Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources
Atmospheric heating alters the compositions and textures of micrometeorites. To understand the changes and to test a proposed relationship between a micrometeorite's petrographic texture and its degree of heating, we made elemental and multiple isotope analyses of stony cosmic spherules (sCS) c...
Published in: | Geochimica et Cosmochimica Acta |
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Online Access: | http://hal.in2p3.fr/in2p3-00024809 https://doi.org/10.1016/j.gca.2004.11.027 |
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ftccsdartic:oai:HAL:in2p3-00024809v1 2023-05-15T18:23:18+02:00 Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources Taylor, S. Alexander, C.M.O'D. Delaney, J. Ma, P. Herzog, G.F. Engrand, C. Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM) Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS) 2005 http://hal.in2p3.fr/in2p3-00024809 https://doi.org/10.1016/j.gca.2004.11.027 en eng HAL CCSD Elsevier info:eu-repo/semantics/altIdentifier/doi/10.1016/j.gca.2004.11.027 in2p3-00024809 http://hal.in2p3.fr/in2p3-00024809 doi:10.1016/j.gca.2004.11.027 ISSN: 0016-7037 EISSN: 0016-7037 Geochimica et Cosmochimica Acta http://hal.in2p3.fr/in2p3-00024809 Geochimica et Cosmochimica Acta, Elsevier, 2005, 69, pp.2647-2662. ⟨10.1016/j.gca.2004.11.027⟩ [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph] info:eu-repo/semantics/article Journal articles 2005 ftccsdartic https://doi.org/10.1016/j.gca.2004.11.027 2020-12-26T21:52:51Z Atmospheric heating alters the compositions and textures of micrometeorites. To understand the changes and to test a proposed relationship between a micrometeorite's petrographic texture and its degree of heating, we made elemental and multiple isotope analyses of stony cosmic spherules (sCS) collected from the South Pole Water well. Specifically, we analyzed the elemental compositions of 94 sCS and the isotopic ratios of Fe, K and O, on 43, 12 and 8 of these sCS, respectively. Our results show that sCS classified as strongly heated generally have lower concentrations of volatile and moderately volatile elements. Of the 43 spherules analyzed for Fe isotopes, only 5 have δ57Fe >5‰. In contrast, enrichment of 41K is pervasive (δ41K >0 in all 12 spherules analyzed) and large (up to 183‰). The determination of K isotope abundances in sCS may therefore be useful in deciphering thermal histories. Three of the eight sCS analyzed for O isotopes are mass fractionated with δ18O >30‰. We attribute two of these three δ18O enrichments to evaporative losses of oxygen in the atmosphere and the third to the presence in the parent material of an exotic phase, perhaps a sulfate or a carbonate. The K isotope and O isotope data are broadly consistent with the proposed textural classification. Because most spherules were not heated enough to fractionate Al, Mg, or Si, we compared the measured Mg/Al and Si/Al ratios directly to those of conventional meteorites and their matrices. $\sim$ 30% of the sCS have compositions outside the range defined by the bulk and the matrix compositions of known meteorite groups but consistent with those of pyroxene- and olivine-rich materials and may be samples of chondrules. The other 70% have Mg/Al and Si/Al ratios similar to those of CI, CM, CO, and CV chondrites. Natural variability of the Mg/Al and Si/Al ratios precludes the assignment of an individual sCS to a particular class of C-chondrite. Article in Journal/Newspaper South pole Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) South Pole Geochimica et Cosmochimica Acta 69 10 2647 2662 |
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Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
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ftccsdartic |
language |
English |
topic |
[PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph] |
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[PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph] Taylor, S. Alexander, C.M.O'D. Delaney, J. Ma, P. Herzog, G.F. Engrand, C. Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources |
topic_facet |
[PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph] |
description |
Atmospheric heating alters the compositions and textures of micrometeorites. To understand the changes and to test a proposed relationship between a micrometeorite's petrographic texture and its degree of heating, we made elemental and multiple isotope analyses of stony cosmic spherules (sCS) collected from the South Pole Water well. Specifically, we analyzed the elemental compositions of 94 sCS and the isotopic ratios of Fe, K and O, on 43, 12 and 8 of these sCS, respectively. Our results show that sCS classified as strongly heated generally have lower concentrations of volatile and moderately volatile elements. Of the 43 spherules analyzed for Fe isotopes, only 5 have δ57Fe >5‰. In contrast, enrichment of 41K is pervasive (δ41K >0 in all 12 spherules analyzed) and large (up to 183‰). The determination of K isotope abundances in sCS may therefore be useful in deciphering thermal histories. Three of the eight sCS analyzed for O isotopes are mass fractionated with δ18O >30‰. We attribute two of these three δ18O enrichments to evaporative losses of oxygen in the atmosphere and the third to the presence in the parent material of an exotic phase, perhaps a sulfate or a carbonate. The K isotope and O isotope data are broadly consistent with the proposed textural classification. Because most spherules were not heated enough to fractionate Al, Mg, or Si, we compared the measured Mg/Al and Si/Al ratios directly to those of conventional meteorites and their matrices. $\sim$ 30% of the sCS have compositions outside the range defined by the bulk and the matrix compositions of known meteorite groups but consistent with those of pyroxene- and olivine-rich materials and may be samples of chondrules. The other 70% have Mg/Al and Si/Al ratios similar to those of CI, CM, CO, and CV chondrites. Natural variability of the Mg/Al and Si/Al ratios precludes the assignment of an individual sCS to a particular class of C-chondrite. |
author2 |
Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM) Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS) |
format |
Article in Journal/Newspaper |
author |
Taylor, S. Alexander, C.M.O'D. Delaney, J. Ma, P. Herzog, G.F. Engrand, C. |
author_facet |
Taylor, S. Alexander, C.M.O'D. Delaney, J. Ma, P. Herzog, G.F. Engrand, C. |
author_sort |
Taylor, S. |
title |
Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources |
title_short |
Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources |
title_full |
Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources |
title_fullStr |
Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources |
title_full_unstemmed |
Isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: Implications for heating histories and sources |
title_sort |
isotopic fractionation of iron, potassium, and oxygen in stony cosmic spherules: implications for heating histories and sources |
publisher |
HAL CCSD |
publishDate |
2005 |
url |
http://hal.in2p3.fr/in2p3-00024809 https://doi.org/10.1016/j.gca.2004.11.027 |
geographic |
South Pole |
geographic_facet |
South Pole |
genre |
South pole |
genre_facet |
South pole |
op_source |
ISSN: 0016-7037 EISSN: 0016-7037 Geochimica et Cosmochimica Acta http://hal.in2p3.fr/in2p3-00024809 Geochimica et Cosmochimica Acta, Elsevier, 2005, 69, pp.2647-2662. ⟨10.1016/j.gca.2004.11.027⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1016/j.gca.2004.11.027 in2p3-00024809 http://hal.in2p3.fr/in2p3-00024809 doi:10.1016/j.gca.2004.11.027 |
op_doi |
https://doi.org/10.1016/j.gca.2004.11.027 |
container_title |
Geochimica et Cosmochimica Acta |
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69 |
container_issue |
10 |
container_start_page |
2647 |
op_container_end_page |
2662 |
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