黄沙坪铅锌多金属矿床成矿机理及其预测研究

【作者】 刘悟辉；

【导师】 戴塔根； 徐文炘；

【作者基本信息】 中南大学 ， 矿产普查与勘探， 2007， 博士

【摘要】 本文在充分分析和综合前人工作成果的基础上，以宏观地质为基础，重点对前人研究的较为薄弱的热力学计算、同位素分布及演化特征、微量元素分布及演化特征入手，以多因复成成矿理论为指导，对矿床的物质来源、矿床成因、矿床的成矿作用以及矿床定位预测作了许多新的尝试和研究。通过对比研究黄沙坪、水口山、东坡、瑶岗仙、香花岭五大矿田的区域构造特征、区域地球化学异常特征以及区域重磁异常特征，总结了湖南大型矿床产出的构造及重磁、化探异常特征。根据黄沙坪矿田的地质特征、岩浆岩岩石学和岩石化学特征、微量元素及稀土元素地球化学特征，对矿区岩浆来源、成岩机制以及演化特征进行了详尽的研究，得出矿区的成矿岩体的形成具有多源、多因、多阶段的特点的新认识。用挥发作用、混合作用、水岩交换作用模型考查碳酸盐岩的碳氧同位素变化原因，获得雨水+岩浆流体混合再与碳酸盐岩发生同位素交换作用的模式；用二组正常铅、短期内形成的异常、两阶段异常铅和简单三阶段异常铅等模式考察矿区铅同位素组成，获得两阶段异常铅模式可以很好解释矿区的铅同位素组成；用同位素平衡系数外推法获得两组δ₃₄S∑S值，两组δ³⁴S_∑S值表明热液中硫可能有岩浆和沉积地层两种来源。首次通过成矿物理化学环境研究，获得矽卡岩阶段成矿温度为430℃～570℃；成矿压力约为1000×10⁵Pa；XCO₂在0.22～0.01之间；由于流体温度下降和H₂0参与活动，使得晚期矽卡岩成岩流体温度下降，XCO₂下降；硫化物阶段成矿压力为0.9×10⁵Pa～300×10⁵Pa，盐度为13.9～34wt（％），成矿温度为200℃～350℃，并获得各成矿阶段的硫、氧和二氧化碳逸度值及pH值。通过硫化物阶段温度、氧逸度、硫逸度、pH值和矿物包裹体的盐度的测定，计算出硫化物成矿时金属元素的搬运形式，并得出第一阶段铜、锌和第二阶段铅、锌、银的搬运形式，主要以氯络合物为主，氢羟基络合物和硫化氢络合物次之；第二阶段碲是以HTe^-、HTeO₃^-、H₂TeO₃形式搬运为主。通过对黄沙坪铅锌多金属矿床地质特征、成矿地质条件、成矿作用、控矿因素、地球化学特征以及成矿过程的分析，认为矿床的形成经历了地台阶段的沉积成矿阶段、沉积成岩成矿阶段和地洼阶段的岩浆热液成矿阶段。并通过对黄沙坪铅锌矿成矿岩体、构造、地层多因素耦合成矿定位机制的综合研究，总结了找矿标志；同时针对具体的找矿预测靶区开展了卓有成效的地质、构造地球化学和三频激电找矿预测研究。更多还原

【Abstract】 Huangshaping lead-zinc deposit is a large-scale oer deposit, which is needed to find new resource urgely because of long time mining. Therefor it has a great theory and practice significance for researching for mineralization mechemism and metallogenic prediction. From points of isotopic and trace elements compostion and their evolution features, ad based on the polygenetic metallogenic theory, the origin of mineralization material, ore deposit genetics, minerogenesis and location prediction of orebodies were thoroughly researched.The anomaly characteristics of regional structure, geochemistry, magnetogravity were concluded by comparing their features of Huangshaping, Shuikoushan, Dongpo, Yaogangxian and Xianghualing polymetal ore deposits.Based on the features of geology, magmatic rocks’ lithology and petrochemistry, trace elements and rare earth elements, the source and diagenesis mechanism of magmatc rocks and their evolution were deeply discussed from which the new understanding of multiple sources, polygenetics and multi-phase were gainedChecking the reason of change of carbon and oxigen isotope in barbonate by volatile action, mixing action rock-water exchanging action has comfirmed that there is an isotope exchanging in carbonate for rainwater + magma fluid and carbonate. The anomaly lead pattern with two stages can explain the isotope compostion by checking the patterns of two groups of normal lead, two stage anamaly lead formed short time and three stage anamaly lead. The two groups ofδ³⁴SΣS values obtained by extrapolation confirmed that there sedimentary and magmatic origins for sulfur in hydrothermal solution.The researching on physical-gecchemical environment has shown that the skarn-formed temperature are 430℃～570℃; ore-formed pressure is 1000×10⁵Pa: Xco₂ is between 0.22～0.01, and the temperature of early stage skarn-formed fluid is more high and with high Xco₂.With the temperature decreasing of the fluid and joining of H₂O, which made temperature and Xco₂ of later skarn-formed fluid down.The pressure in the stage of mineralization for sulphide are 0.9×10⁵pa～300×10⁵Pa, the salinity are 13.9～34wt（%） and temperature are 200℃～350℃.The migration forms of metal elements have been obtained by the temperature, oxgen fugacity sulfur fugacity pH value and salinity of mineralization stage, the migration forms of lead zinc and silver are mainly chlorine complex and hydroxyl complex and hydrogen sulfide complex in the first stage and HTe,HTeO₃,H₂TeO₃ in the secondary stage.By synthetic analysis the geological features, mineralization conditions, metallogeny, ore-controlling factors, geochemical features and ore-forming process, it was suggested that formation of Huangshaping ore deposit underwent multiple phases of sedimentary mineralization, sedimentary and diagenesis mineralization phases in platform stage and magmatic fluid mineralization phase. Furhtermore, by integrating different location factors of the orebodies including magmatic intrusions, structures, strata, symbols of ore-hunting were summarized. Meanwhile, synthesis exploration works such as geological survey, structure geochemical and geophysical survey aimed to the target area were undertaken.更多还原