气候变化领域集成服务门户(CCPortal): Decorated dislocations in naturally deformed olivine with C-type fabric: A case study in the Lüliangshan garnet peridotite from the North Qaidam ultrahigh-pressure belt, NW China

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DOI	10.1016/j.tecto.2021.228971
	Decorated dislocations in naturally deformed olivine with C-type fabric: A case study in the Lüliangshan garnet peridotite from the North Qaidam ultrahigh-pressure belt, NW China
	Liu W.; Xu H.; Shi F.
发表日期	2021
ISSN	00401951
卷号	814
英文摘要	This paper presents a detailed case study of decorated dislocations of olivine with C-type fabric in the Lüliangshan garnet peridotite from the North Qaidam ultrahigh-pressure (UHP) metamorphic belt in NW China. Electron backscatter diffraction (EBSD) measurements reveal a weak C-type fabric in olivine, i.e., the crystallographic [100] axes form a weak point maximum subnormal to the foliation while the [001] axes form a girdle in the foliation plane with a weak point maximum subparallel to the lineation. Oriented hydrous mineral of sodic amphibole and pyroxene were found in porphyroclastic garnet indicating considerable water content in the parental majoritic garnet at high pressure conditions. However, the water content of olivine and garnet is below the detection limit (less than a few ppm wt. H2O) of the instrument (a Nicolet 6700 FTIR with Continuum FTIR Microscope). Two distinctive deformation features of decorated olivine grains were recognized: (1) linear morphologies of many dislocations with long straight segments parallel to the [001] orientation, which are likely screw dislocations with b = [001]; (2) olivine grains with planar dislocation, subgrain boundaries or undulose extinction are scarce in thin sections under optical microscopy. The dislocation structures and densities in olivine are heterogeneous at multi-scales. The mean 3D dislocation density and the estimated differential stress based on the dislocation density piezometer are 0.4–0.8 × 10−12 m−2 and 65–108 MPa, respectively. Decorated dislocations and EBSD analyses suggest the most likely dominant activation slip systems with b = [001]. Considering that most C-type fabric of olivine are reported from UHP garnet peridotites, we emphasize the important effects of high pressure and relatively low temperature on the formation of the C-type fabric in olivine. © 2021
关键词	C-type olivine fabric Decorated dislocation Garnet peridotite North Qaidam UHP metamorphism
英文关键词	Belts; Garnets; High pressure effects; Screw dislocations; Temperature; Deformation feature; Differential stress; Dislocation densities; Dislocation structures; Electron back scatter diffraction; High-pressure condition; Planar dislocations; Ultrahigh pressure belts; Olivine; deformation; dislocation; garnet; olivine; peridotite; ultrahigh pressure metamorphism; water content; China; Qaidam Mountains; Qinghai
语种	英语
来源期刊	Tectonophysics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/208016
作者单位	State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
推荐引用方式 GB/T 7714	Liu W.,Xu H.,Shi F.. Decorated dislocations in naturally deformed olivine with C-type fabric: A case study in the Lüliangshan garnet peridotite from the North Qaidam ultrahigh-pressure belt, NW China[J],2021,814.
APA	Liu W.,Xu H.,&Shi F..(2021).Decorated dislocations in naturally deformed olivine with C-type fabric: A case study in the Lüliangshan garnet peridotite from the North Qaidam ultrahigh-pressure belt, NW China.Tectonophysics,814.
MLA	Liu W.,et al."Decorated dislocations in naturally deformed olivine with C-type fabric: A case study in the Lüliangshan garnet peridotite from the North Qaidam ultrahigh-pressure belt, NW China".Tectonophysics 814(2021).