气候变化领域集成服务门户(CCPortal): Deformation of mafic schists from subducted oceanic crust at high pressure and temperature conditions

CCPortal

DOI	10.1016/j.tecto.2019.228217
	Deformation of mafic schists from subducted oceanic crust at high pressure and temperature conditions
	Okazaki K.; Hirth G.
发表日期	2020
ISSN	00401951
卷号	774
英文摘要	We conducted triaxial deformation experiments using a Griggs-type solid pressure-medium apparatus on two mafic schists that experienced different peak metamorphic conditions from the Sambagawa metamorphic belt; a greenschist and an epidote-amphibole schist. At a confining pressure of 1 GPa, 400 °C and strain rate of 10–5 1/s, differential stresses for all mafic schists were higher than 1 GPa. The greenschist samples were weaker than epidote-amphibolite samples under all experimental conditions. Microstructures of recovered samples of greenschist indicate that deformation of mafic schist is accommodated by semi-brittle deformation. Samples of the epidote-amphibole schist deformed at 500 °C show shear localization along a single fault oriented parallel to the foliation, while mechanical data shows no rapid stress drop. On the surface of the fault, we observe the formation of slickensides with little gouge. All sample types exhibit a high stress exponent (n > 15) and strain rate strengthening (i.e., positive a–b values); frictional behavior that inhibits earthquake nucleation. Differential stress increased with increasing confining pressure, while the friction coefficient decreased with increasing confining pressure and temperature. Greenschist and epidote-amphibolite facies metamorphism typically occurs at hot subduction zones such as Cascadia and southwest Japan. The lack of seismicity within the subducting oceanic crust at hot subduction zones could be explained by semi-brittle deformation, or frictional sliding with a positive (a – b) during deformation of these types of metamorphic rocks. Weak and aseismic fault zones in subducting slabs might promote slab-mantle decoupling at the corner of the mantle wedge, and detachment and underplating of oceanic crust from the subducting slab to forearc crust. © 2019 Elsevier B.V.
关键词	Greenschist Mafic schist Metamorphic rock Rheology Semi-brittle deformation Subduction zone
英文关键词	Deformation; Friction; Rheology; Rock pressure; Silicate minerals; Strain rate; Structural geology; Brittle deformation; Experimental conditions; Friction coefficients; Greenschist; High-pressure and temperatures; Mafic schist; Metamorphic conditions; Subduction zones; Metamorphic rocks; brittle deformation; greenschist; high pressure; mafic rock; oceanic crust; rheology; subduction zone; temperature profile
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/207839
作者单位	Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 200 Monobe-otsu, Nankoku, Kochi 783-8502, Japan; Department of Earth, Environmental and Planetary Sciences, Brown University, 324 Brook Street Box 1846, Providence, RI 02912, United States
推荐引用方式 GB/T 7714	Okazaki K.,Hirth G.. Deformation of mafic schists from subducted oceanic crust at high pressure and temperature conditions[J],2020,774.
APA	Okazaki K.,&Hirth G..(2020).Deformation of mafic schists from subducted oceanic crust at high pressure and temperature conditions.Tectonophysics,774.
MLA	Okazaki K.,et al."Deformation of mafic schists from subducted oceanic crust at high pressure and temperature conditions".Tectonophysics 774(2020).