安徽铜陵新桥矿区中生代岩浆作用与成矿

发布时间：2018-06-05 15:51

本文选题：矶头岩体 + 岩石学和地球化学　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：新桥铜硫铁多金属矿床是安徽铜陵矿集区内一个典型的矽卡岩型矿床,其成因与矿区内的矶头岩体密切相关。本文在前人研究基础上,对新桥矿区进行了综合野外调查,并针对矶头侵入岩进行了详细的岩相学观察以及年代学、矿物学和地球化学分析,重点讨论了新桥矿区中生代岩浆作用及其成矿意义。野外调研结果证实,矶头岩体是一个复式岩株,主要由石英闪长岩和闪长玢岩组成,其中常可以见到闪长质至辉长闪长质和富云母包体。LA-ICP-MS锆石U-Pb测年结果表明,矶头石英闪长岩和闪长玢岩分别形成于(141.6±1.1)Ma和(129.9±0.6)Ma,属于早白垩世两期岩浆活动的产物。镜下可见主岩与包体中的大量斑晶具有不平衡结构,包括不规则环带和圆化边以及筛状和嵌晶结构等。矶头侵入岩属于准铝质的高钾钙碱性岩石系列,微量元素和稀土元素地球化学以及矿物学分析资料结合岩相学观察结果表明,矶头侵入岩属于壳幔混源岩浆岩,在其形成过程中经历了结晶分异、同化混染和岩浆混合作用。综合本区地质地球化学资料,认为在岩石圈伸展减薄背景下,演化的高温辉长闪长质岩浆上侵至13~15 km,在中地壳发生分异结晶、同化混染和岩浆混合作用,形成石英闪长质和闪长质岩浆。后在构造扰动与岩浆脉动下,石英闪长质和闪长质岩浆分两期沿构造薄弱面上侵至7~8 km,经冷却结晶形成矶头岩体。在岩浆演化后期,岩浆热液活动带来的大量成矿物质通过接触交代和层间热液交代作用在合适的地方不断聚集形成了新桥铜硫铁矿床。
[Abstract]:Xinqiao copper-sulphur iron polymetallic deposit is a typical skarn type deposit in Tongling ore concentration area of Anhui province. Its genesis is closely related to the Jitou rock body in the ore area. On the basis of previous studies, a comprehensive field survey was carried out in Xinqiao mining area, and detailed petrographic observation, geochronology, mineralogy and geochemical analysis of the intrusive rocks in Jitou were carried out. The Mesozoic magmatism and its metallogenic significance in Xinqiao mining area are discussed. The results of field investigation show that the Jitou rock body is a complex rock plant, mainly composed of quartz diorite and diorite porphyrite. Among them, the U-Pb dating results of diorite to pyroxenite and mica rich xenoliths. LA-ICP-MS zircon dating show that the rock mass is mainly composed of quartz diorite and diorite porphyrite. Jitou quartz diorite and diorite-porphyrite were formed in 141.6 卤1.1)Ma and 129.9 卤0.6Ma. they belong to the early Cretaceous magmatism. It can be seen that a large number of porphyry crystals in the main rock and inclusions have unbalanced structures under the microscope, including irregular ring zones and rounded edges, sieve and embedded structures, and so on. The geochemistry of trace elements and rare earth elements and mineralogical analysis data combined with petrographic observation indicate that the intrusive rocks belong to crust-mantle magmatic rocks. In the process of its formation, it has undergone crystallization differentiation, assimilation and magma mixing. Based on the geological and geochemical data of this area, it is considered that under the background of extensional thinning of lithosphere, the evolution of high-temperature pyroclase diorite magma transgression to 1315km, resulting in differential crystallization, assimilation and magma mixing in the middle crust. Forming quartz diorite and diorite magma. After the tectonic disturbance and magmatic pulsation, quartz diorite and diorite magma intruded up to 78 km along the weak surface of the structure in two stages, and formed the Qitou rock body by cooling and crystallization. In the late stage of magmatic evolution, a large number of ore-forming materials resulted from magmatic hydrothermal activity accumulated in a suitable place through contact metasomatism and interlayer hydrothermal metasomatism to form Xinqiao copper pyrite deposit.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.2;P588.11

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