Methane abiogenic

Horita J, Bemdt ME (1999) Abiogenic methane formation and isotope fractionation under hydrothermal conditions. Science 285 1055-1057... 

Gold, T., Soter, S. (1982) Abiogenic methane and the origin of petroleum. Energy Explore. Exploit., 1, 89-104. 

Despite the arguments presented in this paper against carbon isotopic equilibrium between CO2 and CH4, chemical equilibrium and an abiogenic methane source in TVZ and Taranaki,... 

An estimate of the annual methane flux into the atmosphere can be calculated by adding the sinks and the annual increase. These data (Table II) indicate that a flux of 375-475 trillion tons(Tg) per year would be required to account for an annual increase of50-60 trillion tons (7). Estimates of sources of atmospheric methane indicate that up to 83% is biogenic in origin (5). The other abiogenic... 

Horita and Berndt (1999) studied the abiogenic formation of methane under conditions present at hydrothermal vents. Solutions of bicarbonate (HCO3 ) were subjected to temperatures of 470-670 K and a pressure of 40 MPa. Under these conditions, CO2 was reduced only very slowly to methane. Addition of a nickel-iron alloy, which corresponds closely to the minerals in the Earth s crust, led to a clear increase in the reaction rate of methane synthesis. The following reaction is assumed to occur ... 

These redox reactions are abiogenic, whereas the methane sinks are thought to be biogenic, such as the anaerobic oxidation of methane by archaea as observed at the Lost City vent fields (Figure 19.20). Microbial production of methane has also been observed at this site. 

Sherwood-Lollar et al. 1993,2002). In contrast to thermogenic hydrocarbons where higher hydrocarbons (ethane, propane, butane) are enriched in and D relative to methane, abiogenic alkanes may be depleted in C and D relative to methane. These depletion patterns relative to methane may be produced by polymerization reactions of methane precursors (Sherwood-Lollar et al. 2002). 

Lin, L.-H., and Onstott, T.C., 2006. Unravelling abiogenic and biogenic sources of methane in the Earth s deep subsurface. Chem. Geol., 226, 328—39. 

Fig. 5.61 Methane sources based on isotopic composition and relative abundance (abiogenic = derived from mande C02 ...

Sometimes faults are growing into the upper mantle. This happens if the lower crust is overheated as beneath the sedimentary basins. Then amphiboles are unstable (Figure 1) and the faults appear at the Moho. This point is tightly connected with the problem of hydrocarbons abiogen origin because there is assumption that excess methane is dissolved in the asthenosphere. 

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