Genetics, age, and crystallization history of group IC iron meteorites

The IC iron meteorite group is characterized utilizing nucleosynthetic mass-independent isotopic compo-sitions and 182W age constraints, coupled with siderophile element concentration measurements and modeling of crystal-liquid fractionation processes. The six IC irons analyzed, Arispe, Bendego, Chihuahua City, Nocoleche, NWA 2743, and Winburg have indistinguishable Mo and W genetic isotopic compositions and are consistent with derivation from the same parent body, which formed in the non -carbonaceous (NC) nebular reservoir. A pre-exposure l182W value (parts-per-million deviations in iso-topic ratios from terrestrial standards) for the six IC irons of-337 & PLUSMN; 5 corresponds to a metal-silicate seg-regation age of 1.0 & PLUSMN; 0.4 Myr after calcium-aluminum-rich inclusion (CAI) formation. This age is similar to those determined for other NC iron groups. Siderophile element abundances of the IC irons are generally similar and characterized by minor depletions in the more volatile siderophile elements. Highly sidero-phile element (HSE) distributions among the IC group suggest that the initial parent body core was S-rich, with preferred model results indicating an initial melt composition with-18 wt% S, 2 wt% P and 0.03 wt % C. Processes in addition to fractional crystallization, such as late-stage parent body modification, pos-sibly as a result of impacts, and subsequent metal-melt mixing, are required within the first 100 Myr of Solar System history to explain the range of HSE abundances.& COPY; 2022 Elsevier Ltd. All rights reserved.