Geology Club Seminar
In southern Tibet, voluminous granitoids of the Gangdese batholith emplaced between ~200 Ma to 20 Ma provide a spatiotemporal window into the geochemical and tectonic evolution of the crust throughout the India-Asia collision. Indirect geochemical proxies for estimating crustal thickness have recently become popularized as a method for reconstructing the crustal evolution of the Tibetan Plateau throughout collision. In this talk I evaluate the validity of isotopic and geochemical tracers for crustal thickness, and present new data for a suite of granitoids along a N-S transect near Lhasa, Tibet. Hf and O isotope geochemistry of whole rocks and constituent zircons together with whole-rock chemistry reveal a coherent magmatic history of Gangdese granitoids. I compare zircon and whole-rock εHf data with previous Nd-based thermoisotopic models, which indicate that the Lhasa block maintained a wedge-shaped crustal geometry from the early Jurassic until the onset of collision. I will also present preliminary findings of coupled quartz and zircon Ti thermobarometry.