Hydrothermal petroleum at the seafloor and organic matter alteration in sediments of Middle Valley, Northern Juan de Fuca Ridge

Abstract

Sediments from high heat flow areas of Middle Valley, Northern Juan de Fuca Ridge, contain traces of bitumens with insignificant amounts of thermogenic components and mainly lipid material which has experienced accelerated diagenesis. These sediments have been exposed to mild hydrothermal conditions (50–120°C), based on their bitumen compositions. The hydrothermal bitumen in a barite alteration products. The aliphatic fraction represents the mildly transformed and immature matter and the major polynuclear aromatic hydrocarbons are the high temperature constituents (>300°C). The ¹⁴C age of this bitumen is about 29 000 aBP, reflecting rapid organic carbon cycling.