Thoroughly anomalous chromium in Orgueil

F. A. Podosek, U. Ott, J. C. Brannon, C. R. Neal, T. J. Bernatowicz, P. Swan, S. E. Mahan

Research output: Contribution to journalArticle

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Abstract

Stepwise dissolution of bulk Orgueil reveals that all of the Cr in the whole rock is isotopically anomalous, with an anomaly pattern that is thus far unique. Most of the Cr (along with other major and minor cations) is dissolved by acetic and nitric acids; it is deficient in 54Cr by ∼5 ∈. Subsequent treatment with hydrochloric acid dissolves a small fraction of the Cr with positive 54Cr anomalies, up to ∼210 ∈. Mass balance indicates that whole rock Cr is isotopically normal within analytical uncertainties. The least extravagant interpretation of these results is that some mineral phase is enriched in a heavy-Cr nucleosynthetic component, while most of the Cr is a homogenized mixture of diverse nucleosynthetic components that would be normal except for lack of the postulated heavy Cr carrier. The carrier is likely, but not necessarily, presolar interstellar grains. Its identity is unknown and constrained only circumstantially: it must be relatively rich in Cr, it is substantially soluble in hydrochloric acid, and it is not magnetite or spinel/chromite. Scanning electron microscope (SEM) examination of Orgueil reveals candidate Cr-rich oxides, silicates, sulfides and phosphides, but none of these can be identified yet as the heavy Cr carrier. Whether presolar or not, the carrier is not chemically resistant and likely not thermally refractory, thereby differing from most other phases known to host isotopic anomalies. Its survival (or production) thus establishes constraints on a different regime of nebular history.

Original languageEnglish
Pages (from-to)617-627
Number of pages11
JournalMeteoritics and Planetary Science
Volume32
Issue number5
Publication statusPublished - Sep 1997

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chromium
hydrochloric acid
anomaly
anomalies
rocks
chromite
nitric acid
acetic acid
rock
spinel
phosphides
chromites
magnetite
mass balance
refractories
silicate
cation
dissolution
sulfide
oxide

ASJC Scopus subject areas

  • Geophysics

Cite this

Podosek, F. A., Ott, U., Brannon, J. C., Neal, C. R., Bernatowicz, T. J., Swan, P., & Mahan, S. E. (1997). Thoroughly anomalous chromium in Orgueil. Meteoritics and Planetary Science, 32(5), 617-627.

Thoroughly anomalous chromium in Orgueil. / Podosek, F. A.; Ott, U.; Brannon, J. C.; Neal, C. R.; Bernatowicz, T. J.; Swan, P.; Mahan, S. E.

In: Meteoritics and Planetary Science, Vol. 32, No. 5, 09.1997, p. 617-627.

Research output: Contribution to journalArticle

Podosek, FA, Ott, U, Brannon, JC, Neal, CR, Bernatowicz, TJ, Swan, P & Mahan, SE 1997, 'Thoroughly anomalous chromium in Orgueil', Meteoritics and Planetary Science, vol. 32, no. 5, pp. 617-627.
Podosek FA, Ott U, Brannon JC, Neal CR, Bernatowicz TJ, Swan P et al. Thoroughly anomalous chromium in Orgueil. Meteoritics and Planetary Science. 1997 Sep;32(5):617-627.
Podosek, F. A. ; Ott, U. ; Brannon, J. C. ; Neal, C. R. ; Bernatowicz, T. J. ; Swan, P. ; Mahan, S. E. / Thoroughly anomalous chromium in Orgueil. In: Meteoritics and Planetary Science. 1997 ; Vol. 32, No. 5. pp. 617-627.
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