Xie Xiangang¹, Guo Zhengfu¹, Zhang Maoliang², Xu Sheng²

(¹Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; ²School of Earth System Science, Tianjin University, Tianjin 300072, China)

Abstract: Melt inclusions are small droplets of magma entrapped within phenocryst minerals of volcanic rocks, representing the original carbon content of the magma, which can be used direct object to study volcanic deep carbon release. Some of the most CO₂-rich magmas in deep erupted by volcanoes, such as Tibetan Plateau. Here, we focus on the post-collision volcanic activity of the Lhasa and Qiangtang terranes on the Tibetan Plateau and characterize olivine and pyroxene hosted melt inclusions. We determined CO₂ content in bubble melt inclusions and calculated the total CO₂ output. Finding that the average CO₂ content of volcanic rocks is approximately 1.73 ± 0.59 wt.% in the Lhasa terrane and 0.46 ± 0.30 wt.% in the Qiangtang terrane, with the Lhasa terrane showing higher CO₂ concentrations. Based on volcanic rock volumes of the Lhasa and Qiangtang terranes, we estimated the CO₂ fluxes from post-collision volcanic activity to be 0.151 ± 0.052 pg yr⁻¹ and 0.047 ± 0.007 pg yr⁻¹, respectively, with the Lhasa terrane contributing a higher CO₂ flux. Integrating these findings with previous estimates of CO₂ emissions from the Linzizong volcanic rocks, which erupted during the same period as the Qiangtang volcanic activity (~ 40 Ma), we find that the total amount of CO₂ output was greater than that from the Lhasa terrane. This is consistent with the global cooling trend and the decline in atmospheric CO₂ observed during key periods from the Eocene to the Miocene. So, we suggest that the elevated atmospheric CO₂ concentration during the Middle Eocene Climatic Optimum, around 40 Ma, may have been driven by volcanic activity from the Linzizong and Qiangtang volcanic eruptions, as well as the Lhasa volcanic activity during the Middle Miocene Climatic Optimum. Our results provide preliminary data for simulating deep CO₂ emissions caused by the India-Asia collision during geological history. In the future, it is still necessary to optimize the research results based on obtaining more data to reduce the uncertainty caused by the differences in magma composition, eruption volume, and spatial-temporal distribution of post-collisional volcanic activity.

Key words: Volcanic activity; CO₂ emission; Tibetan Plateau; Melt inclusion

Author Profile:

Xiangang Xie, Male, Postdoctoral Researcher, PhD, mainly engaged in Volcanic gas geochemistry research. E-mail: xiangangxie@mail.iggcas.ac.cn.