Thurston Island (West Antarctica) Between Gondwana Subduction and Continental Separation: A Multistage Evolution Revealed by Apatite Thermochronology

The first low-temperature thermochronological data from Thurston Island, West Antarctica, provide insights into the poorly constrained thermotectonic evolution of the paleo-Pacific margin of Gondwana since the Late Paleozoic. Here we present the first apatite fission track and apatite (U-Th-Sm)/He data from Carboniferous to mid-Cretaceous (meta-) igneous rocks from the Thurston Island area. Thermal history modeling of apatite fission track dates of 145-92 Ma and apatite (U-Th-Sm)/He dates of 112-71 Ma, in combination with kinematic indicators, geological information, and thermobarometrical measurements, indicate a complex thermal history with at least six episodes of cooling and reheating. Thermal history models are interpreted to reflect Late Paleozoic to Early Mesozoic tectonic uplift of pre-Jurassic arc sequences, prior to the formation of an extensional Jurassic-Early Cretaceous back-arc basin up to 4.5 km deep, which was deepened during intrusion and rapid exhumation of rocks of the Late Jurassic granite suite. Overall Early to mid-Cretaceous exhumation and basin inversion coincided with an episode of intensive magmatism and crustal thickening and was followed by exhumation during formation of the Zealandia-West Antarctica rift and continental breakup. Final exhumation since the Oligocene was likely triggered by activity of the West Antarctic rift system and by glacial erosion.