Middle-Late Jurassic magmatism in the west central Lhasa subterrane, Tibet: Petrology, zircon chronology, elemental and Sr-Nd-Pb-Hf-Mg isotopic geochemistry

Mesozoic magmatic rocks are widespread in the Lhasa terrane, but most of them cretaceous age. Because Jurassic relatively rare and our knowledge on such earlier magmatism context tectonic setting evolution is limited. In this study, we focus mid-late granitoids that occur west central subterrane. We present results a systematic study these granitoid tonalite composition together with hosted mafic enclaves. dated 4 representative samples 2 enclaves using zircon U-Pb method gives age range 167–154 Ma. All have Sr-Nd-Pb isotopic compositions (87Sr/86Sr = 0.713941–0.718417, εNd(t) −14 to −9.8, 206Pb/204Pb 18.806–18.936, 207Pb/204Pb 15.739–15.764, 208Pb/204Pb 39.257–39.798) similar gneisses from basement suggesting magmas parental tonalitic largely crustal origin, which also supported by petrographic observations. Both wide span εHf(t) −15.9 −0.2 − 13.8 −7.4, respectively. These show varying δ26Mg ranging −0.40 −0.18, an average −0.27 ± 0.06‰ (2SD) best understood as representing Mg continental crust terrane. observations allow us conclude basaltic melts derived metasomatized mantle were involved petrogenesis granitoids. Specifically, southward subduction Bangong-Nujiang Ocean lithosphere subsequent slab rollback wedge lithospheric above, whose melting produced magmas. Underplating intrusion caused generation study.