RELATION OF COAL QUALITY TO COAL BED THICKNESS, APPALACHIAN BASIN, USA

Analysis of chemical and thickness data for over 3,000 channel samples from Pennsylvanian coal beds in the Appalachian Basin (U.S. Geological Survey Open-File Report 97-134) define characteristics of mean ash yield and sulfur, iron, and selected trace element concentrations (as-received, whole-coal basis) in relation to coal bed age and thickness (thick = ³28 in; thin = <28 in).  The low ash yield and S, Fe, As, Hg, Se, Ti, and Zr content of thick Morrowan coal beds suggest they were derived from ombrogenous peat that received low amounts of inorganic input, primarily from atmospheric deposition.  The low concentrations of S, Fe, As, and Hg in thick Morrowan and Atokan coal, relative to thin Morrowan and Atokan coal, suggest significant cycling or leaching loss of these elements during peat accumulation.  Thus, Atokan coal is also interpreted to be derived from ombrogenous peat.  The relatively high ash, Se, Ti, and Zr in thick Atokan coal, compared to thick Morrowan coal, may be the result of more intense (aerobic?) degradation of organic matter or more atmospheric (volcanic?) deposition in peat during the Atokan.  The high ash yield and S, Fe, As, Hg, Se, Ti, and Zr content of both thick and thin Desmoinesian, Missourian, and Virgilian (DMV) coal, compared to thick and thin Morrowan coal, suggest that the DMV coal beds were derived from topogenous peat that received inorganic input from surface water in the drainage basin in addition to atmospheric deposition.  In general, major and trace element concentrations are inversely related to coal bed thickness within a stratigraphic interval; Se, Ti, and Zr in Atokan coal beds are exceptions.

interval    thick     n    ash    S     Fe     As     Hg    Se     Ti      Zr

                   in                %     %     %    ppm  ppm  ppm   ppm  ppm

DMV         ³28  1,033  12     2.9   2.0    21    0.22   3.3     800    21

DMV         <28     486  13     2.8   2.1    36    0.25   3.6     910    24

Atokan       ³28    315   11    1.0    0.55  10    0.13   5.2  1,200    27

Atokan       <28    229   10    1.5    1.0    20    0.17   4.7     890    20

Morrowan  ³28    671    7.6  1.1    0.59  13    0.11   3.1     670    15

Morrowan  <28    493    7.4  1.6    0.95  29    0.15   2.7     547    13