For the ethene-ethane, propene-propane, benzene-toluene and CO2-CH4 proxies minimum temperature for phase separation at estimated reaction zone depth are shown. They are based on assumed attainment of chemical equilibrium according to reactions: CH4(aq) + 2H2O = CO2(aq) + 4H2(aq)C2H4(aq){ethene} + H2(aq) = C2H6(aq){ethane}C3H6(aq){propene} + H2(aq) = C2H8(aq){propane}C6H5CH3(aq){toluene} + 2H2O ==> C6H6(aq){benzene} + CO2(aq) + 3H2(aq)