of the Geochemical-Abundance-Index (GAI) indicated in this table. TOTAL-ELEMENT CONTENT (mg/kg or %) AV.-CRUSTAL- GEOCHEMICAL-ABUNDANCE INDEX (GAI) ELEMENT Mafic Mafic Mafic Mafic ABUNDANCE Mafic Mafic Mafic Mafic


Mg 3.1% 3.6% 3.6% 3.2% 2.3% 0 0 0 0 Ca 7.8% 5.1% 6.9% 7.8% 4.1% 0 0 0 0 Ag 0.8 0.8 2.7 1.4 0.07 3 3 5 4 Cu 850 520 2,100 940 50 4 3 5 4 Zn 110 120 130 130 75 0 0 0 0 Cd 0.5 0.9 1.2 1.1 0.11 2 2 3 3 Pb 6 5 5 3 14 0 0 0 0 Cr 220 170 220 250 100 1 0 1 1 Ni 140 120 130 100 80 0 0 0 0 Co 58 36 64 48 20 1 0 1 1 Mn 1,800 1,200 1,400 1,400 950 0 0 0 0 Hg <0.01 <0.01 <0.01 <0.01 0.05 0 0 0 0 Sn 2.1 2.8 3.6 2.4 2.2 0 0 0 0 Sr 83 110 81 88 370 0 0 0 0 Ba 69 150 61 28 500 0 0 0 0 Th 0.29 0.14 0.21 0.32 12 0 0 0 0 U 0.22 0.30 0.17 0.21 2.4 0 0 0 0 Tl 0.52 0.43 1.8 0.32 0.6 0 0 1 0 V 280 210 280 250 160 0 0 0 0 As 5 8 <1 62 1.5 1 2 0 5 Bi 0.80 1.9 2.3 4.4 0.048 3 5 5 6 Sb 2.0 1.2 0.11 0.82 0.2 3 2 0 1 Se 1.3 0.39 1.8 0.82 0.05 4 2 5 3 Mo 21 190 55 86 1.5 3 6 5 5 B <50 <50 <50 <50 10 0 0 0 0 P 190 200 230 240 1,000 0 0 0 0 F 630 1,600 1,200 830 950 0 0 0 0


11578-RP-001-EV-0020_0

Table 4.4: Mineralogical Results for Waste-Bedrock Samples

Felsic Felsic Mafic Mafic Mafic (GCA6062) (GCA6188) (GCA6070) (GCA6192) (GCA6066)

Component Abundance Component Abundance Component Abundance Component Abundance Component Abundance

quartz dominant quartz dominant

quartz major quartz major quartz major Ca-amphibole hornblende Ca-amphibole

plagioclase minor plagioclase minor plagioclase minor plagioclase minor muscovite

calcite accessory calcite accessory pyrrhotite accessory chlorite accessory calcite accessory chlorite chlorite chlorite muscovite chlorite

Ca-amphibole clinozoisute muscovite K-feldspar biotite clinozoisite

pyrite trace Fe-dolomite trace pyrite trace calcite trace pyrite trace

chalcopyrite pyrite chalcopyrite pyrrhotite pyrrhotite scheelite chalcopyrite chalcopyrite chalcopyrite

scheelite molybdenite muscovite clinozoisite magnetite titanite

Notes: dominant = greater than 50 %; major = 20-50 %; minor = 10-20 %; accessory = 2-10 %; and, trace = less than 2 %.

11578-RP-001-EV-0020_0

Table 5.1: Acid-Base-Analysis, Salinity and Net-Acid-Generation Results for Low-Grade-Ore Samples

GCA- DRILLHOLE & EC-(1:2) TOTAL-S SO4-S SULPHIDE- TOTAL-C CO3-C ANC NAPP NAG AFP SAMPLE LITHOTYPE DOWN-HOLE pH-(1:2) [mS/cm] (%) (%) S (%) (%) kg H2SO4/tonne NAG-pH CATEGORY

NO. INTERVAL (m) (%) GCA6163 Felsic SRD052, 69-72 9.9 0.088 <0.01 nm <0.01 0.25 nm 26 nc nm nm NAF GCA6164 Felsic SRD067, 96-99 9.9 0.097 0.17 <0.01 0.16 0.59 nm 36 -31 <0.5 9.8 NAF GCA6165 Felsic SRD075, 52-54 9.9 0.084 <0.01 nm <0.01 0.27 nm 21 nc nm nm NAF GCA6166 Felsic SRD065, 93-96 9.7 0.10 0.09 nm 0.09 0.32 nm 29 nc nm nm NAF GCA6167 Felsic GTD003, 63-66 10.0 0.075 <0.01 nm <0.01 0.22 nm 14 nc nm nm NAF

