【作者】 李发源；

【导师】 顾雪祥； 唐菊兴； 阳正熙；

【作者基本信息】 成都理工大学 ， 矿物学、岩石学、矿床学， 2003， 硕士

【摘要】 许多密西西比河谷型(MVT)铅锌矿床中都含有具经济意义的锗(Cd)、镉(Ge)、镓(Ga)等分散元素。本文以天宝山、大梁子矿床为例，探讨MVT铅锌矿床中分散元素的赋存状态及富集机制。 天宝山、大梁子矿床严格受“层、相、位”的控制，属后生热液层控矿床，也是典型的密西西比河谷型铅锌矿床。 矿床地质特征以及常微量元素、稀土元素、同位素、成矿流体等地球化学特征的研究表明，矿床成矿物质是多来源的，天宝山矿床成矿物质主要来自上部地壳和造山带各种沉积岩，大梁子矿床成矿物质主要来自震旦系灯影组地层；两个矿床成矿溶液主要来自大气降水；硫大部分来源于同时期的海相沉积地层(震旦系灯影组)中被细菌还原的海水硫酸盐。 大量光、薄片观察和电子探针分析表明，天宝山、大梁子铅锌矿床中分散元素主要以类质同象形式存在。Cd主要赋存在浅色和中色闪锌矿中，而Ga、Ge主要赋存在方铅矿中，分散元素在热液成矿期的中、晚阶段大量富集。 Cd、Ge、Ga等分散元素可能形成了部分氯化物络合物或者被Pb、Zn的络合物吸附而随之一起迁移；含矿热液带来的热能使矿化围岩中有机质发生热降解作用产生甲烷，从而导致硫酸盐的还原和金属硫化物的沉淀。与Pb、Zn金属一起迁移而来的Cd、Ge、Ga等分散元素在有利的物化条件下便以类质同象的方式替代相应离子而进入闪锌矿、方铅矿的晶格并逐渐富集成矿。更多还原

【Abstract】 In many Mississippi valley type (MVT) Pb-Zn deposits, dispersed elements such as Cd, Ge, and Ga may reach to economically significant enrichment. Taking the Tianbaoshan and Daliangzi Pb-Zn deposits as examples, this thesis discusses the occurrence state and enrichment mechanism of dispersed elements in the MVT Pb-Zn deposits.The Tianbaoshan and Daliangzi Pb-Zn deposits, strictly controlled by "formations, phases and structures", are typical MVT Pb-Zn deposits. They also belong to the epigenetic hydrothermal strata-bound deposit.Studies on geology of the deposits and geochemistry of trace elements, REEs, isotopes, ore-forming fluids show that the ore-forming materials came from varied sources. Ore-forming materials of the Tianbaoshan deposit was chiefly derived from different sedimentary rocks of the upper crust and orogen, while those of the Daliangzi deposit mainly from the Sinian Dengying Formation. Meteoric waters were the major source of the ore-forming solution. Sulfide sulfur came from marine sulfates that were reduced by bacteria in the Sinian Dengying Formation.Based on observation of many polished and thin sections and analyses of electron microprobe, the author suggests that dispersed elements in both the Tianbaoshan and the Daliangzi deposits occur as isomorphism. Cd chiefly occurs in sphalerite with moderate to light colors, while Ga and Ge are mainly enriched in galena. Predominant amounts of the dispersed elements occur at the middle and late stages of the hydrothermal ore-forming epoch.Dispersed elements like Cd, Ge, and Ga were transported in the form of chlorine complexes or adsorbed by chlorine complexes of Pb and Zn. Thermal degradation of organic materials resulted in the generation of CH4 which further initiated the reduction of sulfates and the precipitation of sulfides. Under favorable physico-chemical conditions, dispersed elements such as Cd, Ge, and Ga that were co-transported with Pb and Zn may have replaced corresponding ions and accumulated as the mode of isomorphism.更多还原