The Famenin fall and other ordinary chondrites intermediate between H and L groupsOPEN ACCESS 

Hamed Pourkhorsandi, Jérôme Gattacceca, Pierre Rochette, Thomas Smith, Lydie Bonal, Massimo D’Orazio, Bertrand Devouard, Corinne Sonzogni, Vinciane Debaille

Meteoritics & Planetary Science
accepted for publication, February 2022


Update (26 March 2022, published in MAPS): LINK

“The Famenin meteorite fell around 08:30 am local time (GMT+4.5) on 27 June 2015 on the roof of a house in Famenin town, NW Iran. A single 640 grams stone was recovered, shattered into several pieces upon impact. The shape of the impact hole and the relative position of the recovered meteorites indicate a N-NW fall direction. Famenin is an ordinary chondrite with well preserved chondrules of various types, (Fe,Ni) metal, troilite, phosphate, and chromite. The organic matter systematics and the olivine and low-Ca compositional distributions (percent mean deviations 18% and 31%, respectively) indicate it is a type 3.4/3.8 chondrite. Considering the average chemical compositions of olivine (Fa17.5±4.7) and low-Ca pyroxene (Fs16.8±7.5), average Co content of the kamacite (5.6 mgg-1), and Cu/Ni and Ga/Ni ratios, Famenin should be classified as an H chondrite. However, saturation magnetization is 26.0 Am2/kg, indicating a bulk metal content similar to L chondrites. Similarly, the whole rock Ni and Co contents (13073 and 540 µgg-1, respectively), and average chondrule diameter (550 µm) are closer to typical values for L chondrites than H chondrites. The (Fe,Ni) metal modal abundance (5 vol%), magnetic susceptibility, and possibly whole rock oxygen isotopic composition indicate intermediate properties between H and L chondrites. Noble gas composition and cosmic ray exposure (CRE) ages of Famenin and El Médano 195 (another intermediate ordinary chondrite) shows their gas-rich character and an older ejection age from their parent body than those for the majority of H and L chondrites. Famenin, together with similar intermediate ordinary chondrites, increases the diversity of this meteorite clan and suggests the existence of a separate ordinary chondrite group with a composition broadly intermediate between H and L groups for which a different designation (HL) is proposed. Ordinary chondrites likely originate from more than three parent bodies (H, L, and LL) as traditionally proposed.”