| 班- 怒带东段丁青蛇绿岩中镁铁质岩石年代学及构造背景 |
| |
| 引用本文： | 薄容众,杨经绥,李观龙,瑞会超,熊发挥,张承杰,董玉飞,卢雨潇,陈晓坚.班- 怒带东段丁青蛇绿岩中镁铁质岩石年代学及构造背景[J].地质学报,2019,93(10):2617-2638. |
| |
| 作者姓名： | 薄容众 杨经绥 李观龙 瑞会超 熊发挥 张承杰 董玉飞 卢雨潇 陈晓坚 |
| |
| 作者单位： | 中国地质大学(北京)地球科学与资源学院,北京,100083;自然资源部深地动力学重点实验室,中国地质科学院地质研究所,北京,100037;自然资源部深地动力学重点实验室,中国地质科学院地质研究所,北京,100037;中国地质大学(武汉)地球科学学院,武汉,430074;中国冶金地质总局第二地质勘察院,福州,350108 |
| |
| 基金项目： | 本文由国家自然科学基金项目(41672063,41773029,41720104009)，中国地质调查局地质调查项目(DD20160022- 01, DD20160023- 01, DD20190060)以及深地动力学国家重点实验室自主课题(J1901- 15)联合资助。 |
| |
| 摘 要： | 丁青蛇绿岩位于班公湖-怒江缝合带东段,分为东、西两个蛇绿岩体,丁青西蛇绿岩体缺乏基性岩年代学研究。对丁青西地质填图显示,蛇绿岩主要由方辉橄榄岩、纯橄榄岩、辉绿岩、玄武岩及辉长岩组成。其中玄武岩、辉长岩及辉绿岩出露在宗白区域,玄武岩和辉绿岩与下侏罗统沉积岩呈构造接触,辉长岩呈岩脉侵入到下侏罗统沉积岩中。岩石地球化学研究表明,玄武岩和辉长岩同属于碱性基性岩石,其中玄武岩具有典型洋岛玄武岩的稀土和微量元素特征,可能形成于与地幔柱有关的洋岛环境。在玄武质凝灰岩中挑选出的锆石测年,获得U-Pb年龄为198.7±3.8Ma,属早侏罗世。辉长岩的稀土和微量元素含量低于典型洋岛玄武岩,但其REE和微量元素具有OIB的特征,与典型OIB相比,辉长岩的HREE发生了一定程度富集。辉长岩锆石的U-Pb年龄为164.3±2.6Ma,认为辉长岩在形成过程中受到了软流圈地幔和岩石圈下部LVZ中富集熔体的共同作用,其形成于大陆边缘裂谷环境;辉绿岩成分属于拉斑系列岩石,其REE和微量元素曲线显示辉绿岩同时具有N-MORB和E-MORB的特征。辉绿岩锆石U-Pb年龄为114.2±1.3Ma,其形成晚于玄武岩。结合区域地质,认为辉绿岩形成于受地幔柱影响的弧后扩张脊环境。本研究提供了丁青西蛇绿岩新的年代学和岩石学证据,为探讨丁青蛇绿岩的形成和演化历史提供了新的证据。
|
| 关 键 词： | 班公湖-江怒缝合带 丁青 镁铁质岩石 锆石U-Pb年代学 地球化学 |
| 收稿时间： | 2019/9/3 0:00:00 |
| 修稿时间： | 2019/9/29 0:00:00 |
Geochronology and tectonic setting of mafic rocks in the Dingqing ophiolite in the eastern segment of the Bangongco- Nujiang suture zone |
| |
| BO Rongzhong,YANG Jingsui,LI Guanlong,RUI Huichao,XIONG Fahui,ZHANG Chengjie,DONG Yufei,LU Yuxiao and CHEN Xiaojian.Geochronology and tectonic setting of mafic rocks in the Dingqing ophiolite in the eastern segment of the Bangongco- Nujiang suture zone[J].Acta Geologica Sinica,2019,93(10):2617-2638. |
| |
| Authors: | BO Rongzhong YANG Jingsui LI Guanlong RUI Huichao XIONG Fahui ZHANG Chengjie DONG Yufei LU Yuxiao and CHEN Xiaojian |
| |
| Abstract: | The Dingqing ophiolite is located in the eastern segment of the Bangongco- Nujiang suture zone and is divided into the eastern and western rock mass. However, there has been no chronological report on mafic rocks in the western ophiolite of the Dingqing. The geological mapping of the western ophiolite shows that ophiolite is mainly composed of harzburgite, dunite, diabase, basalt and gabbro. Basalt, gabbro and diabase outcrop mainly in the Zongbai area, with basalt and diabase in tectonic contact with the Lower Jurassic sedimentary rocks, and the gabbro dykes dipping into the Lower Jurassic sedimentary rocks. Lithogeochemical study indicates that basalt and gabbro are both alkaline rocks, and basalts have the characteristics of rare earth and trace elements of typical oceanic island basalts, suggesting that it formed in the ocean island environment associated with mantle plumes. The dating for zircons selected from basaltic tuff yielded a U- Pb age of 198. 7±3. 8 Ma, indicating the Early Jurassic. Gabbro contains lower contents of rare earth and trace elements than typical oceanic island basalt, but its REE and trace elements have the characteristics of OIB. Compared with the typical OIB, gabbro is enriched in HREE to a certian extent. Zircon from gabbro has a U- Pb age of 164. 3±2. 6 Ma, suggesting that gabbro formed in the continental marginal rift environment and was affected jointly by and the upwelling asthenosphere and enriched melting of LVZ integration at the bottom of the lithosphere. The composition of diabase indicates that it belongs to tholeiitic basalt, and the REE and trace element diagrams of diabase show the characteristics of N- MORB and E- MORB. Zircon U- Pb age of the diabase is 114. 2±1. 3 Ma, suggesting that diabase formed later than basalt. Combined with regional geology, it is believed that diabase formed in the post- arc expansion ridge environment affected by the mantle plume. This study provides new chronological and petrological evidence for the formation and evolution of Dingqing ophiolite. |
| |
| Keywords: | Bangongco- Nujiang Suture zone Dingqing mafic rocks geochronology tectonic setting |
| 本文献已被 CNKI 万方数据 等数据库收录！ |
| 点击此处可从《地质学报》浏览原始摘要信息 |
| 点击此处可从《地质学报》下载免费的PDF全文 |
|
