Abstract This study provides the first petrographic, crystallographic, and chemical comparison between El Médano 300 (EM 300) and Northwest Africa 8155 (NWA 8155), two particular IAB‐ungrouped iron meteorites. Both contain exceptionally large graphite nodules and “flowers”, providing unique insights into carbon behavior in metallic melts and cooling conditions. Despite these similarities, they differ in their petrography, crystallography, and chemical composition. Whereas EM 300 exhibits a homogeneous metallic phase with rounded kamacite grains, originating from at least two taenite crystals, NWA 8155 displays a heterogeneous composition with elongated kamacite crystals, from a unique taenite crystal, along with martensite and residual taenite. Variations in nickel and highly siderophile elements contents point to different degrees of partial melting, indicating in turn formations within two different metallic pools, most probably on separate parent bodies. Troilite textures in EM 300 (spidery), compared to NWA 8155 (bulky), suggest an impact‐related origin. Abundant small schreibersite grains in EM 300 indicate faster post‐impact cooling. Finally, the absence of silicates in both meteorites suggests efficient metal‐silicate segregation or formation within metallic parent bodies. These results provide new insights into the diversity of thermal and collisional histories among IAB‐ungrouped iron meteorites, supporting the idea that each one may represent a single parent body and therefore reflecting the diversity of early planetesimal natures and evolutions.
Perez et al. (Thu,) studied this question.