Deformation microstructures of lower crustal granulite xenoliths from Hannuoba Cenozoic basalts, China and their geologic implications

	Deformation microstructures of lower crustal granulite xenoliths from Hannuoba Cenozoic basalts, China and their geologic implications
	Chen XiaoDe; Lin ChuanYong; Shi LanBin
刊名	ACTA PETROLOGICA SINICA
	2007-11-01
卷号	23 期号:11 页码:2775-2784
关键词	lower crust lower crustal xenoliths deformation microstructures dislocation substructures deformation mechanism
ISSN号	1000-0569
文献子类	Article
英文摘要	The lower crustal xenoliths brought up rapidly by Cenozoic basalts onto the earth surface may provide direct information about the deformation features and mechanism of the lower crust. The Hannuoba Cenozoic basalts in Hebei Province, North China, contain not only abundant mantle xenoliths, but also lower crustal xenoliths of granulite compositions. The main purpose of this study is to get an insight into the deformation process and mechanism of the lower crust through the microstructural observation of lower crustal xenoliths collected from this region. Optical microscopic observation reveals that microcracking do occur in low-temperature ( < 800 degrees C) xenolith samples, accompanied by the existence of deformation bands, kink bands, deformation twinning and the initiation of dynamically recrystallized new grains. With increasing temperature and pressure, deformation microstructures representative of intracrystalline, plasticity, such as undulatory extinction, deformation twins, intracrystalline deformation bands, kink bands, deformation lamellae and new grains become predominant, while the development of microcracks are mostly caused by plastic mismatch. However, microstructures representative of ductile shear zone in Ivrea granulite terrain are not found in these lower crustal xenoliths. Transmission Electronic Microscopic ( TEM) observation reveals that free dislocations, dislocation array, sub-grain boundary, sub-grains, new grain boundary, deformation twins, and fluid inclusion array are widely developed in plagioclase and pyroxene grains of the xenoliths. All these results indicate that the deformation process in the lower crust of the studied area is dominated by plastic deformation rather than semi-brittle regime. The predominant deformation mechanism is intracrystalline plasticity represented by dislocation glide and dislocation climb including mechanical twining and dynamic recrystallization by grain boundary migration and subgrain rotation.
WOS关键词	TEMPERATURE DEFORMATION ; RHEOLOGY ; MECHANISMS ; DIABASE ; BENEATH ; ROCKS
WOS研究方向	Geology
语种	英语
出版者	SCIENCE CHINA PRESS
WOS记录号	WOS:000254139500009
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/67828]
专题	中国科学院地质与地球物理研究所
通讯作者	Chen XiaoDe
作者单位	Acad Sinica, Inst Geol, Beijing 100029, Peoples R China
推荐引用方式 GB/T 7714	Chen XiaoDe,Lin ChuanYong,Shi LanBin. Deformation microstructures of lower crustal granulite xenoliths from Hannuoba Cenozoic basalts, China and their geologic implications[J]. ACTA PETROLOGICA SINICA,2007,23(11):2775-2784.
APA	Chen XiaoDe,Lin ChuanYong,&Shi LanBin.(2007).Deformation microstructures of lower crustal granulite xenoliths from Hannuoba Cenozoic basalts, China and their geologic implications.ACTA PETROLOGICA SINICA,23(11),2775-2784.
MLA	Chen XiaoDe,et al."Deformation microstructures of lower crustal granulite xenoliths from Hannuoba Cenozoic basalts, China and their geologic implications".ACTA PETROLOGICA SINICA 23.11(2007):2775-2784.