Geochemical and Sr–Nd–Pb–O isotopic compositions of the post-collisional ultrapotassic magmatism in SW Tibet: Petrogenesis and implications for India intra-continental subduction beneath southern Tibet

article i nfo Ultrapotassic lavas having distinct geochemical compositions (K2O/Na2O N2, K2O N3%, and MgO N3%) are common and widespread on the Tibet Plateau, where they are closely linked to N-S-trending normal faults. The Tibetan ultrapotassic rocks range in age from ~8 to 24 Ma, slightly older than the spatially associated potassic rocks (10-22 Ma). These lavas consist mainly of trachyte, trachyandesite, basaltic trachyandesite, phonolite and tephriphonolite. They have high light rare earth element (LREE) and large ion lithophile element (LILE) concentrations, but are low in high field strength elements (HFSE). They are characterized by having extremely radiogenic Sr ( 87