TY - JOUR
T1 - Late Permian age of NH 4 -bearing illite in anthracite from eastern Pennsylvania
T2 - temporal limits on coalification in the central Appalachians
AU - Daniels, E. J.
AU - Aronson, J. L.
AU - Altanar, S. P.
AU - Clauer, N.
PY - 1994
Y1 - 1994
N2 - Authigenic NH 4 -bearing illites in coal fractures from the Anthracite region of eastern Pennsylvania yield individual K/Ar dates of 236-253 Ma (±8 m.y.) and a composite isochron of 253 Ma (±8 m.y.). The age of NH 4 -bearing illite authigenesis should reflect the time at which coal attained anthracite rank, because mineralogical and geochemical evidence indicates that NH 4 -bearing illite formed exclusively during anthracite formation (T = 200-275°C) from organically derived nitrogen and a kaolinite precursor. The oldest K/Ar date of 253 Ma (±8 m.y.) is considered to be a minimum age for NH 4 -illite authigenesis and anthracite formation. Based on the retention of a detrital age signature in the <0.5-μm size fraction of shale samples, as well as theoretical and empirical estimates of illite closure temperatures, the oldest K/Ar date of 253 Ma is estimated to be only slightly younger than the time at which coal-bearing rocks experienced peak temperatures associated with anthracite formation, for which an age range of 265-255 Ma is suggested. -from Authors
AB - Authigenic NH 4 -bearing illites in coal fractures from the Anthracite region of eastern Pennsylvania yield individual K/Ar dates of 236-253 Ma (±8 m.y.) and a composite isochron of 253 Ma (±8 m.y.). The age of NH 4 -bearing illite authigenesis should reflect the time at which coal attained anthracite rank, because mineralogical and geochemical evidence indicates that NH 4 -bearing illite formed exclusively during anthracite formation (T = 200-275°C) from organically derived nitrogen and a kaolinite precursor. The oldest K/Ar date of 253 Ma (±8 m.y.) is considered to be a minimum age for NH 4 -illite authigenesis and anthracite formation. Based on the retention of a detrital age signature in the <0.5-μm size fraction of shale samples, as well as theoretical and empirical estimates of illite closure temperatures, the oldest K/Ar date of 253 Ma is estimated to be only slightly younger than the time at which coal-bearing rocks experienced peak temperatures associated with anthracite formation, for which an age range of 265-255 Ma is suggested. -from Authors
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U2 - 10.1130/0016-7606(1994)106<0760:LPAONB>2.3.CO;2
DO - 10.1130/0016-7606(1994)106<0760:LPAONB>2.3.CO;2
M3 - Article
AN - SCOPUS:84879880384
SN - 0016-7606
VL - 106
SP - 760
EP - 766
JO - Geological Society of America Bulletin
JF - Geological Society of America Bulletin
IS - 6
ER -