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Magnetic anisotropy of HED and Martian meteorites and implications for the crust of Vesta and Mars

Gattacceca, Jérôme, Rochette, Pierre, Gounelle, Matthieu, van Ginneken, Matthias (2008) Magnetic anisotropy of HED and Martian meteorites and implications for the crust of Vesta and Mars. Earth and Planetary Science Letters, 270 (3-4). pp. 280-289. ISSN 0012-821X. (doi:10.1016/j.epsl.2008.03.047) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:88119)

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Official URL
https://doi.org/10.1016/j.epsl.2008.03.047

Abstract

We investigate the petrofabric of crustal rocks from Mars and Vesta through the measurement of the anisotropy of the magnetic susceptibility (AMS) of achondrites. Previous data are integrated with new measurements to obtain a dataset that provide macroscopic information about the magnetic fabric of 41 meteorites of the howardite–eucrite–diogenite clan (HED, falls only) and 16 Martian meteorites. The interpretation takes into account the large contribution of paramagnetism to the magnetic susceptibility of these meteorites. We use a model that allows the computation of the anisotropy degree of the population of ferromagnetic grains and provides a quantitative proxy for the degree of shape preferential orientation of these grains in HED and Martian meteorites. The results also provide quantitative information about the shape of the magnetic fabric (prolate, oblate).In HED achondrites, the ductile FeNi grains are sensitive strain recorders and our magnetic fabric data provide the first quantitative insights to the strain history of the crustal rocks of Vesta. Most HED achondrites are breccias but display a strong and spatially coherent magnetic anisotropy, indicating that intense deformation of FeNi grains took place after brecciation. The average fabric of eucrites, howardites is oblate (i.e. the texture is foliated) whereas the fabric of diogenites is more neutral. The howardite results suggest the existence of an isotropic fraction of ferromagnetic minerals that can be ascribed to the presence of carbonaceous chondrite clasts that have preserved their original magnetic fabric. In this hypothesis, howardites have an intensity of petrofabric very similar to eucrites and diogenites. Thermal metamorphism (itself possibly impact-related) plus lithostatic compaction occurring after brecciation appears as the best candidate to explain the observed petrofabric in eucrites and diogenites, whereas compaction by hypervelocity impacts may be reponsible for the fabric of howardites.Martian meteorites may still possess their primary magmatic fabric. Among Martian meteorites, basaltic shergottites and nakhlites display an oblate fabric (foliated texture) with only limited variations among each group. Olivine–phyric shergottites have a neutral fabric that points to a different petrogenesis. Nakhlites have weaker fabric intensity than shergottites. The fabric intensity is comparable to what is classically observed in terrestrial volcanic and plutonic rocks.

Item Type: Article
DOI/Identification number: 10.1016/j.epsl.2008.03.047
Uncontrolled keywords: anistropy of magnetic susceptibility; Mars; Vesta; HED meteorites; metamorphism; Martian meteorites
Subjects: Q Science > QB Astronomy > QB651 Planets, Minor
Q Science > QC Physics > QC807 Geophysics (for Applied Geophysics see TN269)
Divisions: Divisions > Division of Natural Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Matthias van Ginneken
Date Deposited: 14 May 2021 09:41 UTC
Last Modified: 17 May 2021 09:12 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/88119 (The current URI for this page, for reference purposes)
van Ginneken, Matthias: https://orcid.org/0000-0002-2508-7021
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