| 东昆仑那更康切尔银多金属矿床流纹斑岩锆石U-Pb年代学、地球化学特征及其地质意义 |
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| 引用本文： | 国显正,谢万洪,周洪兵,田承盛,李金超,孔会磊,杨涛,姚学钢,贾群子.东昆仑那更康切尔银多金属矿床流纹斑岩锆石U-Pb年代学、地球化学特征及其地质意义[J].地球科学,2019,44(7):2505-2518. |
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| 作者姓名： | 国显正 谢万洪 周洪兵 田承盛 李金超 孔会磊 杨涛 姚学钢 贾群子 |
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| 作者单位： | 1.中国地质大学地质调查研究院, 湖北武汉 430074 |
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| 基金项目： | 中国地质调查局项目DD20160013 |
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| 摘 要： | 那更康切尔银多金属矿床是青海省目前发现的首个大型银矿床，通过对赋矿流纹斑岩进行岩石学、地球化学、锆石U-Pb定年及Hf同位素研究，结果表明:流纹斑岩LA-ICP-MS锆石U-Pb年龄为217.4±3.1 Ma，形成于晚三叠世；流纹斑岩SiO2的含量在73.08%~75.78%，Al2O3含量介于14.05%~16.04%，Na2O+K2O含量为4.31%~4.77%，K2O含量为4.20%~4.61%，K2O/Na2O比值远大于1，属于钙碱性强过铝钾质火山岩.岩石具有高硅、富铝、富钾的特征，Mg#值介于45~54，具有明显的轻稀土元素富集，重稀土元素亏损的特征；富集大离子亲石元素Rb、Th、K，亏损Ta、Nb、P、Ti等高场强元素；εHf（t）介于－4.4~－9.7，二阶段Hf模式年龄TDM2为1 533~1 864 Ma.综上表明流纹斑岩主要源于中元古代－古元古代下地壳重熔，同时混入幔源物质；赋矿流纹斑岩形成于东昆仑晚三叠世造山后伸展环境.那更康切尔大型银矿床的发现，是东昆仑晚三叠世成矿作用的表现，为区域上寻找同期侵入岩或陆相火山岩有关的多金属矿床奠定基础.
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| 关 键 词： | 流纹斑岩 锆石U-Pb定年 地球化学 那更康切尔银多金属矿床 东昆仑 |
| 收稿时间： | 2018-06-07 |
Zircon U-Pb Chronology and Geochemistry of the Rhyolite Porphyry in the Nagengkangqieer Silver Polymetallic Deposit,East Kunlun and Their Geological Significance |
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| Abstract: | The Nagengkangqieer silver polymetallic deposit located in the East Kunlun orogenic belt is a newly discovered large-scale silver deposit in Qinghai Province. Orebodies of the deposit are mainly hosted in rhyolite porphyry. This paper presents zircon U-Pb dating and Lu-Hf isotopes, whole-rock major and trace elements for rhyolite porphyry in the Nagengkangqieer deposit. The LA-ICP-MS zircon U-Pb analyses for rhyolite porphyry show that rocks formed during the Late Triassic with ages of 217.4±3.1 Ma. The rhyolite porphyry has high contents of SiO2 (73.08%-75.78%), Al2O3 (14.05%-16.04%), with K2O+Na2O ranging from 4.31% to 4.77%, and K2O=4.20%-4.61%, belonging to the high-potassium calc-alkaline strong peralkaline volcanic rocks. These rocks are characterized by high silicon, aluminum and high-potassium, the Mg# values range from 45 to 54; and rhyolite porphyry is depleted in high field strength elements (HFSEs; e.g., Nb, Ta, P, and Ti), and enriched in large-ion lithophile elements (LILEs; e.g., Rb, Th and K); εHf(t) values vary from -4.4 to -9.7, and the two-stage model age of TDM2 ranges from 1 533 Ma to 1 864 Ma. According to the petrology, geochemistry and regional tectonic background, we conclude that the rhyolite porphyry was predominantly derived from partial melting of the Paleoproterozoic-Mesoproterozoic continental crust and some mantle derived material, it formed in extension tectonic settings. The Nagengkangqieer silver polymetallic deposit reflects the Late Triassic mineralization, which is essential for future exploration of polymetallic deposit in the area where intrusive rocks or volcanic rocks in East Kunlun orogenic belt would be very obvious. |
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