Cavezzo—The double face of a meteorite: Mineralogy, petrography, and geochemistry of a very unusual chondrite

1,2Giovanni Pratesi,1Vanni Moggi Cecchi,3Richard C. Greenwood,3Ian A. Franchi,3Samantha J. Hammond,4Mario Di Martino,4,5Dario Barghini,5Carla Taricco,6Albino Carbognani,4Daniele Gardiol
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13695]
1Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via G. La Pira 4, Florence, 50121 Italy
2INAF—Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, Rome, 00133 Italy
3Planetary and Space Sciences, The Open University, Milton Keynes, MK7 6AA UK
4INAF—Osservatorio Astrofisico di Torino, Via Osservatorio 20, Turin, 10025 Italy
5Dipartimento di Fisica, Università degli Studi di Torino, Via P. Giuria 1, Pino Torinese, 10125 Italy
6INAF—Osservatorio di Astrofisica e Scienza dello Spazio, Via Piero Gobetti 93/3, Bologna, 40129 Italy
Published by arrangement with John Wiley & Sons

The Cavezzo meteorite, which fell on January 1, 2020, is the first meteorite detected and recovered by the Italian PRISMA Fireball Network. Two specimens, weighing 3.12 g (specimen 1) and 52.19 g (specimen 2), were collected 3 days after the bolide was observed, thanks to an effective media campaign that encouraged the involvement of local people. The two specimens of this meteorite have not only completely different lithological characteristics but also a different geochemistry and oxygen isotopic composition as well. Specimen 1 is anomalous both for the textural–structural features, varying seamlessly from chondritic to “achondritic,” and a very unusual modal mineralogy—such as the relatively high amount of olivine (63.1 vol%), plagioclase (18.2 vol%), high-Ca pyroxene (10.3 vol%), and chlorapatite (2.1 vol%); and the unusually low content of low-Ca pyroxene (5.8 vol%), metal (0.1 vol%), and troilite (much lesser than 0.1 vol%)—although the compositional values for olivine (Fa 24.24 mol%) and low-Ca pyroxene (Fs 20.41 mol%) appear to be similar to those of the L chondrite group. Conversely, in specimen 2, not only the texture and the crystal chemistry but also the modal mineralogy (low-Ca pyroxene much more abundant than high-Ca pyroxene and occurrence of metal and sulfides) look like those of an ordinary L chondrite. The differences between the two specimens are also confirmed by geochemistry. The oxygen isotope composition of specimen 1 plots at the boundary between the H and L groups (δ17O‰ 3.250; δ18O‰ 4.736; Δ17O‰ 0.788) whereas specimen 2 plots at the boundary of the L and LL fields (δ17O‰ 3.737; δ18O‰ 4.957; Δ17O‰ 1.159). The bulk chemistry shows a different content of many minor and trace elements (including rare earth elements), such as a strong depletion of siderophile and chalcophile elements in specimen 1. The two specimens then do not contain fragments of each other, thus preventing us from classifying this “double face” meteorite as an ordinary chondrite breccia. In detail, specimen 1 can be considered a “xenolith” in which chondritic structure and igneous texture coexist without discontinuity, and therefore, it represents a previously unsampled portion of the L parent body. In summary, these findings support the classification of Cavezzo as an L5 anomalous chondrite.

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