Mineralogy of C1, C2, and CM-like clasts in achondritic and chondritic meteorite breccias
Subhasmita Swain, Enrico Mugnaioli, Anna Musolino, Markus Patzek, Beda Hofmann, Surya Snata Rout
MAPS, Version of Record online: 20 October 2026
“Volatile-rich xenolithic clasts in different meteoritic breccias represent primitive solar system material. Here, we report the mineralogy and organic maturity of C1, C2, and CM-like clasts present within five polymict ureilites, two polymict eucrites, one howardite, and one CR chondrite. Of all the clasts, the C1s are the most abundant, and the majority have mineralogy and organic maturity similar to the CI chondrites. Two C1 clasts show the least altered polyaromatic organic matter, similar to Bells, Essebi, and a CR chondrite. A few C1 clasts have unique mineralogy with abundant Fe-rich olivine surrounding magnetite grains. Such clasts show a Raman signature of mild to moderate heating effects related to impact-shock processing. The Fe-rich olivine within these clasts formed around magnetite grains from an aqueous fluid at a water/rock ratio of 0.1–0.2, T > 150 °C, and high activity of SiO2 and Fe. Additionally, the Fe-rich olivine could have also formed through the reduction of magnetite by H2 gas and SiO2(aq). The CM-like clasts are found only in the studied HED meteorites and have mineralogy and organic maturity similar to the CM chondrites. Only one CM-like clast shows unique Raman signatures, either due to thermal effects or the presence of unique organic precursor material. The C2 clasts show similarities with other C2 clasts in CH/CB chondrites. None of the studied clasts show signatures of high degrees of thermal metamorphism like the subtype ≥3.1 chondrites.”
