A garnet-bearing schist from the southernmost such exposure along the Himalaya in east central Nepal records prograde metamorphism at 32.4±0.3 Ma.Phase equilibria modelling,combined with Ti-in-biotite and quartz ...A garnet-bearing schist from the southernmost such exposure along the Himalaya in east central Nepal records prograde metamorphism at 32.4±0.3 Ma.Phase equilibria modelling,combined with Ti-in-biotite and quartz caxis thermometry,outline a tight-to-hairpin pressure-temperature(P-T)path extending from~515℃ and 5.5 kbar to peak conditions at~575℃ and 7 kbar followed by deformation during the retrograde phase at 480-515℃ and 6-7 kbar.The new geochronology data place an upper bound on the evolution of metamorphism and deformation in the frontal-most part of the Himalaya,which lasted until 17.5 Ma,as indicated by previously published ^(40)Ar/^(39)Ar data.The P-T-time data from this part of the Himalaya,as well as that from more hinterlandward portions of the orogen,outline a progressive,stepwise,commonly out-of-sequence evolution.Further data from along the orogen indicates that this evolution is not a local phenomenon,but instead characterizes the tectonics of this system as a whole.展开更多
基金supported by an NSERC Discovery Grant and Accelerator SupplementCanadian Foundation for Innovation John Evans Leadership Fund award to K.Larson+1 种基金Stipend and research support for S.Shrestha was provided by an NSERC Postgraduate Scholarshipa UBC Okanagan Fipke Scholar Award。
文摘A garnet-bearing schist from the southernmost such exposure along the Himalaya in east central Nepal records prograde metamorphism at 32.4±0.3 Ma.Phase equilibria modelling,combined with Ti-in-biotite and quartz caxis thermometry,outline a tight-to-hairpin pressure-temperature(P-T)path extending from~515℃ and 5.5 kbar to peak conditions at~575℃ and 7 kbar followed by deformation during the retrograde phase at 480-515℃ and 6-7 kbar.The new geochronology data place an upper bound on the evolution of metamorphism and deformation in the frontal-most part of the Himalaya,which lasted until 17.5 Ma,as indicated by previously published ^(40)Ar/^(39)Ar data.The P-T-time data from this part of the Himalaya,as well as that from more hinterlandward portions of the orogen,outline a progressive,stepwise,commonly out-of-sequence evolution.Further data from along the orogen indicates that this evolution is not a local phenomenon,but instead characterizes the tectonics of this system as a whole.
