Refractory inclusions in the pristine carbonaceous chondrites DOM 08004 and DOM 08006

• Published in: Meteoritics & Planetary Science
• Main Authors: Simon, Steven B., Grossman, Lawrence
• Other Authors: National Aeronautics and Space Administration
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1111/maps.12452; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fmaps.12452; https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.12452

Abstract The Antarctic carbonaceous chondrites DOM 08004 and DOM 08006 have been paired and classified as CO 3.0s. There is some uncertainty as to whether they should be paired and whether they are best classified as CO chondrites, but they provide an opportunity for the study of refractory inclusions that have not been modified by parent body processes. In this work, refractory inclusions in thin sections of DOM 08004 and 08006 are studied and compared with inclusions in ALHA 77307 ( CO 3.0) and Acfer 094 (C3.0, ungrouped). Results show that the DOM samples have refractory inclusion populations that are similar to each other but not typical of CO 3 chondrites; main differences are that the DOM samples are slightly richer in inclusions in general and, more specifically, in the proportions of grossite‐bearing inclusions. In DOM 08004 and DOM 08006, 12.4% and 6.6%, respectively, of the inclusions are grossite‐bearing. This is higher than the proportion found in Acfer 094 (5.2%), whereas none were found in ALHA 77307. Like those in Acfer 094, DOM inclusions are small (mostly <100 μm across) and fine‐grained, and thin rims of aluminous diopside±melilite are very common. Also like Acfer 094, most phases in the DOM inclusions have FeO contents higher than expected for primary refractory phases. In addition to typical inclusions, some unusual ones were found in DOM 08004, including a perovskite‐rich one with a rare, recently reported Sc‐, Al‐oxide and davisite; a very grossite‐rich inclusion with a small, hibonite‐rich core enclosed in a grossite mantle; and a relict, grossite‐rich inclusion enclosed in an Al‐rich chondrule. The CAI populations in the DOM samples are similar to each other and, based on grossite abundances, FeO enrichments and occurrences of rims are more Acfer 094‐like than CO 3‐like. An earlier history on an FeO‐rich parent was previously favored over nebular equilibria or in situ reactions to account for FeO enrichments in CAI s in the otherwise pristine chondrite Acfer 094, and a similar history ...