Projects

Magnetic pore fabrics: Predicting pore geometry, permeability anisotropy and preferred flow directions based on magnetic anisotropy data

Understanding the migration of fluids through the subsurface is essential for maintaining clean sources of water, using geothermal energy, and modeling the flow of petroleum and emplacement of ore deposits. These fluids move from pore to pore at micrometer scales. When pores are elongated and preferentially aligned, flow will be easier and faster in some directions than in others, giving rise to preferred flow directions. The aim of this project is to develop the use of magnetic methods to rapidly characterize pore fabrics. These new methods also have the potential for higher resolution than traditional methods, and can be applied to studies in geology, environmental, and material sciences.

Swiss National Science Foundation project 176917 >>

University of Bern press release >>

Strain localization in fault zones

Magnetic anisotropy, and in particular the contributions to magnetic anisotropy of paramagnetic (silicates, carbonates) vs ferromagnetic (iron oxides) minerals, allow investigating details of the strain field, its spatial variation and in particular strain localization around fault and thrust zones.

Collaborators: Claudio Robustelli Test (University of Torino)

Material characterization

Magnetic properties, including susceptibility, saturation magnetization, remanence and coercivity help characterize materials, e.g., thin films and nanoparticles.

Collaborators: Joelle Medinger (University of Fribourg), Erik Poloni (ETH Zürich), Nicholas Hendricks (CSEM)

Rock and paleomagnetic constraints on mapping and timing of vein formation in the Oman ophiolite

Magnetic properties and their correlation to rock chemistry help mapping units that are not exposed at the surface, and also help trace hydrothermal alteration. Additionally, magnetic remanence recorded in and around veins provides information on the timing of vein formation.

Collaborators: Larryn W. Diamond (University of Bern), Raphael Kuhn (University of Bern), Thomas Belgrano (former University of Bern, now University of Southampton)

Investigating correlations between magnetic anisotropy, seismic anisotropy and rock texture

Both magnetic and seismic anisotropies are often used as proxies for the alignment of minerals in rocks. This alignment provides valuable information about dynamic processes on our planet, e.g. flow patterns and emplacement paths. Anisotropy of physical properties is often preferred to direct texture determination, because it can be measured more efficiently. For reliable anisotropy-based tectonic and geodynamic interpretations, a thorough and detailed understanding of the directional and magnitude relationships between physical anisotropies and texture is crucial. We are investigating these relationships both experimentally and numerically, for example in amphibolites and peridotites.

Collaborators: Karsten Kunze (ETH Zurich), Alba Zappone (ETH Zurich), Ann Hirt (ETH Zurich)

Environmental magnetism to study air pollution

Some pollutants are strongly magnetic, and therefore, magnetic methods can be used as powerful and efficient proxies for pollution. Measuring magnetic properties of leaves or needles of trees allows estimating the concentration and grain size of pollutants, and can be used to map air pollution.

Collaborators: Neomi Widmer (BSc student, University of Bern), Ronny Lehmann (BSc student, University of Bern), City of Zürich

Environmental magnetism in lake sediments

Rock magnetic methods provide valuable insight into the iron mineralogy in lake sediments, which help characterize the environmental conditions in the lake. We determine the type and grain size of iron oxides and iron sulfides based on the lake sediments' magnetic properties. Changes in magnetic mineralogy are then related to changes in enviromental or climate conditions.

Collaborators: Artin Ali (MSc student, University of Bern), Hendrik Vogel (University of Bern)

Paleomagnetic signature of alteration in the New Caledonia ophiolite

The peridotes of the New Caledonia ophiolite experienced a long history of alteration; starting with serpentinization processes at the ocean ridge, alteration during obduction, and weathering at the surface. Alteration processes lead to changes in magnetic mineralogy. Whenever new magnetic minerals are formed, they get magnetized in the field at the time of alteration. Hence, paleomagnetism may allow to disentangle different alteration events.

Collaborators: Eric Ferré (University of Louisiana at Lafayette), Christian Teyssier (University of Minnesota)

Structural investigation of domes

Domes have complicated internal structures related to their formation and emplacement. Anisotropy of magnetic susceptibility is one way to characterize their structural features. This project uses magnetic anisotropy in addition to an extensive set of field observations and petrologic analyses to better understand domes.

Collaborators: Clémentine Hamelin (PhD student, University of Minnesota), Christian Teyssier (University of Minnesota), Donna Whitney (University of Minnesota)

Isolating components of magnetic anisotropy for more reliable anisotropy corrections in paleomagnetism

Paleomagnetic studies use a rock’s magnetic history to make e.g. plate tectonic reconstructions, and one of the main assumptions made is that the rock’s magnetization indicates the direction of the field at the time of magnetization. It is known that rock deformation or compaction can lead to deflection of the magnetization, which, if not accounted for, will cause major problems for paleogeographic reconstructions. The aim of this project will be to provide an improved correction technique based on the isolated magnetic anisotropy of the mineral that carries the remanent magnetization. These results will benefit both the paleomagnetism and archeomagnetism communities, and possibly exploration scientists who model magnetic anomalies.

Swiss National Science Foundation project 167608

Influence of magnetic fabric on strong magnetic anomalies

The Earth’s magnetic field measured at the surface is a superposition of the field generated in the Earth’s core, external field and contributions from magnetic minerals in the crust. Differences in magnetization of rocks in the Earth’s crust usually cause spatial variations in the observed magnetic field, termed magnetic anomalies. As the shape and amplitude of these anomalies depends on the geometry of the source body, they can be used to model the shallow sub-surface. However, anomaly shape and amplitude also depend on the direction of magnetization, which is not necessarily parallel to the inducing field in the presence of remanence or anisotropy. To quantify the effect of magnetic anisotropy on an anomaly, we investigated magnetic fabrics, directions of remanent magnetization and magnetic anomalies associated with the Bjerkreim Sokndal layered intrusion, Rogaland, Southern Norway. Due to modal layering and solid state deformation, these rocks possess a strong magnetic fabric. In addition to characterizing the fabric, we investigated how anisotropy affects the direction of remanent magnetization, and the anomalies measured over the intrusion. These results can be applied to interpretation of anomalies in other areas with anisotropic rocks, such as ore deposits or fault zones.

Swiss National Science Foundation project 155517. Additional funding: IRM Visiting Fellowship, NTNU and The Research Council of Norway (to Suzanne McEnroe)

Magnetic anisotropy of common rock-forming minerals

The aim of this project was to characterize magnetic anisotropy in single crystals of the common rock-forming minerals olivine, pyroxene, amphibole, mica, and feldspar. During the first part of the study, existing measurement procedures were improved to allow for a more precise determination of magnetic anisotropy in samples with weak susceptibility. Then, magnetic anisotropy was described for each mineral group, with a special focus on how it relates to the crystal structure and chemical composition. Finally, the newly determined single crystal properties were used to model magnetic fabrics in rocks whose mineralogy and preferred orientation of minerals is known. The results from this project allow researchers to quantitatively interpret magnetic fabrics, and will help to understand complex magnetic fabrics.

Swiss National Science Foundation projects 129806 and 143438 (to Ann Hirt)