Melt inclusion constraints on volcanic CO2 releases from the Tibetan Plateau

Studying volcanic CO₂ releases during geological periods is essential for unraveling the complex interactions between Earth's interior, atmosphere, oceans, and biosphere. Such studies provide critical insights into the mechanisms driving climate change, mass extinctions, and the evolution of life on Earth. The uplift of the Tibetan Plateau has had a significant impact on global climate change, yet the assessment of CO₂ releases from contemporaneous volcanic activities has received relatively little attention.

Melt inclusions trapped within phenocryst minerals of volcanic rocks represent a unique and powerful tool for studying the origin and evolution of magma. They also serve as direct evidence for investigating CO₂ releases from volcanic activity. In this study, we focus on the post-collision volcanic rocks of the Lhasa terrane (12–15 Ma) and the Qiangtang terrane (35–40 Ma) in the southern Tibetan Plateau. We characterized olivine- and pyroxene-hosted melt inclusions, determined the CO₂ content in bubble melt inclusions, and calculated the total CO₂release. Our results show that the average CO₂ content in volcanic rocks is approximately 1.73 ± 0.59 wt% in the Lhasa terrane and 0.46 ± 0.30 wt% in the Qiangtang terrane. Based on the estimated volumes of volcanic rocks, we calculated the CO₂ fluxes from post-collision volcanic activities in the Lhasa and Qiangtang terranes to be 0.151 ± 0.052 Pg yr⁻¹ and 0.047 ± 0.007 Pg yr⁻¹, respectively.

When combined with previous estimates of CO₂ emissions from the Linzizong volcanic rocks (~50 Ma) in the Qiangtang terrane, our findings reveal that the total CO₂ release from the Qiangtang terrane exceeded that from the Lhasa terrane. This pattern aligns with the global cooling trend and declining atmospheric CO₂ levels observed between the Eocene and Miocene. We propose that the elevated atmospheric CO₂ concentrations during the Middle Eocene Climatic Optimum (~40 Ma) were likely driven by volcanic activity from the Linzizong and Qiangtang volcanic eruptions. Similarly, volcanic activity in the Lhasa terrane may have contributed to the elevated CO₂ levels observed during the Middle Miocene Climatic Optimum. Although uncertainties remain, our results provide preliminary data for modeling deep-sourced CO₂ emissions associated with the India-Asia collision during geological history.