Oxygen-isotopic compositions of low-FeO relicts in high-FeO host chondrules in Acfer 094, a type 3.0 carbonaceous chondrite closely related to CM

Tak Kunihiro, Alan E. Rubin, John T. Wasson

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

With one exception, the low-FeO relict olivine grains within high-FeO porphyritic chondrules in the type 3.0 Acfer 094 carbonaceous chondrite have Δ17O (= δ17O - 0.52 × δ18O) values that are substantially more negative than those of the high-FeO olivine host materials. These results are similar to observations made earlier on chondrules in CO3.0 chondrites and are consistent with two independent models: (1) Nebular solids evolved from low-FeO, low-Δ17O compositions towards high-FeO, more positive Δ17O compositions; and (2) the range of compositions resulted from the mixing of two independently formed components. The two models predict different trajectories on a Δ17O vs. log Fe/Mg (olivine) diagram, but our sample set has too few values at intermediate Fe/Mg ratios to yield a definitive answer. Published data showing that Acfer 094 has higher volatile contents than CO chondrites suggest a closer link to CM chondrites. This is consistent with the high modal matrix abundance in Acfer 094 (49 vol.%). Acfer 094 may be an unaltered CM chondrite or an exceptionally matrix-rich CO chondrite. Chondrules in Acfer 094 and in CO and CM carbonaceous chondrites appear to sample the same population. Textural differences between Acfer 094 and CM chondrites are largely attributable to the high degree of hydrothermal alteration that the CM chondrites experienced in an asteroidal setting.

Original languageEnglish
Pages (from-to)3831-3840
Number of pages10
JournalGeochimica et Cosmochimica Acta
Volume69
Issue number15
DOIs
Publication statusPublished - Aug 1 2005
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology

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