东天山白山斑岩钼矿地质地球化学特征及成因研究

发布时间：2018-02-26 04:09

本文关键词： 白山斑岩型钼矿地球化学 SIMS锆石U-Pb定年锆石Hf同位素成矿机制　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：白山钼矿床位于东天山康古尔-黄山韧性剪切带三岔口-白山斑岩铜钼矿带中,赋矿地层为下石炭统干墩组,成矿岩体为晚三叠世花岗斑岩。本文以白山钼矿为研究对象,对白山钼矿区深部岩体进行了详细的岩相学、岩石地球化学、SIMS锆石U-Pb定年以及锆石原位Hf同位素分析,旨在确定成矿岩体的岩石成因类型、岩体形成时代以及岩浆源区特征,进而分析成矿动力学背景以及矿床形成机制。地球化学特征显示,白山钼矿区深部花岗斑岩富SiO2、Al2O3和碱质,MgO和地幔相容元素Cr、Ni含量低；明显富集Rb、Ba、Th和U等大离子亲石元素,亏损Nb、Ta、Zr和Hf等高场强元素。属高钾钙碱性、准铝质到过铝质的Ⅰ型花岗岩,并具有埃达克岩的地球化学特征。同时,白山钼矿区深部花岗斑岩锆石εHf(t)为正值(+8.3～+12),地壳模式年龄(TDMC)为556～758Ma。以上特征显示白山钼矿区深部花岗斑岩由增厚的新生下地壳部分熔融形成。白山钼矿区深部斑岩体SIMS锆石U-Pb年龄为229.7±3.2Ma,前人获得的辉钼矿Re-Os等时线年龄为225～229Ma,成矿年龄与成岩年龄基本一致。结合前人研究成果,可以确定白山钼矿形成于晚三叠世板内伸展环境。晚石炭世古天山洋盆闭合之后,东天山地区进入碰撞-后碰撞阶段。晚三叠世在板内伸展环境的背景下,新生下地壳因自身增厚或受到幔源底侵岩浆热量的影响,熔融产生埃达克质岩浆,熔融过程中析出的金属及挥发分随埃达克质岩浆一起向上运移,埃达克质岩浆上侵到达地壳浅部,随着温度、压力的降低,成矿金属和流体从岩浆中大量析出,形成含矿热液。含矿热液在岩体上部的围岩中沿裂隙充填、交代,最终形成辉钼矿沉淀。
[Abstract]:The Baishan molybdenum deposit is located in the Sanchaikou-Baishan porphyry copper-molybdenum ore belt in the Kangguer-Huangshan ductile shear zone of East Tianshan. The ore-bearing strata are the Dendun formation of Lower Carboniferous and the ore-forming rock mass is late Triassic granitic porphyry. Detailed lithofacies, geochemistry and zircon U-Pb dating of zircon and in situ HF isotopic analysis of zircon in Baishan molybdenum ore area were carried out in order to determine the petrogenetic type, age of formation and characteristics of magmatic source. The geochemical characteristics of the deep granitic porphyry in Baishan molybdenum ore area show that the deep granitic porphyry is rich in Sio _ 2-Al _ 2O _ 3 and alkaline MgO and the mantle compatible element Cr-Ni, and is obviously enriched in large ion lithophile elements, such as RB _ (b) Ban _ (Th) and U, and so on. Depleted high field strength elements, such as NB, Tazn, Zr and HF, belong to high-potassium calc-alkaline, quasi-aluminous to peraluminous type I granites, and have geochemical characteristics of adakite. The zircon 蔚 Hft of the deep granitic porphyry in the Baishan molybdenum ore area is positive (8.312g, the crustal model age (TDMCT) is 556N758Ma. the above characteristics indicate that the deep granitic porphyry in the Baishan molybdenum ore area is formed by thickening partial melting of the lower crust.) the deep porphyry of the Baishan molybdenum ore area is formed by the partial melting of the thickened lower crust. The SIMS zircon U-Pb age is 229.7 卤3.2Ma. the Re-Os isochron age of molybdenite obtained by predecessors is 225U 229Ma.The metallogenic age is basically consistent with that of diagenesis. It can be determined that the Baishan molybdenum deposit was formed in the late Triassic intraplate extensional environment. After the late Carboniferous Paleo-Tianshan ocean basin was closed, the East Tianshan area entered the collision-post-collision stage. Due to the thickening of the new lower crust or the influence of the heat of the mantle underplating magma, the melting produces the adakitic magma, and the metals and volatile matter precipitated during the melting process migrate upward along with the adakitic magma. With the decrease of temperature and pressure, the ore-forming metals and fluids are precipitated from the magma in large quantities to form ore-bearing hydrothermal solution, which is filled along the fissure in the surrounding rock of the upper part of the rock mass. Molybdenum deposits are formed eventually.
【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】：2015
【分类号】：P618.65

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