In-depth lithological and weathering profile of a waste rock dump St-Arnault, Mélanie; Lorca, Maria Eliana; Klein, Bernard; Mayer, K. Ulrich; Beckie, Roger D.
Over the past ten years, the weathering mechanisms of waste rock at the Antamina Cu-Zn-Mo mine in Peru have been investigated. Recently a rotary vibratory drilling program was performed at two locations in the waste dump. The drill program presented a unique opportunity to gather mineralogical and geochemical information and to study the evolution of the alteration profile through time and depth associated with observed lithologies (e.g. skarns, intrusives, marbles, hornfels). The waste dump under investigation is approximately 400m tall with material that is highly heterogeneous in composition and grain size. A previous study showed that the reactivity of minerals vary with depth within the same borehole, because of variations in pore water chemistry and gas transport. The relationship between the variation in reactivity, the lithology, and the alteration profile is investigated in this study. The results provide information on the heterogeneity of the material in the waste dump. The observation of reactivity compared with lithology from the drill hole highlights the potential presence of complex geochemical mechanisms such as galvanic reaction and secondary mineral precipitation. The results will guide future research and demonstrate the contribution of weathering mechanisms on the long term release of metals from waste rock piles.
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