Late Permian age of NH[sub 4]-bearing illite in anthracite from eastern Pennsylvania. Temporal limits on coalification in the central Appalachians
- Univ. of Illinois, Urbana, IL (United States)
- Case Western Reserve Univ., Cleveland, OH (United States)
- Centre de Geochimie de la Surface, Strasbourg (France)
Authigenic NH[sub 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.). Rh/Sr data for the same samples indicate an isochron of 260 Ma ([+-]44 m.y.), consistent with the more precise K/Ar data. The age of NH[sub 4]-bearing illite authigenesis should reflect the time at which coal attained anthracite rank, because mineralogical and geochemical evidence indicates that NH[sub 4]-bearing illite formed exclusively during anthracite formation (T = 200-275[degree]C) from organically derived nitrogen and a kaolinite precursor. Similar Late Permian K/Ar dates for both NH[sub 4]-rich illite and K-illite in anthracite fractures and lack of correlation between percent NH[sub 4] substitution in illite and the K/Ar date suggest that NH[sub 4] does not influence significantly the closure temperature of illite and, thus, that NH[sub 4]-rich illite can be used for dating the time of authigenesis. Given the uncertainties in closure temperatures for illite as well as the maximum temperatures for anthracite formation, we consider the oldest K/Ar date of 253 Ma ([+-]8 m.y.) to be a minimum age for NH[sub 4]-illite authigenesis and anthracite formation. 33 refs., 4 figs., 4 tabs.
- OSTI ID:
- 7271496
- Journal Information:
- Geological Society of America, Bulletin; (United States), Vol. 106:6; ISSN 0016-7606
- Country of Publication:
- United States
- Language:
- English
Similar Records
Late Permian age of ammonium-bearing illite in Pennsylvania anthracites: Temporal constraints on coalification in the central Appalachians
Clay mineral authigenesis in coal and shale from the Anthracite region, Pennsylvania
Related Subjects
58 GEOSCIENCES
COALIFICATION
AGE ESTIMATION
AMMONIUM COMPOUNDS
ANTHRACITE
APPALACHIAN MOUNTAINS
COMPILED DATA
HYDROCHLORIC ACID
ILLITE
KAOLINITE
LEACHING
PENNSYLVANIA
SHALES
X-RAY DIFFRACTION
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
BLACK COAL
CARBONACEOUS MATERIALS
CHLORINE COMPOUNDS
CLAYS
COAL
COHERENT SCATTERING
DATA
DEVELOPED COUNTRIES
DIFFRACTION
DISSOLUTION
ENERGY SOURCES
FOSSIL FUELS
FUELS
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
MATERIALS
MINERALS
MOUNTAINS
NORTH AMERICA
NUMERICAL DATA
OXYGEN COMPOUNDS
ROCKS
SCATTERING
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
USA
011000* - Coal
Lignite
& Peat- Reserves
Geology
& Exploration
580000 - Geosciences