四川盆地北缘与MVT铅锌矿床共生的古油（气）藏特征及与成矿关系探讨

发布时间：2018-05-06 19:01

本文选题：四川盆地灯影组铅锌矿 + 古油(气)藏　；参考：《成都理工大学》2017年硕士论文

【摘要】：沥青被认为是油气形成、演化历史过程中不可缺少的部分,沥青的存在常常对油气的分布和勘探具有重要的指示作用,同时天然沥青作为一种有机流体与沉积盆地中的一些金属矿床形成具有密切联系,特别是MVT型铅锌矿,与沥青关系十分密切。四川盆地北缘灯影组中铅锌矿,属于MVT型铅锌矿,在这些矿床中可见有大量沥青存在。本文在区域地质背景的基础上,采用野外地质调查、室内有机地球化学分析、扫描电镜与包裹体拉曼分析等研究手段,揭示古油气藏成藏与MVT型铅锌矿成矿之间的关系。研究发现灯影组中发育有两个古岩溶界面,古岩溶带对铅锌矿与古油(气)藏的赋存位置有着明显的控制作用。通过沥青的分布范围,恢复古油藏的分布范围,以灯三段为界发育有两个独立的古油藏,灯三段上部的古油藏在研究区内广泛发育,灯三段下部的古油藏仅在研究区的中部、西部发育,古油藏在东部由于古岩溶作用的影响较小而逐渐尖灭。研究区内的铅锌矿床均产出于古油气藏范围内,铅锌矿床中也见有大量沥青充填,铅锌矿与油气藏具有“你中有我,我中有你”的空间产出特征,表现出油气藏与铅锌矿在空间上存在即共生又分离的特点。通过沥青-泥页岩的生物标志化合物等特征对比研究,发现沥青与泥页岩中的有机质均来源于藻类等低等生物,沉积环境为缺氧且具有一定盐度的还原环境。沥青与泥页岩在沉积环境和母源性质以及成熟度上均显示高度一致性,表明两者有机质来源存在亲缘关系,即沥青有机质的来源为下寒武统郭家坝组泥页岩。根据“地质色层”效应,通过对沥青正构烷烃等生物标志化合物在地球化学指标上的变化规律研究,在表明区内油气的运移方向上具有较好的一致性,都表现出有机质运移方向为自东向西。沥青中存在异常高的Pb、Zn元素,其含量远高于地壳克拉克值,其平均值分别为313×10~(-6)、2934×10~(-6),远远高于MVT铅锌矿床成矿流体所需要的Pb(2.0×10~(-6))和Zn(13×10~(-6))含量,其完全有能力为铅锌成矿提供铅锌元素的能力,说明原油本身可以成为成矿流体的组成部分或直接就是成矿流体。在沥青中发现有闪锌矿、方铅矿等金属包裹物,结合在闪锌矿等矿物中发现的沥青,沥青与闪锌矿在微观上显示出“你中有我,我中有你”的特点。说明铅锌矿的成矿流体来自古油藏。此外,沥青的烃源岩中也发现有闪锌矿、方铅矿等金属包裹物,铅锌矿与沥青在运移方向上具有较好一致性,均表现出自东向西运移的特点,进一步证实了铅锌矿的成矿流体来自古油藏。研究成果表明,研究区内铅锌矿与古油藏无论是在宏观空间展布上还是微观矿物赋存上均显示出“你中有我,我中有你”的特点,显示古油气藏与铅锌矿存在同运、同源的特征,即古油藏的成藏流体就是铅锌矿的成矿流体。
[Abstract]:Asphalt is considered to be an indispensable part of the formation and evolution of oil and gas. The existence of bitumen often plays an important role in indicating the distribution and exploration of oil and gas. At the same time, natural asphalt, as an organic fluid, is closely related to the formation of some metal deposits in sedimentary basins, especially the MVT type lead-zinc deposit, which is closely related to asphalt. The central lead-zinc deposit of Dengying formation in the northern margin of Sichuan Basin belongs to MVT type lead-zinc deposit, in which a large number of bitumen can be found. Based on the regional geological background, the relationship between paleo-reservoir formation and MVT type lead-zinc mineralization is revealed by means of field geological survey, indoor organic geochemical analysis, scanning electron microscope and inclusion Raman analysis. It is found that there are two paleokarst interfaces developed in the Dengying formation, and the paleokarst zone has an obvious controlling effect on the occurrence of lead-zinc ore and paleo-oil (gas) reservoir. Through the distribution range of asphalt, the distribution range of paleo-reservoir is restored. There are two independent paleoreservoirs developed in the boundary of the third member of the lamp, the paleoreservoir of the upper part of the third section of the lamp is widely developed in the study area, and the paleoreservoir of the lower part of the third section of the lamp is only in the middle of the study area. In the west, the paleoreservoir is gradually destroyed in the east due to the small effect of paleokarst. The lead-zinc deposits in the study area are all produced in paleo-oil and gas reservoirs, and a large amount of asphalt filling is also found in lead-zinc deposits. The lead-zinc deposits and oil and gas reservoirs have the spatial characteristics of "you are in each other, you are in me". It shows that oil and gas reservoirs and lead and zinc deposits exist both symbiosis and separation in space. Through the comparative study of biomarkers of asphalt-shale, it is found that the organic matter in asphalt and shale are both derived from algae and other lower organisms, and the sedimentary environment is anoxic and salinity-reducing environment. There is a high consistency between asphalt and shale in sedimentary environment, parent origin and maturity, which indicates that there is a close relationship between the two organic matter sources, that is, the source of bituminous organic matter is the shale of Guojiaba formation in the Lower Cambrian. According to the effect of "geological chromatogram", through the study of the change law of the geochemical index of the biomarkers such as bitumen n-alkanes, it is shown that the migration direction of oil and gas in this area is in good agreement. All show that the migration direction of organic matter is from east to west. The content of Pb ~ (2 +) Zn in asphalt is much higher than the Clarke value of crust, and its average value is 313 脳 10 ~ (-10) ~ (-6) 脳 10 ~ (10) ~ (-6), which is much higher than that of Pb(2.0 脳 10 ~ (10 ~ (-6) and Zn(13 脳 10 ~ (10 ~ (-6) of the ore-forming fluid of MVT lead-zinc deposit. It is fully capable of providing lead and zinc elements for lead-zinc mineralization, indicating that crude oil itself can be a component of ore-forming fluids or a direct ore-forming fluid. There are sphalerite, galena and other metal inclusions found in asphalt, combined with bitumen found in sphalerite and other minerals. Asphalt and sphalerite show the characteristics of "you are in the middle of each other, you are in me". The results show that the ore-forming fluid of lead-zinc ore comes from paleoreservoir. In addition, sphalerite, galena and other metal inclusions are found in the source rocks of bitumen. There is a good consistency between lead-zinc ore and bitumen in the direction of migration, all of which are derived from the characteristics of eastward and westward migration. It is further confirmed that the ore-forming fluid of lead-zinc ore comes from paleoreservoir. The research results show that both the lead and zinc deposits and the paleo-reservoirs in the study area show the characteristics of "you are in the same place", both in the macroscopic space distribution and in the microcosmic mineral occurrence, indicating that the paleo-oil and zinc reservoirs have the same transport with the lead-zinc ore. The homologous characteristic, that is, the reservoir fluid of paleoreservoir is the ore-forming fluid of lead-zinc deposit.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13

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