A Multidisciplinary Approach to Base Metal Exploration in an Area of Extreme Anthropogenic Disturbance: Mt Lofty Ranges, South Australia

Transcription

1 Wheal Ellen smelter Wheal Ellen N Unnamed prospect Rodwell Creek Pyritic layer Dispersion Type Primary Transitional Secondary A Multidisciplinary Approach to Base Metal Exploration in an Area of Extreme Anthropogenic Disturbance: Mt Lofty Ranges, South Australia Andrew K. M. Baker and Rob W. Fitzpatrick CSIRO Land and Water Science Report 9/10 October 2010

2 Enquiries should be addressed to: Dr Andrew Baker: CSIRO Land and Water, Private Bag No 2, Glen Osmond, South Australia Phone: Copyright and Disclaimer 2010 CSIRO To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO. Important Disclaimer CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it.

3 Contents 1. INTRODUCTION ENVIRONMENTAL SETTING CLIMATE VEGETATION AND LANDUSE GEOLOGY AND GEOMORPHOLOGY MINERALISATION REGIONAL BASE METAL EXPLORATION GEOCHEMISTRY PB ISOTOPES FOCUSED BASE METAL EXPLOATION GEOCHEMISTRY PB ISOTOPES DISCUSSION MODEL GEOPHYSICAL EXPLORATION SUMMARY REFERENCES Appendix Appendix Appendix Appendix Appendix iii

4 List of Figures Figure 1 Map indicating the location of the Rodwell Creek study site, the Wheal Ellen Pb/Zn mine and smelter and pyritic layers Figure 2 Regional geologic setting of the Mt Torrens and Rodwell Creek study sites (after Toteff 1999)... 5 Figure 3 Aerial photograph of the Rodwell Creek study site showing drainage in blue and 10 metre contours in brown. Red dots indicate sample sites and green dots represent potential sources of metal (Pb, Zn, Ag and As) contamination. The pyritic layer was identified using aeromagnetic data by Gum (1998)... 8 Figure 4 Map showing selected sample locations from regional geochemical survey of sulfidic seeps and wetlands, in the Kanmantoo geologic province, carried out by Skwarnecki and Fitzpatrick (2003). Drainage is marked in blue, roadways in black and populated areas in purple. Study site is marked as blue square Figure 5 Ratio plots indicating the Pb isotope composition of sulfidic soil-regolith samples, from regional geochemical surveying, relative to Kanmantoo sulfide mineralisation, country rock and anthropogenic contamination. Ellipses define the spread of data and the point within each ellipse represents average Pb isotope composition. The mixing curve estimates the relative contribution of Pb from mineralisation and country rock in each sample Figure 6 Examples of: (a) a permanent saline-sulfidic wetland, (b) a seasonal sulfidic seep and (c) a relict salinesulfidic wetland/seep (very dark grey - 10 YR 3/1) overlain by overbank deposit at the Rodwell Creek study site Figure 7 SEM image of sample RC_12 from a permanently functioning saline-sulfidic wetland. Sample contained pyrite and Pb sulfide was present along the edges of plant root walls Figure 8 SEM image of sample KRS_22 from a permanently functioning saline-sulfidic wetland. Sample contained pyrite and Pb and Zn sulfide was present along the edges of plant root walls Figure 9 Ratio plots indicating the Pb isotope composition of soil-regolith samples (red triangles), from the Rodwell Creek study site, relative to Kanmantoo sulfide mineralisation, country rock and anthropogenic contamination (Mt Isa and Broken Hill Pb). Ellipses define the spread of data and the point within each ellipse represents average Pb isotope composition. Green triangles represent the Pb isotope composition of primary sulfide mineralisation (galena) from the Wheal Ellen workings. The mixing curve estimates the relative contribution of Pb from mineralisation and country rock in each sample Figure 10 A 3D block diagram showing the relative positions of: (i) Wheal Ellen in operation from 1857 to 1866 and from 1909 to 1911, (ii) the Wheal Ellen smelter in operation from 1861 to 1866 (iii) unnamed prospect period of operation unknown. The red zones around Wheal Ellen and the Wheal Ellen smelter and the red arrows represent primary anthropogenic dispersion, which produced geochemical groups 3 and 4 soil-regolith (Table 9). The orange arrows represent transitional anthropogenic dispersion. The yellow arrows represent secondary anthropogenic contamination, which produced geochemical group 2 soilregolith (Table 9). The pyritic layer was identified using aeromagnetic data by Gum (1998). The yellow box represents the area depicted in Figure Figure 11 A predictive diagram illustrating the geomorphological changes, which have taken place at the Rodwell Creek study site prior to and following land clearing, mining and smelting. Each landscape slice represents a different time period,: (T1) prior to 1857 before mining and significant land clearance, (T2) iv

5 1857 to 8161 subsequent to mining but prior to smelting at Wheal Ellen, (T3) 1861 to present subsequent to smelting at Wheal Ellen. Blue areas represent permanent seeps and wetlands and the pink areas represent seasonal seeps and wetlands. This diagram represents the area defined by the yellow box in Figure 10. Refer to text for detailed explanation Figure 12 A predictive diagram illustrating the geomorphological and geochemical changes, which have taken place at the Rodwell Creek study site prior to and following land clearing, mining and smelting. The geomorphological effects of land clearing (e.g. erosion, rising water table, decreased groundwater flow through rock fractures) combined with mining and smelting created environments, which promoted the accumulation (formation) of soil-regolith with unique geochemical properties. (T1) Formation of geochemical group 1 wetland soil-regolith. (T2) Formation of geochemical group 2 wetland soil-regolith and the preservation of group 1 soil-regolith. (T3) Formation of geochemical group 3 seasonal wetland soil-regolith, stream channel and overbank sediments. (T3) Formation of geochemical group 4 permanent wetland soil-regolith. Refer to text for detailed explanation Figure 13 Aerial photograph of a portion of the Rodwell Creek study site (refer to Figure 3 for context). Displayed are the relative locations of: (i) soil-regolith sample locations, (ii) resistivity and IP sampling transect, (iii) a resistivity boundary, and (iv) zones of inferred chargeability at depth Figure 14 Two-dimensional resistivity pseudosection reflecting depth of penetration into the subsurface. There is a resistivity boundary marked by the creek with less resistive rocks to the west and more resistive rocks to the east. Resistivity transect A-B is marked on Figure Figure 15 Two-dimensional IP pseudosection reflecting depth of penetration into the subsurface. There are two zones of chargeability defined by the transect. The smaller zone is located 50 m along transect at a depth of approximately 45 m. The larger zone of chargeability is located 150 m along the transect at depths below 60 m. This zone corresponds to the resistivity boundary identified in Figure 14. Resistivity transect A-B is marked on Figure v

6 List of Tables Table 1 Selected geochemical results from sulfidic soil-regolith samples collected as part of a regional geochemical survey of sulfidic seeps and wetlands in the Kanmantoo geologic province by Skwarnecki and Fitzpatrick (2003). Samples were analysed by ICP-MS/ICP-OES, on mixed acid digests according to the methods outlined in Appendix 1. Detection limits are displayed. Background element concentrations were calculated as the 50 th percentile and the threshold concentrations at the 90 th percentile [as determined by Skwarnecki et al. (2002)]. Red values exceed threshold concentrations and are considered anomalous Table 2 Lead isotope results from sulfidic soil-regolith samples selected from the regional geochemical survey of sulfidic seeps and wetlands in the Kanmantoo geologic province by Skwarnecki and Fitzpatrick (2003). Isotope analysis carried out as part of this study Table 3 Estimation of Pb contributions from country rock and Kanmantoo sulfide mineralisation in samples (AC refers to samples with anthropogenic Pb contamination). Sulfidic soil-regolith samples are ranked according to prospectivity based on the percentage and concentration () of Pb derived from Kanmantoo sulfide mineralisation (1 = most prospective) Table 4 Prospectivity of sulfidic soil-regolith samples from the Kanmantoo geological province based on geochemical and Pb isotope analysis Table 5 Sulfidic soil-regolith samples from permanent sulfidic seeps and wetlands. Red values exceed threshold concentrations established by Skwarnecki et al. (2002). NA = not applicable Table 6 Soil-regolith samples from seasonal sulfidic seeps and wetlands. No data exists to establish background and threshold concentrations. To aid discussion, relict sulfidic soil-regolith samples are compared to background and threshold values for sulfidic soil-regolith established by Skwarnecki et al. (2002). Red values exceed threshold concentrations Table 7 Soil-regolith samples from relict sulfidic seeps and wetlands. No data exists to establish background and threshold concentrations. To aid discussion relict sulfidic soil-regolith samples are compared to background and threshold values for sulfidic soil-regolith established by Skwarnecki et al. (2002). Red values exceed threshold concentrations Table 8 Stream sediment samples from Rodwell Creek and its tributaries. ND - No data exists to establish background and threshold concentrations. * Indicates stream overbank deposits. Red values exceed threshold concentrations established by Skwarnecki et al. (2002) Table 9 Samples from the Rodwell Creek study site grouped according to bulk geochemistry Table 10 Lead isotope ratio data for Rodwell Creek soil-regolith samples and Wheal Ellen mineralisation samples Table 11 Estimation of Pb contributions from country rock and Kanmantoo sulfide mineralisation in soilregolith samples from the Rodwell Creek study site vi

7 Acknowledgments Thanks to Graham Carr and the late Geoff Denton (CSIRO) for providing Pb isotope data and constructive advice. We would like to acknowledge the efforts of CSIRO staff for their support and advice in the laboratory and field: Marian (Swanny) Skwarnecki, Mark Thomas, Richard Merry, Brett Thomas, Graham Heinson, Phil Slade, Mark Raven, Mark Fritz, Benn Britton, Adrian Beech and Sean Forrester. vii

