气候变化领域集成服务门户(CCPortal): Ultramafic pseudotachylytes in high-pressure metamorphogenic peridotite from Luobusha, Tibet: a record of crustal paleo-earthquakes

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DOI	10.3389/feart.2023.1267211
	Ultramafic pseudotachylytes in high-pressure metamorphogenic peridotite from Luobusha, Tibet: a record of crustal paleo-earthquakes
	Zhang, Haoran; Xu, Xiwei; Yang, Saihong
发表日期	2023
EISSN	2296-6463
卷号	11
英文摘要	In this paper, we report an occurrence of ultramafic pseudotachylytes, providing fault-rock evidence of paleo-earthquakes, from the Luobusha ophiolite complex in the Yarlung Zangbo suture zone. The pseudotachylytes form hairline-thin aphanitic veinlets and vein networks bounded by micro-damage zones cutting through the host harzburgite, forming flow banding in some places. The pseudotachylyte veins are dominated by close-knit ultrafine-grained minerals consisting of olivine, orthopyroxene, serpentine, spinel, and magnetite, cemented by an extremely fine matrix. As the primary component of the pseudotachylyte veins, olivine occurs as microphenocryst showing zoning from core to rim and as irregularly shaped microlite immersed in the interstitial material. Zoned crystals of olivine developed with Mg-rich cores and more Fe-rich rims. Microlite diagnosis of crystallization in a quenched melt includes dendritic, skeletal, and poikilitic olivine crystals, which are typical of ultramafic pseudotachylyte. The olivine microlites contain higher amounts of Ca, Al, and Cr but a lower Ni content compared with the host harzburgite olivine. Irregularly shaped chrome-spinel crystals are chemically zoned as well, indicating an Fe-rich rim overgrowth. Ni sulfide droplets interspersing among the matrix imply melt occurrence. The presence of a micro-fibrous and micro-vesicular interstitial matrix also indicates a melting-related origin. Ultracataclastite veins associated with pseudotachylyte transecting serpentine are observed, which convey that heat was generated during rapid comminution and injection. The characteristic petrography, microtextures, and chemical inhomogeneities meet the criteria of ultramafic pseudotachylyte and reveal a mixed genesis via a combination of crushing and melting. The development of extremely tiny globular prograde serpentine inclusions (similar to 100 nm) in the olivine microlites is ascribed to the dehydration reaction of serpentine to olivine within the pseudotachylyte. The Luobusha metamorphogenic peridotite was subjected to serpentinization after having emplaced in the crust and subsequently to high-pressure metamorphism. The pseudotachylytes were generated in the crust after the high-pressure metamorphism and did not descend to a greater depth. Flash ultra-comminution associated with frictional heating may release fluids via localized heat-driven prograde reactions in the crust.
关键词	pseudotachylyte quench melt dehydration high-pressure metamorphism Luobusha
英文关键词	GRAIN-GROWTH KINETICS; FOSSIL EARTHQUAKES; GARNET PERIDOTITES; ZONE; INTERMEDIATE; SUBDUCTION; OPHIOLITE; DEFORMATION; LHERZOLITE; MASSIF
WOS研究方向	Geosciences, Multidisciplinary
WOS记录号	WOS:001087238900001
来源期刊	FRONTIERS IN EARTH SCIENCE
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/283458
作者单位	China Earthquake Administration; China University of Geosciences - Beijing; Chinese Academy of Sciences; National Astronomical Observatory, CAS
推荐引用方式 GB/T 7714	Zhang, Haoran,Xu, Xiwei,Yang, Saihong. Ultramafic pseudotachylytes in high-pressure metamorphogenic peridotite from Luobusha, Tibet: a record of crustal paleo-earthquakes[J],2023,11.
APA	Zhang, Haoran,Xu, Xiwei,&Yang, Saihong.(2023).Ultramafic pseudotachylytes in high-pressure metamorphogenic peridotite from Luobusha, Tibet: a record of crustal paleo-earthquakes.FRONTIERS IN EARTH SCIENCE,11.
MLA	Zhang, Haoran,et al."Ultramafic pseudotachylytes in high-pressure metamorphogenic peridotite from Luobusha, Tibet: a record of crustal paleo-earthquakes".FRONTIERS IN EARTH SCIENCE 11(2023).