Multi-stage pyrite genesis and epigenetic selenium enrichment of Greenburn coals (East Ayrshire)

Bullock, L. A., Parnell, J., Perez, M., Boyce, A. , Feldmann, J. and Armstrong, J. G.T. (2018) Multi-stage pyrite genesis and epigenetic selenium enrichment of Greenburn coals (East Ayrshire). Scottish Journal of Geology, 54(1), pp. 37-49. (doi: 10.1144/sjg2017-010)

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Abstract

Carboniferous coals of the Ayrshire Coalfield are enriched in selenium (Se) relative to average UK and world compositions, substituting for sulphur in pyrite. Greenburn surface mine coals are characterized by syngenetic concretionary pyrite (c. 15% total area), occurring as bedding-parallel banding, and later-formed (epigenetic) cross-cutting pyrite in cleats (c. 9% total area). In these, sulphur isotope compositions for both syngenetic and epigenetic pyrite include isotopically light and heavy variants, suggesting diagenetic and hydrothermal fluid formation. Late/post-Visean cleat-filling pyrite is enriched in Se (up to 266 ppm) compared to the earlier-formed material (Se up to 181 ppm). Anomalous Se may have been sourced from near-by sulphidic Dalradian metamorphic rocks. Initial Se sequestration is associated with syngenetic pyrite mineralization, absorbed from seawater and pore waters, with additional Se introduced from fluids mobilized during epigenetic pyrite formation. Cleats from local brittle fracturing provided channels for fluid flow and a locus for precipitation of comparatively high-Se pyrite. Permian dolerite intrusions may have provided an enrichment source and/or fluid distribution mechanism. The Se concentrations of the Greenburn coals relate to multi-stage mineralization, with cleat-filling pyrite showing the highest Se content, and highlight the potential for high Se in similarly altered and fractured coal deposits worldwide.

Item Type:Articles
Additional Information:Funding provided by NERC Security of Supply programme (grant NE/L001764/1).
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Boyce, Professor Adrian
Authors: Bullock, L. A., Parnell, J., Perez, M., Boyce, A., Feldmann, J., and Armstrong, J. G.T.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Scottish Journal of Geology
Publisher:Geological Society Publishing House
ISSN:0036-9276
ISSN (Online):2041-4951
Published Online:10 January 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in Scottish Journal of Geology 54(1): 37-49
Publisher Policy:Reproduced under a Creative Commons License

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