Abstract
Empirical relationships between magnetic fabrics and deformation have long served as a fast and efficient way to interpret rock textures. Understanding the single crystal magnetic properties of all minerals that contribute to the magnetic anisotropy of a rock, allows for more reliable and quantitative texture interpretation. Integrating information of single crystal properties with a determination whether or not mineral and magnetic fabrics are parallel may yield additional information about the texture type. Models based on textures and single crystal anisotropies help assess how the individual minerals in a rock contribute to the rock’s anisotropy, and how the individual anisotropy contributions interfere with each other. For this, accurate and reliable single crystal data need to be available. This review paper discusses magnetic anisotropy in single crystals of the most common rock-forming minerals, silicates and carbonates, in relation to their mineralogy and chemical composition. The most important ferromagnetic minerals and their anisotropy are also discussed. This compilation and summary will hopefully lead to a deeper understanding of the sources of magnetic anisotropy in rocks, and improve the interpretation of magnetic fabrics in future structural and tectonic studies.
Highlights
The preferred alignment of minerals in a rock can provide important information in geodynamic, structural and tectonic studies, e.g., to investigate transport or deformation processes
A fast and efficient way of characterizing this alignment is based on magnetic fabrics, e.g., anisotropy of magnetic susceptibility (AMS) or anisotropy of magnetic remanence (AMR), which are commonly used as proxies for rock textures [1,2,3,4,5,6,7]
For example, k1 can be deviated from the macroscopic lineation by up to 90◦, even though both magnetic and mineral fabrics are defined by hornblende [17,18,19]
Summary
The preferred alignment of minerals in a rock can provide important information in geodynamic, structural and tectonic studies, e.g., to investigate transport or deformation processes. High-field methods are preferred again in the most recent single crystal studies [61,62,63,64] Because of their abundance, and their importance in defining fabrics, the magnetic anisotropy of phyllosilicates has been studied extensively. Even single crystals may contain iron oxides, which have a preferred orientation because they exsolved parallel to distinct crystallographic directions or planes [79,80,81] These exsolutions can contribute to, or completely dominate the crystal’s low-field anisotropy [62,63,73]. This review paper discusses single crystal magnetic anisotropy for rock-forming minerals in the silicate and carbonate group, and summarizes data on accessory minerals that are important in magnetic studies, i.e., iron oxides and sulfides
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