北淮阳成矿带东段新元古代花岗岩体成因及其找矿指示OA

Neoproterozoic felsic intrusions are widely exposed in the eastern segment of the Beihuaiyang Metalorgenic Belt,dominated by syenogranitic gneiss with subordinate syn-to post-tectonic syenogranite intrusions.These plu-tons host spatially and temporally associated with Pb-Zn mineralization,rendering their petrogenesis pivotal for constraining the tectonic evolution and metallogenic framework of the belt.This study focuses on the Neoprotero-zoic granitoids from the Maotanchang area,integrating zircon U-Pb geochronology,whole-rock major-and trace-element geochemistry.LA-ICP-MS zircon U-Pb dating yields concordant weighted mean 206Pb/238U ages of(803.2±1.3)Ma for the syenogranitic gneiss and(803.9±1.4)Ma for the syenogranite,indicating coeval emplace-ment during the Mid-Neoproterozoic(～804 Ma).Geochemically,both rock types are silica-rich(w(SiO2)=65.85％～75.74％),and markedly Mg-poor(w(MgO)=0.05％～0.93％;Mg#=21～47).Chondrite-normalized REE patterns display strong light-REE enrichment((La/Yb)N=33.1～50.57),steep heavy-REE depletion,and pro-nounced negative Eu anomalies(δEu=0.19～0.33).Trace element spider diagrams exhibit marked enrichment in Rb,Th,U,K,Pb,Zr,Hf,Ce,Nd,and La,coupled with systematic depletions in Sr,Ba,Ti,Nb,Ta,and P.Petroge-netic discrimination classifies both units as A-type granites.Their geochemical signatures point to partial melting of potassium-rich,felsic lower-to-middle crust.This melting event occurred during regional lithospheric exten-sion following the culmination of the Jinningian Tongbai-Dabie orogeny.Given the tight spatiotemporal associa-tion between these A-type intrusions and Pb-Zn mineralization,this work provides new guidance for future Pb-Zn deposit exploration targeting in the eastern Beihuaiyang Belt.