Tellurium Enrichment in Jurassic Coal, Brora, Scotland
Department of Geology & Petroleum Geology, Meston Building, University of Aberdeen, King’s College, Aberdeen AB24 3UE, UK
Trace Element Speciation Laboratory (TESLA), Department of Chemistry, Meston Building, University of Aberdeen, King’s College, Aberdeen AB24 3UE, UK
Author to whom correspondence should be addressed.
Minerals 2017, 7(12), 231; https://doi.org/10.3390/min7120231
Received: 31 October 2017 / Revised: 20 November 2017 / Accepted: 21 November 2017 / Published: 23 November 2017
(This article belongs to the Special Issue Toxic Mineral Matter in Coal and Coal Combustion Products)
Mid-Jurassic pyritic coals exposed at the village of Brora, northern Scotland, UK, contain a marked enrichment of tellurium (Te) relative to crustal mean, average world coal compositions and British Isles Carboniferous coals. The Te content of Brora coal pyrite is more than one order of magnitude higher than in sampled pyrite of Carboniferous coals. The Te enrichment coincides with selenium (Se) and mercury (Hg) enrichment in the rims of pyrite, and Se/Te is much lower than in pyrites of Carboniferous coals. Initial pyrite formation is attributed to early burial (syn-diagenesis), with incorporation of Te, Se, Hg and lead (Pb) during later pyrite formation. The source of Te may have been a local hydrothermal system which was responsible for alluvial gold (Au) in the region, with some Au in Brora headwaters occurring as tellurides. Anomalous Te is not ubiquitous in coal, but may occur locally, and is detectable by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS).