Petrogenesis Of Zhangshiying Intrusive Complex In Central Henan Province, China

Zhangshiying Intrusive Complex(ZIC) is located in the south margin of North China Craton and at the junction of the eastern Qinling and Dabie orogen.Based on the field investigation and former work, this study divede ZIC into three kind of rocks, including hornblende quartz syenite(HQS), granite porphyry (GP) and quartz porphyry(QP). There are many enclaves(MEs) only in HQS which is invaded by GP and QP. QP invades into GP as well. The ziron SHRIMP U-Pb ages of HQS, GP and QP are 107.3±2.4 Ma, 106.7±2.5 Ma and 101±3 Ma, respectively. They demonstrate that ZIC is the product of the late period of Middle Cretaceous.HQS and MEs the MEs therein are shoshonitic and metaluminous-weakly peraluminous rocks, but GP and QP are high-K calc-alkline and strongly peraluminous rocks. According to the characteristics of their field geology, mineralogy, geochemistry, QP magma is mainly controlled not by fractionation crystallization process or interaction between melt and fluid, but by source rock partial melting. HQS is the product of magma mixing between GP magma and magma originated from depth represented by the MEs. GP is derived from lower crust (30-35 km) composed of clay-rich pelitic source rock at temperature of >875℃. QP is the cognate magma of GP and assimilates some Neoarchean crust. Magma represented by the MEs is originated by partial melting of foundered lower crustal ecologite in mantle (>50 km), Then it ascend fast to shallow crust (< 6km) mixing with GP magma there to form HQS.According to this research and the study results about the late Mesozoic in this region, we can conclude that the whole eastern China lithosphere is extensive betweem 135Ma and 100Ma. This large scale regional extension of lithosphere could be the incentive of the ecologitic lower crustal foundering, which is the deep process of ZIC origin and of the extensive mineralization at the time and of magmatic events and thermal disturbance of the same age as ZIC in this region, at south margin of North China Craton.