8 Executive Summary Lead isotope and geochemical data were used to rank the prospectivity of sulfidic soil-regolith samples collected as part of a regional geochemical survey by Skwarnecki and Fitzpatrick (2003). The sulfidic soil-regolith sample with the most anomalous Pb isotope and geochemical signature was collected from a saline-sulfidic wetland in Rodwell Creek. This area was selected for more focused base metal exploration. Soil-regolith samples were collected upstream and downstream from the identified anomalous sample site. Samples were collected from: (i) permanent sulfidic seeps and wetlands, (ii) seasonal sulfidic seeps and wetlands, (iii) stream channel sediments and (iv) stream overbank sediments. Soil morphology and geochemical analyses (including Pb isotopes) were used to distinguish characteristic signatures, which were produced by: (i) anthropogenic contamination (historic mining and smelting), (ii) zones of sulfide enrichment and (iii) country rock (background). These data were used to construct a predictive conceptual model, which helped explain the relationships between historical events at the Rodwell Creek study site (land clearance, mining and smelting [Pb/Z/Ag/Au/pyrite]) and the (i) morphology, (ii) geochemistry and (iii) Pb isotope composition of various sample media. The predictive conceptual model was used to separate anthropogenic geochemical signatures from those that were likely to have originated from unidentified, hidden zones of sulfide enrichment. Thus, a sub-section of the Rodwell Creek study site was identified as worthy of focussed mineral exploration. Geophysical prospecting (IP and resistivity surveys) was carried out and a disseminated zone of potential sulfide enrichment was identified. viii

9 1. Introduction Acid sulfate soils form under modern freshwater and saline conditions in inland settings, especially in the higher rainfall (> 500 mm per annum) Mediterranean environments of Australia (Fitzpatrick et al. 2002). These changes are caused by contemporary land clearing, which results in erosion, rising of local water tables and excess discharge of saline-sulfatic groundwater in mid-slope and valley floor landscape positions. This often results in the formation of seasonally and/or permanently waterlogged soil profiles, which are dominated by wetland vegetation. An accumulation of organic matter and waterlogging by saline-sulfatic groundwater promotes bacterial reduction of sulfate to sulfide. Within these wetland environments 1, pyrite enriched sulfidic materials form, which are often associated with metal accumulations (e.g. Ba, Cd, Pb, and Zn). Sulfuric materials are generated when these sulfidic materials are eroded and exposed to air. Pyrite is oxidised producing sulfuric acid, which dissolves soil minerals and leads to the precipitation, accumulation and oxidation of iron- and sulfur-rich precipitates. These processes may cause less permeable, Fe-rich layers to form in discharge areas, which can lead to degraded soils, erosion, mobilisation of accumulated metals and poor water quality. According to Skwarnecki et al. (2002), acid sulfate soils may contain geochemical indicators of the presence of blind or concealed sulfide enrichment. The iron sulfide, oxide and oxyhydroxysulphate precipitates that form in and around saline sulfidic soils have a high sorptive capacity for trace elements, which may include indicators of mineralisation (e.g. As, Ba, Cd, P, Pb, Sn and Zn). Skwarnecki et al. (2002) proposed that material associated with inland acid sulfate soils (e.g. sulfidic materials, sulfuric horizons and surface Fe-rich precipitates) constitute a new sampling medium for mineral exploration, which provides a broader dispersion halo around mineralisation than conventional sample types such as rock chip and soil samples. In addition, they believe that this sample media can be used to locate blind mineralisation in areas of cover. This report explains how lead (Pb) isotope and geochemical data were used to rank the prospectivity of sulfidic soil-regolith samples collected previously as part of a regional geochemical survey by Skwarnecki and Fitzpatrick (2003). This resulted in Rodwell Creek being selected for more focused base metal exploration or sampling as part of this study. Isotopic, geochemical and pedological investigations informed the construction of a predictive conceptual model that was used to identify a sub-section of the Rodwell Creek study for further research. 1 These environments are termed saline-sulfidic wetlands. 1

10 2. Environmental Setting This work was conducted at the Rodwell Creek study site, which is located near Strathalbyn, 40 km SE of Adelaide in the eastern Mount Lofty Ranges, South Australia (Figure 1; 34 o S 138 o E; Adelaide 1: sheet SI54-13). Landscapes in this region host deeply weathered soil-regolith profiles with high concentrations of stored salts, and base metal mineralization that contributes to degraded saline seepages and poor stream water quality. Figure 1 Map indicating the location of the Rodwell Creek study site, the Wheal Ellen Pb/Zn mine and smelter and pyritic layers Climate The climate is Mediterranean and representative of the eastern part of the Mount Lofty Ranges, with wet, cool winters (June to August) and hot, dry summers (December to February). 2

11 2.2. Vegetation and landuse Since European settlement, the native vegetation of South Australia has been extensively modified. Little data exist on the extent of pre-european forest and woodland cover. However, anecdotal reports from the Adelaide Hills suggest that, prior to clearing, native vegetation consisted of river red gum (Eucalyptus camaldulensis) woodland. These trees remain prominent adjacent to water courses and roadways in the Eastern Mt Lofty Ranges. The river red gum is a perennial, single stemmed, large-bole, medium-sized to tall tree (30-40 m tall) (Bren and Gibbs 1986). It may reach ages of 500 to 1000 years (Jacobs 1955). The river red gum is commonly found growing on riverine sites with permanent or seasonal water (Brooker et al. 2002). They are often associated with gleyed heavy clay soil along river banks and on floodplains subject to frequent or periodic flooding, preferring deep moist subsoils with high clay content (Costermans 1989). These trees obtain water from rainfall, groundwater and river flooding. They posses deep sinker roots that grow down towards zones of higher water supply and are effective in conducting water (Heinrich 1990), hence, the high water use of the river red gums contributes to maintaining the watertable at lower depths (Dalton 1990). Post land clearing (to allow grazing), a mix of pasture species now dominate the local vegetation including subterranean clover (Trifolium subterraneum L.) and cocksfoot (Dactylis glomerata L.) with invasions of salvation jane (Echium plantagineum L.), storksbill (Erodium moschatum L.) and soursob (Oxalis pes-caprae L.) that are now grazed by sheep and cattle (Cox and Ashley 2000). Wetland vegetation is associated with wet soils in areas of groundwater discharge, through water and surface water discharges on lower slopes, terraces and valley floors. Species include: (i) cumbungi (Typha sp.) associated with permanently saturated soils of inner wetlands, (ii) rush (Juncus spp.) associated with permanently and seasonally saturated soil of inner wetlands and erosional channels, (iii) streaked arrowgrass (Triglochin striata) and creeping monkey flower (Mimulus repens) associated with seasonally saturated soil in transitional zones around wetlands. Tall wheat grass (Agropyron elongatum) and puccinellia (Puccinellia ciliata) is often found surrounding saline wetlands. Land use is predominantly sheep or cattle grazing on pasture that, in places, has resulted in significant erosion and land degradation. Increasingly, land is being used for more intensive purposes such as viticulture and cereal cropping. Commercial pine plantations have been established in areas of the Torrens River catchment, which is an important source of urban water supply. 3

12 2.3. Geology and geomorphology The Normanville Group was deposited in the Early Cambrian during an initial phase of stable platform carbonate-dominated sedimentation (Jago et al. 1994). The Kanmantoo Trough then formed, due to extensional faulting, along the south eastern flank of the Neoproteozoic Adelaide Geosyncline (Gatehouse et al. 1990). The Kanmantoo Trough filled rapidly with mainly immature clastics and some carbonates (Kanmantoo Group) in a dominantly marine environment (Figure 2). Sedimentation of the Kanmantoo Trough ceased in the Mid to Late Cambrian in response to the initial compression associated with the Delamerian Orogeny. Deformation continued through to the Early Ordovician and resulted in complex structural and metamorphic zoning along the fold belt over 300 km in length in the eastern and southern Mount Lofty Ranges. At least two main phases of deformation have been recognised. Metamorphism at low pressure and high temperature locally attained amphibolite facies (Mancktelow 1990; Offler and Fleming 1968; Sandiford et al. 1990), and appears to have coincided with a major period of granite emplacement (Foden et al. 1990). 4

13 Figure 2 Regional geologic setting of the Mt Torrens and Rodwell Creek study sites (after Toteff 1999). The maximum thickness of the Kanmantoo Group is 15 km. The main rock types include sandstone, siltstone and phyllite, with intercalated pelite and minor carbonate. Deposition commenced with the muddy sandstone and siltstone of the Carrickalinga Head Formation, which grades into the crossbedded feldspathic sandstone of the Backstairs Passage Formation. A disconformity separates the Backstairs Passage Formation from the overlying upper parts of the sequence, which comprise interbedded muddy sandstone and siltstone (Tapanappa and Balquhidder Formations), and dominantly fine-grained clastic rocks of the Talisker Calc-siltstone and Tunkalilla Formation (Daily and Milnes 1971; 1973). 5

