| 石榴石U-Pb定年对山西义兴寨金矿床角砾岩筒时间的限制和金矿成因的指示 |
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| 引用本文： | 张立中,陈蕾,王国平,邓晓东,李建威.石榴石U-Pb定年对山西义兴寨金矿床角砾岩筒时间的限制和金矿成因的指示[J].地球科学,2020,45(1):108-117. |
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| 作者姓名： | 张立中 陈蕾 王国平 邓晓东 李建威 |
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| 作者单位： | 1.紫金矿业集团股份有限公司矿产地质勘查院, 福建厦门 361006 |
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| 基金项目： | 国家重点研发计划项目2016YFC0600104国家自然科学基金项目41325007 |
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| 摘 要： | 山西义兴寨金矿床是五台山-恒山金矿集区内最为典型的金矿床，也是山西省最大的金矿床.矿区产出有4个角砾岩筒，与金矿的形成具有紧密的联系.然而，有关该矿床角砾岩筒的形成时间和机制的研究十分欠缺，角砾岩筒与金矿化的关系仍不清楚.通过对角砾岩筒内的矽卡岩角砾中的石榴石和切割角砾岩的石英斑岩中的锆石开展了LA-ICPMS原位U-Pb同位素分析，结果表明角砾岩和石英斑岩的形成时间分别为140±2 Ma和141±1 Ma，从而精确限制了角砾岩筒的形成时间.以上研究表明，义兴寨矿区4个角砾岩筒的形成时间与石英斑岩侵位时代和金矿形成时间完全一致，表明角砾岩筒是岩浆分异的气液流体导致围岩发生隐爆而形成，而金矿化也可能与岩浆释放的热液流体直接相关.
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| 关 键 词： | 石榴石U-Pb定年 角砾岩筒 隐爆 义兴寨金矿 岩石学 |
| 收稿时间： | 2018-10-15 |
Garnet U-Pb Dating Constraints on the Timing of Breccia Pipes Formation and Genesis of Gold Mineralization in Yixingzhai Gold Deposit,Shanxi Province |
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| Abstract: | Yixingzhai gold deposit, located in Wutaishan-Hengshan gold district, is the most important and largest gold deposit in Shanxi Province. Spatial distribution of the four breccia pipes shows the well relation with gold mineralization in Yixingzhai deposit. However, robust constraints on the timing of the breccia pipes formation in this deposit are lacking. The relationship between the gold mineralization and breccia formation is also ambiguous. In this paper, systematic U-Pb dating of garnet crystals from skarn breccia and zircon grains from the quartz porphyry were carried out by using laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). The garnet grains yielded the 207Pb-corrected weighted mean 206Pb/238U dates of 140±2 Ma, which is remarkably consistent with U-Pb age of zircon grains (141±1 Ma) from the quartz porphyry in this deposit. This demonstrates that the formation of breccia pipes was genetically related to the coeval magmatism. Therefore, we proposed that gas and hydrothermal fluid released from magma increase the fluid pressure, causing the formation of breccia pipes by cryptoexplosion of the wall rocks. The age of the breccia pipes is also consistent with the formation time of gold mineralization, suggesting that the hydrothermal gold mineralization may link with the fluids released from magma. |
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