NORTHWEST AFRICA (NWA) 12563 and ungrouped C2 chondrites: Alteration styles and relationships to asteroids

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Hewins, R.H., Zanetta, P.-M., Zanda, B., Le Guillou, C., Gattacceca, J., Sognzoni, C., Pont, S., Piani, L., Rigaudier, T., Leroux, H., Brunetto, R., Maupin, R., Djouadi, Z., Bernard, Sylvain, Deldicque, D., Malarewicz, V., Dionnet, Z., Aléon-Toppani, A., King, A., Borondics, F.
• Other Authors: Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement IRD : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Unité Matériaux et Transformations - UMR 8207 (UMET), Centrale Lille-Institut de Chimie - CNRS Chimie (INC-CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales Paris (CNES), Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), ANR-19-CE31-0027,HYDRaTE,Distribution of HYdrogen in the protoplanetary Disk and deliveRy to the Terrestrial planEts(2019), ANR-10-LABX-0038,P2IO,Physics of the 2 infinities and the origins(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: C2-ungrouped chondrites; Amorphous silicate; Hyperspectral cartography; Chondrite parent bodies; Chondrite-asteroid connection; [SDU]Sciences of the Universe [physics]; Tagish; Tagish Lake
• Online Access: https://hal.science/hal-03278825; https://hal.science/hal-03278825/document; https://hal.science/hal-03278825/file/Hewins-GCA-2021-HAL.pdf; https://doi.org/10.1016/j.gca.2021.06.035

International audience Many asteroids in the main belt have spectra like those of Mighei-type CM chondrites, but some Near Earth Objects (NEO) resemble less well known types of C2 chondrite. Northwest Africa (NWA) 12563, a new find with affinities to C2 chondrites, could help us understand the differences between observations of CM2 chondrites and bodies that are currently being studied by the Hayabusa2 and OSIRIS-REx space missions. NWA 12563 contains 14% chondrules supported by 86% fine grained matrix consistent with CM2 chondrites, but differs from them in other respects. In both matrix and chondrules, olivine is unaltered and pyroxene shows incipient alteration. Metal in chondrules is pseudomorphed by serpentine, and mesostasis is replaced by serpentine-saponite and chlorite. Many Type I chondrules have highly irregular shapes resulting from fracturing and selective metal replacement. Type II porphyritic chondrules are clusters of phenocrysts set in matrix-like material. Type II chondrules may be kinked and partially disbarred. The matrix of NWA 12563 differs from CM2 chondrites in the absence of tochilinite-cronstedtite intergrowths. It contains hydrated and oxidized amorphous silicate (Fe3+/∑Fe ~75%) richer in magnesium than in other chondrites (with embedded sulfides). Serpentine-saponite is also present, as well as abundant framboidal magnetite.NWA 12563 has similarities to a number of ungrouped magnetite-rich and 18O-rich chondrites (Bells, Essebi, Niger I, WIS 91600, Tagish Lake, and MET 00432) that we call C2-ung1, as opposed to C2-ung2 chondrites (poorer in 18O and magnetite). The oxygen isotopic composition coupled with a magnetic susceptibility of log χ = 4.67 places NWA 12563 with these ungrouped chondrites in a cluster distinct from CM2 chondrites. NWA 12563 is closest to WIS 91600 among the C2-ung1 chondrites in alteration style and light element compositions. WIS 91600, however, has suffered light thermal metamorphism, suggesting that NWA 12563 might represent its altered but unheated ...