Petroleum from Northeast Pacific Ocean Hydrothermal Systems in Escanaba Trough and Guaymas Basin

Keith A. Kvenvolden, Bernd R. T. Simoneit

Asphaltic petroleum is associated with polymetallic sulfide in sediment of the northeastern Pacific Ocean at two active oceanic spreading axes--the Escanaba Trough (ET) at the southern end of the Gorda Ridge and the Guaymas Basin (GB) in the Gulf of California. In both areas, the petroleum was derived from hydrothermally altered organic matter in the sediment that blankets the ridge axes. A petroleum geochemical comparison between two samples shows differences that can be attributed to the sources and thermal histories of the organic matter. The results, coupled with sedimentological and kinetic considerations, indicate that the organic matter in the sediment at ET is dominantly terrigenous, whereas at GB it is mainly marine. The data are consistent with petroleum formati n by intense heating of short duration, but at GB the temperatures may have been lower and the heating times longer than at ET.

The future economic implications of these petroleum occurrences are uncertain. A preliminary analysis, however, suggests that hydrothermally derived petroleum at active oceanic spreading axes will not be a particularly promising resource because of the great water depths and distances from shore, and the lack of suitable long-term traps. The geochemistry of hydrothermal petroleum may, however, provide valuable information for understanding petroleum genesis and the origin of organic matter in some sulfide-rich ore deposits.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.