Diagenetic stability of the isotopic composition of phosphate-oxygen: Palaeoenvironmental implications

J. M. McArthur, A. Herczeg

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26 Citations (Scopus)

Abstract

Meteoric diagenesis of the Lower Pliocene Varswater Formation phosphate deposit, Cape Province, South Africa, has altered the chemistry of the francolite component. The isotopic composition of the phosphate-oxygen has been changed, as have other chemical and isotopic parameters that are known to be susceptible to meteoric diagenesis. Reduced major axis regressions between δ 18O PO4 and Sr/Ca, 87Sr/ 86Sr and francolite-δ 13C CO3, and the correlation of francolite-δ 18O CO3 and francolite-δ 13C CO3, predict an original isotopic composition of +30.7‰ (SMOW) for francolite-δ 18O CO3 and + 22.7‰ (SMOW) for francolite-δ 18O PO4. These data fix the temperature of phosphogenesis at 16°C and the δ 18O of the phosphatizing fluid as +0.3‰ (SMOW).

Original languageEnglish
Pages (from-to)119-124
Number of pages6
JournalGeological Society Special Publication
Volume52
DOIs
Publication statusPublished - 1990
Externally publishedYes

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