用旋转式磁化率仪和卡帕桥对岩样磁组构的比测
COMPARATIVE MEASUREMENTS OF MAGNETIC FABRIC BETWEEN KAPPA BRIDGES AND MINISEPS
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摘要: 磁化率各向异性(AMS)是岩石的普遍特性,它反映岩石磁性矿物的择优取向,即磁组构(Magnetic fabric).近三十年来,磁组构技术逐渐应用于地质和地球物理学,显示广阔的研究前景.测量磁组构的仪器有多种,原理不一,故有必要用同一样品在不同原理的仪器上进行比测,以便确认数据的一致性和可靠性.用黄土、变质岩、玄武岩及掺有铁粉的断层泥制成正方体或圆柱体样品,在卡帕桥(KLY-1和KLY-2)和旋转式磁化率仪(Minisep)上进行比测发现:(1)前者的精度(即重复性)在多数情况下优于后者;2)用旋转式磁化率仪测量之前,必须先测得样品z轴的体磁化率,其标定值取决于厂家在标准样品上标示的数值及被测样品与标准样品的相对体积.就旋转样品测量AMS而言,其标定值应为z轴体磁化率测量标定值的一半.Abstract: The Anisotropy of Magnetic Susceptibility (AMS) is a ubiquitous feature of rocks which reflects a tendency about the alignment of magnetic grains of minerals in it,i.e. magnetic fabric. In the last 30 years,the technique of magnetic fabric has been widely and efficiently applied to geology and geophysics,showing its prospects. Different principles are used for the development of instruments for AMS measurement. The consistency and reliability of the results obtained by different instruments should be checked and confirmed for a specimen through comparative measurements. The test was carried out by Kappa bridges (KLY-1,2) and Mi-niseps (Molspin Ltd.,U. K.) using cubic or cylindric specimens which are of different materials,i.e. loess,metamorphic rock,basalt or a compressed mixture of fault clay and SD magnetite. Consequently,(1) it is found that the repeatability of measurement by a Kappa bridge is often slightly better than that by a Minisep. (2) The calibration value for measuring the Kz depends on the susceptibility printed on the standard sample and the volumetric ratio of the standard specimen and to the specimen measured. And the calibration value for the spin measurement should be half the above-said calibration value for Kz measurement.
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[1] Maher, B. A., 1996. Characterisation of soils by minera 1 magnetic measurements. Phys. Earth Piattct. Ints., 42. 76——92.
[2] Walton, D., 1983. Viscous magnetisarion. Nature, 305, 61G——619.
[3] Ising, E., 1942. On the magnetic properties of mrved clay. f'rkiu Tstror, Fysik, 29A(5), 1——37.
[4] 许同春、刘秀铭、曹继秀,1987.岩石磁性组构的研究前景.国际地震动态,3: 1——6.
[5] Hrouda, F., 1982. Wghetic anisotropy of rocks and its application in geology and geophysvcs. Geophys.Sura., S, 37——82.
[6] 贺绍英、孙世伟,1985.用无定向磁力仪测量磁化率张量与剩余磁化强度矢量.物探与化探,9,281——288.
[7] Hrouda, F,Stephenson, A., Woltar, L., 1983. On the standardization of measurements of the anisotropy of magnetic susceptibility. Phys. Earth Planet Ints., 32, 203——208.
[8] Collinson, D. W., 1983. Methods in Rock Magnetism and Palacomagnetism——Techniques and Instrumen——tation Chapman & Hall, London. 503.
[9] Scriba, H., Heller, F., 1978. Measurements of anisotropy of magnetic susceptibility using inductive magne——tometers. J. Geuphysics, 44, 341——352.
[10] Fisher, R. A., 1953. Dispersion on a sphere, Proc. Roy. Soc., London, A217, 295——305.[1] Maher, B. A., 1996. Characterisation of soils by minera 1 magnetic measurements. Phys. Earth Piattct. Ints., 42. 76——92.
[2] Walton, D., 1983. Viscous magnetisarion. Nature, 305, 61G——619.
[3] Ising, E., 1942. On the magnetic properties of mrved clay. f'rkiu Tstror, Fysik, 29A(5), 1——37.
[4] 许同春、刘秀铭、曹继秀,1987.岩石磁性组构的研究前景.国际地震动态,3: 1——6.
[5] Hrouda, F., 1982. Wghetic anisotropy of rocks and its application in geology and geophysvcs. Geophys.Sura., S, 37——82.
[6] 贺绍英、孙世伟,1985.用无定向磁力仪测量磁化率张量与剩余磁化强度矢量.物探与化探,9,281——288.
[7] Hrouda, F,Stephenson, A., Woltar, L., 1983. On the standardization of measurements of the anisotropy of magnetic susceptibility. Phys. Earth Planet Ints., 32, 203——208.
[8] Collinson, D. W., 1983. Methods in Rock Magnetism and Palacomagnetism——Techniques and Instrumen——tation Chapman & Hall, London. 503.
[9] Scriba, H., Heller, F., 1978. Measurements of anisotropy of magnetic susceptibility using inductive magne——tometers. J. Geuphysics, 44, 341——352.
[10] Fisher, R. A., 1953. Dispersion on a sphere, Proc. Roy. Soc., London, A217, 295——305.
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