四川盆地北缘MVT型铅锌矿床中热液流体的形成与演化

发布时间：2018-04-22 18:33

本文选题：米仓山 + MVT　；参考：《成都理工大学》2015年硕士论文

【摘要】：对四川盆地北缘米仓山地区灯影组MVT型铅锌矿床的实地勘测表明,研究区铅锌矿与古油藏遗留的沥青在空间上呈共生关系,二者均集中分布于灯四段顶部位置,铅锌矿含矿层位相对较薄,沥青在垂向与平面上的分布范围均远大于铅锌矿。手标本及镜下可见到沥青与铅锌矿共生,镜下可见少数闪锌矿中包裹有沥青,显示二者有一定的成因联系。通过对灯影组白云岩储层中各类自生矿物,如闪锌矿、方铅矿、石英、白云石、重晶石、萤石等之间的空间交切关系分析,厘定研究区共有七期古地质流体:第一期盐水流体主要形成中晶白云石,第二期古油藏流体形成第一世代沥青,第三期成矿热液流体形成石英、白云石、第一世代铅锌矿和第一世代重晶石,第四期流体为第二期古油藏,形成第二世代沥青,第五期盐水流体形成晶粒白云石、石英,第六期成矿热液流体形成第二世代闪锌矿,第七期盐水流体形成石英、萤石、第二世代重晶石等矿物。对各期古地质流体形成的自生矿物进行流体包裹体研究,发现第三期成矿热液流体与第七期盐水流体形成的重晶石中主要发育液相H2O包裹体、气液H2O包裹体,捕获有菱锶矿(SrCO3)、毒重石(BaCO3)、自然硫(S)子矿物,第五期与第七期盐水流体形成的石英、萤石中主要发育气液H2O包裹体、甲烷包裹体。通过流体包裹体显微测温,揭示两期古油藏形成时间分别为中寒武世末期、二叠世—中三叠世。在第二期古油藏裂解成天然气藏后,一度保存条件较好,压力系数达到1.29-1.83,但喜马拉雅运动期灯影组地层发生大规模隆升,气藏遭受破坏,气水界面上移,形成的自形石英中包裹有沥青。两期铅锌矿成矿时间与古油气藏成藏时间有明显匹配性。米仓山地区在两期古油气藏成藏期间形成的自生矿物中,其捕获的气液H2O包裹体和甲烷包裹体中均含CH4、CO2、H2S,尤其是两期重晶石中的自然硫子矿物,均暗示古油气藏成藏期间可能发生过TSR反应,为铅锌成矿提供硫源。
[Abstract]:The field survey of the Dengying MVT type lead-zinc deposit in the Michang Mountain area of the northern margin of Sichuan Basin shows that there is a symbiotic relationship between the lead-zinc deposit and the asphalt left over from the paleoreservoir in the study area, both of which are concentrated on the top of the fourth member of the Dengshan formation. The ore-bearing horizon of lead-zinc ore is relatively thin, and the distribution range of asphalt in vertical and plane is much larger than that in lead-zinc ore. Bitumen and lead-zinc ore can be seen symbiosis in hand specimen and mirror, and a few sphalerite are wrapped in asphalt under microscope, indicating that there is a certain genetic relationship between them. The spatial intersecting relationships between various authigenic minerals such as sphalerite, galena, quartz, dolomite, barite and fluorite in dolomite reservoir of Dengying formation are analyzed. There are seven paleo-geological fluids in the study area: the first phase of saltwater fluid mainly forms mesocrystalline dolomite, the second phase of paleoreservoir fluid forms first generation bitumen, the third stage of ore-forming hydrothermal fluid forms quartz, dolomite, The first generation lead-zinc ore and the first generation barite, the fourth phase fluid is the second phase paleoreservoir, forms the second generation bitumen, the fifth stage brine fluid forms the grain dolomite, the quartz, the sixth stage metallogenic hydrothermal fluid forms the second generation sphalerite, The seventh brine fluid forms quartz, fluorite, second generation barite and other minerals. The fluid inclusions of the authigenic minerals formed by paleo-geological fluids are studied. It is found that in the barite formed by the third hydrothermal fluid and the seventh brine fluid, there are mainly liquid H2O inclusions and gas-liquid H2O inclusions. The quarts formed in the fifth and seventh phases of brine fluid are trapped in the quarts of SrCO _ 3, BaCO _ 3, S _ (S) minerals, and the gas-liquid H _ 2O inclusions and methane inclusions are mainly developed in fluorite. By microthermometry of fluid inclusions, it is revealed that the formation time of the two Paleo-reservoirs is the end of the Middle Cambrian, the Permian and the Middle Triassic respectively. After the second phase paleo-reservoir was cracked into natural gas reservoir, the condition of preservation was good, the pressure coefficient reached 1.29-1.83, but during the Himalayan movement period, the formation of Dengying formation occurred large-scale uplift, the gas reservoir was destroyed, and the gas-water interface was moved up. The formed self-shaped quartz is covered with asphalt. The metallogenic time of lead-zinc ore in two periods is obviously matched with that of paleo-oil and gas reservoir. In the authigenic minerals formed during the formation of paleooil and gas reservoirs in the Micang Mountain area, the captured gas-liquid H2O inclusions and methane inclusions contain Ch _ 4CO _ 2C _ 2H _ 2S, especially the natural sulfur minerals in the barites of the two periods. It is suggested that TSR reaction may have occurred during the formation of paleo-oil and gas reservoirs, which can provide sulfur source for lead-zinc mineralization.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.4

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