In message <[log in to unmask]>  writes:
> Dear all,
>
> My name is Graham Shields and I am a doctoral student at the ETH Zurich
> studying isotope stratigraphy around the Precambrian/Cambrian boundary in
> China and Mongolia.
>
> I would like to ask if anyone has experience with the interpretation of
> sulphur isotopes in phosphate. There is very little in the literature about
> this subject and I cannot believe that this avenue has been so little
> explored. Work carried out here in Zurich, in Bochum (courtesy of Harald
> Strauss) and at Vermont (courtesy of Stephen Howe) suggests that seawater
> sulphur isotope ratios have been preserved in peloidal phosphates from the
> Cambrian. Some sulphates are very slightly enriched in 34S. Any info.,
> comments would be most welcome before I start to put all this down on
> paper.
>
> Graham
>
> Dear Graham,

Sea water sulfate may indeed be preserved in most pelloidal phosphates. However,
if sulfate was partly reduced in interstitial water, the remaining sulfate
became heavier. Hence, the redox of the depositional & early diagenetic
environments of phosphorite formation may determine how much off the sulfur time
curve the sample may be. Indeed we observed in Phosphoria Formation Permian
phosphorites. (Piper & Kolodny, 1987) a correlation between delta-S and the
sulfate/phosphate ratio in the apatite. This study + some work by McArthur et al
(1986), Bliskovski et al. (1977) and Nathan and Nielsen (1980) were reviewed
(briefly) by myself and B. Luz in a chapter in "Isotopic Signatures and
Sedimentary Records" (editors Clauer & Chaudhuri), 1992, Springer Verlag. You
may want to look it up there. The least you will find is those references
yehoshua


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Yehoshua Kolodny,
Dept of Geology, The Hebrew University . Jerusalem. ISRAEL 91904
PHONES: off:(972) 2-6584685; dept.:2-6584686; home 2-636879;FAX:(972-2) 662581
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