Geological di-hydrogen (H2) and methane (CH4) are essential contributors of energy and carbon sustaining deep biosphere environments on Earth and contributing to its habitability. The production of H2-CH4 fluids was commonly attributed to serpentinization and associated Fischer-Tropsch like reactions. However experimental investigations show that the kinetic of such a process is very sluggish, potentially hindering CH4 production in natural systems. In contrast, the discovery of solid organic compounds associated with serpentinites has leaded to the emergence of new paradigms in which their detsabilization could be a source of geological CH4 and more complex organic molecules synthesis. Although solid organic compounds were first identified at serpentinite host hydrothermal systems near mid-ocean ridges, growing observations show that they extend to subduction zones. In these environments, the extreme pressure (P), temperature (T) and oxygen fugacity (fO2) conditions could even favour their formation over inorganic carbonates, potentially making them the largest source of deep abiotic CH4 on Earth. Here, we report the natural occurence of solid organic compounds in HP-HT rocks from the Western Alps and explore the P-T-fO2 conditions of their stability and formation in subduction zones using piston-cylinder and multi-anvil presses.