Textural and mineralogical diagnostics of sulfide-rich iron meteorites

This work presents a systematic petrographic and mineralogical investigation of 13 meteorites (selected samples of IAB, IIE, ungrouped irons, and ordinary chondrites) that are sulfide-rich or have a connection to sulfide-rich samples via micro- and macro-structural features. Despite shared similarities, these samples exhibit a wide variety of features (e.g., modal abundance, structures ranging from slow-cooled subsolidus samples to rapidly cooled ones) within the same group of irons (e.g., IIE). By utilizing backscattered electron (BSE) imaging and electron microprobe analysis (EMP), this work establishes a diagnostic framework that categorizes samples based on their formation history rather than chemical grouping alone. The studied set is subdivided into three distinct groups: (A) high-Ni slow-cooled samples (e.g., San Cristobal); (B) slow-cooled subsolidus samples (e.g., Watson 001) exhibiting Widmanstätten pattern and equilibrium phase separation; and (C) rapid-cooled melts (e.g., RBT 04299, LEW86211) defined by primary dendritic or cellular solidification structures and high sulfide abundance. MET 00428 is identified as a B-C group hybrid, preserving evidence of both rapid solidification and subsequent annealing. Groups B and C align with compositional division of IIE irons as “main” (Group B) and Cu-rich (Group C) sets, confirming the importance of complementary descriptive details alongside compositional data for classification purposes.