Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic Remanence
Abstract Micron to sub‐micron sized ferromagnetic inclusions in rock forming silicate minerals may give rise to particularly stable remanent magnetizations. When a population of inclusions have a preferred crystallographic or shape orientation in a rock, the recorded paleomagnetic direction and inte...
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| Format: | Article |
| Language: | English |
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Wiley
2022-02-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2021GC010272 |
| _version_ | 1797638019450142720 |
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| author | O. Ageeva G. Habler S. A. Gilder R. Schuster A. Pertsev O. Pilipenko G. Bian R. Abart |
| author_facet | O. Ageeva G. Habler S. A. Gilder R. Schuster A. Pertsev O. Pilipenko G. Bian R. Abart |
| author_sort | O. Ageeva |
| collection | DOAJ |
| description | Abstract Micron to sub‐micron sized ferromagnetic inclusions in rock forming silicate minerals may give rise to particularly stable remanent magnetizations. When a population of inclusions have a preferred crystallographic or shape orientation in a rock, the recorded paleomagnetic direction and intensity may be biased by magnetic anisotropy. To better understand this effect, we investigated plagioclase grains from oceanic gabbro dredged from the Mid‐Atlantic Ridge at 11°–17°N. The plagioclase grains contain abundant needle and lath shaped magnetite inclusions aligned along specific directions of the plagioclase lattice. Electron back scatter diffraction and anisotropy of magnetic remanence measurements are used to correlate the orientation distribution of the magnetite inclusions in the host plagioclase that contains multiple twin types (Manebach, Carlsbad, Albite, and Pericline) with the bulk magnetic anisotropy of the inclusion‐host assembly. In non‐modified plagioclase, the anisotropy ellipsoid of magnetic remanence has oblate shapes that parallels the plagioclase (010) plane. It is suggested that recrystallization of magnetite inclusions during hydrothermal overprint shifts the relative abundance of the inclusions pertaining to the different orientation classes. We show that the maximum axis of the anisotropy ellipsoid of magnetic remanence parallels the plagioclase [001] direction, which in turn controls the recorded remanent magnetization direction. Our results are relevant for paleointensity and paleodirection determinations and for the interpretation of magnetic fabrics. |
| first_indexed | 2024-03-11T12:57:39Z |
| format | Article |
| id | doaj.art-8e03472f8a3c4ce184f377f412382943 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:57:39Z |
| publishDate | 2022-02-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-8e03472f8a3c4ce184f377f4123829432023-11-03T17:00:27ZengWileyGeochemistry, Geophysics, Geosystems1525-20272022-02-01232n/an/a10.1029/2021GC010272Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic RemanenceO. Ageeva0G. Habler1S. A. Gilder2R. Schuster3A. Pertsev4O. Pilipenko5G. Bian6R. Abart7Department of Lithospheric Research University of Vienna Vienna AustriaDepartment of Lithospheric Research University of Vienna Vienna AustriaDepartment of Earth and Environmental Sciences Ludwig Maximilians University Munich GermanyChristian Doppler Laboratory for Interfaces and Precipitation Engineering (CDL‐IPE) Institute of Materials Science and Technology, TU Wien Vienna AustriaInstitute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry Russian Academy of Sciences Moscow RussiaSchmidt Institute of Physics of the Earth Russian Academy of Sciences Moscow RussiaDepartment of Lithospheric Research University of Vienna Vienna AustriaDepartment of Lithospheric Research University of Vienna Vienna AustriaAbstract Micron to sub‐micron sized ferromagnetic inclusions in rock forming silicate minerals may give rise to particularly stable remanent magnetizations. When a population of inclusions have a preferred crystallographic or shape orientation in a rock, the recorded paleomagnetic direction and intensity may be biased by magnetic anisotropy. To better understand this effect, we investigated plagioclase grains from oceanic gabbro dredged from the Mid‐Atlantic Ridge at 11°–17°N. The plagioclase grains contain abundant needle and lath shaped magnetite inclusions aligned along specific directions of the plagioclase lattice. Electron back scatter diffraction and anisotropy of magnetic remanence measurements are used to correlate the orientation distribution of the magnetite inclusions in the host plagioclase that contains multiple twin types (Manebach, Carlsbad, Albite, and Pericline) with the bulk magnetic anisotropy of the inclusion‐host assembly. In non‐modified plagioclase, the anisotropy ellipsoid of magnetic remanence has oblate shapes that parallels the plagioclase (010) plane. It is suggested that recrystallization of magnetite inclusions during hydrothermal overprint shifts the relative abundance of the inclusions pertaining to the different orientation classes. We show that the maximum axis of the anisotropy ellipsoid of magnetic remanence parallels the plagioclase [001] direction, which in turn controls the recorded remanent magnetization direction. Our results are relevant for paleointensity and paleodirection determinations and for the interpretation of magnetic fabrics.https://doi.org/10.1029/2021GC010272plagioclase hosted magnetite micro‐inclusionsshape and crystal orientation relationshipsmagnetic fabricanisotropy of magnetic remanence |
| spellingShingle | O. Ageeva G. Habler S. A. Gilder R. Schuster A. Pertsev O. Pilipenko G. Bian R. Abart Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic Remanence Geochemistry, Geophysics, Geosystems plagioclase hosted magnetite micro‐inclusions shape and crystal orientation relationships magnetic fabric anisotropy of magnetic remanence |
| title | Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic Remanence |
| title_full | Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic Remanence |
| title_fullStr | Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic Remanence |
| title_full_unstemmed | Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic Remanence |
| title_short | Oriented Magnetite Inclusions in Plagioclase: Implications for the Anisotropy of Magnetic Remanence |
| title_sort | oriented magnetite inclusions in plagioclase implications for the anisotropy of magnetic remanence |
| topic | plagioclase hosted magnetite micro‐inclusions shape and crystal orientation relationships magnetic fabric anisotropy of magnetic remanence |
| url | https://doi.org/10.1029/2021GC010272 |
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