Base metal mobility linked to brine and hydrocarbon migration at the Huincul High in the Neuquén Basin, Argentina: Implications for the formation of sediment-hosted base metal deposits

This contribution discusses the discovery of PbZn mineralization in hydrocarbon exploration drill holes hosted in siliciclastic Jurassic rocks below the Cretaceous sediment hosted Cu mineralization located north of the Huincul High. In the Early Cretaceous, hydrocarbon and basinal water expulsion took place from the oil source rocks (Los Molles Formation) into the reservoir rocks Lajas Formation (Middle Jurassic), after the formation of diagenetic quartz overgrowths. Marcasite, pyrite and illite + illite-smectite mixed layer minerals then formed together with hydrocarbons. Marcasite (δ34S −3.5 and −2.2‰) and pyrite (δ34S −11.6 to 18.1‰) precipitated via bacterial sulfate reduction from fluids showing temperatures 100 °C close to the feeder zones a