Multiple sources and magmatic evolution of the Late Triassic Daocheng batholith in the Yidun Terrane: Implications for evolution of the Paleo-Tethys Ocean in the eastern Tibetan Plateau

Abstract Granitoids with diverse composition and tectonic settings provide important tools for exploring crustal evolution regional geodynamic history. Here we present an integrated study using petrological, mineralogical, zircon U-Pb geochronological, whole-rock geochemical, isotopic data on the Late Triassic Daocheng batholith in Yidun Terrane a view to understanding petrogenesis of compositionally its implications Paleo-Tethys Ocean eastern Tibetan Plateau. The different lithological units batholith, including granodiorite, monzogranite, quartz diorite, abundant mafic microgranular enclaves granodiorite (MME I) monzogranite II), show identical crystallization ages 218–215 Ma. mineral assemblage chemical are those tonalitic-granodioritic melts generated under water-unsaturated conditions. insignificant Eu anomalies low magmatic temperatures indicate hydrous melting source. relatively narrow range Sr-Nd isotopes, as well trace element Hf compositions suggest homogeneous source magma. Our modeling suggests that rock was produced by 20–50% lower melting. monzogranites display more evolved larger variations Sr-Nd-Hf isotopes than which attributed assimilation fractional process. This is evidenced presence metasedimentary enclave inherited grains Neoproterozoic Paleozoic ages, non-cotectic trend composition, shown initial 87Sr/86Sr ratios Sr. diorites MMEs showing similar andesitic primary magma have high εHf(t) values characterized enrichment LILEs depletion HFSEs. They were derived from partial lithospheric mantle had been metasomatized slab fluids. both rocks typical igneous texture higher rare earth (REE) incompatible concentrations their host granites. fine-grained margins, acicular apatite, plagioclase megacrysts mingling overgrowth amphibole around pyroxene, ocelli rimmed biotite, oscillatory zones all indicative diffusion. Their enriched imply equilibrium Based comparison coeval subduction-related magmatism, propose subduction subsequent rollback (Garzê-Litang Ocean) oceanic possible mechanism triggered magmatism within