Contrasts in maceral textures in progressive metamorphism versus near-surface hydrothermal metamorphism

The contrast in the textures of high reflectance vitrinite and liptinite in the Ragged edge exposures of western Kentucky's Herrin (No. 11) coal versus the macerals in regionally metamorphosed anthracites opens a window into the metamorphic mechanisms prevailing for both of the Ragged edge and regionally metamorphosed coals. Regionally (Barrovian) metamorphosed anthracite, at least in the cases noted in this study, was at a bituminous rank at the onset of enhanced metamorphism, contributing to the preservation of the bituminous-like appearance of the anthracite macerals. Exceptions are possible where melting and subsequent coking occurred, but melting is generally absent in the Barrovian-style Pennsylvania anthracites and the igneous/coal contact zone was sufficiently distant from the Cretaceous Colorado and New Mexico anthracites such that melting was not present. In contrast, the high-rank portions of the Ragged edge are lodged within and/or adjacent to high volatile bituminous coal; in some cases, metamorphosed fragments are juxtaposed with anthracite-rank fragments. High-reflectance vitrinites within the Ragged edge coal have textures reminiscent of peat and low-rank coals with no evidence of the softening of the vitrinite, suggesting that the metamorphism was the consequence of localized hydrothermal events influencing the peat or, at the most, the low-rank precursor to the extant high volatile bituminous coal.