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Minerals 2016, 6(2), 52; doi:10.3390/min6020052

Geoenvironmental Characterisation of Heap Leach Materials at Abandoned Mines: Croydon Au-Mines, QLD, Australia

Transforming the Mining Value Chain (TMVC) ARC Industrial Transformation Research Hub, School of Physical Sciences, University of Tasmania, Private Bag 79, Hobart, Tasmania 7001, Australia
Academic Editor: Bernhard Dold
Received: 10 April 2016 / Revised: 23 May 2016 / Accepted: 25 May 2016 / Published: 31 May 2016
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Abstract

Heap leaching is a well-established metallurgical technology which allows metal recovery (e.g., Au, Cu, U) from low-grade ores. However, spent heap leach materials remaining at abandoned or historic mine sites may represent a potential source of contamination. At the Croydon Au-mines, heap leaching operations (1984–1985) were performed on mineralized rhyolites hosting sulphides including pyrite, galena, arsenopyrite and minor sphalerite. Characterization of spent heap leach materials (n = 14) was performed using established geochemical and mineralogical techniques, supplemented by automated mineralogical evaluations. Whilst these materials contained low sulphide-sulphur (0.08 to 0.41 wt %) and returned innocuous paste pH values (pH 5.1 to 8.6), they were classified uncertain by net acid producing potential/net acid generating criteria. This was likely due to the reaction of secondary mineral phases (i.e., beudantite, hidalgoite, kintoreite and Fe-As-Pb oxides) during these tests. It is hypothesised that during heap leaching, gangue sulphides have differentially reacted with the cyanide lixiviant, pre-conditioning the formation of these complex secondary phases during surficial oxidation, after heap leaching termination. These materials are considered to represent a moderate geoenvironmental risk as dissolved Pb in basal leachates is in excess of the World Health Organization (WHO 2006) guideline values. Considering this, these materials should be included in ongoing rehabilitation works at the site. View Full-Text
Keywords: heap leach; AMD; automated microscopy; mineral-liberation-analyser; mineralogy heap leach; AMD; automated microscopy; mineral-liberation-analyser; mineralogy
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Parbhakar-Fox, A. Geoenvironmental Characterisation of Heap Leach Materials at Abandoned Mines: Croydon Au-Mines, QLD, Australia. Minerals 2016, 6, 52.

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