【作者】 向君峰；

【导师】 毛景文； 谢桂青；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2009， 硕士

【摘要】 张士英岩体位于河南省中部舞钢市庙街乡一带、东秦岭与西大别交汇部位,大地构造位置属于华北地台南缘。根据野外地质调查及前人工作,本研究将张士英岩体解体为角闪石英正长岩、花岗斑岩和石英斑岩脉,其中仅在角闪石英正长岩中大量发育暗色岩石包体。野外切割关系表明,花岗斑岩侵入角闪石英正长岩,石英斑岩侵入前两者。张士英岩体中角闪石英正长岩、花岗斑岩和石英斑岩的锆石SHRIMP U-Pb年龄分别为107.3±2.4 Ma、106.7±2.5 Ma和101±3 Ma,说张士英岩体形成于中白垩世末期110～100 Ma,是中国东部中白垩世大规模花岗岩侵位事件末期的产物,也是中国东部晚中生代大规模岩浆作用晚期的产物。角闪石英正长岩及其中的暗色包体属于钾玄岩系列,而正长花岗斑岩和石英斑岩属于高钾钙碱性系列,分别具有准铝质、弱过铝质和强过铝质的地球化学特征。岩体地质、矿物学特征与岩石地球化学特征的研究表明花岗斑岩岩浆的形成主要受源岩部分熔融过程的控制,而结晶分离作用与流体-熔体相互作用不是其成岩过程中的主要控制因素;角闪石英正长岩是花岗斑岩岩浆与以暗色岩石包体为代表的源自深部的岩浆发生混合作用形成的。花岗斑岩的物质来源为与长英质泥岩成分相当的下地壳(30～35 km)部分熔融的产物,其岩浆起源温度>875℃,石英斑岩与花岗斑岩可能是同源岩浆,并混染了新太古代地壳物质形成的。暗色包体所代表的岩浆是由下地壳榴辉岩拆沉到深度大于50 km的地幔中发生部分熔融形成的,岩浆形成以后快速上升侵位到地壳浅部(<6 km)并与花岗斑岩岩浆发生混合形成角闪石英正长岩。综合约135 Ma以来的区域岩石学、构造地质及地球物理研究成果表明,当时整个中国东部岩石圈均处于伸展作用阶段,这种区域性的岩石圈伸展作用可能是下地壳榴辉岩发生拆沉的诱因。下地壳榴辉岩的拆沉作用是张士英岩体形成的深部动力学原因,也是东秦岭地区135～110 Ma期间大规模成矿作用的深部过程。区内与张士英岩体同期的岩浆活动以及热扰动年龄的存在也共同受这一深部动力学过程的制约。更多还原

【Abstract】 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.更多还原