Dongbo MORB-Type Isotropic Gabbro Emplaced as an Oceanic Core Complex in Western Yarlung Zangbo Suture Zone, Tibet

被引：9
|
作者：
Liu F. [1 ]
Lian D. [1 ,2 ]
Niu X. [1 ]
Zhao H. [1 ,3 ]
Feng G. [1 ]
Yang J. [1 ]
机构：
[1] Key Laboratory of Deep-Earth Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing
[2] School of Earth Sciences and Engineering, Nanjing University, Nanjing
[3] School of Earth Sciences and Resources, China University of Geosciences, Beijing
来源：
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | 2018年 / 43卷 / 04期
关键词：
Dongbo ophiolite; Geochemistry; Oceanic core complex; Tibet; Yarlung Zangbo suture zone; Zircon U-Pb age;
D O I：
10.3799/dqkx.2018.702
中图分类号：
学科分类号：
摘要：
The tectonic setting and genesis of the ophiolites in the southern belt (SB) of the western Yarlung Zangbo ophiolitic belt are still controversial. They occur much larger peridotite massifs in contrast with those in the northern belt that are made discontinuously of lensoidal ophiolitic bodies in serpentinite matrix mélanges. The Dongbo ophiolite in the SB has been investigated and mapped, especially a 1 002.06 m dominant peridotite core has been drilled in the northwestern margin in 2015. Geochemical and geochronological (U-Pb zircon age) data from isotropic gabbros are presented in this paper. Dongbo ophiolite consists dominantly of harzburgite, minor dunite and mafic intrusions, associated with thin oceanic crust. Dismembered Late Juarassic to Early Cretaceous volcanic-sedimentary sequences of seamounts overlie the peridotites in the margins. Detachment and ductile shear faults, mylonite and mylonitic serpentinite and ophiolitic breccia are found in the mantle peridotites. In-situ LA-ICP-MS analysis of zircon grains from isotropic gabbros yields 129.0±1.8 Ma.The geochemical data of these gabbros are characterized by low Si, K, P, Fe, Ti and high Ca, Mg, showing N-MORB-like chondrite-normalized REE patterns and remarkable Th, Nb, Sr and Pb negative anomalies in N-MORB normalized spider diagrams. It is proposed that part of Dongbo peridotite and isotropic gabbro formed in a slow-spreading mid-ocean ridge which exhumed along detachment faults as an oceanic core complex. © 2018, Editorial Department of Earth Science. All right reserved.
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页码：952 / 974
页数：22
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