Contribution of continental subduction to very light B isotope signatures in post-collisional magmas: Evidence from southern Tibetan ultrapotassic rocks

Understanding the subduction and recycling of continental crust is crucial for reconstructing long-term evolutionary history Earth's mantle crust. The Himalaya-Tibet orogen arguably world's best natural laboratory investigating these processes. Cenozoic post-collisional ultrapotassic volcanic rocks are common in Lhasa block southern Tibet they can provide important clues to crust-mantle interaction a well-characterized collision zone. sources processes that generated lavas contribute our understanding thermal compositional characteristics deep geodynamic this region, including Indian subduction. In contribution, we report Sr-Nd-Pb-O-B isotope elemental chemistry data (13-11 Ma) from TangraYumco-Xuruco rift (TYXR) block. arc-like trace-element signatures markedly enriched Sr-Nd-Pb-O compositions indicate mafic originate source containing recycled crustal components. Unlike pre-collisional (?64 with B/Nb (0.85-1.89) ?11B (?9.0 ?2.5‰) values, TYXR much lower (0.05-0.85) (down ?20.5‰) values resemble Miocene K-rich western Anatolia. These Anatolian have been formed by either progressive dehydration stalled slab or deep-subducted However, some samples ratios than MORB, consistent fluid-starved source. negative conjunction low cannot be explained addition melts oceanic sediments, which generally yield but higher MORB (e.g., Armenia rocks). Given upper its similar Sr-Nd-Pb isotopic lavas, it clear contain significant component derived subducted Combined temporal evolution regional magmatism, tectonics geophysical data, propose break-off tearing induced magmatism Our case study provides evidence contributes very light B magmas, suggests isotopes potential discriminate between