Earth degassing is a critical carbon source, but its contribution to Cenozoic atmospheric CO₂ variations is not well known. Here, Prof. GUOZhengfu at Institute of Geology and Geophysics (IGG) of Chinese Academy of Sciences found that the metamorphic and volcanic CO₂ emission rates on Tibetan Plateau correlate well with the global atmospheric CO₂ curve, which suggested the India-Asia collision was the primary driver of changes in atmospheric CO₂ over the past 65 Ma. This work was published in Nature Communications. 

Earth’s climate Cooling in Cenozoic are thought to be related to the decreasing atmospheric CO₂ concentrations, however, factors leading to such decreases remain highly controversial. The tectonic and volcanic contributions towards atmospheric CO₂ from deep terrestrial sources have been studied using the India-Asia collision, to take towards quantifying our understanding of Earth's Cenozoic atmosphere. 

Based on systematic geochemical data and analysis of magmatic rocks in Tibet, scientists proposed a three-stage evolution model of Cenozoic magmatism in Tibet and atmospheric CO₂ variations. A continental collision-derived CO₂ flux model (CCFM) was developed to estimate the CO₂ emission flux from magmatism and metamorphism across the whole Cenozoic. Calculated results yield a broad range of CO₂ degassing fluxes from ~0.0001 to 10 Pg (1Pg = 10⁹ Tons) in Cenozoic, and may also be divided into three stages.  

Figure 1: Deep CO₂ emissions from Dagejia hydrothermal field in Tibetan plateau. (Image by Prof. GUO's group)  

The strong correlation between magmatic activity, source region composition, modelled CO₂ outgassing rate and atmospheric CO₂ concentration is fully consistent with a causal link between India-Asia collision and global CO₂ variations, and the related paleo-climate changes in Cenozoic, which highlights the carbon contribution from subduction-induced carbonate metasomatism in continental collisional zones. 

“This study has taken the quantification of metamorphic and volcanic sources of CO₂ to a new level of precision and documentation. In the geological past, mountain building was apparently atmosphere building”, reviewed by the website of Department of Earth and Environmental Sciences, Ludwig Maximilian University of Munich. 

The study was done in collaboration with scientists from University of Leeds and Ludwig Maximilian University of Munich, and was supported by the Strategic Priority Research Program (B) and Key Research Project of Frontier Sciences of Chinese Academy of Sciences, the National Natural Science Foundation of China, the Second Tibetan Plateau Scientific Expedition and Research Program and the National Key Research and Development Program of China. 

Figure 2: Types of CO₂ emissions from volcanic field (modified from Ruddiman, 2008).  

Contact: 
GUO Zhengfu  
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics 
Phone: 86-01-82998393
E-mail: zfguo@mail.iggcas.ac.cn 

Reference: 
India-Asia collision as a driver of atmospheric CO₂ in the Cenozoic