Proton micro-probe analysis of framboidal pyrite and associated maceral types in a Devonian black shale

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5895388

Graham, U M; Robl, T L ^[1]; Robertson, J D ^[2]

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1. Univ. of Kentucky, Lexington, KY (United States). Center for Applied Energy Research
2. Univ. of Kentucky, Lexington (United States). Dept. of Chemistry

Framboids are spherical, raspberry-like aggregates of pyrite which are typically associated with organic matter in black shales. Because framboids are often intimately intergrown with macerals of the kerogen in black shales the objectives of this study were to: (1) Select tramboidal pyrite with close spatial relationship to distinct maceral types; (2) Determine the trace-element variations within different maceral types and that of framboidal pyrite occurring adjacent to those macerals and; (3) Examine whether the S/Fe ratios of the tramboids vary based on different maceral-type association. This study investigates a Devonian-Mississippian black shale from East-Central Kentucky. The organic-rich matrix consists predominantly of bituminite, alginite and to lesser extent of vitrinite. Most framboids range between < 1[mu]m and 27 [mu]m in size and typically occur as clusters which are engulfed by lamellar flowing vitrinite, indicating that the framboids were already present before compaction. 161 PIXE-analyses were performed in both macerals and framboids. To understand the likelihood of framboid precursors in macerals the authors checked the constancy of the S, Fe and trace-element content in the immediate vicinity of the framboid particle. Moreover, the authors analyzed traverses through framboids associated with the three different maceral types. The S/Fe ratio of the framboids is always that of stoichiometric pyrite. The combined results suggest that the framboids may have formed independent of the sulfur and trace-element concentration among the macerals. Globular, partly translucent grains were observed to have great resemblances in size and trace-element contents compared to those of framboids. The S/Fe ratio of these grains was typically well in excess of 2.0 suggesting that the transparent matrix may have been a sulfur-rich phase that possibly serves as precursor for the framboids.

• OSTI ID: 5895388
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
040500* -- Oil Shales &amp; Tar Sands-- Properties &amp; Composition
BITUMINOUS MATERIALS
BLACK SHALES
CARBONACEOUS MATERIALS
CHEMICAL ANALYSIS
CHEMISTRY
DEVONIAN PERIOD
GEOCHEMISTRY
GEOLOGIC AGES
KEROGEN
MACERALS
MATERIALS
MATTER
MINERALS
NONDESTRUCTIVE ANALYSIS
ORGANIC MATTER
ORIGIN
PALEOZOIC ERA
PIXE ANALYSIS
PYRITE
ROCKS
SEDIMENTARY ROCKS
SHALES
SULFIDE MINERALS
X-RAY EMISSION ANALYSIS