Niumiao and Tong'' an intrusive bodies of NE Guangxi: Petrology,zircon SHRIMP U-Pb geochronology and geochemistry
桂东北牛庙闪长岩和同安石英二长岩:岩石学、锆石SHRIMP U-Pb年代学和地球化学

The Niumiao and Tong' an intrusive bodies are composed of diorite and quartz monzonite, respectively. Their zircon SHRIMP U-Pb ages are 163 4Ma and 160 4Ma, respectively. These rocks are enriched in Al, alkalies, K, Rb, Ba, Th, U, Pb, Sr etc. LILE's and REE, Nb, Ta, Zr, Hf etc. HFSE's, and with an OIB affinity in incompatible elements distribution pattern. They belong to the high-K or the shoshonitic association and were essentially generated by partial melting of the enriched subcontinental lithospheric mantle and via an AFC model. The widespread mafic microgranular enclaves are remains from mingling of more mafic magmas with host dioritic or quartz monzonitic magmas. The variation and transition in chemical compositions of enclaves reflect differences in formation and evolution paths of their parental magmas. These intrusive bodies were emplaced at the post-orogenic stage under an extensional and thinning environment within the South China continental crust. Upwelling and underplating of the asthenospheric mantle along the trans-lithospheric deep faults were responsible for melting of the enriched subcontinental lithospheric mantle and overlying middle-lower crust, and for generating the early Yanshanian dioritic and granitic magmas in this region.