| 西藏冈底斯成矿带甲马和知不拉铜多金属矿床的Re-Os同位素年龄及其意义 |
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| 引用本文：.2005.Molybdenite Re-Os dating of Jiama and Zhibula polymetallic copper deposits in Gangdese metallogenic belt of Tibet and its significance [J].Mineral Deposits,24(5):481~489 |
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| 基金项目:国家自然科学基金（40272047）、国家重点基础发展计划（2002CB412609）和中国地质调查局地质大调查项目（200310200008） |
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| 中文摘要:文章首次对冈底斯成矿带的甲马和知不拉铜_铅_锌矿床的辉钼矿进行了Re_Os同位素定年。甲马矿区辉钼矿的模式年龄介于15.4～15.5 Ma之间，7件样品得到187Re-187Os等时线年龄为（15.18±0.98） Ma。知不拉矿区辉钼矿样品的模式年龄介于16.88～17.06 Ma之间，5件样品得到187Re-187Os等时线年龄为（16.90±0.64） Ma。获得的Re_Os年龄与冈底斯成矿带驱龙、拉抗俄和冲江、厅宫等斑岩铜矿床的成矿年龄一致，明显晚于侏罗纪拉萨弧间盆地的发育时限。据此作者认为甲马和知不拉等铜_铅_锌矿床不属于喷流型矿床，而是冈底斯成矿带斑岩_矽卡岩成矿系统的组成部分，是岩浆_热液流体系统在不同的深度条件下与富钙围岩交代成矿的产物。 |
| 中文关键词:地球化学 铜多金属矿床 Re_Os年龄 斑岩_矽卡岩成矿系统 甲马 知不拉 西藏 |
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| Molybdenite Re-Os dating of Jiama and Zhibula polymetallic copper deposits in Gangdese metallogenic belt of Tibet and its significance |
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| Abstract:The origin of the Jiama and the Zhibula polymetallic copper deposits in the Gangdese metallogenic belt, southern Tibet, is a problem of long controversy. This paper gives for the first time the highly precise Re_Os age of molybdenite from these two polymetallic copper deposits. The Re_Os model ages of 7 molybdenite samples from the Jiama deposit vary from (15.4±0.2) Ma to (15.5±0.2) Ma, yielding an isochron age of (15.18±0.98) Ma. The Re_Os model ages of 5 molybdenite samples from the Zhibula deposit vary from (16.88±0.28) Ma to (17.06±0.27) Ma, yielding an isochron age of (16.90±0.64) Ma. These ages are much younger than the ages of the Gangdese inter_arc sedimentary basin development and the ages of collisional granitic intrusive rocks in the Gangdese belt, but are obviously consistent with the ore_forming ages of the near_by porphyry copper deposits, such as Qulong, Lakang'e, Chongjiang and Tingguan in the Gangdese metallogenic belt. These Re_Os ages suggest that the Jiama and the Zhibula polymetallic copper deposits were formed in the same porphyry_skarn ore_forming system in a post_collisional extensional tectonic setting of Miocene epoch. The porphyry copper deposits and the skarn type polymetallic copper deposits in the Gangdese metallogenic belt were formed by different ore_forming processes of the magmatic_hydrothermal system in different wall rocks. |
| keywords:geochemistry, copper polymetallic deposit, Re_Os age, porphyry_skarn ore_forming system, Jiama, Zhibula, Tibet |
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