3.4 GUO Zhengfu

Fluxes and origin of greenhouse gases from typical volcanic-geothermal fields in China

Zhengfu Guo 1,2,3*, Maoliang Zhang 1,2,3, Lihong Zhang 1,2,3, Yutao Sun 1,2,3, Ming Lei 1,2,3, Wenbin Zhao 1,2,3, Lin Ma 1,2,3

1 Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

2 Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China

3 University of Chinese Academy of Sciences, Beijing 100049, China

* Corresponding author: zfguo@mail.iggcas.ac.cn

Deep-seated carbon could be transported from Earth’s interior into atmosphere by volcanic activities, which play an important role in geologic carbon degassing and its effects on global climate. In addition to volcanic eruptions, quiescent volcanoes could also release large amounts of magmatic CO2 into the atmosphere. Therefore, quantitative studies on evaluating the contribution of volcanic activities to rising of atmospheric CO2 concentration are critical, especially in the context of global warming. During the past few years, we have estimated the fluxes of greenhouse gases released from typical volcanic-geothermal fields (i.e. Changbaishan, Tengchong, Wudalianchi and Yangbajing) in China using closed chamber method and gas-water chemistry methods. It is indicated that the total flux of greenhouse gases (referring mainly to CO2) from the studied volcanic fields is c. 8.13×106 t·a-1, taking up about 6% of the total CO2 flux from global volcanoes. Volcanic gases emitting from Pacific tectonic domain (examplied by Changbaishan and Wudalianchi) and Thethys tectonic domain (examplied by Yangbajing and Tengchong) display different signatures on flux of greenhouse gases and gas geochemistry. In comparison with Pacific tectonic domain, the fluxes of greenhouse gases from volcanic field associated with Thethys tectonic domain are higher. In addition, volcanic gases from Thethys tectonic domain are characterized by higher degree of crustal contamination than those of Pacific tectonic domain, indicating different tectonic settings and mechanisms of magma evolution between oceanic subduction zone and continental subduction zone.