DOI: 10.1016/j.tecto.2021.228971
论文题名: 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
作者: Liu W. ; Xu H. ; Shi F.
刊名: Tectonophysics
ISSN: 00401951
出版年: 2021
卷: 814 语种: 英语
中文关键词: 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
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 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/170849
Appears in Collections: 气候变化与战略
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作者单位: State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan, 430074, China
Recommended Citation:
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]. Tectonophysics,2021-01-01,814