A Petrographic P-Axis as an Independent State Coordinate of Coal Organic Matter: Decoupling of Organic Sulfur and Inorganic Fe–S Subsystems

Olga N. Shagarova 

This study proposes an architectural framework for coal organic matter in which geochemical behavior emerges from the interaction of partially independent subsystems rather than from a single maturity or redox gradient. Using a globally compiled coal dataset, we introduce the P-axis—a petrographic coordinate derived exclusively from the balance between gelified and tissue-preserved vitrinite components—and demonstrate that reproducible geochemical organization recurs along this axis across multiple basins and countries. The results show that organic sulfur, inorganic Fe–S redox, lithogenic, alkali-fluid, and rank-related subsystems exhibit distinct patterns of organization, indicating that gelification, thermal maturity, and inorganic Fe–S redox are overlapping but non-identical process systems. The framework provides a reproducible, multidimensional approach to characterizing coal organic matter architecture beyond conventional single-proxy interpretations.