云南博卡金矿床地球化学特征及矿床成因探讨

发布时间：2018-05-08 03:13

本文选题：博卡金矿床 + 地球化学　；参考：《成都理工大学》2017年硕士论文

【摘要】：云南博卡金矿床是川滇黔多金属成矿区域内发现的大型矿床。大地构造位置处于扬子地台西缘康滇地轴云南段北端,矿床赋存于元古界昆阳群地层中。因此研究博卡金矿床对于矿区外围找矿具有十分重要的意义。在对成矿地质背景、矿床地质特征、金矿地球化学特征、流体包裹体特征分析的基础上,开展了博卡金矿床成矿物质来源、矿床成因、成矿模式等方面的研究。主要取得了以下的认识:(1)博卡金矿床位于扬子地台西缘,矿区内出露地层主要为中元古界昆阳群,矿区主要赋矿层位为因民组、落雪组和黑山组。含矿层位主要集中在浅变质岩系中,主要为各种蚀变构造角砾岩、含碳质粉砂岩和碳质板岩;矿石主要以石英脉型和黄铁矿型为主;围岩蚀变分布于剪切破碎带内,蚀变类型主要有:硅化、钠长石化、黄铁矿化、碳酸盐化、褐铁矿化、绿帘石化、孔雀石化和绿泥石化等,硅化、黄铁矿化和碳酸盐化是矿床热液蚀变的最佳组合。(2)对博卡金矿床岩浆岩常量元素地球化学特征、微量元素和稀土元素地球化学特征进行的研究,表明岩浆岩属于硅酸不饱和类的碱性辉长岩-碱性玄武岩类(SiO2含量为43.24%~52.05%,?为43.24%~52.05%,AR为1.14%~1.83%)。岩石LREE/HREE为0.34~3.62,轻稀土元素富集。?Ce的值为0.61~0.94,Ce异常不明显,?Eu为0.67~1.03,表现出弱负异常。微量元素与稀土元素特征表明岩浆在成岩演化过程受到地壳物质的同化混染,矿区的构造环境属于板内玄武岩区域。(3)石英微量元素和稀土元素地球化学特征表明石英具有不同期次的特性,流体可能为同一流体体系不同阶段的产物,且早期阶段流体温度高于晚期阶段。对方解石微量元素和稀土元素地球化学特征的研究表明方解石为热液流体形成。因此,博卡金矿床属于热液成因矿床。(4)通过对博卡矿床石英的氢氧同位素、氦氩同位素、流体包裹体特征分析,得出博卡金矿的成矿流体具有上地幔和地壳混合流体的特征,同时也是变质热液与大气降水的混合流体。石英流体包裹体成分分析表明成矿流体由高温、高盐度向低温、低盐度方向演化。金属硫化物的硫铅同位素表明成矿物质来源复杂,主要来源于上地幔,受到赋矿围岩(辉绿岩或碳质板岩)的影响,同时也受到其他来源的影响。(5)综合前人对博卡金矿成矿年代学研究,博卡金矿成矿年龄在40~59Ma,表明博卡金矿形成于古新世至始新世早期。喜马拉雅期的构造和热液作用对成矿的影响较大。(6)结合本区矿床地质特征、岩石地球化学特征、流体包裹体特征,以及对其成矿地质条件、成矿物质来源、成矿时代和成矿作用的分析,认为博卡金矿床受脆韧型剪切带控制,同时与变质热液流体作用有关的中低温热液型矿床。
[Abstract]:The Boka gold deposit in Yunnan is a large deposit found in the polymetallic metallogenic region of Sichuan, Yunnan and Guizhou. The tectonic position is located at the northern end of the Yunnan section of the Kang Dian axis of the western margin of the Yangtze platform. The deposit is located in the Kun Yang group of the Proterozoic. Therefore, the study of the Boka gold deposit is of ten important significance for the prospecting in the periphery of the mining area. Based on the geological features of the bed, geochemical characteristics of gold deposits and characteristics of fluid inclusions, the origin of ore forming minerals in the Boka gold deposit, the genesis of the deposit and the metallogenic model have been studied. (1) the Boka gold deposit is located on the western margin of the Yangtze platform, and the outcropping strata in the mining area are mainly in the Middle Proterozoic Kunyang group and the mine. The main ore bearing strata in the area are the people's group, the snowfall group and the Heishan formation. The ore bearing strata are mainly concentrated in the metamorphic rock series, mainly a variety of altered tectonic breccia, carbonaceous siltstone and carbonaceous slate, mainly quartz vein type and pyrite type, and the rock alteration is distributed in the shear fracture zone, and the alteration types are mainly silicification and sodium long. Fossilization, pyrite mineralization, carbonation, browning, epidochemistry, peacock petrifaction, and green mud petrochemistry, silicification, pyrite mineralization and carbonation are the best combinations of hydrothermal alteration in the deposit. (2) the geochemical characteristics of the permanent elements of magmatic rocks, trace elements and rare earth elements in the Boka gold deposit indicate that magmatic rocks The basic gabbro - alkaline basalt (SiO2 content is 43.24%~52.05%, 43.24%~52.05%, AR 1.14%~1.83%). The rock LREE/HREE is 0.34~3.62, the light rare earth element is enriched. The value of the Ce is 0.61~0.94, the Ce abnormality is not obvious, and the Eu is 0.67~1.03, showing the weak negative anomaly. The characteristics of trace elements and rare earth elements indicate magma. The tectonic setting of the mining area belongs to the intraplate basalt region. (3) the geochemical characteristics of the quartz trace elements and rare earth elements indicate that the quartz has the characteristics of different stages, and the fluid may be the product of the different stages of the same fluid system, and the fluid temperature in the early stage is higher than that in the late stage. The study of the geochemical characteristics of trace elements and rare earth elements shows that calcite is a hydrothermal fluid. Therefore, the Boka gold deposit is a hydrothermal ore deposit. (4) through the analysis of the hydrogen and oxygen isotopes, the helium and argon isotopes and the fluid inclusions in the quartz of the Boka deposit, the ore-forming fluid of the Boka gold deposit has the upper mantle and the earth. The analysis of the composition of quartz fluid inclusions indicates that the ore-forming fluid is evolved from high temperature, high salinity to low temperature and low salinity. The sulfur and lead isotopes of metallic sulphides indicate that the source of metallogenic material is complex, mainly from the upper mantle and the surrounding rock (Hui Lvyan). The influence of the carbonaceous slate is also influenced by other sources. (5) the age of the Boka gold mineralization is 40~59Ma, which indicates that the Boka gold deposit was formed in the Paleocene to the early Eocene in the Boka gold mineralization. (6) combined with the geological characteristics of the deposit in this area, the Himalaya period has a great influence on the mineralization. The characteristics of rock geochemistry, fluid inclusions, and analysis of its metallogenic geological conditions, source of metallogenic material, metallogenic epoch and mineralization are considered to be controlled by the brittle ductile shear zone of the Boka gold deposit and the medium and low temperature hydrothermal deposit related to the action of the metamorphic hydrothermal fluid.

【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

【参考文献】