Mineral magnetism of dusty olivine: A credible recorder of pre-accretionary remanence

Lappe, Sophie-Charlotte L. L. and Church, Nathan S. and Kasama, Takeshi and Fanta, Alice Bastos da Silva and Bromiley, Geoff and Dunin-Borkowski, Rafal E. and Feinberg, Joshua M. and Russell, Sara and Harrison, Richard J. (2011) Mineral magnetism of dusty olivine: A credible recorder of pre-accretionary remanence. Geochemistry Geophysics Geosystems - GCubed, 12. Q12Z35. DOI https://doi.org/10.1029/2011GC003811

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The magnetic properties of olivine-hosted Fe-Ni particles have been studied to assess the potential of “dusty olivine” to retain a pre-accretionary remanence in chondritic meteorites. Both body-centered (bcc) and face-centered cubic (fcc) Fe-Ni phases were formed by reduction of a terrestrial olivine precursor. The presence of Ni complicates the magnetic properties during heating and cooling due to the fcc-bcc martensitic transition. First-order reversal curve (FORC) diagrams contain a central ridge with a broad coercivity distribution extending to 600 mT, attributed to non-interacting single-domain (SD) particles, and a “butterfly” structure extending to 250 mT, attributed to single-vortex (SV) states. SD and SV states were imaged directly using electron holography. The location of the SD/SV boundary is broadly consistent with theoretical predictions. A method to measure the volume of individual SD particles using electron holography is presented. Combining the volume information with constraints on coercivity, we calculate the thermal relaxation characteristics of the particles and demonstrate that the high-coercivity component of remanance would remain stable for 4.6 Ga, even at temperatures approaching the Curie temperature of pure Fe. The high coercivity of the particles, together with the chemical protection offered by the surrounding olivine, is likely to make them resistant to shock remagnetization, isothermal remagnetization and terrestrial weathering, making dusty olivine a credible recorder of pre-accretionary magnetic fields.

Item Type: Article
Uncontrolled Keywords: 2011AREP; IA63;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Geochemistry Geophysics Geosystems - GCubed
Volume: 12
Page Range: Q12Z35
Identification Number: https://doi.org/10.1029/2011GC003811
Depositing User: Sarah Humbert
Date Deposited: 21 Dec 2011 15:34
Last Modified: 23 Jul 2013 10:03
URI: http://eprints.esc.cam.ac.uk/id/eprint/2304

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