| 西藏洞嘎金矿床地质特征、原位硫同位素组成及成因探讨 |
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| 引用本文：何青,郎兴海,王旭辉,邓煜霖,王涌涛,吴伟哲,谢鸿儒,詹宏宇,刘洲基,姜楷.2023.西藏洞嘎金矿床地质特征、原位硫同位素组成及成因探讨[J].地球学报,44(6):1000-1016. |
| DOI：10.3975/cagsb.2023.021401 |
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| 基金项目:四川省科技计划项目(编号: 2020JDJQ0042);国家自然科学基金项目(编号: 41972084);成都理工大学珠峰科学研究计划(编号: 2020ZF11407) |
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| 中文摘要:洞嘎金矿位于西藏雄村矿集区, 是冈底斯成矿带较早发现且投入开采的金矿, 但研究程度低, 矿床成因存在较大争议。本文通过系统的矿床地质特征研究, 开展了硫化物原位硫同位素测试, 分析成矿物质来源, 进而探讨洞嘎金矿的成因。洞嘎金矿体受控于雄村组凝灰岩中的裂隙系统, 矿体呈脉状产出, 已探获金金属资源量9.55 t, 达到中型规模。矿石构造主要为脉状-细脉状构造, 金主要以包裹金和粒间金的形式赋存于黄铁矿和黄铜矿中。根据脉体穿插关系及矿物共生组合特征, 将洞嘎金矿的成矿过程划分为热液成矿期与表生氧化期, 其中热液成矿期为主成矿期, 可进一步划分为3个成矿阶段: 成矿早阶段、成矿主阶段及成矿晚阶段。洞嘎金矿床硫化物的硫同位素δ34S= –1.57‰~+5.26‰, 平均值+1.69‰, 具明显的塔式分布, 表明硫源具岩浆硫的特点。结合前人已发表的数据, 我们认为洞嘎金矿属于斑岩铜金成矿系统外围的热液脉型金矿床, 深部可能存在斑岩型铜金矿床, 找矿潜力极大。洞嘎金矿的成矿物质来源主要为地幔, 有少量的地壳物质(俯冲沉积物)加入。洞嘎金矿床的金与绿泥石密切相关, 该绿泥石主要为溶蚀-迁移-结晶机制形成, 绿泥石形成过程导致含金热液流体成分及物理化学性质发生改变, 使得成矿流体中的金发生卸载, 最终在凝灰岩的裂隙系统中形成洞嘎金矿床。 |
| 中文关键词:洞嘎金矿 地质特征 原位硫同位素 成矿物质来源 矿床成因 |
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| Geological Characteristics, In-situ Sulfur Isotope Composition, and Genesis of the Dongga Gold Deposit in Xiongcun Area, Tibet |
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| Abstract:The Dongga gold deposit is located in the Xiongcun ore collection area, which is a previously discovered gold mine that is a part of the Gangdese metallogenic belt. However, less research has been conducted in this area, and the genesis of the deposit has not been uniformly agreed upon. A special systematic geological study of the deposit was conducted on the Dongga gold deposit, and the source of the mineralized material was explored by conducting an in-situ sulfur isotope analysis of the sulfides. Subsequently, the genesis of the Dongga gold deposit was discussed. The Dongga gold deposit is controlled by a fracture fissure system of a volcanic mechanism, and 9.55 tons of gold metal have been detected, suggesting a medium-sized scale. The ore bodies are vein-like and nearly parallel to each other. The gold is mainly in the form of inclusions and intergranular gold in pyrite and chalcopyrite. According to the vein interpenetration relationship and mineral coeval combination, the Dongga gold deposit formation process can be divided into hydrothermal metallogenic and epithermal oxidation stages. The hydrothermal metallogenic stage is the general metallogenic stage, which can be further divided into the early metallogenic, main metallogenic, and late metallogenic stages. The δ34S of the Dongga gold deposit ranges from –1.57‰ ~ +5.26‰, with an average value of +1.69‰; it shows a clear tower distribution, indicating a magmatic sulfur source. Combined with previously published data, we believe that the Dongga gold deposit belongs to the hydrothermal vein-type gold deposit on the periphery of the porphyry Cu ± Au metallogenic system. Porphyry type Cu-Au deposits may be present at depths, with considerable potential for the presence of ore. The source of its mineralized material is majorly the mantle, with a small amount of crustal material added in the form of subduction sediments. The gold in the Dongga gold deposit is closely related to chlorite, which is mainly formed by the dissolution migration crystallization mechanism. The formation process of chlorite changes the composition and physical and chemical properties of gold-bearing hydrothermal fluid, which makes the gold in the ore-forming fluid unload, and finally forms Dongga gold deposits in the tuff fracture system. |
| keywords:Dongga gold deposit geological characteristics in-situ sulfur isotopes ore-forming material source deposit genesis |
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