Impact of Solid Hydrocarbon on the Composition of Fluid Phase at the Subduction (Experimental Simulation)

Experiments conducted in the olivine-serpentine-anthracene-metal (FeNi) system have shown that the recrystallization of olivines occurs under substantially reduced conditions with active participation of hydrocarbons, especially paraffins; moreover, their amount increases with increasing pressure and temperature. During the decomposition of serpentine, a large amount of water is released; therefore, the fluid at relatively low P-T parameters (2 GPa, 1100 degrees C) has mainly water-hydrocarbon composition. With an increase in pressure up to 3-4.5 GPa and temperature up to 1300-1400 degrees C, the composition of the fluid changes greatly towards an increase in the relative amount of hydrocarbons, while the main share is occupied by light (C1-C4) aliphatic hydrocarbons. Therefore, a biogenic material with a carbon-hydrogen composition can make a certain contribution to the carbon budget in subduction processes when falling into the subduction zones and may affect the oxygen fugitivity in the subducted slab.