APPLICATION OF MLA IN REACTIVE TRANSPORT MODELING OF WEATHERING PROCESSES IN INTENSELY STRATIFIED TAILINGS

摘要

Reactive transport simulations have been applied to investigate possible effects of stratification on the potential of sulfide-bearing mine tailings to form protective cemented layers and to retain toxic elements. Our research is based on a German tailings site, which material is intensely stratified on a mm-cm scale. Multiple cemented layers have been observed in the oxidized part of the tailings, mainly consisting of jarosite, gypsum, as well as gel phases including amorphous iron arsenate, ferrihydrite, amorphous silica and alumino silicates. For the purpose of reactive transport modeling, detailed information on changes in mineralogical composition is indispensable. In this paper, the application of Mineral Liberation Analysis (MLA) was investigated. MLA generally results in a microscopic image of the identity and quantity of mineral particles and assemblages, as well as of the geometry of particles and pores. An MLA image of a polished thin section of a representative sequence of mm-thin strata was measured, and the results were input in a ID reactive transport model. Although the MLA image may be perfect for input in 2D pore scale models, its application in ID reactive transport models requires extracting and summarizing the image data for individual lamina. The resulting reactive transport model was found to be very successful in reproducing the observed cemented layers and arsenic retention in these layers.