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

Liam A. Bullock (Corresponding Author), John Parnell, Magali Perez, Adrian Boyce, Joerg Feldmann, Joseph G. T. Armstrong

Research output: Contribution to journalArticle

4 Citations (Scopus)
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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.
Original languageEnglish
Pages (from-to)37-49
Number of pages13
JournalScottish Journal of Geology
Volume54
Issue number1
Early online date10 Jan 2018
DOIs
Publication statusPublished - May 2018

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