气候变化领域集成服务门户(CCPortal): Intrinsic Elastic Anisotropy of Westerly Granite Observed by Ultrasound Measurements, Microstructural Investigations, and Neutron Diffraction

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DOI	10.1029/2020JB020878
	Intrinsic Elastic Anisotropy of Westerly Granite Observed by Ultrasound Measurements, Microstructural Investigations, and Neutron Diffraction
	Lokajíček T.; Vasin R.; Svitek T.; Petružálek M.; Kotrlý M.; Turková I.; Onysko R.; Wenk H.R.
发表日期	2021
ISSN	21699313
卷号	126 期号:1
英文摘要	Westerly granite (WG) has been generally accepted as an isotropic homogeneous rock. Here, we return to WG and observe significant elastic anisotropy using multidirectional ultrasonic sounding on spherical samples at pressures up to 400 MPa. Thermal treatment of WG leads to formation of microcracks that reduce elastic wave velocities and increase its elastic anisotropy. The 3D distribution of P-wave velocities at low pressure is close to orthorhombic symmetry. Application of hydrostatic pressure closes most of thermally induced microcracks and decreases elastic anisotropy of WG, but at high pressure the anisotropy is practically reversed compared to low pressure: maximum P-wave velocity direction at low pressures is near minimum velocity direction at high pressure and vice versa. To understand this effect, microstructures of the rock were investigated by optical and scanning electron microscopy. Preferred orientations of four major rock-forming minerals—quartz, orthoclase, plagioclase, and biotite—were measured by time-of-flight neutron diffraction, which confirms significant crystal alignment. All these data were used to numerically model anisotropic elastic properties of WG. It is shown that WG possesses weak intrinsic elastic anisotropy related mainly to the preferred orientation of feldspars formed during igneous crystallization. Observed microcracks are mostly related to the cleavage planes of feldspars and biotite, and thus also demonstrate preferred orientation. Higher preheating temperatures produce larger quantity of longer microcracks. A numerical model shows that these microcracks act against the weak intrinsic elastic anisotropy of WG, and define the elastic anisotropy at low pressures. © 2020. American Geophysical Union. All Rights Reserved.
英文关键词	Elastic anisotropy; Microstructural analysis; Neutron diffraction; Ultrasonic sounding; Westerly granite
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/187398
作者单位	Department of Physical Properties of Rocks, Institute of Geology of the Czech Academy of Sciences, Prague, Czech Republic; Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Russian Federation; Institute of Criminalistics Praha, Prague, Czech Republic; SG Geotechnika, a.s., Praha, Prague, Czech Republic; Department of Earth and Planetary Science, University of California, Berkeley, CA, United States
推荐引用方式 GB/T 7714	Lokajíček T.,Vasin R.,Svitek T.,et al. Intrinsic Elastic Anisotropy of Westerly Granite Observed by Ultrasound Measurements, Microstructural Investigations, and Neutron Diffraction[J],2021,126(1).
APA	Lokajíček T..,Vasin R..,Svitek T..,Petružálek M..,Kotrlý M..,...&Wenk H.R..(2021).Intrinsic Elastic Anisotropy of Westerly Granite Observed by Ultrasound Measurements, Microstructural Investigations, and Neutron Diffraction.Journal of Geophysical Research: Solid Earth,126(1).
MLA	Lokajíček T.,et al."Intrinsic Elastic Anisotropy of Westerly Granite Observed by Ultrasound Measurements, Microstructural Investigations, and Neutron Diffraction".Journal of Geophysical Research: Solid Earth 126.1(2021).