Abstract
Distinguishing natural from mining-derived sulfate in surface water is particularly challenging in high-altitude catchments hosted in intensely hydrothermally altered lithologies.
Two compliance monitoring stations downstream of two high-sulfidation epithermal deposits (VD and PL) were investigated using a triple-tracer Bayesian isotope mixing model (δ³⁴SSO4, δ¹⁸OSO4, δ¹⁸Owater; MixSIAR). Natural hydrothermal and geothermal sources dominate sulfate loading at both stations: at TAG_mid (VD), DPB and TAG_sup account for ~66% of the sulfate budget, with mining-related contributions (~8%) smaller than the unaccounted source fraction.
At TAG_low (PL), the upstream TAG_mid reach contributes ~74%, propagating the predominantly natural signal downstream. In contrast to sulfate, dissolved As decreases ~600-fold between TAG_mid and TAG_low, while total As loads remain near-conservative (~4.5% decrease), indicating phase transfer to the particulate fraction through Fe-hydroxide co-precipitation induced by lime treatment rather than mass removal from the system.
Co-authors
Camilo Raúl de los Hoyos1, Claudina González1, Juana María Canavessi1, Matthew Leybourne2, Daniel Layton-Matthews2, Alejandro Verri Kozlowski1, Robert Bowell3
1: SRK Consulting (Argentina) S.A., Salta, Argentine Republic; 2: Queen’s Facility for Isotope Research, Kingston, Canada; 3: SRK Consulting (UK) Ltd., Cardiff, Wales
