Pressure-driven regime shifts in graphitization rewrite carbon fate during metamorphism

The fate of organic carbon at convergent margins depends in part on its transformation into relatively inert graphite, yet the influence of precursor composition remains poorly constrained. Here we show that two organic precursors, vitrinite and liptinite, follow distinct graphitization pathways under high-pressure and high-temperature conditions. Vitrinite undergoes progressive structural ordering, whereas liptinite transforms more slowly at intermediate pressures owing to inherited defects and inhibited structural coalescence. Although both precursors respond strongly to pressure, their chemistry governs transitions between the processes that ultimately limit transformation rates. In this work, we develop a precursor-specific kinetic framework that integrates graphitization along geological pressure-temperature histories. Applications to representative Alpine tectonic units indicate that graphitization can continue during post-peak decompression or reheating. Precursor-dependent path integration further influences the modeled partitioning between graphite-like carbon and low-order reactive carbon fluxes. These results highlight how precursor chemistry and geological history jointly control carbon ordering, retention potential, and flux partitioning at convergent margins. This study demonstrates that pressure, metamorphic duration and organic precursor type are key controls on graphitization. The resulting kinetic framework provides constraints on carbon retention and structural partitioning during metamorphism and subduction.