High-temperature hematite and spinel phases in iron-rich slags produced in shales above burned coal seams
Ultrametamorphic effects (1300+ /sup 0/C) in shales above burned coal seams in the Powder River Basin, Wyoming, include the formation of droplets and stalactites of congealed iron-rich melt (40.3 wt.% SiO/sub 2/, 35.5% Fe as Fe/sub 2/O/sub 3/, 13.5% Al/sub 2/O/sub 3/, 2.2% MgO, 5.0% CaO, 0.3% MnO, 1.0% K/sub 2/O, 0.5% TiO/sub 2/, 1.3% P/sub 2/O/sub 5/, <0.2% Na/sub 2/O, 0.55% LOI, total 100.2%). This melt, quartz-normative and comparable to an iron-rich basalt, formed along fractures which served as chimneys for escape of burning gases; pyrite or other iron-rich concretions in the shale may have been the source of the iron in the melts. Oxide phases, dominantly intergrown hematite+magnetite, in the droplets reflect a high-T, low-P, high-f(O/sub 2/) environment. Hematite ranges from nearly pure Fe/sub 2/O/sub 3/ near the droplet rims (Hm-1) to Al- and Ti-rich in the interiors (Hm-2 to -5). Magnetite contains Mg and Al (Mt-1); in the droplet interiors it is richer in Mg and Al (Mt-2 = host+lamellae) and contains lamellae of exsolved hercynite spinel (Sp-1). Near droplet rims, hematite occurs with magnesioferrite spinel (Mf-1) enriched in Mn and Zn (up to 7 wt.% ZnO), a product of reaction with gases during cooling. Averaged microprobe analyses are provided.
- OSTI ID:
- 6447314
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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58 GEOSCIENCES
COAL MINES
FIRES
SLAGS
CHEMICAL COMPOSITION
MINERALOGY
WYOMING
COAL DEPOSITS
COAL
COAL SEAMS
COMBUSTION PRODUCTS
GEOCHEMISTRY
HEMATITE
MINERALIZATION
POWDER RIVER BASIN
PYRITE
SHALES
SPINELS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHEMISTRY
ENERGY SOURCES
FEDERAL REGION VIII
FOSSIL FUELS
FUELS
GEOLOGIC DEPOSITS
IRON COMPOUNDS
IRON ORES
IRON OXIDES
IRON SULFIDES
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MATERIALS
MINERAL RESOURCES
MINERALS
MINES
MONTANA
NORTH AMERICA
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
UNDERGROUND FACILITIES
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