Conference Agenda

We present initial results from a combined structural and geochemical assessment designed to improve AMD classification at the Martabe gold mine, Indonesia. Martabe conforms to a classic epithermal acid sulfate model displaying local variations in structure and geochemistry that are difficult to constrain using existing resource models. Fracture-controlled mineralisation and oxidation explains the observed irregular and incomplete “oxidation zones” in which Jarosite, a non-sulfide cause of AMD is found. Supported by outcrop analogues such as the Rodalquilar gold mine in SE Spain, these observations imply detailed grade control drilling is justified to improve model resolution and improve waste rock management efficiency.

The effectiveness of a proposed low permeability cover system for historical mining waste at the abandoned Abbey Consols lead-zinc mine, Wales, UK, was tested using laboratory columns. A reduced infiltration rate could still result in release of metals reducing the benefits of the cover system. Two column scenarios simulated average infiltration conditions and a reduced infiltration rate (the low permeability cover). Results showed the reduced infiltration column produced higher concentrations of key solutes (cadmium, lead and zinc) but a lower load. Zinc and cadmium loads narrowed between the two columns over time suggesting the low permeability cover benefit diminishes.

Traces of water-rock interaction in two drill cores from the West field of the former Ibbenbüren anthracite coal were related to both diagenesis and relatively recent weathering processes along open fractures. The coupled appearance of kaolinite-dickite-illite minerals in weathered and unweathered rock sections was clearly connected to the burial history of the Carboniferous sequence. In contrast, the formation of iron (oxide-) hydroxides together with the presence of oxidized pyrite in weathering profiles along both sides of the fractures was positively related to the geochemical footprint of the coal mine drainage.

Current Finnish practices in waste rock characterization may result in improper drainage quality prediction. In this paper, we present a case study involving such inadequate predictions. Our results demonstrated that the waste rock materials with relatively low contents of harmful elements and S can still produce poor-quality drainage, and the waste rock characterization approach developed by the government should be re-evaluated. Special attention should be paid to low carbon content, low neutralization potential, and geochemical properties of single rock types rather than average concentrations of the whole rock mass.