REDOX FACIES OF HYDROCARBONS AND THE FORMATION OF OIL

Abstract

The endogenic nature of hydrocarbons (HC) and their heterogeneity has been substantially refined by their findings in hydrothermal fields in the global system of ocean ridges. The methane composition (CO2 + CH4 + H2O) was initially found in hydrothermal solutions and fluid inclusions captured by rock-forming minerals and apatite of olivine gabbro and norite. Association of methane with many other HCs was revealed afterward. Heavy saturated HCs (CH2.125–CH2.069) were described from the Rainbow methane hydrothermal field (Mid-Atlantic Ridge) characterized by massive sulfide mineralization. HCs in association with methane are represented by gaseous alkanes, such as ethane (C2H6), propane (C3H8), butane (C4H10), and pentane (C5H12), as well as benzene (C6H6) and toluene (C7H8), in the Juan de Fuca hydrothermal field of the northeastern Pacific.