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Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/1568

Authors: Hao, J.*
Gu, Z.*
Zhou, J.*
Title: Anisotropy of magnetic susceptibility of rocks induced by experimental deformation
Issue Date: Mar-1997
Series/Report no.: 40/2
URI: http://hdl.handle.net/2122/1568
Keywords: anisotropy
rheology
ductile deformation
high-temperature
high-stress experiment
seismomagnetism
Abstract: In the present paper, the influence of the rheological process on the Anisotropy of Magnetic Susceptibility (AMS) of rocks is studied experimentally. The cylindrical samples of quartz-magnetite rock undergo a process under the confining stress of 300 MPa, temperature of 500-800 °C and strain rate of 5 ´ 10-5 - 1 ´ 10-4/s. The residual deformation after the above process ranges 9-42%, depending on the experimental condition. It is found that the magnetic susceptibilities and the shapes of magnetic grains in these samples are almost isotropic before deformation. After being deformed, these samples show certain amounts of anisotropy of magnetic susceptibility and the axes of maximum principal susceptibilities deviate from the original ones more or less. Furthermore, the grains become oblate-ellipsoidal and a certain preferred orientation occurs. The grain shape anisotropy seems to be the main reason for AMS formation. It appears that there is a limitation of the piezomagnetic theory in explaining some tectonomagnetic phenomena. The results obtained in this study imply that ductile deformation at high temperature and pressure in depth during a long time-process may result in another kind of response in rock magnetism, which could be a new mechanism of tectonomagnetic variation.
Appears in Collections:04.02.07. Instruments and techniques
04.02.04. Magnetic and electrical methods
Annals of Geophysics

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