Future Directions in Rock Magnetism

Abstract:

Rock magnetism explains how a rock becomes magnetized and retains its magnetization over geologic time intervals. A wealth of information has been collected on the magnetic properties of constituent minerals. Rock magnetic methods are amongst the most sensitive in detecting iron minerals in natural or synthetic materials. However, several fundamental topics are still inadequately understood. These include the theories of multi-domain magnetism and the depositional or post-depositional acquisition of magnetism in sediments. A serious problem in working with natural materials is the variability of physical properties due to differences in composition and grain size, and interactions between grains. Great advances have been made in the synthesis of iron nanoparticles, thus controlled systems offer a key to gaining new insights into the role that physical parameters play in bulk magnetization behavior. Better models can be constructed in a system when only a few physical factors play a role. Information from these types of studies provides the basis for a better understanding of natural systems. For example, they clarify how environmental conditions affect iron mineralogy and the role of diagenetic processes in the acquisition of remanence in a sediment, and they explain conditions that lead to the growth of ferromagnetic minerals in relation to remagnetization. Experimental results have advanced our understanding of the single-crystal anisotropy of minerals and how these contribute to the total anisotropy in a rock. The combination of deformation experiments and their effects on magnetic anisotropy can provide new insights into ferromagnetic textures, which may play a role in the deflection of remanence in inclination flattening. Future progress in these fields will depend on a closer alliance between experiment, theory and modeling.