Secondary mineral formation and trace-element reservoirs in weathered waste rock: Integration of quantitative mineralogy and conventional mineralogical techniques

Sulfide minerals and secondary minerals associated with sulfide oxidation were characterized using automated quantitative mineralogy techniques in samples of weathered and freshly blasted waste rock from the Detour Lake Mine, Ontario, Canada. Associations and mineral habits of secondary minerals suggest heterogeneous and dynamic geochemical conditions within the historical waste-rock pile, and the formation of secondary minerals in microenvironments associated with oxidizing sulfide minerals. Electron-probe microanalyses of sulfide grains and alteration rims applied to the modal mineralogy determined by quantitative mineralogy permitted a calculation of trace elements in these reservoirs. The calculations revealed an under-estimation of trace elements by quantitative mineralogy when mass-balance calculations were considered.