大渡河金成矿带黄铁矿标型特征及意义

发布时间：2018-05-14 02:18

本文选题：大渡河金成矿带 + 黄铁矿　；参考：《成都理工大学》2017年硕士论文

【摘要】：大渡河金成矿带位于康滇地轴南北向构造带北端,鲜水河、龙门山与攀西裂谷所构成的三叉裂谷交汇形成的特殊构造部位。近年来的地质勘探工作表明,该研究区具有“三层楼”的构造格局,与之相对应的矿床也有“三层楼”格局的分布特点,分别为基底中金矿床、盖层中金矿床、界面中金矿床。不同层位的金矿床的载金矿物主要为黄铁矿,这说明黄铁矿对大渡河流域金矿床的成因有重要的指示意义。本文对大渡河金成矿带不同赋矿层位金矿床中黄铁矿的标型特征进行研究,通过野外地质考察、室内测试分析,并结合前人研究成果,得出以下认识:大渡河金成矿带不同赋矿层位金矿床中的矿物成分组合基本类似,金属矿物主要为黄铁矿,其次有方铅矿、黄铜矿等,主要载金矿物为黄铁矿,脉石矿物为石英。盖层中金矿床的围岩主要为碳酸盐岩,基底中金矿床的围岩主要为花岗岩。盖层中金矿床的黄铁矿晶形主要为立方体,少见五角十二面体;界面中金矿床的黄铁矿以聚形为主,少量立方体单形;基底中金矿床黄铁矿晶形主要为五角十二面体、立方体。这说明三者的成矿温度有区别,五角十二面体单晶在基底中出现最多,说明基底的成矿温度最高,适宜五角十二面体形成;盖层成矿温度较低,适合立方体的形成。不同赋矿层位金矿床黄铁矿的热电性有着明显的差别。盖层中金矿床黄铁矿导电类型为P型,基底中金矿床黄铁矿导电类型为N型,界面中金矿床以N型为主,夹杂少量P型。导电类型可指示温度,基底中黄铁矿形成温度最高,盖层中黄铁矿形成温度最低,界面中黄铁矿形成温度介于两者之间。但三者均符合中—低温热液矿床的形成温度,三类金矿床应该都属于中—低温热液矿床。不同赋矿层位的黄铁矿微量元素均以U富集为主,说明三者具有相同的物质来源,即深部热液,基底中的U富集程度最高,受到岩浆源区(深源)流体活动影响程度更高。盖层中的Sr亏损程度更高,受到了地壳的混染作用。黄铁矿的稀土元素特征表明,基底中黄铁矿稀土元素总量ΣREE=8.60×10~(-6),与上地幔稀土元素总量ΣREE=7.30×10~(-6)相当;盖层中黄铁矿稀土元素总量ΣREE=25.29×10~(-6),与上地壳稀土元素总量类似,说明了盖层中的成矿物质可能有地壳物质的参与。不同赋矿层位黄铁矿均表现为Eu异常、Ce无异常,说明大渡河金成矿带成矿流体为还原性流体。盖层、基底、界面中黄铁矿均呈现轻稀土相对富集的右倾型,说明三者具有相同的物质来源即深部幔源。
[Abstract]:The Daduhe gold metallogenic belt is located at the northern end of the north-south structural belt of the Kangdian axis and the special structural position formed by the intersection of the Trident rift of Xianshuihe, Longmenshan and Panxi rift. The geological exploration work in recent years shows that the study area has the structure pattern of "three stories" and the corresponding deposit has the distribution characteristic of "three stories" pattern, namely, the gold deposit in the basement, the gold deposit in the caprock and the gold deposit in the interface. Pyrite is the main gold bearing material of gold deposits in different horizons, which indicates that pyrite is of great significance to the genesis of gold deposits in the Dadu River Basin. In this paper, the typomorphic characteristics of pyrite in gold deposits of different ore-bearing strata in the Daduhe gold metallogenic belt are studied. Through field geological investigation, laboratory test and analysis, and combined with previous research results, The conclusions are as follows: the mineral composition of the gold deposits in different ore-bearing strata of the Daduhe gold metallogenic belt is basically similar, the main metal minerals are pyrite, the next are galena, chalcopyrite and so on, and the main gold bearing minerals are pyrite. The gangue mineral is quartz. The rock mass of gold deposit in caprock is mainly carbonate rock, and that of gold deposit in basement is granite. The pyrite crystal shape of the gold deposit in caprock is mainly cubic and rarely pentagonal dodecahedron; the pyrite in the interfacial gold deposit is mainly polymorphic and a few cubic simplex; the pyrite crystal shape of the gold deposit in the basement is mainly pentagonal dodecahedron and cube. This shows that the metallogenic temperature of the three is different. The pentagonal dodecahedron crystal appears most in the substrate, indicating that the metallogenic temperature of the substrate is the highest and suitable for pentagonal dodecahedron formation, while the caprock metallogenic temperature is relatively low, which is suitable for the formation of cubes. There are obvious differences in the thermoelectric properties of pyrite in different ore-hosting gold deposits. The conductivity type of pyrite in caprock gold deposit is P type, pyrite in basement gold deposit is N type, N type is dominant in interface gold deposit, and a small amount of P type is involved. The temperature of pyrite formation is the highest in the basement and the lowest in the caprock. The temperature of pyrite formation at the interface is between the two. But they all accord with the formation temperature of the intermediate-low temperature hydrothermal deposit, and the three kinds of gold deposits should all belong to the intermediate-low temperature hydrothermal deposit. The main trace elements of pyrite in different ore-bearing strata are U enrichment, which indicates that the three have the same material source, that is, deep hydrothermal solution, the highest degree of U enrichment in the basement and the higher degree of influence by the fluid activity in the magmatic source area (deep source). The Sr depletion in the caprock is higher and is affected by the crustal mixing. The characteristics of rare earth elements in pyrite indicate that the total amount of rare earth elements 危 REE=8.60 脳 10 ~ (10) ~ (6) in the basement is equivalent to that in the upper mantle (危 REE=7.30 脳 10 ~ (10) ~ (-6), and the total amount of rare earth element 危 REE=25.29 脳 10 ~ (10) ~ (-6) in the cap is similar to the total amount of rare earth elements in the upper crust. It is suggested that the ore-forming material in the caprock may involve the crustal material. Pyrite in different ore-bearing strata is characterized by EU anomaly and ce anomaly, indicating that the ore-forming fluid in the Daduhe gold metallogenic belt is a reductive fluid. Pyrite in the caprock, basement and interface all show a right-dip type of relative enrichment of LREE, indicating that the three have the same material source, that is, the deep mantle source.
【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】：P618.51

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