Constraints of geochemistry, geochronology and Sr-Nd-Hf isotopes on the Xinzhai peralu-minous granite in northern Guangxi:implications for petrogenesis and tectonic significance

LA-ICP-MS zircon U-Pb dating shows that the Xinzhai granites, emplaced in northern Guangxi, were generated in Mid-dle Ordovician (465±2Ma).These granites are characterized by uniform silicon content (SiO₂=68.54%~4.57%), enrichment of alkali val-ues and considerable enrichment of K values (K₂O+Na₂O=7.61%~8.31%, K₂O/Na₂O=1.77~2.35), concentration of peraluminous (A/CNK=1.09~2.39) and high large ion lithophile elements (LILE)(e.g., Rb, K, Th) but relative depletion of high field-strength el-ements (HFSE)(e.g., Nb, Ta, P, Ti) and Sr.They belong to S-type granite.Granitic samples have homogeneous Sr-Nd isotope compositions (I_Sr=0.71137~0.71328, ε _Nd (t)=-7.89~-7.26).Zircon Hf isotope compositions of the Xinzhai granites have relatively wide ranges (¹⁷⁶Hf/¹⁷⁷Hf=0.28232~0.28252, ε_Hf(t)=-6.18~+0.61, T_DM2=1.67~2.11Ga).The authors hold that the Xinzhai granites were likely generated by partial melting of Paleoproterozoic metapelite, with the addition of small amounts of mafic magma mantle-derived material.The Xinzhai S-type granites might have been the petrological response to the second activity of the Kwangsian orogen in northern Guangxi, which provided new evidence for the establishment of the Early Paleozoic tectonic-magma events in South China.