Abstract
Francolite, the phosphorus-bearing mineral of nearly all sedimentary phosphorites, has a variable chemical composition which can be represented by (Ca, Mg, Sr, Na)10(PO4, SO4, CO3)6F2–3. It is now well established that this mineral can form authigenically in organic-rich muds1 or by replacement of precursor carbonate2 but the origin of some phosphorite deposits is still in dispute or unknown. Recently the isotopic composition of structural PO4–O, CO3–C+O, and SO4–S has been considered in attempts to resolve this problem3–9. Structural CO3–C has proved particularly useful in discriminating between phosphatized carbonates and authigenic phosphorites, the former preserving the δ13C of its precursor and the latter containing a substantial proportion of lighter carbon generated by anaerobic bacterial degradation of organic matter4,5. From new δ34S data we present here a more refined interpretation of the formational environment. δ34S values heavier than that of sea-water indicate that genesis has occurred within the bacterial sulphate reduction zone whilst δ34S values lighter than that of seawater delimit formation to a zone between sulphate reducing and overlying oxic conditions where isotopically light H2S is re-oxidized.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Bremner, J. M. J. geol. Soc. Lond. 137, 773–786 (1980).
Cullen, D. J. SEPM Spec. Publ. No. 29, 139–148 (1980).
Kolodny, Y. & Kaplan, I. R. J. sedim. Petrol. 40, 954–959 (1970).
McArthur, J. M., Coleman, M. L. & Bremner, J. M. J. geol. Soc. Lond. 137, 689–673 (1980).
Benmore, R. A., McArthur, J. M. & Coleman, M. L. Proc. Int. Seminar and Field Workshop on phosphorite (IGCP-156), Udaipur, India (in the press).
Benmore, R. A. thesis, Univ. College London (in preparation).
Bliskovskiy, V. Z., Grinenko, V. A., Migdisov, A. A. & Savina, L. I. Geochem. Int. 8, 148–155 (1978).
Nathan, Y. & Nielsen, H. SEPM Spec. Publ. No. 29, 73–78 (1980).
Longinelli, A. & Nutti, S. Earth planet. Sci. Lett. 5, 13–16 (1968).
Culkin, F. in Chemical Oceanography (eds Riley, J. P. & Skirrow, G.) (Academic, London, 1965).
Redfield, A. C. Am. Sci. 46, 202–226 (1958).
Baturin, G. N. Oceanology, 12, 849–855 (1972).
Claypool, G. E., Holser, W. T., Kaplan, L. R., Saka, J. & Zak, I. Chem. Geol. 28, 199–260 (1980).
Irwin, H., Curtis, C. & Coleman, M. L. Nature 269, 209–213 (1977).
Craig, H. Geochim. cosmochim. Acta 3, 53–92 (1953).
McCrea, J. M. J. Chem. Phys. 18, 849–57 (1950).
Coleman, M. L. & Moore, M. P. Analyt. Chem. 50, 1594 (1978).
Schoell, M., Faber, E. & Coleman, M. L. Org. Geochem. (in the press).
Burnett, W. C., Veeh, H. H. & Soutar, A. SEPM Spec. Publ. No. 29, 61–71 (1980).
Nathan, Y. & Sass, E. Chem. Geol. 34, 103–111 (1981).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Benmore, R., Coleman, M. & McArthur, J. Origin of sedimentary francolite from its sulphur and carbon isotope composition. Nature 302, 516–518 (1983). https://doi.org/10.1038/302516a0
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/302516a0
This article is cited by
-
Overgrowths of large authigenic apatite crystals on the surface of conodonts from Cantabrian limestones (Spain)
Facies (2012)
-
Pétrographie et géochimie comparées des pellets phosphatés et de leur gangue dans le gisement phosphaté de Ras-Draâ (Tunisie). Implications sur la genèse des pellets phosphatés
Swiss Journal of Geosciences (2010)
-
Organic components in phragmocones of boreal triassic ammonoids: Implications for ammonoid biology
Paläontologische Zeitschrift (1991)
-
The Multiple Factors and Multiple Stages Involved in Sedimentary Ore Genesis
Chinese Journal of Geochemistry (1990)
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.