哀牢山构造带西南缘长安铜钼金矿集区地质特征及控矿因素分析

发布时间：2018-10-14 19:11

【摘要】：哀牢山构造带是我国重要的贵金属和有色金属成矿区带。长安铜钼金矿集区位于哀牢山金属成矿带西南部的金平推覆体中南部,由长安金矿、铜厂铜钼矿和长安冲铜钼矿等多金属矿床组成。矿集区内岩浆活动主要发生在喜山期,岩石类型为从基性到中酸性的岩石系列,包括辉长岩、辉绿岩、正长岩、正长斑岩、花岗斑岩和少量花岗闪长岩组合,多呈岩基或小岩株产出,多类型多期次岩体侵入最终构成复式岩体,属于准铝质-弱过铝质的碱性富钾岩类。岩石地球化学特征与哀牢山-金沙江构造带南段碱性带内的碱性岩浆岩特征一致,岩浆为来源于含金云母的尖晶石相地幔的部分熔融形成富钾质碱性岩浆。锆石LA-ICP-MS U-Pb定年结果表明矿集区内岩浆活动发生于37~21Ma。其中,形成于35~21Ma的花岗斑岩和正长斑岩对斑岩型铜钼矿和破碎蚀变岩型金矿的形成有直接或间接控制作用。矿集区内主要发育两组走向北西、倾向北东的逆冲断裂和走向北东倾向北西的层间走滑断裂构造。它们在空间上控制了岩体和矿体的空间分布,是导矿和储矿构造。长安矿集区内的斑岩铜钼矿体呈板状、叠瓦状、透镜状、条带状、斑杂状及块状产于斑岩和碳酸盐接触地带。围岩蚀变具有明显的分带性,即从岩体向碳酸盐岩依次为云英岩化、矽卡岩化和碳酸岩化。其中,钼矿主要分布在云英岩化带,铜矿主要分布在矽卡岩化带。金矿分布于岩体外部构造破碎带中,围岩主要为粉砂岩类,硅化、黄铁矿化和碳酸岩化蚀变明显,矿化主要与硅化和黄铁矿化有关。稳定同位素结果表明斑岩铜钼矿成矿物质和成矿流体主要来源于岩浆,金矿成矿物质来源于岩浆,成矿流体为岩浆流体和地下水的混合物。成矿作用形成于35~21Ma。构造地质学、岩石学、同位素地质学分析结果表明新生代岩浆沿矿集区内北西向和北东向两组断裂交汇地带侵入,岩浆期后热液与围岩发生交代作用,形成云英岩化、矽卡岩化和碳酸岩化蚀变,Cu、Mo等成矿物质以硫化物的形式析出,形成铜钼矿。同时,中低温流体沿构造带向外运移,在远离岩体的构造破碎带中与地下流体会合,致使成矿流体的物理化学条件发生巨大变化,促使携带金元素的络合物分解,在发生硅化、黄铁矿化和碳酸岩化蚀变的同时金随石英、黄铁矿或方解石一起沉淀,形成金矿床。
[Abstract]:Ailaoshan tectonic belt is an important metallogenic zone of precious metals and nonferrous metals in China. Changan copper-molybdenum gold deposit is located in the south and central of Jinping nappe in the southwest of Ailaoshan metallogenic belt. It is composed of Changan gold deposit, Tongchang copper-molybdenum deposit and Changan chong copper-molybdenum deposit and other polymetallic deposits. Magmatic activity in the ore concentration area mainly occurred in the Himalayan period, and the rock types are from basic to intermediate acid rock series, including gabbro, diabase, syenite, granitic porphyry and a small amount of granodiorite assemblage. Most of them occur in rock base or small rock, and many types of intrusions constitute complex rock bodies, which belong to the type of alkaline potash rich rocks with quasi-aluminite and weak peraluminite. The petrogeochemical characteristics are consistent with the alkaline magmatic rocks in the alkaline zone of the southern Ailaoshan-Jinshajiang structural belt. The magma is derived from the partial melting of the spinel mantle containing phlogopicite to form potash alkaline magma. The results of zircon LA-ICP-MS U-Pb dating indicate that magmatic activity occurred in the ore concentration area at 37 ~ 21 Ma. Among them, granitic porphyry and syenite porphyry formed in 35~21Ma have direct or indirect control on the formation of porphyry copper-molybdenum deposit and broken altered rock type gold deposit. There are two groups of thrust faults trending to the north and east and interlayer strike-slip faults trending to the north to the west in the ore concentration area. They control the spatial distribution of rock mass and orebody in space and are ore-conducting and ore-storage structures. The porphyry copper-molybdenum bodies in Changan ore concentration area are plate-like, imbricate, lenticular, banded, variegated and massive in porphyry and carbonate contact zone. The alteration of the surrounding rock has obvious zonation, that is, from the rock mass to the carbonate rock, it is followed by quartzization, skarnization and carbonatilization. The molybdenum ore is mainly distributed in the dolomization zone, and the copper deposit is mainly distributed in the skarn zone. The gold deposit is distributed in the structural fracture zone outside the rock mass, and the surrounding rock is mainly siltstone, silicification, pyrite and carbonatizing alteration. The mineralization is mainly related to silicification and pyrite mineralization. The results of stable isotopes show that the ore-forming material and ore-forming fluid of porphyry copper-molybdenum ore are mainly derived from magma, the ore-forming material of gold ore comes from magma, and the ore-forming fluid is a mixture of magmatic fluid and groundwater. The mineralization was formed at 35 ~ 21 Ma. The results of tectonic geology, petrology and isotopic geology analysis indicate that the Cenozoic magma intruded along the intersection zone of faults in the NW and NNE directions in the ore concentration area, resulting in the metasomatism of the hydrothermal solution and the surrounding rock in the post-magmatic period, resulting in the formation of dolomite. Skarn and carbonatized alteration, Cu,Mo and other ore-forming materials precipitate in the form of sulphide to form copper-molybdenum ore. At the same time, the intermediate-low temperature fluid moves outward along the tectonic belt and converges with the underground fluid in the tectonic fracture zone far from the rock mass, which results in great changes in the physical and chemical conditions of the ore-forming fluid, which promotes the decomposition of the complex carrying gold elements and silicification. At the same time, gold deposits are precipitated with quartz, pyrite or calcite during the alteration of pyrite and carbonatite to form gold deposits.
【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】：P618.41;P618.65;P618.51

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