Geochronology of Mexican mineral deposits. IV: the Cinco Minas epithermal deposit, Jalisco

Abstract Two 40Ar/39Ar ages at 24.50 ± 0.07 and 23.46 ± 0.26 Ma (latest Oligocene) were obtained in this paper for adularia separates from vein material of the Cinco Minas low sulfidation epithermal deposit in Jalisco, southwestern Mexico. Such ages confirm the migration of metallogenic activity along with volcanism as the Sierra Madre Occidental migrated southwards since the latest Oligocene and into the Miocene. These deposits are synchronous to andesitic volcanism nearby. In addition, these ages indicate the occurrence of epithermal mineralization prior to the climactic event of ignimbrite flare-up in the Miocene. This makes necessary to refine previous ideas in the metallogeny of southwestern Mexico, which suggested a scenario in which the formation of epithermal and other types of hydrothermal deposits in the region were produced almost exclusively as a result of the early Miocene peak episode of volcanism.