PHENOLS IN HYDROTHERMAL PETROLEUMS AND SEDIMENT BITUMEN FROM GUAYMAS BASIN, GULF OF CALIFORNIA

The aliphatic, aromatic and polar (NSO) fractions of seabed petroleums and sediment bitumen extracts from the Guaymas Basin hydrothermal sys tem have been analyzed by gas chromatography and gas chromatography-ma ss spectrometry (free and silylated). The oils were collected from the interiors and exteriors of high temperature hydrothermal vents and re present hydrothermal pyrolyzates that have migrated to the seafloor by hydrothermal fluid circulation. The downcore sediments are representa tive of both thermally unaltered and thermally altered sediments. The survey has revealed the presence of oxygenated compounds in samples wi th a high degree of thermal maturity. Phenols are one class of oxygena ted compounds found in these samples. A group of methyl-, dimethyl- an d trimethyl-isoprenoidyl phenols (C-27-C-29) is present in all of the seabed NSO fractions, with the methyl- and dimethyl-isoprenoidyl pheno ls occurring as major components, and a trimethyl-isoprenoidyl phenol as a minor component. A homologous series of n-alkylphenols (C-13-C-33 ) has also been found in the seabed petroleums. These phenols are most likely derived from the hydrothermal alteration of sedimentary organi c matter. The n-alkylphenols are probably synthesized under hydrotherm al conditions, but the isoprenoidyl phenols are probably hydrothermal alteration products of natural product precursors. The suites of pheno ls do not appear to be useful tracers of high temperature hydrothermal processes. Copyright (C) 1996 Elsevier Science Ltd