| 西藏罗布真矿区林子宗群火山岩锆石U-Pb年龄、地球化学特征及其地质意义 |
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| 引用本文： | 赵亚云,杨春四,吕金梁,刘晓峰,刘波,郑常云,刘远超,李莉,付海龙.西藏罗布真矿区林子宗群火山岩锆石U-Pb年龄、地球化学特征及其地质意义[J].现代地质,2019,33(1):73-84. |
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| 作者姓名： | 赵亚云 杨春四 吕金梁 刘晓峰 刘波 郑常云 刘远超 李莉 付海龙 |
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| 作者单位： | 1.西藏自治区地质矿产勘查开发局 第二地质大队,西藏 拉萨 8500032.中国科学院矿物学与成矿学重点实验室,广东 广州 5106403.西藏自治区地质矿产勘查开发局,西藏 拉萨 850000 |
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| 基金项目： | 中国地质调查局项目“西藏昂仁—谢通门朱诺铜矿整装勘查区矿产调查与找矿预测”(121201004000150017-95);中国地质调查局项目“西藏昂仁—谢通门朱诺铜矿整装勘查区矿产调查与找矿预测”(121201004000160901-47);中国地质调查局项目“西藏昂仁—谢通门朱诺铜矿整装勘查区矿产调查与找矿预测”(121201004000160901-22) |
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| 摘 要： | 罗布真铅锌多金属矿床位于冈底斯火山-岩浆活动带的中南部,矿区内广泛发育林子宗群火山岩,岩性为英安岩和流纹质晶屑凝灰岩。LA-ICP-MS锆石U-Pb定年结果显示,罗布真矿区内林子宗群英安岩的成岩年龄为(49.14±0.86) Ma,应属于帕那组火山岩地层,并非前人所认为的典中组。岩石具有高K、低Ti的特征,属于高钾钙碱系列;相对富集Rb、Th、U、K、Zr、Hf等元素,亏损Nb、Ta、P、Ti、Sr等元素,且轻重稀土分馏明显,具有明显的负铕(δEu=0.50~0.65)异常。在印度-亚洲大陆汇聚的过程中,新特提斯洋向欧亚大陆俯冲,约50 Ma发生了大规模的火山、岩浆作用,同时岩浆-热液成矿作用也进入高峰期,林子宗群火山岩的形成时代与该时代一致,形成于陆陆碰撞形成的板内环境。罗布真矿区林子宗群火山岩年龄的厘定,揭示了冈底斯带林子宗群帕那组火山岩具有赋矿潜力,对认识该地区林子宗群火山岩与热液脉型铅锌多金属矿化的关系具有指导意义。
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| 关 键 词： | LA-ICP-MS锆石U-Pb年龄 林子宗群 帕那组 罗布真 西藏 |
| 收稿时间： | 2018-02-13 |
| 修稿时间： | 2018-11-05 |
Zircon U-Pb Age,Geochemical Characteristics and Significance of the Linzizong Group Volcanic Rocks in the Luobuzhen Orefield,Tibet,China |
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| ZHAO Yayun,YANG Chunsi,Lü Jinliang,LIU Xiaofeng,LIU Bo,ZHENG Changyun,LIU Yuanchao,LI Li,FU Hailong.Zircon U-Pb Age,Geochemical Characteristics and Significance of the Linzizong Group Volcanic Rocks in the Luobuzhen Orefield,Tibet,China[J].Geoscience——Journal of Graduate School,China University of Geosciences,2019,33(1):73-84. |
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| Authors: | ZHAO Yayun YANG Chunsi LÜ Jinliang LIU Xiaofeng LIU Bo ZHENG Changyun LIU Yuanchao LI Li FU Hailong |
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| Institution: | 1. No. 2 Geological Team, Tibet Autonomous Region Geological Mining Exploration and Development Bureau, Lhasa, Tibet 850003, China2. Key Laboratory of Mineralogy and Metallogeny, Chinese Academy of Sciences, Guangzhou, Guangdong 510640, China3. Tibet Autonomous Region Geological Mining Exploration and Development Bureau, Lhasa, Tibet 850000, China |
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| Abstract: | The Luobuzhen Pb-Zn polymetallic deposit is located in the middle-southern part of the Gangdese magmatic belt. The Linzizong Group (Gp.) volcanic rocks are widely distributed in the mining area, and contain mainly dacite and rhyolitic crystal tuff. LA-ICP-MS zircon U-Pb dating reveals that the dacite was formed at (49.14±0.86) Ma, which was coeval with the Pana Formation volcanic sequence but not the Dianzhong Formation. The rocks are characterized by high K but low Ti contents and are high-K calc-alkaline. The elements of Rb, Th, U, K, Zr, Hf and LREEs are enriched, while Nb, Ta, P, Ti, Sr and HREEs are depleted, and clear LREE/HREE fractionation is present. The volcanic rocks also have negative Eu-anomalies (δEu=0.50 to 0.65). The Neo-Tethys oceanic slab likely subducted beneath Eurasia during the incipient India-Asia collision. Extensive volcanism-plutonism occurred and mineralization reached a peak at ~50 Ma. The dacite volcanism was coeval with the regional magmatism, which suggests that the dacite was formed in an intraplate tectonic environment. This work re-determined the age of the Linzizong Gp. volcanic rocks and implied that the Pana Formation volcanic rocks in the Gangdese belt are potentially ore-bearing. Our finding also provides significant implication and prospecting guidance to understand the relationship between the Linzizong Gp. magmatism and the hydrothermal vein-type Pb-Zn polymetallic mineralization. |
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| Keywords: | LA-ICP-MS zircon U-Pb age Linzizong Group Pana Formation Luobuzhen Tibet China |
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