14 The landscape of much of the eastern Mount Lofty Ranges region comprises undulating low hills. Altitude varies from 400 to 500 m with local relief between 30 and 50m. A northeast to southwest topographic high east Rodwell Creek bisects the area. Small catchments to the west drain into the Onkaparinga and Torrens catchment systems, whilst catchments to the east form part of the Murray Darling Basin system Mineralisation Regional Mineralisation The Kanmantoo Group hosts a number of different styles of mineralisation. Most significant mineralisation has been historically confined to the Tapanappa Formation and the Talisker Calc- Siltstone. There is a sequence boundary at the base of the Talisker Calc-Siltstone that is associated with Pb-Zn mineralisation in the Karinya Syncline (Figure 2) (Dyson et al. 1994). Exploration has focussed on the pyritic silt/mudstone of the Talisker Calc-Siltstone and Tapanappa Formation because of the occurrence of ore bodies spatially coincident with these units (Flottmann et al. 1996). The wide variety of mineralisation styles occurring within the sediments of the Kanmantoo Trough formed during basin most likely development either below the basin floor in discordant deposits (e.g. Kanmantoo, Bremer) or close to the sediment-seawater interface as concordant deposits (e.g. Aclare, Wheal Ellen) (Both 1990; Seccombe et al. 1985) Local Mineralization Wheal Ellen The Wheal Ellen deposit is located in the NW corner of the Rodwell Creek study site (Figure 1). It is located approximately 1.5 km NW and 2 km along drainage depressions from the saline-sulfidic wetlands sampled as part of this study and as part of Skwarnecki and Fitzpatrick (2003) regional geochemical sampling. Wheal Ellen ore body is a potential source of heavy metal that has been concentrated in saline-sulfidic wetlands within the Rodwell Creek study site. This mine was discovered in 1856 and is the largest Pb-Zn ore body that has been worked in the Kanmantoo area. It was worked for two short periods from 1857 to 1866 and then from 1909 to During the 1950s six diamond drill holes were completed by the Department of Mines and Energy, which provided information on the nature and extent of the ore deposit at Wheal Ellen (Wade and Cochrane 1954). Limited studies of the deposit were conducted in the late 1970s and early 1980s (Seccombe et al. 1985; Spry 1976; Spry et al. 1988). During the mid 1990s an attempt was made to rehabilitate the mine site by re-vegetation and filling-in the mine shafts. 6

15 The main sulfide minerals associated with the Wheal Ellen ore zone are sphalerite, galena, pyrite and chalcopyrite together with silver and gold (Wade and Cochrane 1954). Spry (1976) described the following three types of ore: (i) high-grade ore consisting of a massive matrix of sphalerite and galena studded with pyrite euhedra, (ii) lower grade, laminated and disseminated ore with variable amounts of sulfide, and (iii) vein mineralisation containing sphalerite, galena and pyrite with the addition of arsenopyrite. Wheal Ellen Smelter smelting took place 1.2 km upstream from the easternmost sample site at the Rodwell Creek study site (Figure 3). This is also a likely source of elevated heavy metal contamination in sediments and saline-sulfidic wetlands in this area. Aeromagnetically interpreted pyrite horizon Gum (1998) identified a potential pyritic horizon in the SE corner of the Rodwell Creek study site (Figure 3). This horizon was interpreted from aeromagnetic data and has not been ground-truthed. The inferred horizon does not represent a potential source of heavy metal in saline-sulfidic wetlands because it is located downstream of all sample sites. It does however suggest that there may be pyritic horizons, at depth in the area, that show no surface expression or aeromagnetic signature. 7

16 Figure 3 Aerial photograph of the Rodwell Creek study site showing drainage in blue and 10 metre contours in brown. Red dots indicate sample sites and green dots represent potential sources of metal (Pb, Zn, Ag and As) contamination. The pyritic layer was identified using aeromagnetic data by Gum (1998). 3. Regional Base Metal Exploration Skwarnecki and Fitzpatrick (2003) carried out a regional geochemical survey of sulfidic seeps and wetlands in the Kanmantoo region, which covered an area of 1000 km 2. This survey was based on the premise that black sulfidic, sulfuric and sulfide-containing materials and gels associated with saline wetlands and seeps concentrate elements (As, Ba, Bi, Cd, Cu, P, Pb, Sn, Tl and Zn) indicative of underlying sulfide mineralisation (Skwarnecki et al. 2002). Scavenging of elements in sulfides has occurred because of co-precipitation of these elements from groundwater with Fe sulfides/oxides. Skwarnecki et al. (2002) found that, at a prospect scale in the Mount Lofty Region, sulfidic seeps and wetland (when present) may capture geochemical dispersion halos of up to 750 m in width around the mineralised zones, compared to up to 200 m for soils and up to 700 m for stream sediments. 8

17 3.1. Geochemistry Skwarnecki and Fitzpatrick (2003) collected approximately 150 samples from saline-sulfidic wetlands throughout the Kanmantoo geological province. Five sulfidic material samples were chosen for follow up work based on bulk geochemical analysis (Table 1). Four samples were chosen because they contained one or more elements, associated with sulfide mineralisation, which exceeded predetermined thresholds [90 th percentile - as determined by Skwarnecki et al. (2002)]. Sample KRS_142 was selected for follow up work because of its close proximity to anomalous sample KRS_143 (Figure 4). Samples were ranked according to prospectivity (1 = most prospective) based on the number of elements, associated with sulfide mineralisation that exceeded threshold (Table 1). Sample KRS_22, which was considered most prospective, also contained the highest concentrations of Pb and Zn. Table 1 Selected geochemical results from sulfidic soil-regolith samples collected as part of a regional geochemical survey of sulfidic seeps and wetlands in the Kanmantoo geologic province by Skwarnecki and Fitzpatrick (2003). Samples were analysed by ICP-MS/ICP-OES, on mixed acid digests according to the methods outlined in Appendix 1. Detection limits are displayed. Background element concentrations were calculated as the 50 th percentile and the threshold concentrations at the 90 th percentile [as determined by Skwarnecki et al. (2002)]. Red values exceed threshold concentrations and are considered anomalous. As Ba Bi Cd Cu P Pb Sn Tl Zn Detection Background (50 th percentile) < Threshold (90 th percentile) Sample As Ba Bi Cd Cu P Pb Sn Tl Zn Prospectivity Ranking KRS_ KRS_ KRS_ B.D KRS_ B.D KRS_

18 Figure 4 Map showing selected sample locations from regional geochemical survey of sulfidic seeps and wetlands, in the Kanmantoo geologic province, carried out by Skwarnecki and Fitzpatrick (2003). Drainage is marked in blue, roadways in black and populated areas in purple. Study site is marked as blue square Pb Isotopes The Pb isotope compositions of sulfidic soil-regolith samples were measured to further differentiate between chemical anomalies, which were derived from sulfide mineralisation, country rock and anthropogenic contamination (Section 4.2). Soil-regolith samples were analysed according to the methods outlined in Appendix 2. Lead isotope ratios are presented in Table 2. 10

19 Table 2 Lead isotope results from sulfidic soil-regolith samples selected from the regional geochemical survey of sulfidic seeps and wetlands in the Kanmantoo geologic province by Skwarnecki and Fitzpatrick (2003). Isotope analysis carried out as part of this study. Sample 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb Pb Conc () KRS_ KRS_ KRS_ KRS_ KRS_ Lead isotope ratio plots for sulfidic soil-regolith samples, relative to Kanmantoo sulfide mineralisation, country rock and anthropogenic contamination, are presented in Figure 5. The Pb signature for Kanmantoo sulfide mineralisation was obtained by measuring the isotope composition of samples from zones of Pb/Zn sulfide enrichment within the Kanmantoo geological province. Twenty one samples were measured for Pb isotope composition, from the Angus, Mt Torrens, Aclare and Wheal Ellen prospects (Section 2.4) and included: (i) galena derived from the mineralised zone, (ii) gossans, and (iii) laterites proximal to mineralisation (CSIRO 2003) (Appendix 5). The country rock Pb signature was defined by the isotope composition of nine samples of unmineralised Talisker Calc- Siltstone (CSIRO 2003) and three unmineralised soil samples (Gulson et al. 1981) from the Kanmantoo region (Appendix 5). Mt Isa and Broken Hill Pb signatures were used to define anthropogenic contamination in the Kanmantoo geological province (Cumming and Richards 1975). 11

20 207 Pb/204 Pb Vs. 206 Pb/204 Pb 208 Pb/204 Pb Vs. 206 Pb/204 Pb 15.8 Country rock 40 Analytical precision KRS_ Pb/204 Pb Analytical precision Regional survey samples KRS_143 KRS_142 KRS_8 KRS_22 KRS_147 Kanmantoo sulfide mineralisation 208 Pb/204 Pb Regional survey samples KRS_22 Kanmantoo sulfide mineralisation KRS_143 KRS_147 KRS_8 Country rock Mixing curve Anthropogenic contamination Anthropogenic Contamination Pb/204 Pb Pb/204 Pb % Mineralisation Mixing curve 0% Mineralisation Figure 5 Ratio plots indicating the Pb isotope composition of sulfidic soil-regolith samples, from regional geochemical surveying, relative to Kanmantoo sulfide mineralisation, country rock and anthropogenic contamination. Ellipses define the spread of data and the point within each ellipse represents average Pb isotope composition. The mixing curve estimates the relative contribution of Pb from mineralisation and country rock in each sample. Estimates of country rock Pb and Kanmantoo sulfide mineralisation Pb in sulfidic soil-regolith samples are displayed in Table 3. Sulfidic soil-regolith samples were ranked according to prospectivity based on the percentage and concentration () of Pb derived from Kanmantoo sulfide mineralisation (1 = most prospective). Table 3 Estimation of Pb contributions from country rock and Kanmantoo sulfide mineralisation in samples (AC refers to samples with anthropogenic Pb contamination). Sulfidic soil-regolith samples are ranked according to prospectivity based on the percentage and concentration () of Pb derived from Kanmantoo sulfide mineralisation (1 = most prospective). Sample Total Pb () Mineralisation % Country Rock % Mineralisation Pb () Country Rock Pb () Prospectivity Ranking KRS_ KRS_ KRS_ KRS_ AC AC AC AC 4 KRS_

