| 其他摘要 | In this dissertation through the research on TOC (total organic carbon) content, dissolvable organic matter content, and compositons of saturated hydrocarbons, aromatic hydrocarbons, fatty acids, and their δ13C of 6 seep-carbonate samples recoverd from Bush Hill and Alaminos Canyon in Gulf of Mexico, the source, maturation and sedimentary environment of the organic matter are discussed.
The TOC contents of Bush Hill seep-carbonates are from 0.78% to 9.02%, organic contents range from 5.77 mg/g to -65.06mg/g. Apparently even-odd preference of high molecular weight alkanes, Fluoranthene and Pyrene compounds in GC-B sample, whose TOC content is up to 9.02%, indicate that GC-B sample was influenced by seeping oil. δ13C values of n-alkanes and n-fatty acids are respectively from -27.64‰ to -32.36‰ and from -26.52‰ to -39.99‰, and similar to the values of bacteria and oil reservoir, which implys that the organic matter is form the deep oil reservoir. In other four seep-carbonates and one Alaminos Canyon seep-carbonate n-alkanes are dominated by low molecular weight alkanes and without even-odd preference, long-branched and cyclic hydrocarbons, Ttriaromatic-sterane and Methyl-ttriaromatic-sterane are present, which show that organic matter were mainly from bacteria and lower organism.
The maturation parameters, C29ββ/(ββ+αα) is 0.28-0.40,C2920S/(20S + 20R) is 0.42 to 0.6 ,and（TA(Ⅰ)/C26-C28（TA(Ⅱ)) is 0.49, show that maturation of organic matter is relatively low.
UCM (unresolved complex mixture) is unapparently in AC-E sample , but apparently in all samples from Bush Hill. the presence of the UCM is due to the microbial degradation. The degraded n-alkanes mixing with long-branched and cyclic hydrocarbons form unresolved complex mixtures, and thus UCM is considered as a direct proof of microbial degradation. The content of dibenzothiophene, fluorene and dibenzofuran in AC-E and all Bush Hill samples (Dibenzothiophene>Fluorene>Dibenzofuran), and the 13C-depleted iso-/aniso-fatty acids(-63.95‰和-50.48‰), indicate that the formation of the carbonates in these areas involved the bacteria actitivity and anaerobic oxidation of methane.
Key words: Gulf of Mexico, seep-carbonate, anaerobic oxidation of methane |
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