Origin of Late Cretaceous, enclave-bearing granitoids in southern Tibet: Implications for magma recharge and crustal thickening

Exposures of enclave-bearing granitoids can provide rare opportunities to directly evaluate the connection between compositional variability and depth origin arc magmatic rocks. The ∼1000 km long Gangdese batholith is a composite with composition from mafic felsic; SiO2 ranges 51 wt% 70 wt%. New zircon U−Pb dating Nyemo plutons, Renbu Xigaze plutons in consistent their emplacement crystallization Late Cretaceous (ca. 90−85 Ma). Mafic enclaves (MMEs) are characterized by low (50.9−56.0 wt%) Nb/U, Ce/Pb, Nb/La ratios coupled enrichment light earth elements large ion lithophile depletion high field strength elements. These geochemical features, combined depleted whole-rock εNd(t) (+4.2 +4.7) εHf(t) (+9.0 +13.8), suggest that they were derived partial melting mantle source associated subduction-related fluids. (55.6−66.9 display adakitic characteristics, such as Y Yb contents, Sr/Y La/Yb ratios. Their positive (+4.0 +5.5) (+6.9 +14.3) values, well incompatible elements, indicate juvenile lower crust. Geochemical modeling suggests diversities MMEs inherited heterogeneous sources. This genetic relationship indicates underplated basaltic magmas could have supplied sufficient heat trigger thickened crust thus formation granitoid. In this regard, rocks mirror evolution crustal thickness. Our results reveal was ∼50 during (90−85 Ma) record thickening prior Cenozoic Indo-Asia collision.