Biomaker and Carbon Isotope Geochemistry of Pyrolytic and Chemosynthetic Processes in Sedimented Hydrothermal Systems

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This is a continuing and collaborative research effort with biologists on the hydrothermal emanations, primarily in Guaymas Basin, with follow up studies on material from the Northeastern Pacific (Middle Valley, Juan de Fuca and Gorda Ridges), African Rift Valley (Lake Tanganyika), and a hot spot under a continent (Yellowstone Park). The organic matter (petroleum) brought to the seabed by hydrothermal circulation represents the rapidly generated pyrolytic products from organic detritus at depth and is a carbon source for the hemosynthetic food web. This type of carbon cycling and its geological fate will be studied in a sedimented rift system which is hydrothermally.active, receiving primarily terrestrial organic detritus (Escanaba Trough). This will be done by coupling organic and isotope geochemistry to examine interrelationships between post.depositional pyrolytic alteration of organic matter (petroleum), biodegradation/weathering processes and chemosynthetic carbon fixation. Chemical reactions (e.g. aromatization, dehydration, isomerization) with temperature constraints also will be studied to define formation "windows" for different compound classes. The environmental fate of these compound classes will be examined to assess solubility, oxidative weathering and biodegradation. Key reactions and processes will be simulated in the laboratory by hydrous pyrolysis experiments. Carbon.14 dating of different organic matter fractions will place constraints on the sources and subbottom depths of the alteration of carbonaceous materials. Thus, molecular and isotopic signatures will be able to be used to trace the transfer of carbon from sources through these hydrothermal environments.