Metamorphic History and Sulfide Transformations in the Ksar El Goraane (Morocco) H5 Ordinary Chondrite

Sulfides are essential tracers for understanding the redox conditions, diffusion processes, and thermal mechanisms involved in the formation of ordinary chondrites. Their mineralogical and textural evolution provides valuable constraints on the metamorphic history of parent bodies. In this context, the Ksar El Goraane meteorite, which fell in Morocco in 2018 and is classified as an H5 ordinary chondrite, represents a particularly instructive case for investigating sulfur behavior during thermal metamorphism. Petrographic observations combined with geochemical data obtained by electron probe microanalysis (EPMA) and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the main silicate and sulfide phases and to evaluate their degree of chemical equilibration. The compositions of olivine (Fa18–20), Mg-Rich orthopyroxene, and sodic plagioclase (An10–15) display limited analytical dispersion and well-recrystallized textures, confirming that Ksar El Goraane experienced an equilibrated metamorphic grade consistent with an H5 ordinary chondrite. The sulfide assemblage is dominated by troilite (FeS), iron-rich pyrrhotite (Fe1−xS), and pentlandite ((Fe,Ni)9S8), with minor occurrences of pyrite (FeS2). Textural relationships and chemical homogeneity observed in backscattered electron images and elemental maps indicate progressive re-equilibration during thermal metamorphism. Formation and transformation temperatures of the sulfide phases are inferred through comparison with experimental and empirical constraints reported in the literature. These results suggest early high-temperature crystallization of troilite, followed by sulfur depletion leading to pyrrhotite formation, subsequent low-temperature exsolution of pentlandite, and localized late-stage pyrite crystallization.