Micromagnetic Tomography for Paleomagnetism and Rock-Magnetism

Micromagnetic Tomography for Paleomagnetism and Rock-Magnetism

de Groot, Lennart V. (Universiteit Utrecht)
Fabian, Karl (Norwegian University of Science and Technology (NTNU))
Béguin, Annemarieke (Universiteit Utrecht; Norwegian University of Science and Technology (NTNU))
Kosters, Martha E. (Universiteit Utrecht)
Cortés-Ortuño, David (Universiteit Utrecht)
Fu, Roger R. (Harvard University)
Jansen, Chloë M.L. (Universiteit Utrecht)
Harrison, Richard J. (University of Cambridge)
van Leeuwen, Tristan (Centrum Wiskunde & Informatica (CWI); Universiteit Utrecht)
Barnhoorn, A. (TU Delft Applied Geophysics and Petrophysics)

2021

Our understanding of the past behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g., (volcanic) rocks. Bulk rock samples, however, often contain magnetic grains that differ in chemistry, size, and shape; some of them record the Earth's magnetic field well, others are unreliable. The presence of a small amount of adverse behaved magnetic grains in a sample may already obscure important information on the past state of the geomagnetic field. Recently it was shown that it is possible to determine magnetizations of individual grains in a sample by combining X-ray computed tomography and magnetic surface scanning measurements. Here we establish this new Micromagnetic Tomography (MMT) technique and make it suitable for use with different magnetic scanning techniques, and for both synthetic and natural samples. We acquired reliable magnetic directions by selecting subsets of grains in a synthetic sample, and we obtained rock-magnetic information of individual grains in a volcanic sample. This illustrates that MMT opens up entirely new venues of paleomagnetic and rock-magnetic research. MMT's unique ability to determine the magnetization of individual grains in a nondestructive way allows for a systematic analysis of how geological materials record and retain information on the past state of the Earth's magnetic field. Moreover, by interpreting only the contributions of known magnetically well-behaved grains in a sample, MMT has the potential to unlock paleomagnetic information from even the most complex, crucial, or valuable recorders that current methods are unable to recover.

microCT
micromagnetic tomography
rock-magnetism
scanning magnetometry

http://resolver.tudelft.nl/uuid:dd0d9a4d-bb4e-4eda-b378-043edb1aa848

https://doi.org/10.1029/2021JB022364

2169-9313

JGR Solid Earth, 126 (10)

Institutional Repository

journal article

© 2021 Lennart V. de Groot, Karl Fabian, Annemarieke Béguin, Martha E. Kosters, David Cortés-Ortuño, Roger R. Fu, Chloë M.L. Jansen, Richard J. Harrison, Tristan van Leeuwen, A. Barnhoorn