| 西藏切穷地区早白垩世花岗岩年代学和地球化学特征及其构造环境 |
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| 引用本文： | 黄泽森,江巴多吉,达瓦次仁,塔尔杰.西藏切穷地区早白垩世花岗岩年代学和地球化学特征及其构造环境[J].现代地质,2019,33(4):703-714. |
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| 作者姓名： | 黄泽森 江巴多吉 达瓦次仁 塔尔杰 |
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| 作者单位： | 1.成都理工大学 地球科学学院,四川 成都 6100592.四川省地质矿产勘查开发局二零七地质队,四川 乐山 6142003.西藏工程勘察施工集团有限责任公司,西藏 拉萨 850000 |
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| 基金项目： | 中国地质调查局项目“冈底斯-喜马拉雅铜矿资源基地项目”(121201010000150014-10) |
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| 摘 要： | 西藏谢通门县切穷地区发育面积较广的早白垩世花岗岩岩体。为了进一步查明花岗岩的特征、侵入时代及其形成环境,对其进行了地质学、岩石地球化学及年代学研究。岩体LA-ICP-MS锆石U-Pb定年结果表明,研究区花岗岩岩体侵位年龄主要集中于(129.3±0.8)~(130.5±0.9) Ma,属早白垩世。从岩石地球化学特征来看,研究区花岗岩岩体具有高SiO2(73.19%~76.7%)、富碱(K2O+Na2O=7.81%~8.41%)特征,铝饱和指数(A/CNK)介于0.93~1.12之间,为强过铝质花岗岩;贫CaO(0.32%~7.31%)、MgO(0.01%~1.76%),显示明显的负铕(δEu=0.11~1.25)异常,富集Rb、Th、Nd元素,亏损Nb、Sr、P、Ti、K元素。从形成环境来看,研究区花岗岩具有明显的大陆碰撞环境的特征。研究认为,西藏切穷地区早白垩世花岗岩形成于同碰撞环境,但在后碰撞过程中地壳缩短增厚发生拆沉作用,玄武质岩浆岩底侵,经过中下地壳发生改造重熔形成的。
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| 关 键 词： | 锆石U-Pb定年 岩石地球化学 花岗岩 冈底斯 构造环境 |
| 收稿时间： | 2018-01-21 |
| 修稿时间： | 2018-11-26 |
Geochemistry and Geochronology of Early Cretaceous Granitic Intrusions and Tectonic Setting of Qieqiong Area in Tibet,China |
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| HUANG Zesen,JIANGBA Duoji,DAWA Ciren,TAER Jie.Geochemistry and Geochronology of Early Cretaceous Granitic Intrusions and Tectonic Setting of Qieqiong Area in Tibet,China[J].Geoscience——Journal of Graduate School,China University of Geosciences,2019,33(4):703-714. |
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| Authors: | HUANG Zesen JIANGBA Duoji DAWA Ciren TAER Jie |
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| Institution: | 1. College of Earth Sciences, Chengdu University of Technology, Chengdu,Sichuan 610059, China2. No.207 Geological Team of Sichuan Geology and Mineral Resources Exploration Development Bureau, Leshan,Sichuan 614200, China3. Tibet Engineering Survey Construction Group Co. Ltd., Lhasa,Tibet 850000,China |
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| Abstract: | A wide range of Early Cretaceous granitic intrusions were formed in the Qieqiong area in Tibet.To better understand the geological characteristics, intrusion age and petrogenetic environment, we have studied the geology, geochemistry and geochronology of intermediate granite rocks from the area. LA-ICP-MS zircon U-Pb dating shows that the granitoids were emplaced in the Early Cretaceous, from (129.3±0.8) Ma to (130.5±0.9) Ma.Geochemical analyses show that the granitoids are high in SiO2(73.19%-76.7%), alkali(K2O+Na2O=7.81%-8.41%), with A/CNK=0.93 to 1.12, displaying strong peraluminous characteristics. The rocks have low CaO(0.32%-7.31%) and MgO (0.01%-1.76%), and distinct negative Eu anomalies (δEu=0.11-1.25). Primitive-mantle normalized multi-element spider diagram displays apparent enrichments in Rb, Th and Nd, and marked depletions in Nb, Sr, P, Ti and K.These intermediate granitoids show continental collision geochemical affinities. Considering the regional tectonic setting and published information, we infer that the granites at Qieqiong were formed in the a post-collisionalsetting, when crustal thickening and delamination occurred. The magmas were sourced by basaltic magma underplating and the subsequent partial melting of the middle-lower crust. |
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| Keywords: | zircon U-Pb age whole-rock geochemistry granite Gangdise tectonic setting |
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