Atmospheric CO2 drawdown during the Emeishan flood basalt volcanism

The conventional model linking large igneous provinces (LIPs) to atmospheric CO₂ concentrations (pCO₂) predicts elevated CO₂ during volcanic emplacement, leading to biotic crises. However, this generalization requires testing. Here, we reconstruct pCO₂ variations throughout the Emeishan LIP emplacement (~260 Ma) using carbon isotopes from chlorophyll-derived compounds. Our high-resolution record reveals that pCO₂ declined from ~ 700 ppm to ~ 350 ppm during the early and main flood basalt phases, then increased during subsequent silicic eruptions. This pattern coincides with pre-eruptive crustal uplift driven by mantle plume impingement. We propose that CO₂ consumption associated with enhanced erosion and weathering of kilometer-thick Yangtze craton carbonates from regional uplift might have temporarily exceeded the CO₂ contribution from magmatic degassing. This is supported by geochemical data indicating that the Emeishan basalt is particularly CO₂-poor. Our findings demonstrate that LIP environmental impact begins before the main eruptive phase, highlighting that tectonic-magmatic interactions can produce more complex CO₂ patterns than previously recognized. This may explain why some LIPs caused extinctions, whereas others did not.