Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials
Abstract— Primitive meteorites exhibit certain features that are consistent with aqueous and thermal alteration on asteroids, but O‐isotopic analyses show only a modest heavy‐isotope shift, interpreted as indicating modification in the nebula. To understand the isotopic effects of asteroidal alterat...
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crwiley:10.1111/j.1945-5100.2000.tb01523.x 2023-12-03T10:13:40+01:00 Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials BLAND, P. A. LEE, M. R. SEXTON, A. S. FRANCHI, I. A. FALLICK, A. E. T. MILLER, M. F. CADOGAN, J. M. BERRY, F. J. PILLINGER, C. T. 2000 http://dx.doi.org/10.1111/j.1945-5100.2000.tb01523.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1945-5100.2000.tb01523.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.2000.tb01523.x en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Meteoritics & Planetary Science volume 35, issue 6, page 1387-1395 ISSN 1086-9379 1945-5100 Space and Planetary Science Geophysics journal-article 2000 crwiley https://doi.org/10.1111/j.1945-5100.2000.tb01523.x 2023-11-09T13:51:37Z Abstract— Primitive meteorites exhibit certain features that are consistent with aqueous and thermal alteration on asteroids, but O‐isotopic analyses show only a modest heavy‐isotope shift, interpreted as indicating modification in the nebula. To understand the isotopic effects of asteroidal alteration, we take the L‐group ordinary chondrites weathered in Antarctica as an analogue. The data show that alteration is a two‐stage process, with an initial phase producing only a negligible isotopic effect. Although surprising, a possible explanation is found when we consider the alteration of terrestrial silicates. Numerous studies report pervasive development of channels a few to a few tens of nanometer wide in the incipient alteration of silicates. We observe a similar texture. Alteration involves a restructuring of clay minerals along these narrow channels, in which access of water is restricted. The clay shows a topotactic relationship to the primary grain, which suggests either epitaxial growth of the clay using the silicate as a substrate or inheritance of the original O structure by the clay. Our data suggests the latter: with extensive inheritance of structural polymers by the weathering product, the bulk O‐isotopic composition is comparatively unaffected. This offers an explanation for the lack of an isotopic effect in the weathering of the L chondrites. If substantial modification of chondritic materials may occur without a pronounced isotopic effect, it also reconciles existing O analyses of CV chondrites with an asteroidal model of aqueous alteration. Article in Journal/Newspaper Antarc* Antarctica Wiley Online Library (via Crossref) Meteoritics & Planetary Science 35 6 1387 1395 |
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Wiley Online Library (via Crossref) |
op_collection_id |
crwiley |
language |
English |
topic |
Space and Planetary Science Geophysics |
spellingShingle |
Space and Planetary Science Geophysics BLAND, P. A. LEE, M. R. SEXTON, A. S. FRANCHI, I. A. FALLICK, A. E. T. MILLER, M. F. CADOGAN, J. M. BERRY, F. J. PILLINGER, C. T. Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials |
topic_facet |
Space and Planetary Science Geophysics |
description |
Abstract— Primitive meteorites exhibit certain features that are consistent with aqueous and thermal alteration on asteroids, but O‐isotopic analyses show only a modest heavy‐isotope shift, interpreted as indicating modification in the nebula. To understand the isotopic effects of asteroidal alteration, we take the L‐group ordinary chondrites weathered in Antarctica as an analogue. The data show that alteration is a two‐stage process, with an initial phase producing only a negligible isotopic effect. Although surprising, a possible explanation is found when we consider the alteration of terrestrial silicates. Numerous studies report pervasive development of channels a few to a few tens of nanometer wide in the incipient alteration of silicates. We observe a similar texture. Alteration involves a restructuring of clay minerals along these narrow channels, in which access of water is restricted. The clay shows a topotactic relationship to the primary grain, which suggests either epitaxial growth of the clay using the silicate as a substrate or inheritance of the original O structure by the clay. Our data suggests the latter: with extensive inheritance of structural polymers by the weathering product, the bulk O‐isotopic composition is comparatively unaffected. This offers an explanation for the lack of an isotopic effect in the weathering of the L chondrites. If substantial modification of chondritic materials may occur without a pronounced isotopic effect, it also reconciles existing O analyses of CV chondrites with an asteroidal model of aqueous alteration. |
format |
Article in Journal/Newspaper |
author |
BLAND, P. A. LEE, M. R. SEXTON, A. S. FRANCHI, I. A. FALLICK, A. E. T. MILLER, M. F. CADOGAN, J. M. BERRY, F. J. PILLINGER, C. T. |
author_facet |
BLAND, P. A. LEE, M. R. SEXTON, A. S. FRANCHI, I. A. FALLICK, A. E. T. MILLER, M. F. CADOGAN, J. M. BERRY, F. J. PILLINGER, C. T. |
author_sort |
BLAND, P. A. |
title |
Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials |
title_short |
Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials |
title_full |
Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials |
title_fullStr |
Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials |
title_full_unstemmed |
Aqueous alteration without a pronounced oxygen‐isotopic shift: Implications for the asteroidal processing of chondritic materials |
title_sort |
aqueous alteration without a pronounced oxygen‐isotopic shift: implications for the asteroidal processing of chondritic materials |
publisher |
Wiley |
publishDate |
2000 |
url |
http://dx.doi.org/10.1111/j.1945-5100.2000.tb01523.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1945-5100.2000.tb01523.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.2000.tb01523.x |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_source |
Meteoritics & Planetary Science volume 35, issue 6, page 1387-1395 ISSN 1086-9379 1945-5100 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/j.1945-5100.2000.tb01523.x |
container_title |
Meteoritics & Planetary Science |
container_volume |
35 |
container_issue |
6 |
container_start_page |
1387 |
op_container_end_page |
1395 |
_version_ |
1784260517522571264 |