Secondary graphitization in mantle-derived rocks

Journal Article · Thu Sep 01 04:00:00 EDT 1988 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1988)016<0804:SGIMDR>2.3.CO;2· OSTI ID:6820210

Pasteris, J D

The assemblage magnesite + graphite +/- CH/sub 4/ has been identified by laser Raman microprobe spectroscopy in fluid inclusions in olivine grains in the Kao kimberlite and the Duluth Complex troctolite. In both cases, the assemblage (essentially Eggler's EMOG oxygen-fugacity buffer) is believed to arise from secondary reactions rather than from primary igneous processes. The known stability field in P-T-f/sub O/sub 2// space of the EMOG buffer, coupled with some other petrologic constraints imposed by the host rocks, indicates in both cases that the carbon-bearing assemblage was precipitated at low pressures and temperatures (less than or equal to 2 kbar, less than or equal to 550/sup 0/C) at oxygen fugacities within about 1 log (f/sub O/sub 2//) unit below the fayalite-magnetite-quartz (FMQ) buffer. The laser Raman microprobe provides compositional and structural data on the coexisting phases (including carbon) that further constrain the stability field of the natural assemblages.

• Research Organization: Washington Univ., St. Louis, MO (USA)
• OSTI ID: 6820210
• Journal Information: Geology; (United States), Journal Name: Geology; (United States) Vol. 16:9; ISSN GLGYB
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
011000* -- Coal
Lignite
&amp; Peat-- Reserves
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&amp; Exploration
AFRICA
CARBON
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
EARTH MANTLE
ELEMENTAL MINERALS
ELEMENTS
GRAPHITE
IGNEOUS ROCKS
KIMBERLITES
LAMPROPHYRES
LASER SPECTROSCOPY
MATERIALS
MINERALS
NATURAL OCCURRENCE
NONMETALS
ORIGIN
OXYGEN
RAMAN SPECTROSCOPY
RESERVOIR PRESSURE
RESERVOIR TEMPERATURE
ROCKS
SOUTH AFRICA
SPECTROSCOPY
VOLCANIC ROCKS