Crust–Mantle Architecture Remodelled by Mantle Plumes:Evidence From Late Permian(ca.260 Ma) Gabbro–Monzonite Association in the Inner Zone of the Emeishan Large Igneous ProvinceOA

Crust-mantle architecture in large igneous provinces(LIPs) controls magma generation and crustal growth.The coeval gabbro and monzonite in the inner zone of the Emeishan Large Igneous Province(ELIP) provide a key opportunity.They display different whole-rock and mineral compositions,indicating different sources and melting conditions.The gabbro displays moderate TiO_(2)and MgO contents,with Ti/Y ratios of 408-413.Its elevated Nb/Ta and Zr/Hf ratios,evolved zircon Hf isotope,and apatite chemistry suggest a volatile-poor primitive melt,which was derived from the melting of sub-continental lithospheric mantle.The monzonite displays high Zr and Nb contents,TFeO/MgO and 10,000 × Ga/Al ratios,indicating high-temperature melting of mafic lower crust,the high Sr contents suggest plagioclase incorporation into the melts.Its relatively depleted isotopic compositions(ε_(Nd)(t)=+3.2 to+3.7;ε_(Hf)(t)=+0.87 to+0.88) reveal a juvenile crust source region.Apatite in the monzonite indicates a volatilerich melt,supporting a high-temperature crustal melting origin.This geochemical dichotomy illuminates a two-stage crustal evolution model:(1) melting of plume-modified lithospheric mantle to generate the gabbro,followed by(2) thermal remelting of the juvenile mafic crust to form the monzonite.Such plume-induced crust-mantle interaction offers a window into understanding crust-mantle architecture in global LIPs.