Anisotropy of magnetic susceptibility in the Montes de Toledo area (Hercynian Iberian Belt, Spain) and its petrostructural significance
Published:January 01, 2004
A. Gil-Imaz, L. Barbero, 2004. "Anisotropy of magnetic susceptibility in the Montes de Toledo area (Hercynian Iberian Belt, Spain) and its petrostructural significance", Magnetic Fabric: Methods and Applications, F. Martín-Hernández, C. M. Lüneburg, C. Aubourg, M. Jackson
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Anisotropy of magnetic susceptibility data are presented for samples from the anatectic complex of Toledo and the Mora batholith. The units located at the axial part of the Central Hercynian belt are separated by an important listric fault. Anatectic granites (Layos granite), epizonal granites (Mora granite) and, to a lesser extent, high-grade metamorphic rocks and metasediments are considered in this work in order to characterize their magnetic fabric and determine their structural significance in the framework of a large-scale extensional deformation of Late Variscan age. Samples from the Layos granites (footwall) show a magnetic lineation compatible with the stretching related to ductile shear deformation of the Toledo shear zone, which was responsible for the exhumation of the anatectic complex. During the exhumation, the folding of a previous metamorphic foliation in the anatectic complex took place, which is also recognized from the magnetic pattern of the minimum susceptibility axes of Layos granite. On the contrary, the magnetic fabric of the epizonal Mora granites (hanging wall), which intruded at the beginning of the extensional Late Variscan tectonics, mainly reflects magmatic processes.
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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.