Subduction of Indian continent beneath southern Tibet in the latest Eocene (~ 35 Ma): Insights from the Quguosha gabbros in southern Lhasa block

摘要: Abstract Geophysical data illustrate that the Indian continental lithosphere has northward subducted beneath Tibet Plateau, reaching Bangong–Nujiang suture in central Tibet. However, when started to subduct, and whether crust injected into mantle southern Lhasa block, are not clear. Here we report new results from Quguosha gabbros of LA-ICP-MS zircon U–Pb dating two samples gives a ca. 35 Ma formation age (i.e., latest Eocene) for gabbros. The gabbro geochemically characterized by variable SiO 2 MgO contents, strongly negative Nb–Ta–Ti slightly Eu anomalies, uniform initial 87 Sr/ 86 Sr (0.7056–0.7058) e Nd (t) (− 2.2 − 3.6). They exhibit Sr–Nd isotopic compositions different those Jurassic–Eocene magmatic rocks with depleted characteristics, but somewhat similar Oligocene–Miocene K-rich enriched characteristics. We therefore propose an crustal component was added lithospheric subduction at least prior Eocene (ca. 35 Ma). interpret mafic magmas have been generated partial melting metasomatized sediments, which entered channel(s) then probably accreted or underplated overlying during continent. Continental likely played key role Tibetan plateau earlier date than previously thought.