Plastic flow of coesite eclogite in a deep continent subduction regime: Microstructures, deformation mechanisms and rheologic implications

doi:10.1016/j.epsl.2005.06.021

	Plastic flow of coesite eclogite in a deep continent subduction regime: Microstructures, deformation mechanisms and rheologic implications
	Zhao, ZY ; Wei, CJ ; Fang, AM
刊名	EARTH AND PLANETARY SCIENCE LETTERS
	2005-08-30
卷号	237 期号:1-2 页码:209-222
关键词	Uhp Deformation Deformation Microstructures Deformation Mechanisms Coesite Eclogite Rheology
ISSN号	0012-821X
DOI	10.1016/j.epsl.2005.06.021
文献子类	Article
英文摘要	Ultrahigh pressure (UHP) metamorphic rocks are continental crust that once has been subducted to mantle depth and subsequently exhumed to the surface in collisional orogenic belts. Despite the long distance transport of the UHP rocks in a deep subduction channel and the fast strain rate required for rapid exhumation, little evidence for UHP deformation is found in the exhumed UEP terrains so far identified. Some UHP rocks have even preserved primary igneous and volcanic structures. These observations have led to the postulation that the stress level is low (a few MPa) in the deep subduction zones. Deformation microstructures of some eclogite mylonites from a ductile shear complex in the Sulu UHP metamorphic belt, eastern China, provide for the first time convincing evidence that dislocation creep is the predominant deformation mechanism for the major constituent minerals of the UHP rocks in a highly strain-localized shear zone at the UHP conditions. Omphacite, phengite and kyanite are the main strain-accommodating phases and are dynamically recrystallized through progressive subgrain rotation and grain boundary migration. Coesite is either fractured, with irregular extinction in the moderately deformed eclogite or pseudomorphed by polycrystalline quartz aggregates that have a foam structure. Garnet does not show optically discernable plastic deformation. P-T conditions for the deformation are estimated to be P approximate to 3.3 GPa and T approximate to 624 degrees C using garnet-omphacite-kyanite-phengite-coesite/quartz thermobarometry, suggesting that deeply subducted continental crust remains "cold'' at the upper mantle depths. Large part of the deeply subducted crust remains relatively undeformed. Strain is strongly localized into narrow shear zones. Stress level in the deep subduction channel is extrapolated on the order of tens of MPa, much higher than it was previously thought. (c) 2005 Elsevier B.V. All rights reserved.
WOS关键词	ULTRA-HIGH-PRESSURE ; DORA-MAIRA MASSIF ; EASTERN CHINA ; BEARING ECLOGITES ; METAMORPHIC ROCKS ; JIANGSU PROVINCE ; WESTERN ALPS ; DABIE-SHAN ; EXHUMATION ; UHP
WOS研究方向	Geochemistry & Geophysics
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000232047400015
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/65015]
专题	中国科学院地质与地球物理研究所
通讯作者	Zhao, ZY
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China 2.Peking Univ, Sch Earth & Space Sci, Beijing 100871, Peoples R China
推荐引用方式 GB/T 7714	Zhao, ZY,Wei, CJ,Fang, AM. Plastic flow of coesite eclogite in a deep continent subduction regime: Microstructures, deformation mechanisms and rheologic implications[J]. EARTH AND PLANETARY SCIENCE LETTERS,2005,237(1-2):209-222.
APA	Zhao, ZY,Wei, CJ,&Fang, AM.(2005).Plastic flow of coesite eclogite in a deep continent subduction regime: Microstructures, deformation mechanisms and rheologic implications.EARTH AND PLANETARY SCIENCE LETTERS,237(1-2),209-222.
MLA	Zhao, ZY,et al."Plastic flow of coesite eclogite in a deep continent subduction regime: Microstructures, deformation mechanisms and rheologic implications".EARTH AND PLANETARY SCIENCE LETTERS 237.1-2(2005):209-222.