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

Multi-stage pyrite genesis and epigenetic selenium enrichment of Greenburn coals (East Ayrshire)
Multi-stage pyrite genesis and epigenetic selenium enrichment of Greenburn coals (East Ayrshire)
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.
0036-9276
37-49
Bullock, Liam A.
c6ffb9b0-0a54-4ab2-9edb-f97280e6ce2d
Parnell, John
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Perez, Magali
496b62b9-ca3a-4b78-aaf7-4d14627f5771
Boyce, Adrian
a1e40a10-98ba-45a9-8582-6327a14d6072
Feldmann, Joerg
301ee755-b3df-4b0e-9c5e-3ca0f7d1ccc5
Armstrong, Joseph G.t.
e787408b-d6cd-4355-963e-8590a0ce11db
Bullock, Liam A.
c6ffb9b0-0a54-4ab2-9edb-f97280e6ce2d
Parnell, John
b86302b0-b930-4b7c-9786-13abc612fef7
Perez, Magali
496b62b9-ca3a-4b78-aaf7-4d14627f5771
Boyce, Adrian
a1e40a10-98ba-45a9-8582-6327a14d6072
Feldmann, Joerg
301ee755-b3df-4b0e-9c5e-3ca0f7d1ccc5
Armstrong, Joseph G.t.
e787408b-d6cd-4355-963e-8590a0ce11db

Bullock, Liam A., Parnell, John, Perez, Magali, Boyce, Adrian, Feldmann, Joerg and Armstrong, Joseph G.t. (2018) Multi-stage pyrite genesis and epigenetic selenium enrichment of Greenburn coals (East Ayrshire). Scottish Journal of Geology, 54 (1), 37-49. (doi:10.1144/sjg2017-010).

Record type: Article

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.

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Accepted/In Press date: 27 October 2017
e-pub ahead of print date: 10 January 2018
Published date: May 2018

Identifiers

Local EPrints ID: 421712
URI: https://eprints.soton.ac.uk/id/eprint/421712
ISSN: 0036-9276
PURE UUID: 45bd27f2-01a4-4832-9ffe-61b921e468fe

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Date deposited: 22 Jun 2018 16:30
Last modified: 13 Mar 2019 18:24

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