Mineral deposits and Cu–Zn–As dispersion–contamination in stream sediments from the semiarid Coquimbo Region, Chile

摘要: This paper presents Cu–Zn–As geochemical data from stream sediment surveys carried out in the three main watersheds of Coquimbo Region Chile. mountainous semiarid realm occupies an area 40,656 km2 between 29° and 32°S. Given that has a long historical record mining activities, important environmental disturbances were expected. However, despite detection major anomalies for Cu, Zn, or As, only one can be unmistakably linked to development mining–metal recovery procedures (Andacollo–Panulcillo). An investigation other two (Elqui Hurtado) reveals causes fully partially account them: (1) type ore deposit associated hydrothermal alteration; (2) regional structural setting (intensity fracturing); (3) climate–landscape. Cu–Au–As epithermal deposits/prospects along so-called El Indio belt are here regarded as sources both Elqui Hurtado anomalies. The strong advanced argillic alteration present some may have induced loss buffering capacity rocks, therefore favoured metal dispersion during later oxidation–leaching sulphides. applies Conversely, given potassic, propylitic phyllic alterations do not affect minor is observed relation Los Pelambres porphyry copper deposit. Besides, located within highly fractured Andean domain (3,000–4,000 m altitude), which conditioned fast unroofing deposits, contributed enhanced circulation meteoric waters, eventually, oxidation, leaching metals. Metal aggravated rainy years response Nino episodes.