Leaching of sulfidic backfill at the Thalanga Copper-Lead-Zinc mine, Queensland, Australia

Thienenkamp, M., and Lottermoser, B.G. (2003) Leaching of sulfidic backfill at the Thalanga Copper-Lead-Zinc mine, Queensland, Australia. In: Proceedings of the Sixth International Conference on Acid Rock Drainage (ICARD). pp. 1133-1134. From: ICARD Sixth International Conference Acid Rock Drainage , 12-18 July 2003, Cairns, Queensland, Australia.

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The placement of sulfidic waste below the groundwater table ensures limited interaction with the hydrosphere and suppression of sulfide oxidation. However, if sulfidic waste is placed above the groundwater table and remains uncovered, the backfill becomes part of the unsaturated zone and is exposed to atmospheric oxygen and leaching. This study aims to establish the leaching behaviour of sulfidic waste placed above the groundwater table and the impact of such leachate on the local aquifer at the Thalanga base metal mine. Mining of the Thalanga copper-lead-zinc deposit resulted in a large final mining void (600 m × 150 m × 70 m) and extensive underground workings. The underground workings were partly filled with tailings and the open pit was partly backfilled with acid producing sulfidic waste rock. In addition, the pit serves as a sink for acidic run-off from adjacent waste rock piles and mine workings. To date, the backfill of sulfidic waste rock placed into the pit has not been capped with benign materials and for most of the dry season, the surface of the backfill is covered by melanterite-type efflorescences. Results of kinetic column leach experiments conducted on the sulfidic waste indicate that Cd, Cu, Zn and SO4 rich waters migrate from the backfilled sulfidic waste into the local unconfined aquifer. However, the seepage of alkaline (pH 7.3 - 8.0), high conductivity (>10 000 µS/cm) tailings waters into the remaining pit void clearly shows that the acid leachate originating from the sulfidic waste rock does not impact beyond the waste repository and its immediate environment. Geochemical modelling implies that minimal or no mixing occurs between the acid waste rock leachate and the alkaline tailings waters.

Item ID: 3535
Item Type: Conference Item (Research - E1)
ISBN: 1-875776-98-2
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The theme of the "ICARD Sixth International Conference Acid Rock Drainage" is "Application and Sustainability of Technologies."

Date Deposited: 13 Jul 2009 05:48
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