PETROLEUM GENERATION, AN EASY AND WIDESPREAD PROCESS IN HYDROTHERMAL SYSTEMS: AN OVERVIEW

Abstract

The conversion of organic matter to petroleum products by hydrothermal activity is an easy process, occurring in nature in many types of environments. Geologically immature organic matter of marine sediments has been shown to be altered to petroleum products by this process in the Guaymas Basin, Escanaba Trough, Bransfield Strait and Atlantis II Deep and this process probably occurs elsewhere in active sedimented rift systems. Contemporary organic detritus and/or viable microorganisms are also converted in part to petroleum-like products when they become entrained by turbulent mixing into hydrothermal vent waters, resulting in their instantaneous hydrous pyrolysis. This latter case occurs in hydrothermal vent fields without a sedimentary cover emanating directly from oceanic ridges, as for example on the East Pacific Rise at 13°N and 21°N and on the Mid-Atlantic Ridge at 26°N. This process is probably also ubiquitous for all actively venting sediment-starved oceanic ridges. The hydrocarbon products generated in these areas have been compared in terms of composition, organic matter sources and analogy to reservoir petroleum. They represent a major carbon source for chemosynthetic assimilation by vent biota and are compositionally similar to normal petroleum.