Distribution of Ree's in Hcl/HNO3-residues of Antarctic Uoc's and Its Implications To Their Metamorphic Geneses On UOC Parent Bodies

Mitsuru Ebihara, Koh lchl HlRANO, Hiromasa Ozaki

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Abstract

In order to understand the metamorphic history of the parent bodies of unequilibrated ordinary chondrites (UOC's), we compare REE distributions in the HCl/HNOj (add)-residues of seven Antarc-tic UOC' s with those of equilibrated ordinary chondrites (EOC's), REE parameters designated to characterize the abundance pattern of REE's—normalized La abundance, normalized La/Lu abun-dance ratio and the degree of Eu anomaly—were found to be highly variable in the acid-residues of UOC's, suggesting that REE's were redistributed on UOC parent bodies. in contrast, the REE parameters are fairly constant in the acid-residues of EOC's, suggesting that REE distribution attained equilibrium on EOC parent bodies. The REE parameters for the acid-residues of UOC's are poorly cor-related with the In, Zn and Se contents in the whole rock samples analyzed in this study, but appear to correlate with carbon content. This implies that REE parameters can be used as indices for the subclassification of UOC's, From the viewpoint of REE distribution, ALH 77011 (and its paired ALH 78038) appears to be one of the least metamorphosed UOC's.

Original languageEnglish
Pages (from-to)425-434
Number of pages10
JournalGeochemical Journal
Volume26
Issue number6
DOIs
Publication statusPublished - 1992 Jan 1
Externally publishedYes

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ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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