21 Sample KRS_22 was identified as the most prospective sulfidic sample based on geochemical and Pb isotope analyses (Table 4). This sample was collected from a saline-sulfidic seep on the banks of Rodwell Creek (Figure 4). Thus, the Rodwell Creek study site was identified as an area for further study. Table 4 Prospectivity of sulfidic soil-regolith samples from the Kanmantoo geological province based on geochemical and Pb isotope analysis. Sample Geochemical prospectivity ranking Pb isotope prospectivity ranking KRS_ KRS_ KRS_8 3 3 KRS_ KRS_ Focused Base Metal Exploation 4.1. Geochemistry As part of this study, soil-regolith samples were collected along Rodwell Creek above and below KRS_22 (Figure 3). Sample media included: (i) Permanent sulfidic seeps and wetlands Wet, boggy areas located in drainage depressions and characterised by wetland vegetation including cumbungi (Typha sp.) and rush (Juncus spp.). Associated soil often smelled of H 2 S (rotten eggs), contained chromium reducible sulfur (Table 5) in the form of pyrite framboids (Figure 7 and Figure 8), had a reduced matrix (chroma 2) and total organic carbon contents of > 4 % (Figure 6 a). (ii) Seasonal sulfidic seeps and wetlands seasonally dry areas located in drainage depressions and characterised by the presence of rush (Juncus spp.). Associated soil had a reduced soil matrix (chroma 2) and total organic carbon contents of > 3.5 % (Figure 6 b). (iii) Relict sulfidic seeps and wetlands Buried soil-regolith that formed drainage channel banks. They had a reduced soil matrix (chroma 2), total organic carbon contents of < 2 % and a sharp contact with the overlying soil-regolith (Figure 6 c). It must be noted that this material was primarily identified based on soil colour and geomorphology (i.e. landscape position). Further work would be required to definitively prove that these materials were derived from sulfidic seeps and wetlands (e.g. mineralogy and micromorphology). (iv) Stream sediments Deposits in stream channel. 13

22 (v) Stream overbank Located on the banks of stream channels. Had a sharp contact with underlying soil-regolith. Commonly overlie relict sulfidic seeps and wetlands (Figure 6 c). Bulk samples were analysed for 49 elements by ICP-MS/ICP-OES, on mixed acid digests according to the methods outlined in Appendix 2. Selected geochemical results are displayed in Table 5 to Table 8. A full set of geochemical data is located in Appendix 4. Functioning Seasonally (a) (b) (c) sulfidic wetland functioning sulfidic seep Overbank Relict sulfidic sediment Figure 6 Examples of: (a) a permanent saline-sulfidic wetland, (b) a seasonal sulfidic seep and (c) a relict saline-sulfidic wetland/seep (very dark grey - 10 YR 3/1) overlain by overbank deposit at the Rodwell Creek study site. Table 5 Sulfidic soil-regolith samples from permanent sulfidic seeps and wetlands. Red values exceed threshold concentrations established by Skwarnecki et al. (2002). NA = not applicable. CRS % Ag As Bi Cd Cu In P Pb S Sb Zn Detection NA Background (50 th percentile) NA ND < ND ND Threshold (90 th percentile) NA ND ND ND 4 54 RC_ RC_ RC_ RC_ KRS_

23 Table 6 Soil-regolith samples from seasonal sulfidic seeps and wetlands. No data exists to establish background and threshold concentrations. To aid discussion, relict sulfidic soil-regolith samples are compared to background and threshold values for sulfidic soil-regolith established by Skwarnecki et al. (2002). Red values exceed threshold concentrations. Ag As Bi Cd Cu In P Pb S Sb Zn Detection Background (50 th percentile) ND < ND ND Threshold (90 th percentile) ND ND ND 4 54 RC_ RC_ RC_ RC_ RC_ RC_ RC_ Table 7 Soil-regolith samples from relict sulfidic seeps and wetlands. No data exists to establish background and threshold concentrations. To aid discussion relict sulfidic soil-regolith samples are compared to background and threshold values for sulfidic soil-regolith established by Skwarnecki et al. (2002). Red values exceed threshold concentrations. Ag As Bi Cd Cu In P Pb S Sb Zn Detection Background (50 th percentile) ND < ND ND Threshold (90 th percentile) ND ND ND 4 54 RC_ RC_ RC_ Table 8 Stream sediment samples from Rodwell Creek and its tributaries. ND - No data exists to establish background and threshold concentrations. * Indicates stream overbank deposits. Red values exceed threshold concentrations established by Skwarnecki et al. (2002). Ag As Bi Cd Cu In P Pb S Sb Zn Detection Background (50 th percentile) ND ND ND ND 7 ND ND 28 ND ND 15.5 Threshold (90 th percentile) ND ND ND ND 30 ND ND 54 ND ND 35 RC_7* RC_9 BD RC_13 BD RC_14* RC_

24 Samples from the Rodwell Creek study site were grouped according to bulk geochemistry (Table 9). Group 1 samples included stream sediment and soil-regolith from relict sulfidic seeps and wetlands. They were characterised by relatively low concentrations of elements, which were related to sulfide mineralisation. Group 2 samples were collected from relict sulfidic seeps and wetlands. They had similar geochemical properties to group 1 samples but were relatively enriched in Cd (9 ) and Zn (2150 ). Group 3 samples included stream channel deposits, overbank deposits and soil-regolith from relict sulfidic seeps and wetlands. Compared to groups 1 and 2, these samples were relatively enriched in elements related to sulfide mineralisation. Zinc and cadmium concentrations were similar in groups 2 and 3. Group 4 samples were collected from permanently wet, sulfidic seeps and wetlands. They had very similar geochemical characteristics to group 3 samples but were relatively enriched in S (0.6 to 3.3 %). Scanning electron microscopy (SEM) examination of sample RC_12 and KRS_22 identified Fe, Pb and Zn sulfide associated with organic matter (plant roots) (Figure 7 and Figure 8). Table 9 Samples from the Rodwell Creek study site grouped according to bulk geochemistry. Geochemical group # Sample media Sample # Geochemical characteristics () RC_6, 8, 9 and 13. Ag < 0.3, As < 4, Bi < 0.8, Cd < 1.4, Cu < 38, Pb < 70, In < 0.05, S < 500, Sb < 0.5 and Zn < 170 Stream sediment and soilregolith from relict sulfidic seeps and wetlands. Soil-regolith from relict sulfidic seeps and wetlands. Stream channel and overbank sediment and soil-regolith from seasonal sulfidic seeps and wetlands. Soil-regolith from functioning, permanently wet, sulfidic seeps and wetlands. RC_15 Ag < 0.3, As < 4, Bi < 0.8, Cd > 9, Cu < 38, Pb < 70, In < 0.05, S < 500, Sb < 0.5 and Zn > 2150 RC_1, 2, 4, 5, 7, 10, 14, 16, 17 and 19 RC_3, 11, 12 and 18 KRS_22 Ag > 2.9, As > 6, Bi > 1.5, Cd > 3.5, Cu > 54, Pb > 1250, In > 0.15, 600 < S < 2400, Sb > 4 and Zn > 1000 Ag > 2.9, As > 6, Bi > 1.5, Cd >3.5, Cu > 54, Pb > 1250, In > 0.15, S > 5500, Sb > 4 and Zn >

25 RC_12 Pyrite (a) Pb sulfide along plant root walls I n t e n s i t y (a) Pb S Si 400 O 300 Al C Mg Na P K Ca Fe Zn Energy (KeV) Pb Pb Pb Figure 7 SEM image of sample RC_12 from a permanently functioning saline-sulfidic wetland. contained pyrite and Pb sulfide was present along the edges of plant root walls. Sample 17

26 KRS_22 Pyrite framboids (a) Pb and Zn sulfides along plant root walls I n t e n s i t y krs22 (5043) s22 A5_6_03.spc Pb (a) S Si O 200 C Al Zn Na Mg P K Ca Fe Zn Energy (KeV) Pb Pb Pb Figure 8 SEM image of sample KRS_22 from a permanently functioning saline-sulfidic wetland. contained pyrite and Pb and Zn sulfide was present along the edges of plant root walls. Sample 4.2. Pb Isotopes Lead isotope analysis was carried out on soil-regolith from groups 1, 3 and 4 (Table 9). Samples included: (i) soil-regolith from a relict saline-sulfidic wetland (RC_08), (ii) overbank sediment 18

27 (RC_07) and (iii) soil-regolith from a functioning saline-sulfidic wetland (KRS_22) (Table 10). Lead isotope data for the Wheal Ellen mineralisation is also presented in Table 10 (CSIRO 2003). Ratio plots for soil-regolith samples and the Wheal Ellen mineralisation, relative to Kanmantoo sulfide mineralisation, country rock and anthropogenic contamination, are presented in Figure 9. Table 10 Lead isotope ratio data for Rodwell Creek soil-regolith samples and Wheal Ellen mineralisation samples. Sample Geochemical group # 206 Pb/ 204 Pb 207 Pb/ 204 Pb 208 Pb/ 204 Pb Pb Conc () RC_ RC_ KRS_ Wheal Ellen_1 Not Applicable No data Wheal Ellen_2 Not Applicable No data Wheal Ellen_3 Not Applicable No data 207 Pb/204 Pb Vs. 206 Pb/204 Pb 208 Pb/204 Pb Vs. 206 Pb/204 Pb 15.8 Country rock 40 Analytical precision 207 Pb/204 Pb Analytical precision Wheal Ellen samples 1,2 &3 KRS_22 Kanmantoo sulfide mineralisation RC_8 RC_7 208 Pb/204 Pb KRS_22 RC_7 Kanmantoo sulfide mineralisation Mixing curve RC_8 Country rock Wheal Ellen samples 1, 2 & Anthropogenic contamination 36 Anthropogenic Contamination Pb/204 Pb Pb/204 Pb RC_7 KRS_22 RC_8 100% Mineralisation Mixing curve 0% Mineralisation Figure 9 Ratio plots indicating the Pb isotope composition of soil-regolith samples (red triangles), from the Rodwell Creek study site, relative to Kanmantoo sulfide mineralisation, country rock and anthropogenic contamination (Mt Isa and Broken Hill Pb). Ellipses define the spread of data and the point within each ellipse represents average Pb isotope composition. Green triangles represent the Pb isotope composition of primary sulfide mineralisation (galena) from the Wheal Ellen workings. The mixing curve estimates the relative contribution of Pb from mineralisation and country rock in each sample. 19

