The effect of inorganic components on organic matter transformation under hydrothermal conditions : constraints from laboratory experiments studying the abiotic oxidation of n octane in presence of iron mineral assemblages additional transition metals and dissolved sulfate Thermochemical sulfate reduction transition metals redox buffers n alkanes fluid rock interaction. Thermochemische Sulfatreduktion Übergangsmetalle Redox Puffer n Alkane Fluid Gesteins Interaktion