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Unravelling the magnetic signal of individual grains in a Hawaiian lava using Micromagnetic Tomography
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  • Martha E Kosters,
  • Rosa A de Boer,
  • Frenk Out,
  • David Ignacio Cortés-Ortuño,
  • Lennart Vincent de Groot
Martha E Kosters
Utrecht University
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Rosa A de Boer
Utrecht University
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Frenk Out
Utrecht University
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David Ignacio Cortés-Ortuño
Utrecht University
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Lennart Vincent de Groot
Utrecht University

Corresponding Author:[email protected]

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Abstract

Micromagnetic Tomography (MMT) is a new technique that allows to determine magnetic moments of individual grains in volcanic rocks. Current MMT studies either showed that it is possible to obtain magnetic moments of relatively small numbers of grains in ideal sample material, or provided important theoretical advances in MMT inversion theory and/or its statistical framework. Here we present a large-scale application of MMT on a sample from the 1907-flow from Hawaii’s Kilauea volcano producing magnetic moments of 1,646 individual grains. To assess the robustness of the MMT results, we produced 261,305 individual magnetic moments in total: an increase of three orders of magnitude compared to earlier studies and a major step towards the number of grains that is necessary for paleomagnetic applications of MMT. Furthermore, we show that the recently proposed signal strength ratio is a powerful tool to scrutinize and select MMT results. Despite this progress, still only relatively large iron-oxide grains with diameters >1.5-2 µm can be reliably resolved, impeding a reliable paleomagnetic interpretation. To determine the magnetic moments of smaller (< 1 µm) grains that may exhibit PSD behavior and are therefore better paleomagnetic recorders, the resolution of the MicroCT and magnetic scans necessary for MMT must be improved. Therefore, it is necessary to reduce the sample size in future MMT studies. Nevertheless, our study is an important step towards making MMT a useful paleomagnetic and rock-magnetic technique.