A joint research team led by Prof. GUO Zhengfu from the Institute of Geology and Geophysics (IGG) of the 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 million years.  

Their findings were published in Nature Communications on June 23.

Earth's climate cooling in Cenozoic (65 million years ago-present) are thought to be related to the decreasing atmospheric CO₂ concentrations, however, factors leading to such decreases remain highly controversial.  

Based on the India-Asia collision, the researchers investigated tectonic and volcanic contributions to atmospheric CO₂ from deep terrestrial sources. 

Through systematic geochemical data and analysis of magmatic rocks in Tibet, the researchers proposed a three-stage evolution model of Cenozoic magmatism in Tibet. The Stage 1 magmas (65-55 Ma) are Andean-type igneous rocks in southern Tibet, Stage 2 magmas (55-25 Ma) are composed of large-scale lava flows and pyroclastic deposits, and Stage 3 magmas (25 Ma-present) are small-volume lava flows distributed in southern and northern Tibet. 

"We developed a continental collision-derived CO₂ flux model (CCFM) to estimate the CO₂ emission flux from magmatism and metamorphism across the whole Cenozoic," said Prof. GUO. Calculated results yielded a broad range of CO₂ degassing fluxes from ~0.0001 to 10 Pg (1Pg = 10⁹ Tons) in Cenozoic. 

Deep CO₂ emissions from Dagejia hydrothermal field in Tibetan plateau. (Image by Prof. GUO Zhengfu'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. 

The study was conducted in collaboration with scientists from University of Leeds and Ludwig Maximilian University of Munich. 

It 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.