Shock-induced metallic iron nanoparticles in olivine-rich Martian meteorites

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doi: 10.1016/j.epsl.2007.07.002
Authors:van de Moortèle, B.; Reynard, B.; Rochette, P.; Jackson, M.; Beck, P.; Gillet, P.; McMillan, P. F.; McCammon, C. A.
Author Affiliations:Primary:
Ecole Normale Supérieure de Lyon, Laboratoire des Sciences de la Terre, Lyon, France
Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, France
University of Minneapolis, United States
University College London, United Kingdom
Universität Bayreuth, Federal Republic of Germany
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 262(1-2), p.37-49. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:2007
Note:In English. Supplemental information/data is available in the online version of this article. 34 refs.; illus., incl. 3 tables
Summary:Magnetic anomalies observed by the Mars Global Surveyor mission are attributed to crustal remanence. SNC (Shergotty-Nakhla-Chassigny) meteorites are likely samples of the Martian crust and are amenable to mineralogical and magnetic measurements essential to the understanding of the origin of magnetic anomalies. The recently discovered chassignite NWA 2737 and lherzolitic shergottite NWA 1950 display unusual magnetic characteristics that argue for a different magnetic carrier than the oxides and sulfides previously invoked in SNC meteorites. NWA 2737, the second member of the chassignite group, is a dunite with unusually dark-brown olivines and large magnetic susceptibility while Chassigny contains green olivines and is nearly a pure paramagnet. Dark olivines are also found in NWA 1950, a lherzolitic shergottite, which has singular magnetic properties when compared with other shergottites. The dark olivine color is due to the presence of Fe and FeNi metal nanoparticles, identified both by TEM and by magnetic measurements. Their size distribution encompasses the superparamagnetic to single domain transition at 30 K (10 nm range) and explains the magnetic properties of the bulk rocks. The formation of these nanoparticles is attributed to heating during the shock events that affected NWA 2737 and NWA 1950. The production of metal particles by shock-induced reduction of olivine has been invoked on surfaces deprived of atmosphere but never observed on Earth or Mars. Therefore, metal formed by shock in the heavily cratered Noachian crust is a possible carrier for crustal magnetic remanence. Widespread surface formation of metal nanoparticles could provide the precursor for the oxidized particles (goethite, hematite) observed in the Martian soils. Abstract Copyright (2007) Elsevier, B.V.
Sections:Meteorites and tektites
Subjects:Achondrites; Chassignite; EBSD data; EDS spectra; Electron microscopy data; Goethite; Hematite; Impacts; Iron; Magnetic domains; Magnetic properties; Magnetic susceptibility; Mars; Martian meteorites; Metals; Metamorphism; Meteorites; Microscope methods; Nanoparticles; Nesosilicates; Northwest Africa Meteorites; Olivine; Olivine group; Orthosilicates; Oxides; Planets; Raman spectra; Regolith; Shergottite; Shock metamorphism; Silicates; Single domains; Size distribution; SNC Meteorites; Soils; Spectra; Stony meteorites; TEM data; Terrestrial planets; X-ray spectra; Electron backscatter diffraction data; Energy dispersive X-ray spectra; Iron-nickel metal; NWA 1950; NWA 2737
Abstract Numbers:07M/4403
Record ID:2008075571
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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