Authors: Carpenter, DJ; Gillow, J


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Carpenter, DJ & Gillow, J 2011, 'Geochemical modelling aids in mine closure – implications of orebody genesis to mine closure approaches', in AB Fourie, M Tibbett & A Beersing (eds), Proceedings of the Sixth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 389-392,

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Safe and successful mine closure represents a fundamental work element that needs to accommodate the geochemical conditions existing at the completion of the mining and ore processing effort. Given the interests in limiting costs and time associated with mine closure efforts enhanced prior understanding of the geochemical conditions likely to exist upon exhaustion of the economic reserves can provide important benefits. The purpose of this paper is to document the benefits associated with geochemical modelling and understanding how the ore formation process may impact mine closure efforts, using one ore deposit type as an example. Specifically, this paper emphasises the geochemical processes leading to the formation of sandstone-hosted uranium roll-type deposits and how the resultant concentrations and distributions of ore and gangue phases need to be incorporated into understanding the geochemical conditions projected to exist at the end of mineral recovery efforts. The paper describes the evolution of geochemical conditions leading to orebody formation and the geochemical effects induced by open pit mining and how these may be used to understand both the geochemical controls and constraints on residual mine water. In addition, a discussion will be provided on how these conditions may be simulated by solution equilibria and kinetic modelling to develop optimum approaches to achieve applicable closure standards. This paper also discusses specific augmentations to existing industry standard solution equilibria and kinetic models and associated thermodynamic databases to maximise the predictive accuracy of the geochemical modelling results. The benefits of understanding the electrochemically reactive behaviour of uranium and associated gangue phases and incorporating this behaviour into mine closure efforts are presented. The culmination of the benefits of the geochemical modelling will ultimately be the development of a sustainable approach to uranium mine closure that is based upon an engineered environment designed to return the orebody to stable geochemical conditions.

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