Plastic Deformation and Seismic Properties in Fore-arc Mantles: A   Petrofabric Analysis of the Yushigou Harzburgites, North Qilian Suture   Zone, NW China

doi:10.1093/petrology/egv053

CORC > 北京大学 > 地球与空间科学学院

	Plastic Deformation and Seismic Properties in Fore-arc Mantles: A Petrofabric Analysis of the Yushigou Harzburgites, North Qilian Suture Zone, NW China
	Cao, Yi ; Jung, Haemyeong ; Song, Shuguang ; Park, Munjae ; Jung, Sejin ; Lee, Jaeseok
刊名	JOURNAL OF PETROLOGY
	2015
关键词	olivine plastic deformation mineral fabric water content fore-arc mantle seismic properties LATTICE-PREFERRED ORIENTATION LITHOSPHERE-ASTHENOSPHERE BOUNDARY SUBDUCTION-RELATED ANTIGORITE RECRYSTALLIZED GRAIN-SIZE DISLOCATION CREEP REGIME ALUMINOUS ORTHO-PYROXENE OLIVINE SINGLE-CRYSTALS HIGH-TEMPERATURE CREEP SHEAR-WAVE ANISOTROPY MAGMA ASCENT RATES
DOI	10.1093/petrology/egv053
英文摘要	The fore-arc mantle above a subducting slab is a unique site where complex partial melting, melt/fluid-rock interaction, and deformation of mantle rocks occur. To constrain these geological and geodynamic processes we analyzed the deformation microstructures, crystal preferred orientations (CPOs or fabrics), and water content in natural harzburgites that occur as exhumed massifs in the North Qilian suture zone, NW China. These harzburgites are very fresh, and have mineral assemblages of olivine (similar to 81-87 vol. %), orthopyroxene (similar to 11-17 vol. %), clinopyroxene (similar to 1-2 vol. %), and spinel (similar to 1 vol. %). Detailed analyses of mineral textures, CPO patterns, and rotation axis distributions suggest that the plastic deformation of olivine and pyroxene was accommodated by activating a series of slip systems of dislocation. The olivine (A-/D-type fabric) shows dominant (010)[100] and/or (001)[100] slip systems, as well as other minor [100]-glide, {0kl}[100], and [001]glide slip systems. The orthopyroxene shows dominant (100)[001] and subordinate (010)[001] slip systems, with minor (100)[010] and (100)[0vw] slip systems. The water content is extremely low in the orthopyroxene (38-44ppm by weight), equilibrated olivine (4-7 ppm), and bulk-rock samples (9-14 ppm). Previously published refractory mineral and whole-rock compositions, as well as estimated low-pressure(similar to 1-2 GPa), high-temperature (similar to 1100-1300 degrees C), low-stress (similar to 1-4 MPa) and water-poor conditions of deformation, suggest that these harzburgites represent a remnant of fossil fore-arc lithospheric mantle that was probably both formed (experienced partial melting and high-temperature melt/fluid-rock reaction) and deformed in a young and warm fore-arc mantle setting (i.e. juvenile subduction zone). Based on these results, a refined schematic model of olivine fabric distributions in subduction zones is proposed. In this model, the A-/D-type olivine fabrics are inferred to be prevalent in fore-arc lithospheric mantle. The opposing polarizing directions of A-/D-type olivine fabrics with other underlying anisotropic sources in the mantle wedge (e.g. B-type olivine fabrics and oriented serpentinite layers) may weaken the trench-parallel fast S-wave anisotropy contributed by the deformed fore-arc mantle, and thus provide an alternative explanation for the short or nearly null delay times of local shear-wave splitting (sourced from intra-slab earthquakes) that have been detected in some fore-arc regions. In addition, topotactic antigorite fabrics after the A-/D-type olivine fabric might play a minor role in contributing to the low P-and S-wave velocities, high V-p/V-s ratios, and large seismic anisotropies that are typically observed in fore-arc mantle.; Mid-career Researcher Program through an NRF - MEST [NRF-2010-0015027, 2015R1A2A1A15052305]; National Natural Science Foundation of China [40825007, 41121062]; SCI(E); ARTICLE; hjung@snu.ac.kr; 10; 1897-1943; 56
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/439393]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	Cao, Yi,Jung, Haemyeong,Song, Shuguang,et al. Plastic Deformation and Seismic Properties in Fore-arc Mantles: A Petrofabric Analysis of the Yushigou Harzburgites, North Qilian Suture Zone, NW China[J]. JOURNAL OF PETROLOGY,2015.
APA	Cao, Yi,Jung, Haemyeong,Song, Shuguang,Park, Munjae,Jung, Sejin,&Lee, Jaeseok.(2015).Plastic Deformation and Seismic Properties in Fore-arc Mantles: A Petrofabric Analysis of the Yushigou Harzburgites, North Qilian Suture Zone, NW China.JOURNAL OF PETROLOGY.
MLA	Cao, Yi,et al."Plastic Deformation and Seismic Properties in Fore-arc Mantles: A Petrofabric Analysis of the Yushigou Harzburgites, North Qilian Suture Zone, NW China".JOURNAL OF PETROLOGY (2015).