The Early Paleozoic granites in the Mohe region of northern Great Xing'an Range: Response to post -collision extension of the Erguna-Xing'an blocks

In this paper, we present petrography, zircon U-Pb ages, Hf isotopic compositions, and whole -rock major- and trace element data for the Early Paleozoic monzogranites in the Mohe region of northern Great Xing'an Range, with the aim of revealing the tectono-magmatic evolution of the Paleo-Asian Ocean tectonic domain during the Early Paleozoic. Zircons from the Early Paleozoic monzogranites in the Mohe region display fine -scale oscillatory growth zoning, together with their high Th/U ratios, implying their magmatic origin. Zircon LA-ICP-MS U-Pb dating results indicate that these monzogranites in the Mohe region were formed during the 482 similar to 456 Ma, representing the products of magmatic activities during Ordovician -Silurian Period. For mineral assemblage, monzogranites are mainly composed of quartz, plagioclase and alkaline feldspar, with minor biotite. Whole -rock major- and trace element analysis shows that the monzogranite samples in the Mohe region have high SiO2, Al2O3 and total alkali contents ( Na2O + K2O), low MgO, Cr and Ni contents, as well as low Mg-# values. These monzogranites belong to sub -alkaline and high -K calc-alkaline series, combined with their metaluminous characteristics, which all point to an I -type affinity. In addition, the monzogranite samples are enriched in large ion lithophile elements ( Rb, Ba, K, Sr) and light rare earth elements, and depleted in high field strength elements (Nb, Ta, P, Ti) and heavy rare earth elements, with obvious Eu negative anomalies, similar to those of igneous rocks derived from crustal materials. Most of positive zircon epsilon(HF)(t) values and corresponding two -stage model ages (1487 similar to 1106Ma) of the monzogranite samples indicate that they were originated by dominant juvenile crustal components accreted during the MesoproterozoicNeoproterozoic, with minor contributions of ancient crustal materials Considering their characteristics of heavy rare earth elements depletions, these granite samples probably originated from partial melting of lower crust of garnet amphibolite facies and amphibolite facies, with insignificant fractional crystallization during magma evolution. Combined with extensive contemporaneous post-orogenic magmatic assemblages ( A -type granites, bimodal igneous rock associations and alkaline intrusions), we argue that the formation of Early Paleozoic granites in the Mohe region are triggered by magmatic underplating due to hot asthenospheric upwelling within a post collision extensional regime after the amalgamation of the Erguna and Xing'an blocks.