HR: 0800h
AN: B51B-0374    [Abstracts]
TI: Resolving the Unresolved Complex Mixtures of Hydrothermal Petroleum Using Comprehensive Two-Dimensional Gas Chromatography - Time of Flight Mass Spectrometry
AU: * Ventura, G T
EM: gventura@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS #4, Woods Hole, MA 02543, United States
AU: Reddy, C M
EM: creddy@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS #4, Woods Hole, MA 02543, United States
AU: Simoneit, B R
EM: simonebe@onid.orst.edu
AF: Petroleum and Environmental Geochemistry Group, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States
AU: Nelson, R K
EM: rnelson@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS #4, Woods Hole, MA 02543, United States
AB: Within hydrothermal systems sedimentary organic matter can be altered by high temperature fluids resulting in the generation of petroleum. These hydrothermal petroleums are compositionally similar to conventional, basin- formed petroleum, with the exception that they often contain substantial mixtures of coeluting organic compounds, which are difficult to resolve by traditional gas chromatographic methods. The coelution of these compounds produces a rapidly rising baseline in gas chromatogram that is referred to as an unresolved complex mixture (UCM). Little is known about these UCMs or why and how they form. In this study we analyzed the apolar fractions of four hydrothermal petroleum samples from the Middle Valley, Juan de Fuca Ridge and Escanaba Trough, Gorda Ridge in the NE Pacific Ocean and the Guaymus Basin, Gulf of California using comprehensive two-dimensional gas chromatography-Time of Flight Mass Spectrometry (GC×GC-ToFMS). The GC×GC-ToFMS chromatograms of these samples elucidate two hydrocarbon subsets. The first subset consists of commonly defined hydrocarbon series such as n-alkanes, alkylcyclohexanes, alkylbenzenes, naphthalenes, tricylic terpanes, steranes, and hopanes. The second subset is dominated by compounds forming the UCM. These compounds form a continuous series of configurational isomers that become increasingly aromatic at higher molecular weights. The UCMs of the hydrothermal petroleum samples vary as a function of the relative intensity, number, and molecular weight range of the contributing configurational isomers. The subset appears to represent areas of mass gain that overprint the first subset in the GC×GC-ToFMS chromatogram. This gain likely reflects an exogenous input or the accumulation of primary organic matter that underwent extensive dehydrogenation and dealkylation. Variation between the second hydrocarbon sample subsets is likely caused by different thermal gradients within the pyrolytic regimes, gaseous solubilization, hydrodynamic alteration from multi-component fluids, and post-depositional alteration from biodegradation and water-washing.
DE: 0428 Carbon cycling (4806)
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 1034 Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424)
DE: 1055 Organic and biogenic geochemistry
DE: 3017 Hydrothermal systems (0450, 1034, 3616, 4832, 8135, 8424)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting