Anisotropy of magnetic susceptibility of rocks measured in variable weak magnetic fields using the KLY-4S Kappabridge
Jiří Pokorný, Petr Suza, František Hrouda, 2004. "Anisotropy of magnetic susceptibility of rocks measured in variable weak magnetic fields using the KLY-4S Kappabridge", Magnetic Fabric: Methods and Applications, F. Martín-Hernández, C. M. Lüneburg, C. Aubourg, M. Jackson
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The theory of the anisotropy of magnetic susceptibility assumes a linear relationship between magnetization and magnetizing field, resulting in field-independent susceptibility. This relationship is valid in diamagnetic and paramagnetic minerals by definition, and also in magnetite in the fields used in common AMS meters. Pyrrhotite, hematite and titanomagnetite may show field variation of susceptibility in the same fields and therefore in principle the linear theory is incorrect for calculating the AMS. Fortunately, the linear theory nevertheless provides accurate determination of the orientations of the principal susceptibilities and of the AMS ellipsoid shape. It gives rise to inaccurate determination of the degree of AMS. Simple techniques are suggested to overcome this problem.
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Magnetic Fabric: Methods and Applications
Fabric is a ubiquitous and significant feature of geological materials. The processes involved in the formation and deformation of rocks and sediments leave their mark on the orientations of the constituent mineral grains. Petrofabrics thus provide essential keys to understanding the history of geological materials. Magnetic anisotropy is directly related to petrofabric, and has become one of the most rapid, sensitive and widely used tools for its characterization. The relationship between magnetic fabric and petrofabric is complex and depends on various factors including the composition, concentration and grain size of mineral grains. Ongoing research in geological applications is paralleled by studies of the fundamental mineral magnetic phenomena involved.
The papers in this book represent the current state of investigations in magnetic anisotropy studies as a discipline that integrates geological interpretations, mineral fabric development, technical advances and rock-magnetic properties.