GCA6168 Mafic SRC103, 93-96 9.9 0.14 0.07 nm 0.07 0.14 nm 14 nc nm nm NAF GCA6169 Mafic SRC098, 135-138 9.9 0.17 0.24 0.03 0.21 0.09 nm 28 -21 <0.5 6.8 NAF GCA6170 Mafic SRD075, 22-24 9.5 0.38 0.25 0.02 0.23 0.57 nm 53 -45 <0.5 9.8 NAF GCA6171 Mafic SRD058, 63-66 10.0 0.13 0.03 nm 0.03 0.11 nm 45 nc nm nm NAF GCA6172 Mafic GTD011, 45-48 10.1 0.12 0.06 nm 0.06 0.15 nm 38 nc <0.5 9.7 NAF GCA6173 Mafic SRD063, 153-156 10.1 0.28 <0.01 nm <0.01 0.38 nm 55 nc nm nm NAF GCA6174 Mafic SRD078, 66-69 10.0 0.10 0.73 <0.01 0.72 0.14 0.10 26 -3.9 <0.5 (<0.5) 6.3 (6.9)* PAF

GCA6162 Quartz-Zone SRD066, 38-40 9.8 (9.7) 0.13 (0.12) <0.01 (<0.01) nm <0.01 0.07 (0.05) 0.01 6.5 (5.3) nc nm nm NAF

Notes: LGO = Low-Grade Ore; EC = Electrical Conductivity; ANC = Acid-Neutralisation Capacity; NAPP = Net-Acid-Producing Potential; NAG = Net-Acid Generation; AFP = Acid-Formation Potential; NAF = Non-Acid Forming; PAF = Potentially-Acid Forming; nm = not measured; nc = not calculated. pH-(1:2) and EC-(1:2) values correspond to pH and EC measured on sample slurries prepared with deionised-water, and a solid:solution ratio of c. 1:2 (w/w). All results expressed on a dry-weight basis, except for pH-(1:2), EC-(1:2), and NAG-pH. Values in parentheses represent duplicates. The NAG-pH values labelled with an asterisk for sample GCA6174 indicate that this sample did acidify to pH 3-4 upon a second addition of the H2O2 reagent.

11578-RP-001-EV-0020_0

Table 5.2: Multi-Element-Analysis Results for Low-Grade-Ore Samples Note: Refer Appendix B for the definition of the Geochemical-Abundance-Index (GAI) indicated in this table. TOTAL-ELEMENT CONTENT (mg/kg or %) AV.-CRUSTAL- GEOCHEMICAL-ABUNDANCE INDEX (GAI) ELEMENT Felsic Mafic Mafic Quartz-Zone ABUNDANCE Felsic Mafic Mafic Quartz-Zone


Mg 0.39% 5.9% 3.6% 0.75% 2.3% 0 1 0 0 Ca 1.2% 8.6% 6.6% 0.19% 4.1% 0 0 0 0 Ag 1.1 3.4 1.5 <0.1 0.07 3 5 4 0 Cu 310 1,800 1,100 56 50 2 5 4 0 Zn 17 160 130 21 75 0 1 0 0 Cd <0.1 1.8 1.5 0.2 0.11 0 3 3 0 Pb 10 5 3 <2 14 0 0 0 0 Cr 34 210 250 16 100 0 0 1 0 Ni 5 60 130 20 80 0 0 0 0 Co 2.0 28 58 2.8 20 0 0 1 0 Mn 190 1,900 1,300 87 950 0 0 0 0 Hg 0.01 0.03 0.02 <0.01 0.05 0 0 0 0 Sn 1.2 9.5 3.1 0.9 2.2 0 2 0 0 Sr 20 32 88 26 370 0 0 0 0 Ba 170 60 37 42 500 0 0 0 0 Th 4.4 0.47 0.27 2.3 12 0 0 0 0 U 1.4 0.47 0.15 0.64 2.4 0 0 0 0 Tl 1.3 0.85 0.74 0.76 0.6 1 0 0 0 V 9 200 230 19 160 0 0 0 0 As 10 2 <1 6 1.5 2 0 0 1 Bi 0.70 11 0.87 0.24 0.048 3 6 4 2 Sb 3.5 1.5 2.0 1.9 0.2 4 2 3 3 Se 0.29 0.94 1.5 0.02 0.05 2 4 4 0 Mo 540 420 240 63 1.5 6 6 6 5 B <50 <50 <50 <50 10 0 0 0 0 P 160 310 230 210 1,000 0 0 0 0 F 650 3,500 1,500 800 950 0 1 0 0


