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Minerals 2015, 5(3), 592-622;

Petrology, Palynology, and Geochemistry of Gray Hawk Coal (Early Pennsylvanian, Langsettian) in Eastern Kentucky, USA

Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY 40511, USA
Kentucky Geological Survey, Lexington, KY 40506, USA
Department of Earth & Space Science, Morehead State University, Morehead, KY 40351, USA
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology (Beijing), Beijing 100083, China
School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia
Author to whom correspondence should be addressed.
Academic Editor: Karen Hudson-Edwards
Received: 13 July 2015 / Revised: 26 August 2015 / Accepted: 31 August 2015 / Published: 11 September 2015
(This article belongs to the Special Issue Minerals in Coal)
Full-Text   |   PDF [5161 KB, uploaded 11 September 2015]   |  


This study presents recently collected data examining the organic petrology, palynology, mineralogy and geochemistry of the Gray Hawk coal bed. From the Early Pennsylvanian, Langsettian substage, Gray Hawk coal has been mined near the western edge of the eastern Kentucky portion of the Central Appalachian coalfield. While the coal is thin, rarely more than 0.5-m thick, it has a low-ash yield and a low-S content, making it an important local resource. The Gray Hawk coal palynology is dominated by Lycospora spp., and contains a diverse spectrum of small lycopods, tree ferns, small ferns, calamites, and gymnosperms. The maceral assemblages show an abundance of collotelinite, telinite, vitrodetrinite, fusinite, and semifusinite. Fecal pellet-derived macrinite, albeit with more compaction than is typically seen in younger coals, was observed in the Gray Hawk coal. The minerals in the coal are dominated by clay minerals (e.g., kaolinite, mixed-layer illite/smectite, illite), and to a lesser extent, pyrite, quartz, and iron III hydroxyl-sulfate, along with traces of chlorite, and in some cases, jarosite, szomolnokite, anatase, and calcite. The clay minerals are of authigenic and detrital origins. The occurrence of anatase as cell-fillings also indicates an authigenic origin. With the exception of Ge and As, which are slightly enriched in the coals, the concentrations of other trace elements are either close to or much lower than the averages for world hard coals. Arsenic and Hg are also enriched in the top bench of the coal and probably occur in pyrite. The elemental associations (e.g., Al2O3/TiO2, Cr/Th-Sc/Th) indicate a sediment-source region with intermediate and felsic compositions. Rare metals, including Ga, rare earth elements and Ge, are highly enriched in the coal ashes, and the Gray Hawk coals have a great potential for industrial use of these metals. The rare earth elements in the samples are weakly fractionated or are characterized by heavy-REE enrichment, indicating an input of natural waters or probably epithermal solutions. View Full-Text
Keywords: trace elements in coal; minerals in coal; epiphyllous fungi; macrinite; Gray Hawk coal trace elements in coal; minerals in coal; epiphyllous fungi; macrinite; Gray Hawk coal

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Hower, J.C.; Eble, C.F.; O'Keefe, J.M.K.; Dai, S.; Wang, P.; Xie, P.; Liu, J.; Ward, C.R.; French, D. Petrology, Palynology, and Geochemistry of Gray Hawk Coal (Early Pennsylvanian, Langsettian) in Eastern Kentucky, USA. Minerals 2015, 5, 592-622.

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