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

摘要

Northwest Africa (NWA) 6583 is a silicate-bearing iron meteorite with Ni = 18 wt%.\udThe oxygen isotope composition of the silicates (Δ′17O = 0.439 &) indicates a genetic link\udwith the IAB-complex. Other chemical, mineralogical, and textural features of NWA 6583 are\udconsistent with classification as a new member of the IAB-complex. However, some unique\udfeatures, e.g., the low Au content (1.13 lg g\ud1) and the extremely reducing conditions of\udformation (approximately 3.5 ΔIW), distinguish NWA 6583 from the known IAB-complex\udirons and extend the properties of this group of meteorites. The chemical and textural features\udof NWA 6583 can be ascribed to a genesis by impact melting on a parent body of chondritic\udcomposition. This model is also consistent with one of the most recent models for the genesis of\udthe IAB-complex. Northwest Africa 6583 provides a further example of the wide lithological\udand mineralogical variety that impact melting could produce on the surface of a single asteroid,\udespecially if characterized by an important compositional heterogeneity in space and time like a\udregolith.