Stepwise fluorination-a useful approach for the isotopic analysis of hydrous minerals

Marshall Haimson, L. Paul Knauth

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31 Scopus citations


Analytical uncertainties in oxygen isotopic studies of hydrous silica have been investigated using a partial fluorination procedure in which fractional oxygen yields are achieved by reducing the amount of fluorine. Stepwise reaction of opaline silica results in a set of sequential oxygen fractions which show a wide range of δ18O values due to variable amounts of water, organic matter, and other impurities, δ-values for successive fractions in non-biogenic opal systematically increase as water is reacted away and then remain constant to within ±0.2%. as the remaining silica reacts, δ-values in biogenic silica increase similarly but then decrease when low 18O oxide(?) impurities begin to react. The troublesome water component in opal is readily removed by Stepwise fluorination. This technique allows more precise oxygen isotope analysis of non-biogenic opal-A, and may improve the analytical precision for biogenic silica and any silicate mineral containing a significant water component.

Original languageEnglish (US)
Pages (from-to)1589-1595
Number of pages7
JournalGeochimica et Cosmochimica Acta
Issue number9
StatePublished - Sep 1983

ASJC Scopus subject areas

  • Geochemistry and Petrology


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