The True Nature of Remanence Carriers Revealed: High-resolution Tomography for Single-Crystal Rock Magnetic Applications
Abstract
The recent development of fast, powerful and easy-to-use finite-element micromagnetic software1 has the potential to revolutionise our understanding of the magnetic properties of remanence carriers. In particular, finite-element methods allow simulations to move beyond the study of idealised particle geometries, which are not representative of the majority of real-world samples.
To take full advantage of these methods, we require characterisation techniques that can yield 3D morphological and chemical information across fields-of-view relevant to single-crystal paleomagnetism (10s to 100s of μm) and with spatial resolution and sensitivity capable of detecting particles in the size range of relevance to rock magnetism (10s to 1000s of nm). Here we summarise recent applications of Scanning Transmission Electron Microscopy (STEM) tomography and X-ray Ptychotomography to characterise remanence carriers in a range of samples of relevance to rock, paleo and environmental magnetism. We discuss the application of X-ray ptychotomography to: - Ancient zircon crystals from the Jack Hills, Western Australia. - Young zircon crystals from the Bishop Tuff. - Micrometeorite spherules extracted from a Jurassic stromatolite. STEM tomography is applied to: - A detrital silicate grain from marine sediment core MD01-24212, containing dendritic inclusions of low-Ti magnetite. - Trabecular magnetite grains from marine sediment core MD01-2444. The use of high-resolution tomography to create micromagnetic models is demonstrated (Fig. 1) and used to highlight how the study of realistic particle geometries takes us beyond our current understanding of magnetic domain states in particles of intermediate size. References - Ó Conbhuí et al. (2018) MERRILL: Micromagnetic Earth Related Robust Interpreted Language Laboratory. G3 1080-1106. - Chang et al. (2016) Widespread occurrence of silicate-hosted magnetic mineral inclusions in marine sediments and their contribution to paleomagnetic recording. JGR: Solid Earth, 121, 8415-8431. Caption Fig. 1 STEM tomography of a detrital silicate grain containing dendritic inclusions of low-Ti magnetite (upper left). Connected regions of magnetite are extracted (upper right), converted to a finite-element mesh (lower left) and then simulated with micromagnetics (lower right).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGP13A..22H
- Keywords:
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- 0699 General or miscellaneous;
- ELECTROMAGNETICSDE: 1594 Instruments and techniques;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1599 General or miscellaneous;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1714 Geomagnetism and paleomagnetism;
- HISTORY OF GEOPHYSICS;
- 0699 General or miscellaneous;
- ELECTROMAGNETICSDE: 1594 Instruments and techniques;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1599 General or miscellaneous;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1714 Geomagnetism and paleomagnetism;
- HISTORY OF GEOPHYSICS