川西嘎村银多金属矿床银的赋存状态、成矿机理研究

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	川西嘎村银多金属矿床银的赋存状态、成矿机理研究
	朱维光
	2001
学位授予单位	中国科学院地球化学研究所
学位授予地点	中国科学院地球化学研究所
学位名称	博士
学位专业	地球化学
关键词	银多金属矿床赋存状态分布特征岩浆热液喷流-沉积成矿机制嘎村川西
摘要	本文从区域地质、矿床地质、矿物学、微量元素与稀土元素地球化学、同位素地球化学、热力学计算和成矿年代学方面系统地研究了嘎村银多金属矿床的矿石矿物特征、银的赋存状态及分布特征、成矿物质的来源、成矿流体的性质及可能来源、银的富集机制、成矿时代。在分析成矿过程的基础上，提出富集模式和找矿方向。首次在矿应中开展的工作有：①对矿床中层状矿石及其石英进行δ~(18)O测定；②对成矿过程中银的迁移形式计算；③矿床的成矿年代学研究。矿物学研究表明，银主要赋存于黝铜矿之中。本次工作首次找到两种银矿物；硫砷铜银矿、硫铅铜矿。同时找到一批蠕虫状微细粒含银矿物，并在矿床中首次发现一种硫盐矿物——硫砷铜矿。微量元素、稀土元素、铅和锶同位素研究表明，银主要来源于岛弧火山岩，同时热液通过水岩反应对流经的围岩也萃取一部分矿物质。流体包裹体、稀土元素、氧化和硫同位素等研究表明，成矿热液为高温酸性、富C1和CO_2的钠质流体，并具有高δ~(18)O和富放射性成因锶的特点。我们认为岩浆热液是成矿流体的主要贡献，海水也部分参与了成矿。通过热力学计算，证实银在成矿流体中基本上以AgCl_2~-形式迁移。银沉淀的机制主要是温度的降低、pH值增大。矿床中的岩石、矿石进行全岩Rb-Sr等时线年龄研究，得出矿床的热液叠加改造的年龄为204 ± 14Ma。这一年龄代表义敦岛弧在印支晚期与扬子大陆的俯冲、碰撞形成造山带的年龄。矿物学研究也证实，成矿晚期或成矿后存在热液交代（叠加）现象。矿床中岩石、矿体产状的直立表明嘎村矿床为后期改造较强烈的矿床。本文初步提出该矿床为后期热液叠加改造的岩浆热液喷流-沉积矿床。
其他摘要	This paper mainly focuses on the characteristics of minerals in ore, the occurrence and distribution of silver, the sources of mineralized substances and fluids, the features of fluids, the ore-forming mechanism and the age of mineralization in the Gacun silver-polymetallic deposit through a series of researches on the geology of area and deposit, the mineralogy, the rare earth elements and trace elements, the isotopes of lead, sulfur, oxygen, strontium, the thermodynamics, the chronology. In addition, the metallogenic model has been established. Finally, the exploration direction has been suggested. Based on the investigation of a consideration number of polished ore sections and electronic microprobe analysis, we have finished systemic works of ore minerals and first found three sulfosalts - eugenite, furutobeite, enargite and a series of fine vermiform minerals which contain silver in this deposit. The data of trace element, REE, Pb and Sr isotope indicate that the ore-forming metals and silver were mostly derived from the volcanic rocks, partially from underlying strata. The comprehensive studies of fluid inclusion, thermodynamics and stable isotope (S and O isotope) have revealed that the ore-forming fluid belongs to NaCl-CO_2-H_2O type hot solution, high temperature and acid property, high δ~(18)O value and rich strontium of radioactive formation. The water of ore-forming fluid was mainly derived from magmatic water, partially from seawater. The silver in ore-forming fluid was dominantly transported in the form of AgCl_2~-. The mechanism of silver deposition was mostly caused by the temperature falling and pH accretion. The whole-rock Rb-Sr isochron age is (204 ± 14)Ma, with Sr isotope initial ratio (~(87)Sr/~(85)Sr)_1 = 0.709994 ± 0.000353. It suggests that the Yiduan island arc's diving and collision orogenic belt possibly altered Gacun deposit. The author concludes that the formation of this deposit processed through two mineralization stages: magmatic water exhalative-sedimentation, deuteric hot water alteration.
页数	84
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3586
专题	研究生_研究生_学位论文矿床地球化学国家重点实验室
推荐引用方式 GB/T 7714	朱维光. 川西嘎村银多金属矿床银的赋存状态、成矿机理研究[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,2001.

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