Variations in the Magnetic Properties of Meteoritic Cloudy Zone
Abstract Iron and stony‐iron meteorites form the Widmanstätten pattern during slow cooling. This pattern is composed of several microstructures whose length‐scale, composition and magnetic properties are dependent upon cooling rate. Here we focus on the cloudy zone: a region containing nanoscale tet...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2020-02-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2019GC008798 |
| _version_ | 1827771770793361408 |
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| author | Claire I. O. Nichols James F. J. Bryson Roberts Blukis Julia Herrero‐Albillos Florian Kronast Rudolf Rüffer Aleksandr I. Chumakov Richard J. Harrison |
| author_facet | Claire I. O. Nichols James F. J. Bryson Roberts Blukis Julia Herrero‐Albillos Florian Kronast Rudolf Rüffer Aleksandr I. Chumakov Richard J. Harrison |
| author_sort | Claire I. O. Nichols |
| collection | DOAJ |
| description | Abstract Iron and stony‐iron meteorites form the Widmanstätten pattern during slow cooling. This pattern is composed of several microstructures whose length‐scale, composition and magnetic properties are dependent upon cooling rate. Here we focus on the cloudy zone: a region containing nanoscale tetrataenite islands with exceptional paleomagnetic recording properties. We present a systematic review of how cloudy zone properties vary with cooling rate and proximity to the adjacent tetrataenite rim. X‐ray photoemission electron microscopy is used to compare compositional and magnetization maps of the cloudy zone in the mesosiderites (slow cooling rates), the IAB iron meteorites and the pallasites (intermediate cooling rates), and the IVA iron meteorites (fast cooling rates). The proportions of magnetic phases within the cloudy zone are also characterized using Mössbauer spectroscopy. We present the first observations of the magnetic state of the cloudy zone in the mesosiderites, showing that, for such slow cooling rates, tetrataenite islands grow larger than the multidomain threshold, creating large‐scale regions of uniform magnetization across the cloudy zone that render it unsuitable for paleomagnetic analysis. For the most rapidly cooled IVA meteorites, the time available for Fe‐Ni ordering is insufficient to allow tetrataenite formation, again leading to behavior that is unsuitable for paleomagnetic analysis. The most reliable paleomagnetic remanence is recorded by meteorites with intermediate cooling rates ( ∼ 2–500 °C Myr −1) which produces islands that are “just right” in both size and degree of Fe‐Ni order. |
| first_indexed | 2024-03-11T12:58:57Z |
| format | Article |
| id | doaj.art-db27a17e0fca49ab8dcdf55a89be8de0 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:58:57Z |
| publishDate | 2020-02-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-db27a17e0fca49ab8dcdf55a89be8de02023-11-03T16:55:47ZengWileyGeochemistry, Geophysics, Geosystems1525-20272020-02-01212n/an/a10.1029/2019GC008798Variations in the Magnetic Properties of Meteoritic Cloudy ZoneClaire I. O. Nichols0James F. J. Bryson1Roberts Blukis2Julia Herrero‐Albillos3Florian Kronast4Rudolf Rüffer5Aleksandr I. Chumakov6Richard J. Harrison7Department of Earth, Atmospheric and Planetary Sciences Massachusetts Insitute of Technology Cambridge MA USADepartment of Earth Sciences University of Cambridge Cambridge UKHelmholtz Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ Potsdam GermanyCentro Universitario de la Defensa Zaragoza SpainHelmholtz Zentrum Berlin, Elektronenspeicherring BESSY II Berlin GermanyESRF—The European Synchrotron Grenoble FranceESRF—The European Synchrotron Grenoble FranceDepartment of Earth Sciences University of Cambridge Cambridge UKAbstract Iron and stony‐iron meteorites form the Widmanstätten pattern during slow cooling. This pattern is composed of several microstructures whose length‐scale, composition and magnetic properties are dependent upon cooling rate. Here we focus on the cloudy zone: a region containing nanoscale tetrataenite islands with exceptional paleomagnetic recording properties. We present a systematic review of how cloudy zone properties vary with cooling rate and proximity to the adjacent tetrataenite rim. X‐ray photoemission electron microscopy is used to compare compositional and magnetization maps of the cloudy zone in the mesosiderites (slow cooling rates), the IAB iron meteorites and the pallasites (intermediate cooling rates), and the IVA iron meteorites (fast cooling rates). The proportions of magnetic phases within the cloudy zone are also characterized using Mössbauer spectroscopy. We present the first observations of the magnetic state of the cloudy zone in the mesosiderites, showing that, for such slow cooling rates, tetrataenite islands grow larger than the multidomain threshold, creating large‐scale regions of uniform magnetization across the cloudy zone that render it unsuitable for paleomagnetic analysis. For the most rapidly cooled IVA meteorites, the time available for Fe‐Ni ordering is insufficient to allow tetrataenite formation, again leading to behavior that is unsuitable for paleomagnetic analysis. The most reliable paleomagnetic remanence is recorded by meteorites with intermediate cooling rates ( ∼ 2–500 °C Myr −1) which produces islands that are “just right” in both size and degree of Fe‐Ni order.https://doi.org/10.1029/2019GC008798meteoritesrock magnetismpaleomagnetism |
| spellingShingle | Claire I. O. Nichols James F. J. Bryson Roberts Blukis Julia Herrero‐Albillos Florian Kronast Rudolf Rüffer Aleksandr I. Chumakov Richard J. Harrison Variations in the Magnetic Properties of Meteoritic Cloudy Zone Geochemistry, Geophysics, Geosystems meteorites rock magnetism paleomagnetism |
| title | Variations in the Magnetic Properties of Meteoritic Cloudy Zone |
| title_full | Variations in the Magnetic Properties of Meteoritic Cloudy Zone |
| title_fullStr | Variations in the Magnetic Properties of Meteoritic Cloudy Zone |
| title_full_unstemmed | Variations in the Magnetic Properties of Meteoritic Cloudy Zone |
| title_short | Variations in the Magnetic Properties of Meteoritic Cloudy Zone |
| title_sort | variations in the magnetic properties of meteoritic cloudy zone |
| topic | meteorites rock magnetism paleomagnetism |
| url | https://doi.org/10.1029/2019GC008798 |
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