| 雅鲁藏布江缝合带西段北亚带的基性岩成因和构造意义 |
| |
| 关键词:Yarlung Zangbo Suture zone ophiolite zircon dating geochemistry Tibet |
| 基金项目:中国地质调查局地质调查项目(编号: 12120115026801、12120115027201、201511022); 国际科技合作专项(编号: 2014DFR21270); 国家重点实验室自主课题(编号: Z1301-a20) |
|
| 摘要点击次数: 5175 |
| 全文下载次数: 2656 |
| 摘要: |
| The Genesis and Tectonic Significance of Mafic Dikes in the Western Part of the Yarlung Zangbo Suture Zone, Tibet |
| The relationship and genesis of the Daba–Xiugugabu (Southern belt) and Dajiweng–Saga (Northern belt) ophiolitic subbelts divided from Saga in the western part of the Yarlung Zangbo suture zone remain unclear. This paper imposes some restrictions on the genesis of the southern and northern subbelts based on geochronology and geochemistry of the Jianabeng and Cuobuzha mafic dikes in the northern belt and a comparative study of rock associations of two belts. The Jianabeng gabbro and Cuobuzha dolerite intruded into harzburgite in the forms of NW-striking lenses and dikes 1 to 3 m in width. LA-ICPMS and SIMS in-situ analysis of zircon grains yielded (125.8±2.6) Ma and (127.0±0.5) Ma respectively. The mafic samples are characterized by high Si, Al, Na, Mg and low Ti, K, P values and plotted into the area of cala-alkali basalt series. Compared with mafic rocks from the Purang, Dongbo and Xiugugabu ophiolites in the Southern belt, the mafic dikes in the two subbelts share similar occurrences and zircon ages (120~130 Ma), showing N-MORB type chondrite-normalized REE patterns and noticeable Nb, Ta and Ti negative anomalies in N-MORB normalized spider diagrams. The above evidence indicates that the mafic rocks from two subbelts had a supra?subduction affinity and were formed in a fore-arc or back basin environment. Combined with fore-arc geochemical characteristics of their wall rock peridotite, the authors preliminarily hold that the two ophiolitic subbelts probably represent the Neo-Tethys ocean fragments in the same tectonic setting. |
| LIU Fei,YANG Jing-sui,LIAN Dong-yang,ZHAO Hui,ZHAO Yi-jue,ZHANG Lan.2015.The Genesis and Tectonic Significance of Mafic Dikes in the Western Part of the Yarlung Zangbo Suture Zone, Tibet[J].Acta Geoscientica Sinica,36(4):441-454. |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|