Soil gas CO2 emissions from active faults: a case study from the Anninghe—Zemuhe fault, Southeastern Tibetan Plateau, China

• Published in: Frontiers in earth science (Lausanne) Vol. 11
• Main Authors: Liu, Fengli, Zhou, Xiaocheng, Dong, Jinyuan, Yan, Yucong, Tian, Jiao, Li, Jingchao, Ouyang, Shupei, He, Miao, Liu, Kaiyi, Yao, Bingyu, Wang, Yuwen, Zeng, Zhaojun, Zhang, Yongxian
• Format: Journal Article
• Language: English
• Published: Frontiers Media S.A 09.05.2023
• Subjects: AZF; carbon dioxide; diffuse degassing; geochemistry; soilgas
• ISSN: 2296-6463; 2296-6463
• DOI: 10.3389/feart.2023.1117862

Introduction: Carbon dioxide emissions from non-volcanic areas are undervalued in the carbon cycle. Methods: First estimates of diffuse CO 2 flux from the Anninghe—Zemuhe fault (AZF), Southeastern Tibetan Plateau, China, which suggests this could equal 15% emissions from all volcanoes in China. Following the accumulation chamber method, CO 2 flux was investigated at 1,483 points, and along 67 profiles crossing the AZF. Results and discussion: Total CO 2 emissions from the AZF were estimated 1.2 Mt yr -1 . The relationship between soil gas CO 2 fluxes, earthquakes, and fault activity was discussed. The intense fault activity in the southern part of the Zemuhe fault (ZMHF) and the northern part of the Anninghe fault (ANH) was inferred, which could have enhanced the porosity of the soil, and accelerated the water-rock interactions and soil gas emission within the fault zone. The chemical and isotopic data indicated that biogenic CO 2 was the primary source of CO 2 from the AZF. Produced by interactions between groundwaters and carbonates, soil gas CO 2 could migrate to the near surface through cracks. Spatial variations of CO 2 flux in soil gas indicate that seismic activity could be responsible for the jumpy variations of CO 2 flux. The diffuse CO 2 from deep faults may contribute considerably to the greenhouse gas cycles.