Fission track thermochronology of Neogene plutons in the Principal Andean Cordillera of central Chile (33-35°S): Implications for tectonic evolution and porphyry Cu-Mo mineralization

Apatite fission track data for Miocene plutons of the western slope of the Principal Andean Cordillera in central Chile (33-35 degrees S) define a distinct episode of enhanced crustal cooling through the temperature range of the apatite partial annealing zone (similar to 125-60 degrees C) from about 6 to 3 Ma. This cooling episode is compatible with accelerated exhumation of the plutons at the time of Pliocene compressive tectonism, and mass wasting on the western slope of the Principal Andean Cordillera in central Chile. The timing coincides with the southward migration of the subducting Juan Femandez Ridge and the development of progressive subduction flattening northward of 33 degrees S. It also corresponds to the time of active magmatic-hydrothermal processes and rapid unroofing of the world class Rio Blanco-Los Bronces and El Temente porphyry Cu-Mo deposits. Zircon fission track ages coincide with previous 40Ar/39Ar dates of the intrusions, and with some of the apatite fission track ages, being coherent with igneous-linked, rapid cooling following magmatic intrusion. The thermochronologic data are consistent with a maximum of about 8 km for Neogene exhumation of the plutons.