11578-RP-001-EV-0020_0

Table 5.3: Mineralogical Results for Low-Grade-Ore Samples

Quartz-Zone Felsic Mafic (GCA6162) (GCA6166) (GCA6170)

Component Abundance Component Abundance Component Abundance

quartz dominant quartz dominant

muscovite major hornblende major quartz minor

plagioclase accessory calcite accessory calcite accessory chlorite plagioclase plagioclase

muscovite chlorite muscovite clinopyroxene clinozoisite pyrite trace pyrite trace chalcopyrite chalcopyrite chlorite pyrrhotite

Notes: dominant = greater than 50 %; minor = 10-20 %; accessory = 2-10 %; and, trace = less than 2 %.

11578-RP-001-EV-0020_0


FIGURES

11578-RP-001-EV-0020_0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

0 10 20 30 40 50 60 70 80

Figure 1

pH-Buffering Curves for Waste-Bedrock Samples

Mafic (GCA6066)Mafic (GCA6068)Mafic (GCA6191)Felsic (GCA6188)

pH

Acid-Consumption (kg sulphuric acid per tonne)

Note: The H2SO4-addition rates employed in the auto-titrations correspond to sulphide-oxidation rates (SORs) of c. 6-7 x 105 mg SO4/kg/flush (= c. 2-3 x 104 kg H2SO4/tonne/year for weekly flushing-drying-cycles) under weathering conditions near-optimal for sulphide-oxidation (viz. typical moisture/aeration-regimes, on a weekly basis, in which sulphide-oxidation is limited by neither the O2-supply [via diffusion], nor H2O-supply/flushing). Given the Sulphide-S values of the waste-bedrock samples, these SORs are up to 104-105 faster than those typical for the circum-neutral weathering, under near-optimal conditions, of mine-waste materials that contain "minute/trace-sulphides" that are not atypically reactive (e.g. framboidal-pyrites, and marcasites). Furthermore, given the aridity of the mine-site, and the restriction of sulphide-oxidation to episodic, transient "weathering-windows", as governed by "wet-spells", the SORs of rock-fines wetted/flushed by infiltration should be at least several fold slower than those indicated above for near-optimal conditions of weathering.

11578-RP-001-EV-0020_0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

0 10 20 30 40 50 60 70 80

Figure 2

pH-Buffering Curves for Low-Grade-Ores Samples

Mafic (GCA6170)Mafic (GCA6173)

pH

Acid-Consumption (kg sulphuric acid per tonne)

Note: The H2SO4-addition rates employed in the auto-titrations correspond to sulphide-oxidation rates (SORs) of c. 6-7 x 105 mg SO4/kg/flush (= c. 2-3 x 104 kg H2SO4/tonne/year for weekly flushing/drying-cycles) under weathering conditions near-optimal for sulphide-oxidation (viz. typical moisture/aeration-regimes, on a weekly basis, in which sulphide-oxidation is limited by neither the O2-supply [via diffusion], nor H2O-supply/flushing). Given the Sulphide-S values of the waste-bedrock samples, these SORs are up to 104-105 faster than those typical for the circum-neutral weathering, under near-optimal conditions, of mine-waste materials that contain "minute/trace-sulphides" that are not atypically reactive (e.g. framboidal-pyrites, and marcasites). Furthermore, given the aridity of the mine-site, and the restriction of sulphide-oxidation to episodic, transient "weathering-windows", as governed by "wet-spells", the SORs of rock-fines wetted/flushed by infiltration should be at least several fold slower than those indicated above for near-optimal conditions of weathering.

11578-RP-001-EV-0020_0


APPENDIX C

LABORATORY REPORTS

11578-RP-001-EV-0020_0

Documents

SPINIFEX RIDGE PROJECT - EPA WAepa.wa.gov.au/sites/default/files/PER_documentation/Appendix M... · SPINIFEX RIDGE PROJECT GEOCHEMICAL CHARACTERISATION OF ... placed on waste-dumps