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Meteorit Planetary Scien - 2022 - Suttle - The Winchcombe meteorite A regolith breccia from a rubble pile CM chondrite.pdf (8.52 MB)

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

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posted on 2023-01-20, 15:50 authored by MD Suttle, L Daly, RH Jones, L Jenkins, M Van Ginneken, JT Mitchell, JC Bridges, LJ Hicks, D Johnson, G Rollinson, R Taylor, MJ Genge, C Schröder, P Trimby, H Mansour, S Piazolo, E Bonsall, T Salge, R Heard, R Findlay, AJ King, HC Bates, MR Lee, NR Stephen, FM Willcocks, RC Greenwood, IA Franchi, SS Russell, CS Harrison, PF Schofield, NV Almeida, C Floyd, P‐E Martin, KH Joy, PJ Wozniakiewicz, D Hallatt, MJ Burchell, LS Alesbrook, V Spathis, LT Cornwell, A Dignam

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. 


STFC are acknowledged for supporting the “Curation and Preliminary Examination of the Winchcombe Carbonaceous Chondrite Fall” project (ST/V000799/1), and Natural History Museum staff for curatorial support. In addition, we acknowledge the following funding sources: AJK and HCB are funded by UK Research and Innovation (UKRI) grant MR/T020261/1. CSH is funded by STFC grant ST/V506904/1. LD thanks the University of Glasgow COVID-19-Research Support Scheme grant, and LD and MRL thank STFC grants (ST/T002328/1) and (ST/W001128/1) for support. The University of Kent thanks STFC for support via a consolidated grant in planetary science (ST/S000348/1). The University of Stirling thanks STFC for support via a training grant quota studentship (ST/V50709X/1). Work at the University of Manchester was supported by STFC grant ST/V000675/1.



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., Taylor, R., Genge, M.J., Schröder, C., Trimby, P., Mansour, H., Piazolo, S., Bonsall, E., Salge, T., Heard, R., Findlay, R., King, A.J., Bates, H.C., Lee, M.R., Stephen, N.R., Willcocks, F.M., Greenwood, R.C., Franchi, I.A., Russell, S.S., Harrison, C.S., Schofield, P.F., Almeida, N.V., Floyd, C., Martin, P.-.-E., Joy, K.H., Wozniakiewicz, P.J., Hallatt, D., Burchell, M.J., Alesbrook, L.S., Spathis, V., Cornwell, L.T. and Dignam, A. (2023), The Winchcombe meteorite—A regolith breccia from a rubble pile CM chondrite asteroid. Meteorit Planet Sci.

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Space Research Centre, School of Physics and Astronomy


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