The Winchcombe meteorite—A regolith breccia from a rubble pile CM chondrite asteroid

Suttle, M. D., Daly, L., Jones, R. H., Jenkins, L., van Ginneken, M., Mitchell, J. T., Bridges, J. C., Hicks, L. J., Johnson, D., Rollinson, G., and others. (2022) The Winchcombe meteorite—A regolith breccia from a rubble pile CM chondrite asteroid. Meteoritics & Planetary Science, . ISSN 1086-9379. E-ISSN 1945-5100. (doi:10.1111/maps.13938) (KAR id:99286)

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Official URL: https://doi.org/10.1111/maps.13938

Abstract

The Winchcombe meteorite is a CM chondrite breccia composed of eight distinct lithological units plus a cataclastic matrix. The degree of aqueous alteration varies between intensely altered CM2.0 and moderately altered CM2.6. Although no lithology dominates, three heavily altered rock types (CM2.1–2.3) represent >70 area%. Tochilinite–cronstedtite intergrowths (TCIs) are common in several lithologies. Their compositions can vary significantly, even within a single lithology, which can prevent a clear assessment of alteration extent if only TCI composition is considered. We suggest that this is due to early alteration under localized geochemical microenvironments creating a diversity of compositions and because later reprocessing was incomplete, leaving a record of the parent body's fluid history. In Winchcombe, the fragments of primary accretionary rock are held within a cataclastic matrix (~15 area%). This material is impact‐derived fallback debris. Its grain size and texture suggest that the disruption of the original parent asteroid responded by intergranular fracture at grain sizes <100 μm, while larger phases, such as whole chondrules, splintered apart. Re‐accretion formed a poorly lithified body. During atmospheric entry, the Winchcombe meteoroid broke apart with new fractures preferentially cutting through the weaker cataclastic matrix and separating the breccia into its component clasts. The strength of the cataclastic matrix imparts a control on the survival of CM chondrite meteoroids. Winchcombe's unweathered state and diversity of lithologies make it an ideal sample for exploring the geological history of the CM chondrite group.

Item Type:	Article
DOI/Identification number:	10.1111/maps.13938
Additional information:	For the purpose of open access, the author(s) has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising
Uncontrolled keywords:	Space and planetary science; geophysics
Subjects:	Q Science
Divisions:	Divisions > Division of Natural Sciences > Physics and Astronomy
Funders:	UK Research and Innovation (https://ror.org/001aqnf71) Science and Technology Facilities Council (https://ror.org/057g20z61)
SWORD Depositor:	JISC Publications Router
Depositing User:	JISC Publications Router
Date Deposited:	20 Mar 2023 12:49 UTC
Last Modified:	27 Feb 2024 12:27 UTC
Resource URI:	https://kar.kent.ac.uk/id/eprint/99286 (The current URI for this page, for reference purposes)

University of Kent Author Information

van Ginneken, M..

Creator's ORCID:	https://orcid.org/0000-0002-2508-7021
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Wozniakiewicz, Penelope J..

Creator's ORCID:	https://orcid.org/0000-0002-1441-4883
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Burchell, M. J..

Creator's ORCID:	https://orcid.org/0000-0002-2680-8943
CReDIT Contributor Roles:

Spathis, V..

Creator's ORCID:
CReDIT Contributor Roles:

Cornwell, Luke.T..

Creator's ORCID:	https://orcid.org/0000-0003-1428-2160
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