Formation of reduced carbonaceous matter in basalts and xenoliths: Reaction of C-O-H gases on olivine crack surfaces
- SRI International, Menlo Park, CA (United States)
- Stanford Univ., CA (United States)
It has been suggested that the formation of reduced carbonaceous matter in basalts and mantle xenoliths occurs by heterogeneous reaction of volcanic gas on fresh, chemically active crack surfaces produced by thermal stresses during eruption and cooling. This hypothesis is supported by experiments at 400-800[degrees]C on (010) surfaces of San Carlos olivine exposed to C-O-H gases generated by the decomposition of oxalic acid and oxalic acid dihydrate. Carbonaceous films form readily on these surfaces and achieve thicknesses comparable to those observed in natural samples (a few nanometers) in a matter of minutes. At relatively oxidizing conditions, the carbonaceous films consist principally of C-C and C-H bonded species with lesser amounts of C-O bonded species. At relatively reducing conditions, the carbonaceous films consist of subequal amounts of C-C/C-H, C-O, and metal-C species. Aliphatic and aromatic hydrocarbons and other thermally labile organic species are associated with carbonaceous films in some natural samples but none were detected in experimental samples from this study, leaving open the question of abiotic synthesis of organic matter on crack surfaces in basalts. Regardless, it is clear from the preliminary experiments reported here that crack surfaces in olivine (and probably other silicate minerals and glasses) are capable of stabilizing compounds that otherwise would not be stable in cooling lava.
- OSTI ID:
- 5782719
- Report Number(s):
- CONF-911017-; CODEN: GCACAK; CNN: 5087-260-1626
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Vol. 57:14; Conference: Annual meeting and exhibition of the Geological Society of America (GSA), San Diego, CA (United States), 21-23 Oct 1991; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON COMPOUNDS
SYNTHESIS
VOLCANIC GASES
CHEMICAL REACTIONS
BASALT
DECOMPOSITION
HYDROCARBONS
OLIVINE
ORGANIC MATTER
OXALIC ACID
TEMPERATURE RANGE 0400-1000 K
CARBOXYLIC ACIDS
DICARBOXYLIC ACIDS
FLUIDS
GASES
IGNEOUS ROCKS
MATTER
MINERALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ROCKS
SILICATE MINERALS
TEMPERATURE RANGE
VOLCANIC ROCKS
400800* - Combustion
Pyrolysis
& High-Temperature Chemistry
400201 - Chemical & Physicochemical Properties