28 Samples RC_07 and KRS_22 have Pb isotope compositions, which match the Pb signature of Kanmantoo sulfide mineralisation (Figure 9). These samples contained no detectable levels of country rock Pb and/or anthropogenic contamination (same isotope ratios as Mt Isa or Broken Hill Pb; Table 11). Sample RC_07 was collected from an overbank deposit and contained 2100 Pb. Sample KRS_22 was collected from a functioning, permanently wet, saline-sulfidic wetland and contained 2850 Pb. Both samples had relatively high concentrations of elements related to sulfide mineralisation in the Kanmantoo geological province (Table 9). Lead isotope ratio mixing plots indicated that sample RC_08 contained 86 % Kanmantoo mineralisation Pb and 14 % country rock Pb (Figure 9). This sample contained no detectable levels Mt Isa or Broken Hill derived Pb contamination (Table 11). Sample RC_08 was collected from a buried soil associated with a relict saline-sulfidic wetland or seep and had a total Pb concentration of 39. This sample had relatively low concentrations of elements related to sulfide mineralisation in the Kanmantoo geological province (Table 9). Table 11 Estimation of Pb contributions from country rock and Kanmantoo sulfide mineralisation in soilregolith samples from the Rodwell Creek study site. Sample Total Pb () Mineralisation % Country Rock % Mineralisation Pb () Country Rock Pb () RC_ RC_ KRS_ Discussion In the Rodwell Creek study site, there were 5 potential sources of contaminants, which were associated with Kanmantoo sulfide mineralisation. Sources included: 1. Background concentrations derived from country rock. 2. A hidden, undiscovered zone of sulfide enrichment. 3. Anthropogenic contamination from the unnamed prospect (Figure 10). 4. Anthropogenic contamination from the Wheal Ellen mine (Figure 10). 5. Anthropogenic contamination from the Wheal Ellen smelter (Figure 10). 20

29 Wheal Ellen smelter Wheal Ellen N Unnamed prospect Rodwell Creek Pyritic layer Dispersion Type Primary Transitional Secondary Figure 10 A 3D block diagram showing the relative positions of: (i) Wheal Ellen in operation from 1857 to 1866 and from 1909 to 1911, (ii) the Wheal Ellen smelter in operation from 1861 to 1866 (iii) unnamed prospect period of operation unknown. The red zones around Wheal Ellen and the Wheal Ellen smelter and the red arrows represent primary anthropogenic dispersion, which produced geochemical groups 3 and 4 soilregolith (Table 9). The orange arrows represent transitional anthropogenic dispersion. The yellow arrows represent secondary anthropogenic contamination, which produced geochemical group 2 soil-regolith (Table 9). The pyritic layer was identified using aeromagnetic data by Gum (1998). The yellow box represents the area depicted in Figure 11. All soil-regolith samples analysed contained anomalous element concentrations according to thresholds established by Skwarnecki et al. (2002). Thus, in addition to background element concentrations derived from country rock, all samples were influenced by undiscovered sulfide enrichment or by anthropogenic contamination (Figure 10). Lead isotopes could only be used to differentiate between country rock Pb and the other four sources of Pb at the Rodwell Creek study site. The three possible sources of anthropogenic contamination (Wheal Ellen, Wheal Ellen smelter and the unnamed prospect) had Pb isotope signatures, which matched Kanmantoo sulfide mineralisation (Figure 9). This is a consequence of the sulfide enrichment at Wheal Ellen and the unnamed prospect being of the same age and formed during basin 21

30 development (Section 2.4). Hence, the effectiveness of Pb isotopes as a tool for base metal exploration was significantly decreased at the modified Rodwell Creek study site. Any new, undiscovered zones of sulfide enrichment are likely to have an isotope signature, which matches the anthropogenic contamination caused by historic Pb/Zn mining and smelting. As a result, Pb isotopes can not be used in isolation to differentiate between true geochemical anomalies and locally derived anthropogenic contamination. The following discussion refers to the geochemical groups presented in Table Geochemical group 1 Soil-regolith in geochemical group 1 contained relatively low concentrations of elements related to sulfide mineralisation in the Kanmantoo geologic province. Sample types included stream channel sediments and soil-regolith associated with relict buried wetlands or seeps (Table 9). Stream sediments collected from drainage depressions below RC_9 and adjacent to RC_13 the unnamed prospect (Figure 3) contained element concentrations that were much lower than those collected within Rodwell Creek (Table 8). Lead and zinc concentrations, proximal to the unnamed prospect, were below 70 and 130 respectively, compared to mean concentrations of 2433 and 2217 in the main channel. Samples RC_9 and RC_13 fell in geochemical group 1 (Table 9) and were most likely produced by background country rock and low level anthropogenic contamination from the unnamed prospect. It was not possible to identify any influence of undiscovered sulfide enrichment in these samples. Geochemical group 1 samples were also collected from buried, relict wetlands located in the banks of the main channel of Rodwell Creek (RC_6 and RC_8) (Figure 3). These samples were anomalous in Cd and Zn and had concentrations of Bi, Cu, P and Pb, which exceeded background levels for the Kanmantoo geological province (Table 7). These relict wetlands were disconformably overlain by overbank sediments from geochemical group 3 (Figure 6 c) that contained relatively high concentrations of elements, which were related to sulfide enrichment (Table 9). Isotope analysis indicated that sample RC_8 contained 14 % country rock Pb and 86 % Kanmantoo mineralisation Pb (Table 11). Thus, the relict wetlands in geochemical group 1 acquired their Pb signature from a zone of sulfide enrichment prior to anthropogenic activity. Subsequent upstream mining and smelting at Wheal Ellen did not alter the geochemical composition of this soil-regolith. 22

31 Geochemical group 2 Soil-regolith in geochemical group 2 contained relatively high concentrations of Cd and Zn. All other elements related to sulfide mineralisation were below threshold concentrations. Samples were collected from relict wetlands or seeps (Table 9). Mining activity at Wheal Ellen from 1857 to 1861 released a primary anthropogenic dispersion halo of Bi, Cd, Cu, P, Pb and Zn in drainage depressions below the mine workings (Figure 10). The higher mobility of Cd and Zn in the weathering environment caused these elements to be dispersed (secondary dispersion) for a greater distance along Rodwell Creek (Figure 10). Thus, relict wetland/seep soil-regolith from geochemical group 2 contained relatively high concentrations of Cd and Zn. Subsequent upstream smelting at Wheal Ellen did not alter the geochemical composition of this soil-regolith Geochemical group 3 Anthropogenic contamination from the Wheal Ellen smelter produced soil-regolith that fell in geochemical groups three and four (Table 9). Crushing and smelting of sulfide ore from Wheal Ellen was previously carried out on the banks of Rodwell Creek from 8161 to 1866 (Figure 10). This released an anthropogenic dispersion halo containing Ag, As, Bi, Cd, Cu, In, P, Pb, Sb and Zn downstream along Rodwell Creek (Figure 10). Thus, anomalous concentrations of these elements are found in geochemical group 3 soil-regolith from along Rodwell Creek, which were sampled from: (i) the stream channel, (ii) stream overbanks and (iii) seasonal saline-sulfidic wetlands and seeps Geochemical group 4 Geochemical group 4 soil-regolith samples were collected from functioning, permanently wet, sulfidic seeps and wetlands. They had similar geochemical characteristics to group 3 soil-regolith but contained much higher concentrations of S (Table 9). This was because of the permanent nature of the wetlands, which promoted bacterial reduction of groundwater sulfate to sulfide. Reducing conditions and high concentrations of organic carbon and heavy metals resulted in the formation of organo-metal complexes and the co-precipitation of metal sulfides (e.g. galena) (Figure 7). 6. Model The following description refers to the predictive model illustrated in Figure 11 and Figure 12. This model explains the geochemical and geomorphological evolution of the landscape around the Rodwell Creek study site prior to and following land clearing, mining and smelting. 23

