Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites
This study explores the petrology of five giant (>400 lm) hydrated fine-grained micrometeorites from the Transantarctic Mountain (TAM) micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a rang...
Published in: | Geochimica et Cosmochimica Acta |
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Online Access: | http://hdl.handle.net/11568/939245 https://doi.org/10.1016/j.gca.2018.11.019 https://www.sciencedirect.com/science/article/pii/S0016703718306495 |
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ftunivpisairis:oai:arpi.unipi.it:11568/939245 2024-02-27T08:35:10+00:00 Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites M. D. Suttle L. Folco M. J. Genge S. S. Russell J. Najorka M. van Ginneken Suttle, M. D. Folco, L. Genge, M. J. Russell, S. S. Najorka, J. van Ginneken, M. 2019 STAMPA http://hdl.handle.net/11568/939245 https://doi.org/10.1016/j.gca.2018.11.019 https://www.sciencedirect.com/science/article/pii/S0016703718306495 eng eng info:eu-repo/semantics/altIdentifier/wos/WOS:000453771600021 volume:245 firstpage:352 lastpage:373 numberofpages:22 journal:GEOCHIMICA ET COSMOCHIMICA ACTA http://hdl.handle.net/11568/939245 doi:10.1016/j.gca.2018.11.019 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85056988307 https://www.sciencedirect.com/science/article/pii/S0016703718306495 info:eu-repo/semantics/openAccess info:eu-repo/semantics/article 2019 ftunivpisairis https://doi.org/10.1016/j.gca.2018.11.019 2024-01-31T17:52:37Z This study explores the petrology of five giant (>400 lm) hydrated fine-grained micrometeorites from the Transantarctic Mountain (TAM) micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these micrometeorites represent 2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of <1.2 in the scheme of Howard et al. (2015)) and reveal a range of alteration styles. Two particles are found to contain pseudomorphic chondrules with thick fine-grained rims, while another micrometeorite contains several aqueously altered CAIs. Their outlines range from welldefined to indistinct, demonstrating that the advanced stages of aqueous alteration progressively remove evidence of coarse-grained components. The remaining two micrometeorites entirely lack coarse-grained components but are similarly altered. Thus, the combined chondrule-to-matrix ratio among these giant micrometeorites is extremely low (6.45 area%), and significantly below the average ratio found in typical CM or CR chondrites (20%, Weisberg et al., 2006). Our findings are consistent with previous analyses from smaller Antarctic micrometeorites, which suggest that chondrules (and CAIs) derived from hydrated carbonaceous chondrite parent bodies are underrepresented among the micrometeorite flux, even when considering contributions from coarse-grained micrometeorites. Therefore, to explain the relative paucity of anhydrous material, we propose that the flux of fine-grained micrometeorites is primarily derived from intensely aqueously altered, primitive C-type asteroids, which have lost the majority of their refractory coarse-grained components by replacement with secondary phyllosilicate minerals. Article in Journal/Newspaper Antarc* Antarctic ARPI - Archivio della Ricerca dell'Università di Pisa Antarctic Geochimica et Cosmochimica Acta 245 352 373 |
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Open Polar |
collection |
ARPI - Archivio della Ricerca dell'Università di Pisa |
op_collection_id |
ftunivpisairis |
language |
English |
description |
This study explores the petrology of five giant (>400 lm) hydrated fine-grained micrometeorites from the Transantarctic Mountain (TAM) micrometeorite collection. For the first time, the extent and mechanisms of aqueous alteration in unmelted cosmic dust are evaluated and quantified. We use a range of criteria, previously defined for use on hydrated chondrites, including phyllosilicate fraction, matrix geochemistry and micro textures. Collectively, these micrometeorites represent 2.22 mm2 of intensely altered hydrated chondritic matrix (with petrologic subtypes of <1.2 in the scheme of Howard et al. (2015)) and reveal a range of alteration styles. Two particles are found to contain pseudomorphic chondrules with thick fine-grained rims, while another micrometeorite contains several aqueously altered CAIs. Their outlines range from welldefined to indistinct, demonstrating that the advanced stages of aqueous alteration progressively remove evidence of coarse-grained components. The remaining two micrometeorites entirely lack coarse-grained components but are similarly altered. Thus, the combined chondrule-to-matrix ratio among these giant micrometeorites is extremely low (6.45 area%), and significantly below the average ratio found in typical CM or CR chondrites (20%, Weisberg et al., 2006). Our findings are consistent with previous analyses from smaller Antarctic micrometeorites, which suggest that chondrules (and CAIs) derived from hydrated carbonaceous chondrite parent bodies are underrepresented among the micrometeorite flux, even when considering contributions from coarse-grained micrometeorites. Therefore, to explain the relative paucity of anhydrous material, we propose that the flux of fine-grained micrometeorites is primarily derived from intensely aqueously altered, primitive C-type asteroids, which have lost the majority of their refractory coarse-grained components by replacement with secondary phyllosilicate minerals. |
author2 |
Suttle, M. D. Folco, L. Genge, M. J. Russell, S. S. Najorka, J. van Ginneken, M. |
format |
Article in Journal/Newspaper |
author |
M. D. Suttle L. Folco M. J. Genge S. S. Russell J. Najorka M. van Ginneken |
spellingShingle |
M. D. Suttle L. Folco M. J. Genge S. S. Russell J. Najorka M. van Ginneken Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites |
author_facet |
M. D. Suttle L. Folco M. J. Genge S. S. Russell J. Najorka M. van Ginneken |
author_sort |
M. D. Suttle |
title |
Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites |
title_short |
Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites |
title_full |
Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites |
title_fullStr |
Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites |
title_full_unstemmed |
Intense aqueous alteration on C-type asteroids: Perspectives from giant fine-grained micrometeorites |
title_sort |
intense aqueous alteration on c-type asteroids: perspectives from giant fine-grained micrometeorites |
publishDate |
2019 |
url |
http://hdl.handle.net/11568/939245 https://doi.org/10.1016/j.gca.2018.11.019 https://www.sciencedirect.com/science/article/pii/S0016703718306495 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
info:eu-repo/semantics/altIdentifier/wos/WOS:000453771600021 volume:245 firstpage:352 lastpage:373 numberofpages:22 journal:GEOCHIMICA ET COSMOCHIMICA ACTA http://hdl.handle.net/11568/939245 doi:10.1016/j.gca.2018.11.019 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-85056988307 https://www.sciencedirect.com/science/article/pii/S0016703718306495 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1016/j.gca.2018.11.019 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
245 |
container_start_page |
352 |
op_container_end_page |
373 |
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