TY - JOUR
T1 - Contrasts in maceral textures in progressive metamorphism versus near-surface hydrothermal metamorphism
AU - Hower, James C.
AU - O'Keefe, Jennifer M.K.
AU - Valentim, Bruno
AU - Guedes, Alexandra
N1 - Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/10/1
Y1 - 2021/10/1
N2 - 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.
AB - 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.
KW - Anthracite
KW - Barrovian metamorphism
KW - Herrin coal
KW - Kentucky
KW - Peat
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U2 - 10.1016/j.coal.2021.103840
DO - 10.1016/j.coal.2021.103840
M3 - Article
AN - SCOPUS:85112344956
SN - 0166-5162
VL - 246
JO - International Journal of Coal Geology
JF - International Journal of Coal Geology
M1 - 103840
ER -