气候变化领域集成服务门户(CCPortal): Pre-Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand

CCPortal

DOI	10.1029/2020JB020196
	Pre-Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand
	Shao Y.; Prior D.J.; Scott J.M.; Negrini M.
发表日期	2021
ISSN	21699313
卷号	126 期号:1
英文摘要	We present a quantitative microstructural and seismic property analysis of harzburgitic and lherzolitic xenoliths from East Otago, New Zealand. Olivine crystallographic preferred orientations (CPOs) are dominated by orthorhombic CPOs with a tight maxima of [100] orthogonal to (010). Orthopyroxene showed the [001] axes aligned (sub)parallel to the [100] axes of olivine and the (100) plane subparallel to the (010) plane of olivine. Misorientations of olivine subgrain boundaries indicate that dislocations with [100] slip vectors are common and CPOs are interpreted as olivine [100] representing the flow direction and (010) the shear plane. Olivine grains are coarse with lobate grain boundaries, indicative of grain boundary migration at high temperatures. Olivine contains numerous subgrains whilst orthopyroxene is mostly strain-free and it is possible that orthopyroxene crystallized from melt during deformation. Clinopyroxene lamellae in orthopyroxene, relate to decompressional cooling prior to Alpine Fault movement. Seismic properties derived from the measured CPOs, indicate P-wave and S-wave anisotropies at mantle conditions of 4%–10% and 3%–9%, respectively. Calculated shear wave splitting delay times of 0.1–0.9 s, for the current lithospheric mantle thickness, fit seismological observations, suggesting that the xenoliths may be representative of the lithospheric mantle that lies below East Otago today. To explain the seismic data, olivine [100] needs to be subhorizontal and parallel to NNW-SSE fast polarization directions with [010] subhorizontal and perpendicular to these directions. This is consistent with the East Otago lithospheric mantle containing a fossil vertical shear zone with NNW-SSE strike slip motion. © 2020. American Geophysical Union. All Rights Reserved.
英文关键词	CPO; East Otago; mantle xenolith; seismic anisotropy
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187411
作者单位	Department of Geology, University of Otago, Dunedin, New Zealand
推荐引用方式 GB/T 7714	Shao Y.,Prior D.J.,Scott J.M.,et al. Pre-Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand[J],2021,126(1).
APA	Shao Y.,Prior D.J.,Scott J.M.,&Negrini M..(2021).Pre-Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand.Journal of Geophysical Research: Solid Earth,126(1).
MLA	Shao Y.,et al."Pre-Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand".Journal of Geophysical Research: Solid Earth 126.1(2021).