32 Time 1 (T1) Prior to 1857 This was the period before mining commenced at Wheal Ellen. Anecdotal evidence indicates that the countryside consisted of rolling hills dominated by river red gum (Figure 11 T1). Eucalyptus camaldulensis is generally dominant in the community, commonly forming open forests or woodlands (Costermans 1989). These trees obtain water from rainfall, groundwater and river flooding. They have deep sinker roots that grow down towards zones of higher water supply and are effective in conducting water (Heinrich 1990). Hence, the high water use of the river red gums contributes to maintaining the watertable at lower depths (Figure 12 T1) (Dalton 1990). This would have promoted the rapid uptake of water and minimised groundwater recharge and surface flow. As a result, erosion would have been less and drainage depressions less incised than those of the present day (Figure 12 T1). The valley, which now accommodates Rodwell Creek, would have been marshy and permanently wet, satiated and very poorly drained (terminology from: Schoeneberger et al. 2002). The majority of the soil profile would have been wet for prolonged periods, which produced the reducing redoximorphic matrix (permanently wet below 10 cm) evident in the relict wetland soilregolith of geochemical group 1 (Figure 6). This type of saturated environment would have favoured the growth of wetland vegetation (e.g. cumbungi and rush), the subsequent formation of organic rich soil and the onset of reducing conditions. Lead isotope analysis indicated that 86 % of the Pb in relict wetland soil-regolith (RC_08), from geochemical group 1, was sourced from Kanmantoo mineralisation (Section 3.2). This was most likely the result of subsurface transport of mineralisation related elements from a zone of sulfide enrichment to the wetland zone in Rodwell Creek (Figure 12 T1). Reducing conditions and high concentrations of organic carbon would have resulted in the formation of organo-metal complexes and the possible co-precipitation of metal sulfides (e.g. galena) (Figure 7). Time 2 (T2) 1857 to 1861 Although the exact date of land clearance at the Rodwell Creek study site is unknown, settlement of Strathalbyn, the nearest significant town, occurred in 1839 (Figure 1). Thus, it is assumed that vegetation clearance occurred a few years prior to the commencement of mining at Wheal Ellen in 1857 (Figure 11 T2). Vegetation clearing would altered hydrology and destabilised hill slopes. Groundwater flow, through rock fractures, may have declined resulting in the drying out of salinesulfidic wetlands along Rodwell Creek. Large rainfall events may have rapidly saturated the soil resulting in surface flow and possible sheet wash. Drainage depressions would have become more incised, thus resulting in erosion of wetland soil-regolith along Rodwell Creek (Figure 11 T2). 24

33 Previously functioning wetlands that contained sulfidic material were scoured by increased stream flow and subsequently covered by overbank sediments (Figure 12 T2). Mining commenced at Wheal Ellen, which resulted in metal contamination of Rodwell Creek. Metals with higher mobility, such as Cd and Zn, were dispersed further along Rodwell Creek than elements such as Ag, Cu Pb and Sb. Saline-sulfidic wetlands, which had resisted erosion, gained increasingly high concentrations of Cd and Zn. This resulted in the formation of geochemical group 2 soil-regolith (Figure 12 T2). The saline-sulfidic wetlands that ceased to function, which had been scoured and covered by overbank sediments experienced no increase in Cd and Zn concentrations (Figure 12 T2). This formed geochemical group 1 soil-regolith. Time 3 (T3) 1861 to present The establishment of the Wheal Ellen smelter around 1861, on the banks of Rodwell Creek, fuelled the need for wood and hence further vegetation clearing (Figure 11 T3). This would have decreased groundwater flow through rock fractures and increased rates of erosion (Figure 12 T3). Following rainfall events, Rodwell Creek would have been subject to even greater water flow. Drying out and further erosion destroyed the majority of the remaining permanent wetlands. Some wetland soilregolith was covered by overbank deposits and preserved to the present day (Figure 6). Crushing and smelting of the Wheal Ellen ore released further metal contamination to Rodwell Creek. Elements such as Ag, As, Bi, Cd, Cu, In, P, Pb, Sb and Zn were released along the creek. The few permanent saline-sulfidic wetlands, which had resisted erosion, gained increasingly high concentrations of these elements. This resulted in the formation of geochemical group 4 soil-regolith (Figure 12 T3). Elevated concentrations of these elements can also be found in: (i) seasonal salinesulfidic wetlands and seeps, (ii) stream channel sediments and (iii) stream overbank sediments (Figure 12 T3). The saline-sulfidic wetlands that had been scoured and covered by overbank sediments prior to smelting only had elevated concentrations of Cd and Zn (Figure 12 T3). This formed geochemical group 2 soil-regolith. 25

34 T1 T2 Unnamed prospect T , 15 16, , 12 7, Wetland/seep Permanent Seasonal N Figure 11 A predictive diagram illustrating the geomorphological changes, which have taken place at the Rodwell Creek study site prior to and following land clearing, mining and smelting. Each landscape slice represents a different time period,: (T1) prior to 1857 before mining and significant land clearance, (T2) 1857 to 8161 subsequent to mining but prior to smelting at Wheal Ellen, (T3) 1861 to present subsequent to smelting at Wheal Ellen. Blue areas represent permanent seeps and wetlands and the pink areas represent seasonal seeps and wetlands. This diagram represents the area defined by the yellow box in Figure 10. Refer to text for detailed explanation. 26

35 Figure 12 A predictive diagram illustrating the geomorphological and geochemical changes, which have taken place at the Rodwell Creek study site prior to and following land clearing, mining and smelting. The geomorphological effects of land clearing (e.g. erosion, rising water table, decreased groundwater flow through rock fractures) combined with mining and smelting created environments, which promoted the accumulation (formation) of soil-regolith with unique geochemical properties. (T1) Formation of geochemical group 1 wetland soil-regolith. (T2) Formation of geochemical group 2 wetland soil-regolith and the preservation of group 1 soil-regolith. (T3) Formation of geochemical group 3 seasonal wetland soil-regolith, stream channel and overbank sediments. (T3) Formation of geochemical group 4 permanent wetland soil-regolith. Refer to text for detailed explanation. 27

36 7. Geophysical Exploration Anthropogenic contamination from historic mining and smelting made it difficult to identify geochemical anomalies derived form undiscovered zones of sulfide enrichment. Geochemical and isotope results indicated that Pb with isotope characteristics identical to Kanmantoo mineralisation has been stored within relict sulfidic soil-regolith along Rodwell Creek (Section 5). This prompted further exploration for sulfide mineralisation, at the Rodwell Creek study site. Induced Polarization (IP) and resistivity surveys were carried out, using a dipole-dipole array, which crosscut the strike of the local geology and ran proximal to soil-regolith samples RC_6 and RC_8 (Figure 13). In the resistivity method, an artificially-generated electric current was induced into the ground and the resultant potential difference was measured at the surface. This method was used to study the horizontal and vertical discontinuities in the electrical properties of the ground. It was also used to detect any threedimensional bodies of anomalous conductivity. The IP method made use of the capacitive action of the subsurface to locate zones where conductive minerals (e.g. pyrite) were disseminated within the host rock. For a concise summary of these geophysical methods refer to (Kearey et al. 2002). Twodimensional pseudosections were constructed of resistivity (Figure 14) and chargeability (Figure 15), which reflected depth of penetration into the subsurface. Figure 13 Aerial photograph of a portion of the Rodwell Creek study site (refer to Figure 3 for context). Displayed are the relative locations of: (i) soil-regolith sample locations, (ii) resistivity and IP sampling transect, (iii) a resistivity boundary, and (iv) zones of inferred chargeability at depth. 28

37 A B Creek Figure 14 Two-dimensional resistivity pseudosection reflecting depth of penetration into the subsurface. There is a resistivity boundary marked by the creek with less resistive rocks to the west and more resistive rocks to the east. Resistivity transect A-B is marked on Figure 13. A B Creek Figure 15 Two-dimensional IP pseudosection reflecting depth of penetration into the subsurface. There are two zones of chargeability defined by the transect. The smaller zone is located 50 m along transect at a depth of approximately 45 m. The larger zone of chargeability is located 150 m along the transect at depths below 60 m. This zone corresponds to the resistivity boundary identified in Figure 14. Resistivity transect A-B is marked on Figure 13. The pseudosection in Figure 14 highlighted two zones of contrasting resistivity. Most rocks conduct electricity by electrolytic rather than electronic processes. Thus, porosity is the major control of rock resistivity. In general, resistivity increases as rock porosity decreases (Kearey et al. 2002). The yellow line in Figure 13 denoting a resistivity boundary marks a geological change from less resistive rocks, on the west side of the creek, to more resistive rocks on the east (Figure 14). Field observations indicated that the rock type on the west side of the creek were lamina-beds of sandy siltstone and to the east were massive quartzitic sandstone beds. The sandstone had a much lower porosity than the siltstone and hence exhibited more resistive properties (Figure 14). The pseudosection in Figure 15 highlighted two zones of chargeability. The smaller zone was located 50 m along the transect at a depth of approximately 45 m. The larger zone was located 150 m along the transect below 60 m. These zones of chargeability are most likely caused by the presence of disseminated metallic sulfides (e.g. pyrite) within the sandy siltstones and quartzitic sandstones. The 29

38 pronounced nature of the IP response suggest that metallic sulfides are disseminated rather than concentrated in the host rock. 8. Summary Lead isotope and geochemical data were used to rank the prospectivity of sulfidic soil-regolith samples collected as part of a regional geochemical survey by Skwarnecki and Fitzpatrick (2003). The sulfidic soil-regolith sample with the most anomalous Pb isotope and geochemical signature was collected from a saline-sulfidic wetland in Rodwell Creek. This area was selected for more focused base metal exploration. Soil-regolith samples were collected upstream and downstream from the previously identified anomalous sample site. Samples were collected from: (i) permanent sulfidic seeps and wetlands (ii) seasonal sulfidic seeps and wetlands, (iii) stream channel sediments and (iv) stream overbank sediments. Soil morphology, Pb isotope analyses and geochemical analyses were used to distinguish between soil-regolith with geochemical and Pb isotope signatures, which were derived from: (i) anthropogenic contamination (historic mining and smelting), (ii) zones of sulfide enrichment and (iii) country rock (background). This allowed the construction of a predictive conceptual model, which helped explain the relationships between historical events at the Rodwell Creek study site (land clearance, mining and smelting [Pb/Z/Ag/Au/pyrite]) and the (i) morphology, (ii) geochemistry and (iii) Pb isotope composition of various sample media. Lead isotopes, in combination with other geochemical tracers and pedological information, are shown to be a valuable tool to determining sources of Pb in complex anthropogenically disturbed systems. The predictive conceptual model was used to separate anthropogenic geochemical signatures from those that were likely to have originated from unidentified, hidden zones of sulfide enrichment. Thus, a sub-section of the Rodwell Creek study site was identified for further mineral exploration. Geophysical prospecting (IP and resistivity surveys) was carried out and a disseminated zone of potential sulfide enrichment was identified. 30

