Stable isotope evidence for the origin of epigenetic pyrite and sphalerite in coal of the Illinois Basin

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:5932972

Whelan, J F; Cobb, J C; Landis, G P

Stable isotope studies indicate that volatiles released during coalification reactions played an important role in the formation of epigenetic pyrite and sphalerite in cleats and nodules of Illinois Basin coals. Pyrite-hosted fluid inclusions had /delta/D and /delta//sup 18/O values that range from -137 to -61 and from -12.3 to -5.2, respectively. Such compositions must reflect either interaction with or generation from the coal organic matter. Pyrite-hosted inclusions contain CO/sub 2/, CO or N/sub 2/, Ar, H/sub 2/S, SO/sub 2/, and a wide variety of hydrocarbons. /delta//sup 34/S values of epigenetic pyrite from the Nos. 2, 5 and 6 coals in Illinois range from -12.4 to -0.1; within individual mines the range is smaller, commonly 4. Such ranges are much smaller than those formed during bacterial sulfate reduction. Literature research suggests that coalification is accompanied by an increase in the proportion of pyritic to organic sulfur, with little change in the coal's total sulfur content. Sphalerite was deposited from MVT brines at temperatures of 90-100/degree/C. Sphalerite-hosted fluids range from D- and /sup 18/O-enriched compositions typical of MVT brines to compositions approaching those of the pyrite-hosted fluids. This range suggests mixing between the sphalerite-depositing fluids and coal-hosted fluids similar to those trapped in the pyrite fluid inclusions. The /delta//sup 34/S values of spatially associated sphalerite and pyrite are quite similar, suggesting either that sphalerite also precipitated from organically-derived sulfur, or that it replaced earlier pyrite. Sphalerite fluid inclusions have lower hydrocarbon contents than pyrite fluid inclusions.

• Research Organization: Geologic Survey, Denver, CO (USA)
• OSTI ID: 5932972
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010600* -- Coal
Lignite
& Peat-- Properties & Composition
011000 -- Coal
Lignite
& Peat-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580400 -- Geochemistry-- (-1989)
BRINES
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
COAL
COAL DEPOSITS
COALIFICATION
DEPOSITION
DIAGENESIS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
ILLINOIS BASIN
IRON COMPOUNDS
IRON SULFIDES
ISOTOPE RATIO
ISOTOPES
KINETICS
MATERIALS
MINERAL RESOURCES
MINERALS
PYRITE
QUANTITATIVE CHEMICAL ANALYSIS
REACTION KINETICS
RESOURCES
SPHALERITE
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
SULFUR CONTENT
SULFUR ISOTOPES
TRANSITION ELEMENT COMPOUNDS