Evaporative Mine Water Controls on Natural Revegetation of Placer Gold Mines, Southern New Zealand

Druzbicka, Joanna; Rufaut, Cathy; Craw, Dave

doi:10.1007/s10230-014-0303-7

Cited by 25 publications

(20 citation statements)

References 34 publications

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“…Part of the Gilberts Gully site has recently been designated a scientific reserve for preservation of salt pans, and our observations on salt environments were obtained from this reserve (Fig. 2B;Chapman Road;Druzbicka et al, 2015). Similarly, an area adjacent to the Butchers Dam gold placer has recently been reserved and also includes salt pans.…”

Section: Methodsmentioning

confidence: 99%

“…Rock major element data on the drill core were obtained by X-ray fluorescence using a Philips 2400 instrument at University of Otago, with international standards for calibration (Stein et al, 2011). Volatile contents, mainly water, was determined by loss on ignition by heating at 1100°C for 1 h. Geochemical data on surface and groundwater compositions were compiled from a range of sources outlined in Craw and Nelson (2000); Craw (2000); Litchfield et al (2002); Craw et al (2013), and Druzbicka et al (2015). Orogenic gold exploration data were compiled from numerous unpublished company reports, as described by Craw et al (2015).…”

Section: Methodsmentioning

confidence: 99%

“…Rainfall is currently sufficiently low to facilitate formation of surface salt deposits derived by evaporation of marine aerosols in rainwater ( Fig. 2B; Table 1; Craw et al, 2013;Druzbicka et al, 2015). Salt pans are particularly common on exposed areas of clay-altered basement, which form an impermeable substrate for evaporative accumulation ( Fig.…”

Section: General Settingmentioning

confidence: 98%

“…Salt pans are particularly common on exposed areas of clay-altered basement, which form an impermeable substrate for evaporative accumulation ( Fig. 2B; Druzbicka et al, 2015). A range of evaporative minerals, dominated by halite, has formed on exposed surfaces of these clay-rich alteration zones (Fig.…”

Section: General Settingmentioning

confidence: 98%

“…Outcrops of the goldbearing unconformity are almost invariably coated with evaporative salts to some extent ( Fig. 2B; Druzbicka et al, 2015).…”

Section: Physically Recycled Goldmentioning

confidence: 98%

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Gold nugget morphology and geochemical environments of nugget formation, southern New Zealand

Craw

Lilly

2016

Ore Geology Reviews

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: General Settingmentioning

confidence: 98%

Section: General Settingmentioning

confidence: 98%

“…Outcrops of the goldbearing unconformity are almost invariably coated with evaporative salts to some extent ( Fig. 2B; Druzbicka et al, 2015).…”

Section: Physically Recycled Goldmentioning

confidence: 98%

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Gold nugget morphology and geochemical environments of nugget formation, southern New Zealand

Craw

Lilly

2016

Ore Geology Reviews

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Evolution of Alkaline Mine Drainage and Unique Biodiversity on Soil-Free Mine Substrates, Southern New Zealand

2023

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Relatively impermeable soil-free substrates (clay-rich outcrops and sediments) exposed at eight abandoned placer gold mines generate alkaline mine drainage through evaporation and minor interaction between water and rock in a semi-arid rain shadow climate. Original mine sluicing a century ago created drainage channels over the land surface that still control the flow of ephemeral surface waters, with localised construction of erosional outwash pans. Ephemeral surface waters and associated evaporitic salts are dominated by halite derived from marine aerosols in rain, yielding circumneutral pH and electrical conductivity (EC) values locally exceeding 50 mS/cm. Weakly altered schist basement rocks and Miocene mudstone exposed at the surface contain abundant calcite, and surface waters are supersaturated with respect to Ca-carbonate minerals with a pH of ≈ 8 and an EC of ≈ 1 mS/cm. Water interaction with albite increases the dissolved Na/Cl molar ratio to > 1, and evaporative formation of Na-carbonate precipitates can raise the pH to > 10. Pyrite oxidation does not offset the alkaline pH in any of these processes, although dissolved sulfate can rise to high levels (> 2000 mg/L; EC ≈ 5 mS/cm), forming evaporative sulfate minerals. Ephemeral waters drain down outcrops and the relatively impermeable erosional pans, leaving salt encrustations with variable mineralogy and associated waters with pH and EC values that are partially controlled by rates of dissolution and reprecipitation of the minerals in the salts. The saline alkaline chemistry of the pans excludes most vegetation and has allowed development of salt-tolerant ecosystems with rare endemic halophytic plants. Maintenance of soil-free halophytic surfaces has potential applications in dryland mine sites around the world, especially as climate change enhances and extends aridity.

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Potential for Pastoral Irrigation Using Sulphate-Rich Waters at Macraes Gold Mine, Southern New Zealand

Rufaut

Weightman

Craw

et al. 2022

Water Air Soil Pollut

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There is growing recognition that elevated dissolved sulphate around mines will lead to significant environmental issues within the industry that need specific management. Various sulphate attenuation engineering methods exist, and so processes that could occur within a mine site are of particular interest. In this pilot study, we investigate the possibility of using high-sulphate mine water (~ 2500 mg/L) for irrigation of farm land. This approach is made feasible from mildly alkaline (pH ~ 8), non-toxic discharge waters at a semi-arid gold mine site. Geochemical models predicted Ca-sulphate will readily precipitate from the mine water at pH 6 and potentially attenuate downstream concentrations of dissolved sulphate. We used the slightly acidic natural soil environment (pH 5–6) of the mine to test initial model predictions in the laboratory and field trials. Ca-sulphate in gypsum formed in experimental soil columns, and the pH of input water lowered by 2–3 units. In the field, only minor soil gypsum was observed, and instead Mg-sulphate and Ca-carbonate were found more readily on evaporation surfaces. Additional terrestrial effects of soil dilution, leaching, and plant uptake of sulphate are discussed. Irrigated pasture had healthy, green plants that supported a potentially dual benefit of mine water irrigation to enhancing farm productivity in the local community. Irrigation is an effective way to manage mine waters with high dissolved sulphate but requires further trials to refine methods and the feed values of pasture.

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Evaporative Mine Water Controls on Natural Revegetation of Placer Gold Mines, Southern New Zealand

Cited by 25 publications

References 34 publications

Gold nugget morphology and geochemical environments of nugget formation, southern New Zealand

Gold nugget morphology and geochemical environments of nugget formation, southern New Zealand

Evolution of Alkaline Mine Drainage and Unique Biodiversity on Soil-Free Mine Substrates, Southern New Zealand

Potential for Pastoral Irrigation Using Sulphate-Rich Waters at Macraes Gold Mine, Southern New Zealand

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