| 西藏雄村斑岩型铜金矿集区I号矿体的硫、铅同位素特征及其对成矿物质来源的指示 |
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| 引用本文：郎兴海,唐菊兴,李志军,黄勇,丁枫,王成辉,张丽,周云.2012.西藏雄村斑岩型铜金矿集区I号矿体的硫、铅同位素特征及其对成矿物质来源的指示[J].地球学报,33(4):459-470. |
| DOI：10.3975/cagsb.2012.04.07 |
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| 基金项目:国家自然科学基金(编号: 41172077);国家973项目(编号: 2011CB403103);西藏天圆矿业资源开发有限公司项目(编号: 2006G-07);中国地质调查局地调项目“西藏大型矿床成矿专属性研究”(编号: 资[2012]03-002-055) |
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| 中文摘要:西藏雄村斑岩型铜金矿集区是近年来西藏冈底斯斑岩铜矿带内发现的一处超大型铜金矿集区, 其形成于与新特提斯洋向北的洋内俯冲作用有关的岛弧环境, 成矿时代为中侏罗世。该矿集区位于冈底斯火山-岩浆弧的中段南缘, 其南侧紧邻日喀则弧前盆地, 目前探明I(原命名为雄村铜矿床)、II、III号铜金矿体规模达大型-超大型, 同时还存在多个矿化异常带。本文以雄村I号矿体为研究对象, 对雄村I号矿体含矿斑岩、赋矿凝灰岩和主要硫化物的硫、铅同位素开展研究, 结果表明: ①含矿斑岩、赋矿凝灰岩和主要硫化物具有较为一致的硫同位素组成, δ34SCDT变化范围为–3.5‰~2.7‰, 平均–1.07‰, 十分接近于零, 塔式分布效应显著, 硫可能主要来自地幔; ②含矿斑岩、赋矿凝灰岩和主要硫化物具有相对一致的铅同位素组成, 均以放射性成因铅含量低为特征, 206Pb/204Pb、207Pb/204Pb和208Pb/204Pb变化范围分别为18.369~18.752、15.473~15.589和38.389~39.1531, 位于地幔与造山带铅演化线之间, 并且相对靠近地幔铅演化线, 显示出铅主要来源于地幔, 可能有少量地壳物质的混染。通过西藏冈底斯斑岩铜矿带碰撞造山环境和岛弧环境(以雄村I号矿体为代表)斑岩型铜矿床的硫、铅同位素组成特征对比, 认为两者的成矿物质来源是相似的, 碰撞造山环境的地壳物质混染较强烈, 而岛弧环境的地壳物质混染较弱。 |
| 中文关键词:硫同位素 铅同位素 雄村 斑岩铜矿床 西藏冈底斯带 |
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| Sulfur and Lead Isotope Characteristics of No. I Ore Body in the Xiongcun Porphyry Copper-Gold Ore Concentration Area of Tibet: Implications for the Source of Metals in the Ore Deposit |
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| Abstract:The Xiongcun porphyry copper-gold ore concentration area, one of the large-size metallogenic areas discovered along the Gangdise porphyry copper belt, occurs in an island arc environment associated with northward intra-oceanic subduction of Neo-Tethys oceanic crust. The ore-forming age of the Xiongcun porphyry copper-gold ore concentration area is middle Jurassic. It is located in the middle of the southern margin of the Gangdise orogenic belt, and its south margin is Shigatse forearc basin. The latest exploration data indicate that there are several potential mineralization-alteration areas and three large-size copper-gold ore bodies (No. I, II and III) in the Xiongcun porphyry copper-gold ore concentration area. In this paper, Xiongcun No. I ore body was chosen as the research object. According to sulfur and lead isotope composition of ore-baring porphyry, tuff and main sulfides of the ore, the authors have reached the following two conclusions: 1) Sulfur isotopic compositions vary in a narrow range of δ34S values from ?3.5‰ to +2.7‰ (?1.07‰ on average) and are close to zero, indicating a mantle sulfur signature. 2) They have uniform Pb isotope compositions with low content of radiogenic Pb. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios vary in the ranges of 18.104-18.432, 15.473-15.533 and 37.918-38.3072, respectively. They are located in the transition zone of mantle Pb and orogen Pb but are closer to the former, reflecting a mixing between the mantle material and minor crust material. Through a comparative study of sulfur and lead isotopes of porphyry copper deposits of the island arc environment (e.g., Xiongcun No. I ore body) and those of the collisional orogenic environment in the Gangdise porphyry copper belt, the authors found that they have similar metal sources, but porphyry copper deposits of the island arc environment have experienced weak contamination of crust materials, whereas porphyry copper deposits of the collisional orogenic environment have experienced strong contamination of crust materials. |
| keywords:sulfur isotope lead isotope Xiongcun porphyry copper-gold deposit Gangdise belt in Tibet |
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