Carbonaceous matter in peridotites and basalts studied by XPS, SALI, and LEED

Journal Article · Wed May 01 00:00:00 EDT 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90312-S· OSTI ID:5891125

Tingle, T N ^[1]; Mathez, E A ^[2]; Hochella, Jr, M F ^[3]

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1. Stanford Univ., CA (United States) SRI International, Menlo Park, CA (United States)
2. American Museum of Natural History, New York, NY (United States)
3. Stanford Univ., CA (United States)

Carbonaceous matter in peridotite xenoliths and basalt from the Hualalai Volcano, in a basalt glass collected directly from an active lava lake on the east rift of Kilauea, in garnet and diopside megacrysts from the Jagersfontein kimberlite, and in gabbros from the Stillwater and Bushveld Complexes has been studied by X-ray photoelectron spectroscopy (XPS), thermal-desorption surface analysis by laser ionization (SALI), and low-energy electron diffraction (LEED). The basalt and two of the four xenoliths from Hualalai and both Jagersfontein megacrysts yielded trace quantities ({le}10 nanomoles) of organic compounds on heating to 700C. Organics were not detected in the rocks from the layered intrusions, and neither carbonaceous matter nor organics were detected in the glass from the lava lake. Where detected, organics appear to be associated with carbonaceous films on microcrack surfaces. Carbonaceous matter exists as films less than a few nm thick and particles up to 20 {mu}m across, both of which contain elements expected to be present in significant quantities in magmatic vapors, namely Si, alkalis, halogens, N, and transition metals. LEED studies suggest that the carbonaceous films are amorphous. The data suggest two possible mechanisms for the formation of the organics. One is that they are a product of abiotic heterogeneous catalysis of volcanic gas on new, chemically active mineral surfaces formed by fracturing during cooling. Alternatively, organics may have been assimilated into the volcanic gases prior to eruption and then deposited on cracks formed during eruption and cooling. In any case, there is no evidence to suggest that the organics represent laboratory or field biogenic contamination.

• OSTI ID: 5891125
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 55:5; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BASALT
CHEMICAL ANALYSIS
CARBONACEOUS MATERIALS
PERIDOTITES
DIOPSIDE
ELECTRON DIFFRACTION
GABBROS
GARNETS
GEOCHEMISTRY
HAWAII
IONIZATION
KIMBERLITES
MONTANA
ORGANIC COMPOUNDS
SOUTH AFRICA
VOLCANOES
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COHERENT SCATTERING
DEVELOPED COUNTRIES
DIFFRACTION
FEDERAL REGION IX
FEDERAL REGION VIII
IGNEOUS ROCKS
LAMPROPHYRES
MATERIALS
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PLUTONIC ROCKS
PYROXENES
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SCATTERING
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SPECTROSCOPY
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VOLCANIC ROCKS
580000* - Geosciences