Multi-spherical interactions driving the generation, accumulation and distribution of natural gases and CO2 resources in the Changling Fault Depression, Songliao Basin, China

This study systematically investigates the genesis, migration, accumulation, and distribution patterns of natural gas and CO 2 in the Changling Fault Depression of the Songliao Basin through an interdisciplinary Earth system framework, focusing on multi-sphere interactions. Integrated analyses employing gas geochemistry, numerical simulations, and core observations reveal that deep magmatic-hydrothermal processes (lithosphere) provide the primary heat and fluid sources, paleoclimate oscillations (atmosphere) modulate organic productivity and preservation efficiency, and lacustrine-level fluctuations (hydrosphere) control reservoir connectivity and gas-phase partitioning. These synergistic controls jointly determine hydrocarbon generation in source rocks, volcanic reservoir evolution, and CO 2 -CH 4 competitive accumulation. Results indicate that natural gas within the Changling Fault Depression is predominantly thermogenic with localized abiotic contributions, as evidenced by δ 13 C 1 values ranging from −56.8‰ to −1.7‰ and the coexistence of both normal and reversed carbon isotopic fractionation sequences. CO 2 exhibits a dominant inorganic mantle-derived origin, characterized by δ 13 C CO2 values between −18.9‰ and −0.6‰. Thermogenic gas preferentially accumulates in volcanic reservoirs of the Quantou and Yingcheng Formations, while CO 2 and CH 4 display planarly complementary distributions, with high-CO 2 concentrations localized in the eastern Changshen area corresponding to low-CH 4 zones. Paleoenvironmental reconstructions reveal a progressive transition from deep to shallow lacustrine conditions, from humid to semi-arid climate regimes, and from freshwater to brackish depositional environments during the Early Cretaceous. Source rocks of the Shahezi Formation exhibit stronger primary productivity and higher hydrocarbon generation potential than those of the Yingcheng Formation, driven by coupled effects of tectonic subsidence, volcanic nutrient input, and redox-controlled organic preservation. Tectonic evolution governs vertical hydrocarbon migration and mantle-derived CO 2 influx through volcanic activity and fault system development, whereas climate-sedimentation coupling under Ferrel circulation and global eustatic cycles regulates organic matter enrichment. This integrated analysis establishes a comprehensive framework for volcanic gas reservoir exploration and CO 2 geological sequestration, contributing to the synergistic advancement of carbon neutrality and energy security strategies.