Discovery of in-situ carbonate petrifactions (coal balls) in the Foord Seam (Westphalian C, Upper Carboniferous), Stellarton, Nova Scotia, Canada: Implications for origin of sulfur in the Foord Seam

Conference · Sun Aug 01 00:00:00 EDT 1993 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:6685438

Lyons, P C; Congdon, R D ^[1]; Cross, A T ^[2]; Gao, Z; Zodrow, E L ^[3]; Gillis, K ^[4]; Calder, J H ^[5]

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1. Geological Survey, Reston, VA (United States)
2. Michigan State Univ., East Lansing, MI (United States)
3. Univ. College of Cape Breton, Sydney (Canada)
4. Nova Scotia Department of Natural Resources, Stellarton (Canada)
5. Nova Scotia Department of Natural Resources, Halifax (Canada)

Carbonate petrifactions (coal balls) were discovered in situ in the 13-m-thick Foord Seam (Westphalian C) at the Westray open-pit mine at Stellarton, Nova Scotia, Canada. These are the first in-situ coal balls discovered in Nova Scotia. This bed, the thickest and oldest coal mined in the Carboniferous coal basins of the Maritime Provinces of Canada, is the uppermost seam of the Albio Member of the Stellarton Formation and is known for its low sulfur content (mean = 0.5% total sulfur), the lowest of all Maritime Canada coals. The coal balls are up to 60 cm in length and are scattered abundantly from the bottom of the top of the seam, including the shale parting. The principal minerals contained in the coal balls (n = 6), as determined by semiquantitative X-ray diffraction (XRD) analysis, are siderite (70-100%), dolomite (0-20%), quartz (0.5%), and traces of a clay mineral (illite ). Calcite and pyrite were detected in trace amounts by SEM-EDAX and by single-crystal XRD analysis. The almost complete absence of pyrite in the coal balls suggests a chemical link with the pyrite-poor Foord Seam. The authors hypothesize that sulfate-rich marine water or recycled marine sulfate from evaporites from the Lower Carboniferous Windsor Group were unavailable in the peat-forming mire, and, therefore, siderite was favored over pyrite. A nonmarine origin of the siderite also is suggested by the nearly pure end-member nature of the siderite (Fe[sub 0.94[+-]0.03] Mg[sub 0.02[+-]0.02] Ca[sub 0.04[+-]0.01] Mn[sub <0.01] Sr[sup <0.01] Ba[sub <0.01]; n = 48) a composition consistent with siderite of freshwater origin. Because of the lack of sulfate or H[sub 2]S to form pyrite, sulfur combined almost exclusively with the organic molecules of the lycopod-rich peat, and this lack of sulfate or H[sub 2]S favored the low-sulfur content of the Foord Seam.

• OSTI ID: 6685438
• Report Number(s): CONF-930981-; CODEN: AABUD2
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 77:8; Conference: Eastern Section meeting of the American Association of Petroleum Geologists: eastern energy, environment and education for the 21st century, Williamsburg, VA (United States), 19-21 Sep 1993; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
COAL SEAMS
SULFUR CONTENT
DOLOMITE
NOVA SCOTIA
PEAT
PYRITE
QUARTZ
SCANNING ELECTRON MICROSCOPY
SIDERITE
X-RAY DIFFRACTION
CANADA
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
COAL DEPOSITS
COHERENT SCATTERING
DEVELOPED COUNTRIES
DIFFRACTION
ELECTRON MICROSCOPY
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC DEPOSITS
IRON CARBONATES
IRON COMPOUNDS
IRON ORES
MATTER
MICROSCOPY
MINERAL RESOURCES
MINERALS
NORTH AMERICA
ORES
ORGANIC MATTER
OXIDE MINERALS
OXYGEN COMPOUNDS
RESOURCES
SCATTERING
SULFIDE MINERALS
TRANSITION ELEMENT COMPOUNDS
011000* - Coal
Lignite
&amp; Peat- Reserves
Geology
&amp; Exploration
010600 - Coal
Lignite
&amp; Peat- Properties &amp; Composition