39 9. References Both RA (1990) Kanmantoo Trough; geology and mineral deposits. In 'Geology of the mineral deposits of Australia and Papua New Guinea; Volume 2.'. (Ed. Hughes) pp (Australasian Institute of Mining and Metallurgy: Melbourne, Victoria, Australia). Bren LJ, Gibbs NL (1986) Relationships between flood frequency, vegetation and topography in a river red gum forest. Australian Forest Research 16, Brooker MIH, Connors JRS, lee AV, Duffy S (2002) EUCLID: eucalypts of southern Australia (CD Rom). CSIRO Publishing, Collingwood. Costermans LF (1989) 'Native trees and shrubs of south-eastern Australia.' (Weldon: Sydney). Cox JW, Ashley R (2000) Water quality of gully drainage from texture-contrast soils in the Adelaide Hills in low rainfall years. Australian Journal of Soil Research 38, CSIRO (2003) Unpublished Pb isotope data base, CSIRO Exploration and Mining, North Ryde, NSW, Australia. Cumming GL, Richards JR (1975) Ore lead isotope ratios in a continuously changing earth. Earth and Planetary Science Letters 28, Daily B, Milnes AR (1971) Stratigraphic notes on lower Cambrian fossiliferous metasediments between Campbell Creek and Tunkalilla Beach in the type section of the Kanmantoo Group, Fleurieu Peninsula, South Australia. Transactions of the Royal Society of South Australia 95, Daily B, Milnes AR (1973) Stratigraphy, structure and metamorphism of the Kanmantoo Group (Cambrian) in its type section east of Tunkalilla Beach, South Australia. Transactions of the Royal Society of South Australia 97, Dalton K (1990) 'Managing our river red gums.' (Soil Conservation Service of New South Wales: Sydney). Dyson IA, Gatehouse CG, Jago JB (1994) The significance of the sequence boundary at the base of the Early Cambrian Talisker Calc-siltstone and its relationship to mineralisation in the Kanmantoo Trough. In 'Geoscience Australia; 1994 and beyond.'. (Eds Freeman, Michael) pp (Geological Society of Australia: Sydney, N.S.W., Australia). Fitzpatrick RW, Skwarnecki M, Raven M, Merry RH, Bonifacio E (2002) Biogeochemical and mineralogical processes in acid sulfate soils: implications for environmental significance. In '17th World Congress of Soil Science'. Bangkok, Thailand. (International Union of Soil Science). Flottmann T, Gum J, Haines PW (1996) Kanmantoo Tectonics, Sedimentology and Metallogeny Excursion. Department of Mines and Energy, South Australia, Field Guide No. 96/40, Adelaide. Foden JD, Turner SP, Morrison RS (1990) Tectonic implications of Delamerian magmatism in South Australia and western Victoria. In 'The evolution of a late Precambrian-early Palaeozoic rift complex; the Adelaide Geosyncline.'. (Eds Jago, B, Moore) pp (Geological Society of Australia: Sydney, N.S.W., Australia). Forrester ST, Janik LJ, Beech TA, McLaughlin MJ (2004) Recent developments in routine soil analysis by mid-infrared; rapid and cost-effective laboratory analysis. ASPAC proceedings (2004). 31

40 Gatehouse CG, Jago JB, Cooper BJ (1990) Sedimentology and stratigraphy of the Carrickalinga Head Formation (low stand fan to high stand systems tract), Kanmantoo Group, South Australia. In 'The evolution of a late Precambrian-early Palaeozoic rift complex; the Adelaide Geosyncline.'. (Eds Jago, B, Moore) pp (Geological Society of Australia: Sydney, N.S.W., Australia). Giblin AM, Carr AR, Andrew AS, Whitford DJ (1994) Exploration of concealed mineralization: Multi-isotopic studies of groundwaters. AMIRA Project 388. Regional hydrogeochemistry of the Kanmantoo fold belt. CSIRO Exploration and Mining14R. Gulson LB, Tiller KG, Mizon KJ, Merry RH (1981) Use of Lead Isotopes in Soils To Identify the Source of Lead Contamination Near Adelaide, South Australia. Environmental Science & Technology 15, Gum J (1998) The sedimentology, sequence stratigraphy and mineralisation of the Silverton Subgroup, South Australia. Unpublished, PhD Thesis, University of South Australia. Heinrich P (1990) The eco-physiology of riparian River Red Gum (Eucalyptus camaldulensis). Australian Water Resources Advisory Council, Final Report No. Final Report. Isbell RF (1996) 'The Australian soil classification.' (CSIRO Australia: Collingwood, VIC, Australia). Jacobs MR (1955) 'Growth Habits of the Eucalypts.' (Forestry and Timber Bureau: Canberra). Jago JB, Dyson IA, Gatehouse CG (1994) The nature of the sequence boundary between the Normanville and Kanmantoo groups on Fleurieu Peninsula, South Australia. Australian Journal of Earth Sciences 41, Janik LJ, Merry RH, Skjemstad JO (1998) Can mid infrared diffuse reflectance analysis replace soil extractions? Australian Journal of Experimental Agriculture 38, Kearey P, Hill I, Brooks M (2002) 'An introduction to geophysical exploration.' (Blackwell Science: Malden, MA). Mancktelow NS (1990) The structure of the southern Adelaide fold belt, South Australia. In 'The evolution of a late Precambrian-early Palaeozoic rift complex; the Adelaide Geosyncline.'. (Eds Jago, B, Moore) pp (Geological Society of Australia: Sydney, N.S.W., Australia). McDonald RC, Isbell RF, Speight JG, Walker J, Hopkins MS (1990) 'Australian soil and land survey field handbook.' (Inkata Press, Melbourne). Offler R, Fleming PD (1968) A synthesis of folding and metamorphism in the Mt Lofty ranges, South Australia. Journal of the Geological Society of Australia 15, Potts PJ (1987) 'A handbook of silicate rock analysis.' (Blackie & Son Limited: Glasgow New York). Sandiford M, Oliver RL, Mills KJ, Allen RV (1990) A cordierite-staurolite-muscovite association, east of Springton, Mt Lofty Ranges; implications for the metamorphic evolution of the Kanmantoo Group. In 'The evolution of a late Precambrian-early Palaeozoic rift complex; the Adelaide Geosyncline.'. (Eds Jago, B, Moore) pp (Geological Society of Australia: Sydney, N.S.W., Australia). Schoeneberger PJ, Wysocki DA, Benham EC, Broderson WD (2002) 'Fieldbook for describing and sampling soils, Version 2.' (Natural Resources Conservation Service, National Soil Survey Center: Lincoln, NE., USA). 32

41 Seccombe PK, Spry PG, Both RA, Jones MT, Schiller JC (1985) Base metal mineralization in the Kanmantoo Group, South Australia; a regional sulfur isotope study. Economic Geology and the Bulletin of the Society of Economic Geologists 80, Skwarnecki M, Fitzpatrick RW (2003) Regional geochemical dispersion in acid sulfate soils in relation to base-metal mineralisation of the Kanmantoo Group, Mt Torrens-Strathalbyn region, eastern Mt Lofty Ranges, South Australia. Cooperative Research Centre for Landscape Environments and Mineral Exploration, CRC LEME Restricted Report No. CRC LEME Restricted Report No 185R, Adelaide. Skwarnecki M, Fitzpatrick RW, Davies PJ (2002) Geochemical dispersion at the Mount Torrens leadzinc prospect, South Australia, with particular emphasis on acid sulfate soils. CSIRO / CRC LEMECRC LEME 174, Adelaide, South Australia. Soil Survey Staff (1999) Soil Taxonomy - a basic system of soil classification for making and interpreting soil surveys, Second Edition. United States Department of Agriculture, Natural Resources Conservation Service, USA Agriculture Handbook No Spry PG (1976) Base metal mineralisation in the Kanmantoo Group, S.A.: the South Hill, Bremer and Wheal Ellen areas. Unpublished B.Sc Honours Thesis, University of Adelaide. Spry PG, Schiller JC, Both RA (1988) Structure and metamorphic setting of base metal mineralisation in the Kanmantoo Group, South Australia. The Australasian Institute of Mining and Metallurgy, Bulletin and Proceedings 293 (1), Sullivan LA, Bush RT, McConchie DM (2000) A modified chromium-reducible sulfur method for reduced inorganic sulfur: optimum reaction time for acid sulfate soil. Australian Journal of Soil Research 38, Toteff S (1999) Cambrian sediment-hosted exhalative base metal mineralisation, Kanmantoo Trough, South Australia. Geological Survey, Report of Investigations No. Report of Investigations, 57. Wade ML, Cochrane GW (1954) Wheal Ellen Mine. Mining Review of South Australia 97,

