Petrographic and Geochemical Anatomy of Lithotypes from the Blue Gem Coal Bed, Southeastern Kentucky

Density gradient centrifugation (DGC) was applied to three benches of the low-sulfur, low-ash Blue Gem coal bed from Knox County, Kentucky. DGC samples were analyzed by proximate, ultimate, PIXE, FTIR, and coal petrographic techniques. The middle lithotype has an ash geochemistry influenced by carbonate associations, with an apparent variation in the carbonate substitution through the density range. The basal lithotype has a higher mineral content than the latter lithotype and appears to be enriched in silicate minerals. Cr, V, Co, Mn, Ti, and Zr are also enriched in the basal lithotype. A number of elements are concentrated in the high-vitrinite (>90%) range including Ga, Ge, and As; but it is less clear whether these trends are associated with the type of vitrinite within this range or are merely a function of the relative concentration of vitrinite.