Depositional age of Jurassic epithermal gold-silver ore in the Deseado Massif, Patagonia, Argentina, based on Manantial Espejo and La Josefina prospects

摘要

Middle to Upper Jurassic bimodal volcanism developed during widespread extensional tectonism within the Deseado Massif in Argentinean Patagonia. This geologic environment led to the formation of numerous epithermal gold-silver deposits that are spatially and temporally related to the volcanic activity. The age constraints of the volcanic rocks that host the veins define Upper Jurassic ages for the volcanism. New U-Pb SHRIMP studies of zircons from ignimbrites from Manantial Espejo and La Josefina epithermal prospects are reported. The Manantial Espejo prospect dates (similar to 167, similar to 163 and 158.9 +/- 0.45 Ma) suggest that mineralization took place 6 My after the deposition of the host rock. The zircons of La Josefina prospect show a concordant age of 152.7 +/- 2.3 Ma that suggests temporal overlapping between volcanism and mineralization.