42 Appendix 1 Soil-regolith sample collection, preparation and analysis The procedures for soil-regolith sample collection, preparation and analytical methods used are summarised in Appendix Figure 1. (i) GPS coordinates recorded, surface and soil features described (vegetation, consistence, colour, texture) (ii) Photograph sample sites (including scale) (iii) Collect 0.5 kg soil samples with clean stainless steel sampling equipment (iv) Transfer sample to air tight jar, evacuate with N 2 and store in ice (v) Representative sample for chip tray (vi) 300g used for saturation extract (vii) 150g freeze dried (viii) 50 g archived in freezer (ix) ICP-OES, Cl -, EC, ph (x) CRS (xi) DRIFTS Appendix Figure 1 Summary of procedures used for soil-regolith sample collection, preparation and analytical methods applied. Abbreviations used: CRS Chromium Reducible Sulfur analysis, ICP-OES - Inductively Coupled Plasma Optical Emission Spectrometry, DRIFTS - Diffuse Reflectance Infrared Fourier Transform Spectral analysis, N 2 nitrogen, Cl - - chloride, EC electrical conductivity. Soil-regolith sample collection Soil-regolith samples were collected using clean, stainless steel equipment to decrease the risk of contamination. At each sample site GPS coordinates were recorded and digital photo were taken to record the context of the sample within the regolith environment. Surface features were described and 34

43 photographed and selected surface samples were collected (i.e. including mineral efflorescence and vegetation). Soil samples were collected from zero to five centimetres and then above and below each observed morphological boundary down the soil profile. Sampling depth was often limited to less than one metre because sample pits frequently filled with groundwater (hydromorphic domain). Soil Munsell colour notation was used to determine matrix and mottle colours with particular focus on redoximorphic features (Soil Survey Staff 1999). Field texturing was carried out according to McDonald et al. (1990) and subsequently verified in the laboratory using Diffuse Reflectance Infrared Fourier Transform Spectral analysis (DRIFTS). Soil consistence was determined according to Schoeneberger et al. (2002) and the presence of organic matter, roots, macrospores and soil fauna was described. A small quantity of sample was placed in a glass beaker and 1 N HCl was added to estimate presence of carbonate and Acid Volatile Sulfur (AVS) (Schoeneberger et al. 2002). Any gas produced was smelt to establish the presence of H 2 S (gas) (rotten egg gas) and hence AVS content. The soil profile was scraped clean and photographed (with scale included). A representative sample was transferred to a chip tray. Approximately 0.5 kg of sample was transferred to an acid washed, glass preserve jar that had been evacuated with N (gas). The jar was sealed with an air-tight lid and stored in ice for transportation back to the laboratory. Soil-regolith sample preparation Approximately 300 g of fresh sample was used for saturation extraction. Fifty grams of sample was archived in a freezer. Approximately 150 g of sample was freeze dried and milled in a Cr-free disc mill (nominal 90% passing through 106 μm). Representative sub-samples were analysed using Diffuse Reflectance Infrared Fourier Transform Spectral analysis (DRIFTS) (Janik et al. 1998) and Chromium Reducible Sulfur analysis (CRS) (Sullivan et al. 2000). Inductively coupled plasma optical emission spectrometry Saturation extracts were analysed for major and minor elements by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) using a Spectroflame Modula (Spectro Analytical Instruments) optimised for high sodium solutions. In this method ions are drawn off a sample into hot ( K) argon plasma. Atomic and ionic emission lines are measured by viewing the appropriate region in the argon plasma tail flame and separation into individual components through a diffraction grating. Emitted light intensity is measured at specific wavelengths by photomultipliers, with elemental concentration directly proportional to intensity (Potts 1987). Elements analysed were: Ca, K, Na, S, Al, B, Cu, Fe, Mn, P, Si, Sr, Zn, As, Cd, Co, Cr, Mo, Ni, Pb, Se. 35

44 Diffuse Reflectance Infrared Fourier Transform Spectral analysis All samples were analysed using Diffuse Reflectance Infrared Fourier Transform Spectral analysis (DRIFTS) after being freeze dried and milled in a Cr-free disc mill (nominal 90% passing through 106 μm). Ground samples were analysed according to the methods described by Forrester et al. (2004). Soil MIR spectra were scanned directly by diffuse reflectance on powdered soil samples. No sample dilution was required. Spectra were recorded in the cm -1 spectral range using a Perkin- Elmer Spectrum-One FTIR instrument with an auto-focusing Perkin-Elmer Diffuse Reflectance accessory, using a one minute scan (Forrester et al. 2004). Spectra interpretation are presented in Appendix B. The spectra were compared to those of soil samples with known properties (Janik et al. 1998) and concentrations measured using partial least squares statistical techniques. Predictions of total organic carbon, ph ca, clay, silt and sand contents and bulk density (BD) for samples are given in Appendix B. The DRIFTS predictions were used to aid in describing and classifying soil profiles according to Soil Taxonomy (Soil Survey Staff 1999) and The Australian Soil Classification (Isbell 1996). 36

45 Appendix 2 Pb isotope sample collection, preparation and analysis Sample Acquisition All samples were collected using clean stainless steel tools to prevent contamination. The Pb isotope composition of groundwater was determined according to the methods outlined in Giblin et al. (1994). Sample Preparation Samples were oven dried at 40 C and milled in a Cr-free disc mill (nominal 90% passing through 106 μm). A representative 25 g sample was sub-sampled and digested with 50% 7N HCl + 50% 7N HNO 3. A double pass through ion exchange columns was used to separate out the Pb. Sample Analysis Samples were analysed for Pb isotopes, at CSIRO Exploration and Mining, North Ryde Minerals Research Laboratories, using a VG ISOMASS 54E solid source thermal ionisation mass spectrometer run in fully automatic mode. Ratios were normalised to accepted values of international standard NBS SRM

46 Appendix 3 Soil properties predicted by Diffuse Reflectance Infrared Fourier Transform Spectral analysis (DRIFTS) Component Clay Silt Sand TOC-glob Bulk Density phca Calibration samples R-Square Units % % % % g/cm 3 RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC

47 Appendix 4 Geochemical data for bulk soil regolith samples. Analysis was conducted on mixed acid digest using ICP-MS and ICP-OES Scheme IC3M IC3M IC3E IC3M IC3E IC3M IC3M IC3M IC3E IC3M IC3E IC3R IC3R IC3R IC3E IC3M Units Detection Sample Depth cm Ag As Ba Bi Ca Cd Ce Co Cr Cs Cu Dy Er Eu Fe Ga RC RC RC 3 Surface RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC 18 Surface RC

48 Scheme IC3R IC3R IC3M IC3E IC3M IC3R IC3E IC3E IC3M IC3E IC3M IC3E IC3E IC3E IC3R IC3M Units Detection Sample Depth cm Gd Ho In K La Lu Mg Mn Mo Na Nd Ni P Pb Pr Rb RC RC RC 3 Surface RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC 18 Surface RC

49 Scheme IC3E IC3M IC3M IC3M IC3M IC3R IC3M IC3E IC3M IC3R IC3M IC3E IC3M IC3M IC3R IC3E Units Detection Sample Depth cm S Sb Se Sm Sr Tb Th Ti Tl Tm U V W Y Yb Zn RC RC RC 3 Surface RC RC RC RC RC RC RC RC RC RC RC RC RC RC RC 18 Surface RC

50 Appendix 5 Lead isotope data Lead isotope data for the Kanmantoo region from: CSIRO (2003) Unpublished Pb isotope data base, CSIRO Exploration and Mining, North Ryde, NSW, Australia. Group 1 Aberfoyle Mount Torrens Galenas Lab Number 208/ / / / /204 Concentration () Run Date Quality Sample Type 0 indicates unspiked High=0 Low=9 1 F373gn reed E+00 4/11/ Sulfides - Galena 2 F374gn E+00 30/10/ Sulfides - Galena 3 F375gn E+00 30/10/ Sulfides - Galena 4 F373gn rel E+00 1/11/ Sulfides - Galena 5 F373gn E+00 30/10/ Sulfides - Galena Group 2 Mount Torrens Base Metal 1 C E+00 3/02/ Sulfides - Other 2 1/ E+00 1/01/ C717 RLD E+00 9/02/ Sulfides - Other 4 C E+00 3/02/ Sulfides - Other 5 4/ E+00 1/01/ / E+00 1/01/ / E+00 1/01/ / E+00 1/01/ / E+00 1/01/ / E+00 1/01/ / E+00 1/01/ Group 3 Mount Torrens Gossan E+03 1/01/ E+03 1/01/ E+03 1/01/ E+02 1/01/

51 Lab Number 208/ / / / /204 Concentration () Run Date Quality Sample Type 0 indicates unspiked High=0 Low= E+02 1/01/ E+03 1/01/ Group 4 Mount Torrens Laterites E+01 1/01/ E+01 1/01/ E+01 1/01/ Group 5 Reference-Mount Torrens 1 1/ E+00 1/01/ E+02 1/01/ E+03 1/01/ E+03 1/01/ E+03 1/01/ E+03 1/01/ / E+00 1/01/ / E+00 1/01/ / E+00 1/01/ / E+00 1/01/ / E+00 1/01/ F375gn E+00 30/10/ Sulfides - Galena 13 F374gn E+00 30/10/ Sulfides - Galena 14 F373gn reed E+00 4/11/ Sulfides - Galena 15 F373gn rel E+00 1/11/ Sulfides - Galena 16 F373gn E+00 30/10/ Sulfides - Galena E+02 1/01/ / E+00 1/01/

52 Lead isotope data for the Kanmantoo region. Samples include unmineralised Talisker Calc-siltstone and soil samples. Sample Type 208/ / / / / /206 Unmineralised Talisker Calc-siltstone Data sourced from: CSIRO (2003) Unpublished Pb isotope data base, CSIRO Exploration and Mining, North Ryde, NSW, Australia Unmineralised soil samples from the Kanmantoo region. Data sourced from: Gulson LB, Tiller KG, Mizon KJ, Merry RH (1981) Use of Lead Isotopes in Soils To Identify the Source of Lead Contamination Near Adelaide, South Australia. Environmental Science & Technology 15, / / / / / /

53