四川盆地北缘灯影组MVT铅锌矿成矿物质来源研究

发布时间：2018-04-01 20:31

  本文选题：MVT铅锌矿　切入点：灯影组　出处：《成都理工大学》2015年硕士论文

【摘要】：四川盆地北缘铅锌矿属于密西西比河谷(MVT)型铅锌矿,主要产于灯影组白云岩中。铅锌矿床中矿石矿物主要为方铅矿、闪锌矿,脉石矿物有萤石、重晶石、沥青、白云石、方解石、石英,其中萤石、重晶石还可富集形成矿床。本区MVT型铅锌矿与古油(气)藏在空间上密切共生/伴生,铅锌矿成矿与油气成藏有一定的成因联系。本文研究了该区区域成矿地质背景,借助各种地球化学分析结果,得出以下认识:(1)该区寒武系郭家坝组及基底岩石成矿元素背景含量值较高,具有提供成矿物质的潜力。(2)矿石的稀土元素配分曲线与该区基底岩石、寒武系郭家坝组炭质泥页岩、灯影组围岩相似度低,在稀土元素参数图解上矿石与基底岩石、寒武系炭质泥页岩、灯影组围岩相关性较差,但寒武系炭质泥页岩与基底岩石却表现出较好的相关性。结合构造演化史,得出基底岩石的风化剥蚀物质为寒武系郭家坝组炭质泥页岩提供了沉积物源。(3)矿石样品的初始87Sr/86Sr介于0.709782-0.71131,平均值为0.71041,具有壳源特征。这表明基底岩石及寒武系郭家坝组地层都可能为铅锌矿提供成矿物质。5件硫化物样品铅同位素数据,206Pb/204Pb介于17.62-18.02,207Pb/204Pb介于15.49-15.63,208Pb/204Pb介于37.57-38.35,铅同位素组成比较稳定,属于正常铅。由铅同位素数据得出成矿模式年龄418-662Ma,成矿物质主要来源于震旦系-寒武系地层。在207Pb/204Pb-206Pb/204Pb、208Pb/204Pb-206Pb/204Pb铅构造演化模式图及△γ-△β图解中,数据落在地壳和地幔之间,表明其成矿物质主要为壳源,但可能有幔源物质混入。萤石Sr同位素证据表明,萤石与白云石具有相同的流体来源,其Ca2+是由围岩的溶解提供的。研究发现,基底中未发现延伸到灯影组地层的深大断裂,灯一段、灯二段白云岩中也未发现断裂及矿石矿物的充填,因此成矿物源直接为基底岩石的可能性很小/几乎没有。烃源岩寒武系郭家坝组炭质泥页岩是直接的矿源层,而由于基底岩石为寒武系地层提供了沉积物源,基底岩浆岩有些为幔源成因,这也就解释了Pb同位素图解中所表现出的幔源物质混入的特征。(4)硫同位素数据表明,闪锌矿样品δ34S介于16-19.4‰,方铅矿样品δ34S介于12.94-16.8‰,黄铁矿样品δ34S平均值为18.7‰;重晶石样品δ34S介于32.2-33.48‰。矿石及重晶石表现出富“重硫”特征。与海水及油田卤水中δ34S值有一定的相似。本文认为S与油田卤水关系密切,即古油(气)藏与铅锌矿成矿有着密切的关系。碳同位素数据表明,脉石矿物白云石、方解石中Ca2+源于碳酸盐岩的溶解。(5)本文对萤石、重晶石的来源做了一定的探讨,认为Ba主要由寒武系郭家坝组提供,Ca主要由围岩白云岩溶解提供。根据研究成果,本文讨论了铅锌矿成矿作用过程,认为烃源岩寒武系郭家坝组炭质泥页岩为铅锌矿的直接矿源层,基底岩石为间接矿源岩,古油(气)藏与铅锌矿成矿有着一定的耦合关系。
[Abstract]:The lead-zinc deposit in the northern margin of Sichuan Basin belongs to the Mississippi Valley MVT type lead-zinc deposit, which mainly occurs in dolomite of the Dengying formation. The ore minerals in the lead-zinc deposit are mainly galena, sphalerite, gangue minerals, fluorite, barite, bitumen, dolomite, etc. Calcite, quartz, fluorite and barite can also be enriched to form deposits. The MVT type lead-zinc deposit and paleooil (gas) are closely associated with each other in space. There is a genetic relationship between lead-zinc mineralization and oil and gas accumulation. This paper studies the regional metallogenic geological background in this area, and makes use of various geochemical analysis results. The following conclusions are obtained: (1) the ore-forming element background value of the Cambrian Guojiaba formation and basement rocks in this area is relatively high, and the REE distribution curve of the ore and the carbonaceous shale of the Cambrian Guojiaba formation are also obtained. The similarity of surrounding rock of Dengying formation is low, the correlation between ore and basement rock, Cambrian carbonaceous shale and surrounding rock of Dengying formation is poor in REE parameter diagram. However, the Cambrian carbonaceous shale shows a good correlation with the basement rocks. It is concluded that the weathering and denudation of the basement rocks provide sediment source for the carbonaceous shale of the Cambrian Guojiaba formation. The initial 87Sr/86Sr of the ore samples is between 0.709782-0.71131, with an average value of 0.71041, which indicates that the basement rocks and the Cambrian Guojia family have the characteristics of crust source. The formation of Ba formation may provide lead isotopic data of 5 sulfide samples of ore-forming materials for lead-zinc deposits. The lead isotopic composition of Pb isotopes is relatively stable. The lead isotopic composition is relatively stable. The lead isotopic composition is relatively stable, and the lead isotopic composition is relatively stable, and the lead isotopic composition is relatively stable. The metallogenic model age is 418-662Ma.The ore-forming material is mainly derived from the Sinian to Cambrian strata. In the 207Pb / 204Pb-206Pb / 204Pb / 208Pb / 204Pb-206Pb lead tectonic evolution model map and 纬-尾 diagram, the data fall between the crust and the mantle. The results show that the ore-forming materials are mainly crustal, but mantle-derived materials may be mixed in. The fluorite Sr isotopic evidence shows that fluorite and dolomite have the same fluid source and their Ca2 is provided by the dissolution of surrounding rock. No deep faults extending to the strata of Dengying formation were found in the basement, nor were faults and mineral fillings found in dolomite in the first section of the first section of the lantern formation and the second member of the second stage of the lantern formation. Therefore, there is little possibility that the source rocks are directly basement rocks. The carbonaceous shale of the Cambrian Guojiaba formation of hydrocarbon source rocks is a direct source of ore, whereas the basement rocks provide sediment sources for the Cambrian strata. Some of the basement magmatic rocks are of mantle origin, which explains the characteristics of mantle material mixing in Pb isotopic diagrams. The sulfur isotope data show that the 未 34s of sphalerite samples is between 16-19.4 鈥，

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