Non-monotonic cooling history in the southern Central Andes recorded by multisystem low-temperature thermochronology

Abstract

Three low-temperature thermochronometers are used to study the temperature and exhumation history of the Sierra Laguna Blanca, a major basement range that rises over 6 km in the backarc region of the Central Andes. Five samples analyzed with zircon (U-Th-Sm)/He thermochronology yield early Carboniferous to early Triassic dates. Ten apatite fission-track samples provide ~50 to 70 Ma ages with shortened, ~11-12 µm track lengths. Ten apatite (UTh-Sm)/He samples yield highly dispersed dates ranging from ~30 Ma to 120 Ma, with eU values ranging from ~50 to 500 ppm. Time-temperature inverse and forward models reveal three major cooling events at the late Paleozoic, late Cretaceous and mid-late Miocene, and a heating event during late Eocene to early Oligocene. This study demonstrates that accumulated radiation damage, in this case caused by very high eU instead of a prolonged low-temperature history, may lead to significant apatite (U-Th-Sm)/He date dispersion