Eight good reasons why the uppermost mantle could be magnetic

Wasilewski et al. (1979) concluded that no magnetic remanence existed in the uppermost mantle and that even if present, such sources would be at temperatures too high to contribute to long wavelength magnetic anomalies (LWMA). However, new collections of unaltered mantle xenoliths indicate that the...

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Authors: Ferré, Eric E., Friedman, Sarah A., Martín Hernández, Fátima, Feinberg, Joshua M., Tille, Jessica L., Ionov, Dmitri A., Conder, James A.
Format: article
Publication Date:2014
Country:España
Institution:Consejo Superior de Investigaciones Científicas (CSIC)
Repository:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/99182
Online Access:http://hdl.handle.net/10261/99182
Access Level:Open access
Keyword:Mantle
Xenolith
Magnetization
Magnetic anomaly
Magnetite
NRM
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spelling Eight good reasons why the uppermost mantle could be magneticFerré, Eric E.Friedman, Sarah A.Martín Hernández, FátimaFeinberg, Joshua M.Tille, Jessica L.Ionov, Dmitri A.Conder, James A.MantleXenolithMagnetizationMagnetic anomalyMagnetiteNRMWasilewski et al. (1979) concluded that no magnetic remanence existed in the uppermost mantle and that even if present, such sources would be at temperatures too high to contribute to long wavelength magnetic anomalies (LWMA). However, new collections of unaltered mantle xenoliths indicate that the uppermost mantle could contain ferromagnetic minerals. 1. The analysis of some LWMA over cratons and forearcs suggest magnetic sources in the uppermost mantle. 2. The most common ferromagnetic phase in the uppermost mantle is stoichiometric magnetite. Assuming a 30. km-thick crust, and crustal and mantle geotherms of 15. °C/km and 5. °C/km, respectively, the 600. °C Curie temperature implies a 30. km-thick layer of mantle. 3. The uppermost mantle is cooler than 600. °C in Archean and Proterozoic shields (>. 350. °C), subduction zones (>. 300. °C) and old oceanic basins (>. 250. °C). 4. Recently investigated sets of unaltered mantle xenoliths contain pure magnetite inclusions in olivine and pyroxene formed in equilibrium with the host silicate. 5. The ascent of mantle xenoliths occurs in less than a day. Diffusion rates in olivine suggest that the growth of magnetite possible within this time frame cannot account for the size and distribution of magnetite particles in our samples. 6. Demagnetization of natural remanent magnetization (NRM) of unaltered mantle xenoliths unambiguously indicates only a single component acquired upon cooling at the Earth's surface. This is most easily explained as a thermoremanent magnetization acquired by pre-existing ferromagnetic minerals as xenoliths cool rapidly at the Earth's surface from magmatic temperatures, acquired during ascent. 7. Modern experimental data suggest that the wüstite-magnetite oxygen buffer and the fayalite-magnetite-quartz oxygen buffer extend several tens of km within the uppermost mantle. 8. The magnetic properties of mantle xenoliths vary consistently across tectonic settings. In conclusion, the model of a uniformly non-magnetic mantle should be revisited. © 2014 Elsevier B.V.Peer ReviewedElsevier2014201420142014info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501http://hdl.handle.net/10261/99182reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Ingléshttp://dx.doi.org/10.1016/j.tecto.2014.01.004info:eu-repo/semantics/openAccessoai:digital.csic.es:10261/991822026-05-22T06:33:51Z
dc.title.none.fl_str_mv Eight good reasons why the uppermost mantle could be magnetic
title Eight good reasons why the uppermost mantle could be magnetic
spellingShingle Eight good reasons why the uppermost mantle could be magnetic
Ferré, Eric E.
Mantle
Xenolith
Magnetization
Magnetic anomaly
Magnetite
NRM
title_short Eight good reasons why the uppermost mantle could be magnetic
title_full Eight good reasons why the uppermost mantle could be magnetic
title_fullStr Eight good reasons why the uppermost mantle could be magnetic
title_full_unstemmed Eight good reasons why the uppermost mantle could be magnetic
title_sort Eight good reasons why the uppermost mantle could be magnetic
dc.creator.none.fl_str_mv Ferré, Eric E.
Friedman, Sarah A.
Martín Hernández, Fátima
Feinberg, Joshua M.
Tille, Jessica L.
Ionov, Dmitri A.
Conder, James A.
author Ferré, Eric E.
author_facet Ferré, Eric E.
Friedman, Sarah A.
Martín Hernández, Fátima
Feinberg, Joshua M.
Tille, Jessica L.
Ionov, Dmitri A.
Conder, James A.
author_role author
author2 Friedman, Sarah A.
Martín Hernández, Fátima
Feinberg, Joshua M.
Tille, Jessica L.
Ionov, Dmitri A.
Conder, James A.
author2_role author
author
author
author
author
author
dc.subject.none.fl_str_mv Mantle
Xenolith
Magnetization
Magnetic anomaly
Magnetite
NRM
topic Mantle
Xenolith
Magnetization
Magnetic anomaly
Magnetite
NRM
description Wasilewski et al. (1979) concluded that no magnetic remanence existed in the uppermost mantle and that even if present, such sources would be at temperatures too high to contribute to long wavelength magnetic anomalies (LWMA). However, new collections of unaltered mantle xenoliths indicate that the uppermost mantle could contain ferromagnetic minerals. 1. The analysis of some LWMA over cratons and forearcs suggest magnetic sources in the uppermost mantle. 2. The most common ferromagnetic phase in the uppermost mantle is stoichiometric magnetite. Assuming a 30. km-thick crust, and crustal and mantle geotherms of 15. °C/km and 5. °C/km, respectively, the 600. °C Curie temperature implies a 30. km-thick layer of mantle. 3. The uppermost mantle is cooler than 600. °C in Archean and Proterozoic shields (>. 350. °C), subduction zones (>. 300. °C) and old oceanic basins (>. 250. °C). 4. Recently investigated sets of unaltered mantle xenoliths contain pure magnetite inclusions in olivine and pyroxene formed in equilibrium with the host silicate. 5. The ascent of mantle xenoliths occurs in less than a day. Diffusion rates in olivine suggest that the growth of magnetite possible within this time frame cannot account for the size and distribution of magnetite particles in our samples. 6. Demagnetization of natural remanent magnetization (NRM) of unaltered mantle xenoliths unambiguously indicates only a single component acquired upon cooling at the Earth's surface. This is most easily explained as a thermoremanent magnetization acquired by pre-existing ferromagnetic minerals as xenoliths cool rapidly at the Earth's surface from magmatic temperatures, acquired during ascent. 7. Modern experimental data suggest that the wüstite-magnetite oxygen buffer and the fayalite-magnetite-quartz oxygen buffer extend several tens of km within the uppermost mantle. 8. The magnetic properties of mantle xenoliths vary consistently across tectonic settings. In conclusion, the model of a uniformly non-magnetic mantle should be revisited. © 2014 Elsevier B.V.
publishDate 2014
dc.date.none.fl_str_mv 2014
2014
2014
2014
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
format article
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/99182
url http://hdl.handle.net/10261/99182
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv http://dx.doi.org/10.1016/j.tecto.2014.01.004
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Elsevier
publisher.none.fl_str_mv Elsevier
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15.81155

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