The Petrology, Geochemistry, and Petrogenesis of E-MORB-type Mafic Rocks from the Guomangco Ophiolitic Mélange, Tibet |
| |
作者姓名: | XU Mengjing LI Cai WU Yanwang and XIE Chaoming |
| |
作者单位: | College of Earth Science, Jilin University, Changchun 130061, China |
| |
基金项目: | This study was funded by the National Funds of Nature Science of China (Grant No. 41272240) and the Project of China Geological Survey (Grant No. 1212011121248). |
| |
摘 要: | The Guomangco ophiolitic melange is situated in the middle part of the Shiquanhe- Yongzhu-Jiali ophiolitic melange belt (SYJMB) and possesses all the subunits of a typical Penrose- type ophiolite pseudostratigraphy. The study of the Guomangco ophiolitic melange is very important for investigating the tectonic evolution of the SYJMB. The mafic rocks of this ophiolitic melange mainly include diabases, sillite dikes, and basalts. Geochemical analysis shows that these dikes mostly have E-MORB major and trace element signatures; this is the first time that this has been observed in the SYJMB. The basalts have N-MORB and IAB affinities, and the mineral chemistry of harzburgites shows a composition similar to that of SSZ peridotites, indicating that the Guomangco ophiolitic melange probably originated in a back-arc basin. The Guomangco back-arc basin opened in the Middle Jurassic, which was caused by southward subduction of the Neo-Tethys Ocean in central Tibet. The main spreading of this back-arc basin occurred during the Late Jurassic, and the basalts were formed during this time. With the development of the back-arc basin, the subducted slab gradually retreated, and new mantle convection occurred in the mantle wedge. The recycling may have caused the metasomatized mantle to undergo a high degree of partial melting and to generate E- MORBs in the Early Cretaceous. E-MORB-type dikes probably crystallized from melts produced by about 20%-30% partial melting of a spinel mantle source, which was metasomatized by melts from low-degree partial melting of the subducted slab.
|
关 键 词: | 蛇绿混杂岩带 地球化学分析 西藏中部 岩石成因 B型 岩石学 基性岩 部分熔融程度 |
收稿时间: | 2014-02-21 |
修稿时间: | 2014-08-19 |
本文献已被 CNKI 维普 万方数据 等数据库收录! |
| 点击此处可从《《地质学报》英文版》浏览原始摘要信息 |
|
点击此处可从《《地质学报》英文版》下载全文 |
|