ORCID Profile
0000-0002-1151-5662
Current Organisation
Universiteit Utrecht
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Publisher: American Geophysical Union (AGU)
Date: 10-2021
DOI: 10.1029/2021JB022364
Abstract: Our understanding of the past behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g., (volcanic) rocks. Bulk rock s les, 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 s le 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 in idual grains in a s le 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 s les. We acquired reliable magnetic directions by selecting subsets of grains in a synthetic s le, and we obtained rock‐magnetic information of in idual grains in a volcanic s le. This illustrates that MMT opens up entirely new venues of paleomagnetic and rock‐magnetic research. MMT's unique ability to determine the magnetization of in idual 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 s le, MMT has the potential to unlock paleomagnetic information from even the most complex, crucial, or valuable recorders that current methods are unable to recover.
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-18114
Abstract: & & Our understanding of the behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g. lavas. Almost all experiments to determine the past state of the Earth& #8217 s magnetic field use bulk s les (typically 1 - 10 cc) and measure their magnetic moment after series of laboratory treatments. Lavas, however, consist of mixtures of different iron-oxide grains that vary in size, shape, and chemistry. Some of these grains are good recorders of the Earth& #8217 s magnetic field others are not. Only a small amount of adverse behaved magnetic grains in a s le already h ers all classical experiments to obtain paleointensities success rates as low as 10-20% are common, i.e. for 80-90% of all lavas vital information on paleointensities is lost before it can be uncovered.& & & & Recently, we showed that it is possible to determine the magnetization of in idual grains inside a synthetic s le using a new technique: Micromagnetic Tomography. The in idual magnetizations of grains are determined by inverting scanning magnetometry data from the surface on the s le onto the known locations, sizes and shapes of the magnetic grains that are obtained from a microCT scan of the s le. The synthetic s le used for our proof-of-concept, however, was optimized for success: the dispersion of magnetic markers was low, and the magnetite grains had a well-defined grain size range. Furthermore, the scanning SQUID microscope used requires the s le to be at 4 K, below the Verweij transition of the magnetite grains.& & & & Here we present the first Micromagnetic Tomography results from natural s les. We used two magnetic scanning techniques that operate at room temperature, a Magnetic Tunneling Junction set-up and a Quantum Diamond Magnetometer, to acquire the magnetic surface scans from a Hawaiian lava and calculated magnetic moments of in idual grains present. We show that it is possible to acquire rock magnetic information as function of grain size from these natural s les and reveal the first results of interpreting a paleomagnetic direction from selected subsets of grains in our s les. These are the first steps towards deriving rock magnetic and paleomagnetic information from subsets of known good recorders inside lava s les, a technique that will revolutionize our field of research.& &
Publisher: Wiley
Date: 07-09-2021
Publisher: American Geophysical Union (AGU)
Date: 06-04-2018
DOI: 10.1002/2017GL076634
No related grants have been discovered for Lennart de Groot.