Geological controls on the sulphur distribution in British Carboniferous coals: a review and reappraisal

The very extensive literature on sulphur in peats and coals is reviewed and four case histories from British coalfields are considered. In the Parkgat e seam (Langsettian) from the Nottinghamshire coalfield, the variation in t he total sulphur content is attributed to pyritic sulphur, with organic sul phur also significant but showing a smaller variation. Sulphate sulphur is negligible. There is a spatial variation in the sulphur concentrations in i ndividual sections (plies) of the Parkgate seam, but this is unrelated to o ther sections of the seam and to identifiable post-depositional controls, t hereby providing indirect evidence of a depositional control on sulphur inc orporation. In the Main Bright (Duckmantian, North Derbyshire coalfield) an d Threequarters seams (Langsettian, North Derbyshire-Nottinghamshire coalfi elds), the depositional control is shown to be related to contemporaneous c hannels. There is a hierarchy of channels and it is concluded that these pr ovided access of more saline waters into the peat mire. Coals associated wi th marine bands often show high sulphur contents, but there are exceptions, particularly in the Scottish Namurian as exemplified by the Upper Hirst se am where it is thought that there was no contemporary ingress of saline wat ers. Three Westphalian depositional provinces are recognised on the basis o f channel sandstone loci and there is the possibility that different source areas influenced the salinity/sulphate content in the mires. There is some evidence of regional differences in the sulphur content of British coals, which is consistent with the distribution of the three provinces. On the ot her hand, there is irrefutable evidence that access of seawater leads to hi gh sulphur coals and possibly the marine influence was more pervasive than is generally recognised. There is supporting geochemical evidence of enrich ment of trace elements in coals which is indicative of a seawater source. ( C) 1999 Elsevier Science B.V. All rights reserved.