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A Sulphur Isotope Study of Iron Sulphides in the Late Precambrian Dalradian Easdale Slate Formation, Argyll, Scotland

Published online by Cambridge University Press:  05 July 2018

A. J. Hall ,
A. J. Boyce  and
A. E. Fallick
A. J. Hall
Affiliation:
Department of Applied Geology, University of Strathclyde, Glasgow G1 1XJ
A. J. Boyce
Affiliation:
Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 0QU
A. E. Fallick
Affiliation:
Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 0QU
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Abstract

Pyritic slates from the late Precambrian, Middle Dalradian Argyll Group Easdale Slate Formation, contain mainly quartz, muscovite and chlorite with variable amounts of dolomite, albite and paragonite. Slates from Easdale Island and Cuan Ferry contain pyrite porphyroblasts with δ34S = + 12 to + 16‰. The pyrite grew during a post-tectonic retrogressive event at the expense ofpyrrhotine which formed during the main regional metamorphism of the Grampian orogeny by reduction of diagenetic pyrite. Slate from Oban contains abundant diagenetic framboidal pyrite and small syn-tectonic pyrite porphyroblasts with δ34S = +22‰. This pyrite was not all reduced to pyrrhotine on metamorphism so there was little retrogressive growth of pyrite. Metamorphism appears to have homogenized local (cm scale at least) isotopic inhomogeneities and preserved an average seawater-sulphate-sulphide isotopic fractionation value. Middle Dalradian seawater-sulphate had a δ34S value of about + 35‰, so the small fractionations are appropriate for bacteriogenic reduction in bituminous sediments, the heavier sulphide in the case of the Oban slate indicating more rapid reduction of sulphate. Lower Dalradian Appin Group, Ballachulish slate contains pyrite with δ34S = +15±2‰ and is best interpreted as forming in the same manner as the Easdale slates of Easdale Island and Cuan Ferry; the sharp increase in late Precambrian ocean-sulphate sulphur isotope signature from +15 to > +30‰ therefore occurred by Lower Dalradian Appin Group times.

Keywords

sulphur isotopesiron sulphideDalradianArgyllScotland
Type
Petrology and Geochemistry
Information
Mineralogical Magazine , Volume 52 , Issue 367 , September 1988 , pp. 483 - 490
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1988

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References

Anderton, R. (1985) Scott. J. Geol. 4, 407-36.CrossRefGoogle Scholar
Allison, I., and Russell, M.J. (1985) J. Sed. Petrology 55, 6,917–18.Google Scholar
Claypool, G.E., Holser, W.T., Kaplan, I.R., Sakai, H., and Zak, I. (1980) Chem. Geol. 28, 199-260.CrossRefGoogle Scholar
Craig, H. (1957) Geochim. Cosmochim. Acta 12, 133-49.CrossRefGoogle Scholar
Ferry, J.M. (1981) Am. Mineral. 66, 908-30.Google Scholar
Fisher, I. St. J., and Hudson, J.D. (1987) In Marine Petroleum Source Rocks (J. Brooks and A. J. Fleet, eds.), Geol. Soc. Special Publ. 26, 69-78.Google Scholar
Hall, A.J. (1982) Mineral. Deposita 17, 40-19.CrossRefGoogle Scholar
Hall, A.J. (1986) Mineral. Mag. 50, 223-9.CrossRefGoogle Scholar
Boyce, A.J., and Fallick, A.E. (1987) Chem. Geol. (Isotope Geoscience Section) 65, 305-10.Google Scholar
Ohmoto, H., and Rye, R.O. (1979) In Geochemistry of Hydrothermal Ore Deposits (H. L. Barnes, ed.), Wiley, New York 509-63.Google Scholar
Pattrick, R.A.D., Russell, M.J., and Coleman, M.L. (1979) Discussions and contributions. Trans. lnstn. Min. Metall. (Sect. B: Appl. Earth Sci.) 88, 18-45.Google Scholar
Peach, B.N., Kynaston, H., and Muff, H.B. (1909) Mems. Geol. Survey of Scotland 36.Google Scholar
Robinson, B.W., and Kusakabe, M. (1975) Anal. Chem. 47, 117-981.CrossRefGoogle Scholar
Russell, M.J., Hall, A.J., Willan, R.C.R., Allison, I., Anderton, R., and Bowes, G. (1984) In Prospecting in areas of glaciated terrain 1984, symposium volume, Instn. Mining Metall., London, 159-70.Google Scholar
Thompson, J.B., Jr. (1972) Proc. 24th Intern. Geol. Congress 10, 27-35.Google Scholar
Willan, R.C.R., and Coleman, M.L. (1983) Econ. Geol. 78, 1619-56.CrossRefGoogle Scholar