| 西藏谢通门县切琼地区典中组流纹岩锆石U-Pb年龄、Hf同位素及地球化学特征 |
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| 引用本文： | 曾成,闫茂强,沈志远,高强,魏俊浩,毛国正,邓永明.西藏谢通门县切琼地区典中组流纹岩锆石U-Pb年龄、Hf同位素及地球化学特征[J].大地构造与成矿学,2022(1):154-174. |
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| 作者姓名： | 曾成 闫茂强 沈志远 高强 魏俊浩 毛国正 邓永明 |
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| 作者单位： | ;1.中国地质大学(武汉)资源学院;2.西藏工程勘查施工(集团)有限公司 |
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| 基金项目： | 国家自然科学基金项目(41772071)资助； |
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| 摘 要： | 西藏中拉萨地块切琼地区广泛发育的林子宗群火山岩被认为是印度大陆与亚洲大陆碰撞火山作用的响应,对于揭示大陆碰撞的时限和过程具有重要的意义。本文对区内流纹岩进行了LA-ICP-MS锆石U-Pb年龄、Hf同位素及全岩元素地球化学研究,结果显示:研究区流纹岩年龄为67.1±0.1 Ma,符合林子宗群典中组火山岩年龄范围。该流纹岩具有富Si、高K、低Ti、过铝质特征;富集轻稀土元素,亏损重稀土元素,(Gd/Yb)N=0.57~1.16,普遍出现负Eu异常(δEu=0.05~0.08),相对富集大离子亲石元素(Pb、Rb、Th、U),亏损高场强元素(P、Ti),并且明显亏损Ba和Sr,属于高钾钙碱性过铝质系列,具有陆源弧火山岩的特点;锆石176Hf/177Hf值在0.282673~0.282804之间,εHf(t)在?2.1~+2.3之间,平均为?0.6,t2DM变化于875~1117 Ma之间。综合分析表明,切琼地区林子宗群典中组流纹岩形成于俯冲构造环境,源于古老地壳物质再循环,且混染了少量幔源物质。对比区域上相关矿床,结合切琼地区已发现矿点,表明切琼地区典中组火山岩具有一定寻找浅成低温热液型、矽卡岩型矿床的潜力。
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| 关 键 词： | 林子宗群 典中组 流纹岩 晚白垩世 中拉萨地块 |
Zircon U-Pb Ages,Hf Isotopes and Geochemistry of the Rhyolite in the Dianzhong Formation from the Qieqiong Area,Xietongmen County,Tibet |
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| ZENG Cheng,YAN Maoqiang,SHEN Zhiyuan,GAO Qiang,WEI Junhao,MAO Guozheng,DENG Yongming.Zircon U-Pb Ages,Hf Isotopes and Geochemistry of the Rhyolite in the Dianzhong Formation from the Qieqiong Area,Xietongmen County,Tibet[J].Geotectonica et Metallogenia,2022(1):154-174. |
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| Authors: | ZENG Cheng YAN Maoqiang SHEN Zhiyuan GAO Qiang WEI Junhao MAO Guozheng DENG Yongming |
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| Institution: | (Faculty of Earth Resources,China University of Geosciences(Wuhan),Wuhan 430074,Hubei,China;Tibet Engineering Exploration and Construction(Group)Co.,Ltd.,Lhasa 850000,Tibet,China) |
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| Abstract: | The Qieqiong area is located in the middle Lhasa block,Tibet,where volcanic rocks of the Linzizong Group are widespread.The Linzizong volcanic succession is regarded as the magmatism response to the continent collision between India and Asia,which is essentially important in discovering the initial collisional time and processes.This paper reports the whole-rock geochemical,Hf isotope and zircon U-Pb geochronological results of the rhyolite in this area.Tthe dating results show that the age of the rhyolite in the study area is 67.1±0.1 Ma and belongs to the volcanic rock of the Dianzhong Formation of the Linzizong Group.Chemical analyses show that the rhyolites in this area have high Si,high K,and low Ti,with peraluminous nature;they are characterized by LREE enrichment and obvious REE differentiation(Gd/Yb)N=0.57–1.16,with significant negative Eu anomalies(δEu=0.05–0.08),they are enriched in LILEs(Pb,Rb,Th and U),depleted in HFSEs(P and Ti),and obviously depleted in Ba and Sr,thus belong to calc-alkalic and peraluminous series with characteristics of continental margin arc volcanic rocks.Zircon grains from the rhyolite have 176Hf/177Hf values in the range of 0.282673 to 0.282804,εHf(t)values in the range of?2.1 to+2.3,and two-stage model ages(t2DM)of 875 Ma to 1117 Ma.Overall,the rhyolite in the Dianzhong Formation from the Qieqiong area was formed in a subduction tectonic setting,derived mainly from recycled crustal material,and mixed with a small amount of mantle-derived magma.Considering the related deposits in the area and the discovered ore spots in the Qieqiong area,we suggest that the volcanic rocks of the Dianzhong Formation in the Qieqiong area have promising potential for epithermal and skarn deposits prospecting. |
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| Keywords: | Linzizong Group Dianzhong Formation rhyolite Late Cretaceous middle Lhasa block |
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