- MSI Auditorium (1st floor)
Michael Stearns will present his PhD defense entitled "Evolution of the Pamir deep crust: the petrochronology record of orogenic thickening and exhumation" on Thursday, July 31 at 12:00 PM in the MSI Auditorium (1st floor).
Abstract: The India-Asia collision is the foremost setting to study continent-continent orogenesis, yet mid–deep crustal exposures are rare. In contrast, the Pamir Plateau provides extensive aerial exposure of the deep crust within six gneiss domes. The domes contain a variety of Cenozoic-age metamorphic and igneous rocks exhumed from 8–10 kbar and ≥700 ºC. The growth and recrystallization of major and accessory phases in these rocks such as garnet, monazite, and titanite record a robust history of the evolution of the plateau through crustal thickening, metamorphism, and subsequent ongoing collapse. Extracting this record requires accurately understanding and directly linking minerals response to the crustal process of interest. Petrochronology by in situ U/Th-Pb chronometry, trace-element analysis, and thermobarometry is the key to unlocking the physiochemical evolution of the Pamir mid–deep crust, and orogenic processes in general around the world. The following dissertation contains I) an evaluation of whether titanite records volume-diffusion closure or (re)crystallization, II) a comparison of the monazite record from the Central Pamir and Northern Himalaya gneiss domes, and III) campaign-style titanite petrochronology investigation of the onset of collapse in the Pamir plateau.