Northwest Africa 4269: a metal-rich eucrite from the Algerian Sahara
Abdelmadjid Seddiki, Bertrand Moine, Jérôme Bascou, Ratiba Kared, Jean Yves Cottin, Marguerite Godard, François Faure, Richard C. Greenwood, Ian A. Franchi
Geochemistry
Volume 85, Issue 4, December 2025, 126363
“Northwest Africa (NWA) 4269 is an anomalous monomict eucrite that is characterized by a very high content of metallic iron (~ 3 %). It shows various textures (relict magmatic sub-ophitic, granulitic areas as coarse and fine-grained). NWA 4269 also shows petrographic evidence of secondary sub-solidus reheating events. Pyroxenes have homogeneous compositions and are iron-rich. NWA 4269 is metamorphosed type 5. It has a normal HED oxygen isotope composition. The chemical composition of NWA 4269 has characteristics similar to that of Nuevo-Laredo trend eucrites. Metal is extremely abundant in the fine-grained areas (~ 10 %). Metal also has a very low Ni content (Ni < 0.1 %) that excludes a direct origin from a chondrite-like impactor. Origin of the pure-Fe groundmass metal remains enigmatic. The high metal content in NWA 4269 can be interpreted as having formed via the reduction of FeO and probably also by desulfidation of pre-existing troilite. Iron metal could have formed by deposition from a Fe-rich fluid that, probably after an event that triggered sudden reduction. NWA 4269 has normal HED oxygen isotope compositions and interpreted as belonging to the 4-Vesta asteroid.”
