Agnese Fazio^1,*, Massimo D’Orazio¹, Luigi Folco¹, Jérôme Gattacceca², Corinne Sonzogni²

¹Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
²CNRS-IRD Aix-Marseille Université, Centre Européen de Recherche et d’Enseignement de Géosciences de l’Environnement (CEREGE), UM34, Aix-en-Provence, France

Northwest Africa (NWA) 6583 is a silicate-bearing iron meteorite with Ni = 18 wt%. The oxygen isotope composition of the silicates (∆′¹⁷O = −0.439 ‰) indicates a genetic link with the IAB-complex. Other chemical, mineralogical, and textural features of NWA 6583 are consistent with classification as a new member of the IAB-complex. However, some unique features, e.g., the low Au content (1.13 μg g⁻¹) and the extremely reducing conditions of formation (approximately −3.5 ∆IW), distinguish NWA 6583 from the known IAB-complex irons and extend the properties of this group of meteorites. The chemical and textural features of NWA 6583 can be ascribed to a genesis by impact melting on a parent body of chondritic composition. This model is also consistent with one of the most recent models for the genesis of the IAB-complex. Northwest Africa 6583 provides a further example of the wide lithological and mineralogical variety that impact melting could produce on the surface of a single asteroid, especially if characterized by an important compositional heterogeneity in space and time like a regolith.

Reference
Fazio A, D’Orazio M, Folco L, Gattacceca J and Sonzogni C (in press) The extremely reduced silicate-bearing iron meteorite Northwest Africa 6583: Implications on the variety of the impact melt rocks of the IAB-complex parent body. Meteoritics & Planetary Science 
[doi:10.1111/maps.12231]
Published by arrangement with John Wiley & Sons

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