Flux and genesis of the carbon release from some Cenozoic volcano-geothermal areas in the Qiangtang terrane, Qingzang Plateau, China

<p indent="0mm"> The Qingzang Plateau, which was produced by the India and Eurasia continental collision, is considered to be an ideal area for investigating the carbon cycling in deep part of the continental subduction-collision zone. Previous researches mainly focused on the flux and process of the CO₂ release from the Cenozoic volcano-geothermal area to the atmosphere at the front of subduction zone. The total flux and mechanism of carbon release in the hinterland of orogenic belt still need to be further constrained. Here, we have firstly carried out the research on the fluxes of CO₂ release from five Ceonozoic volcano-geothermal areas (i.e. Rongma, Xiabiecuo, Quse, Guogencuo and Gangni) within the Qiangtang terrene in the Qingzang Plateau and have discussed the mechanism of CO₂ release from those areas. In-situ measurements of microleakaged CO₂ in soils by using the dynamic closed-chamber method indicate that the average CO₂ fluxes from soils in the Rongma, Xiabiecuo, Quse, Guogencuo and Gangni five volcano-geothermal areas were 22.3, 52.3, 90.8, 194 and 317 (g/m²)/d, respectively, which were slightly lower than those [3.90~792 (g/m²)/d] of soils in the Cenozoic volcano-geothermal areas in the Lhasa terrane. On the basis of above results, it is preliminary estimated that the total flux of CO₂ released to the atmosphere from soils within the volcano-geothermal areas in the Qiangtang terrane is at least 5.50 Mt/yr. This indicates that the Cenozoic volcano-geothermal areas in the hinterland of the Qingzang Plateau has a large carbon release potential. The He-C isotopic geochemical characteristics show that the CO₂ from soils within volcano-geothermal areas in the Qiangtang terraneis was mainly derived from the decarbonization of inorganic carbonate minerals and partly originated from the mantle degassing. The large-scale strike-slip fault systems widely distributed in those five volcano-thermal areas may serve as important pathways for the release of carbon in depth.