Degassing of deep-sourced CO2 from Xianshuihe-Anninghe fault zones in the eastern Tibetan Plateau
Degassing of deep-sourced CO2 from Xianshuihe-Anninghe fault zones in the eastern Tibetan Plateau
复制标题
DOI：
10.1007/s11430-021-9810-x
复制
发表时间：
2021-09
期刊：
影响因子：
--
通讯作者：
Sheng Xu;L. Guan;Maoliang Zhang;J. Zhong;Wei Liu;Xian-gang Xie;Congqiang Liu;N. Takahata
中科院分区：
文献类型：
--
作者：
Sheng Xu;L. Guan;Maoliang Zhang;J. Zhong;Wei Liu;Xian-gang Xie;Congqiang Liu;N. Takahata
青藏高原东南缘大型走滑断裂带沿着分布的中高温地热田正在释放大量的气体。本研究对鲜水河-安宁河断裂带（XSH-ANHFZ）沿线沿着采集的11个温泉水及伴生气泡气样品进行了化学和同位素组成分析。结果表明，温泉沃茨主要来源于不同海拔高度的大气降水补给.由于区域性碳酸盐岩、碳酸盐岩和钠硅酸盐岩的溶解作用，大部分水样中Na+和HCO 3 −显著富集，气体样品中3 He/4 He比值为大气值的0.025-2.73倍。在断裂密集的康定地区，3 He/4 He比值较高，沿鲜水河断裂带向沿着逐渐降低。热液中溶解无机碳（DIC）的浓度为2 ~ 42 mmol L−1，δ 13 CDIC为−6.9‰ ~ 1.3‰，−7.2‰ ~ −3.6‰，Δ 14 C为−997‰ ~ −909‰。结合区域地球化学和地质信息，CO2的来源可归结为深源CO2来自地幔和海相碳酸盐岩变质作用，浅源CO2来自海相碳酸盐岩溶解作用和生物成因CO2。质量平衡模型表明，11±6%的DIC来自浅部碳酸盐矿物的溶解，9±8%来自沉积有机质的热解，80±9%来自深变质成因和幔源CO2。其中，安宁河断裂带（ANHFZ）的深源CO2仅为变质碳，而约为碳酸盐碳。12%，约。XSHFZ中88%的深源CO2分别来自地幔和变质碳。康定地热田的平均深源CO2通量估计为160 t a−1。如果将青藏高原东南缘各断裂带的温泉全部考虑在内，区域深源CO2通量将达到约1000 m3。105t a−1。这些结果表明，非火山区释放的深源CO2可能在全球深源碳脱气总量中占有相当大的比例，应引起重视。
A large number of gases are releasing from the medium-high temperature geothermal fields distributed along the large-scale strike-slip fault zones in the southeastern margin of the Tibetan Plateau. In this study, 11 hot spring water and the associated bubbling gas samples were collected along the Xianshuihe-Anninghe fault zones (XSH-ANHFZ) and analyzed for chemical and isotopic compositions. Theandvalues indicate that hot spring waters are predominantly meteoric origin recharged from different altitudes. Most water samples are significantly enriched in Na+and HCO3−due to the dissolution of regional evaporites, carbonates and Na-silicates.3He/4He ratios of the gas samples are 0.025–2.73 times the atmospheric value. The3He/4He ratios are high in the Kangding region where the dense faults are distributed, and gradually decrease with increasing distance from Kangding towards both sides along the Xianshuihe fault zones (XSHFZ). Hydrothermal fluids have dissolved inorganic carbon (DIC) concentrations from 2 to 42 mmol L−1,δ13CDICfrom −6.9‰ to 1.3‰,from −7.2‰ to −3.6‰ and Δ14C from −997‰ to −909‰. Combining regional geochemical and geological information, the CO2sources can be attributed to deep-sourced CO2from mantle and metamorphism of marine carbonate, and shallow-sourced CO2from the dissolution of marine carbonate and biogenic CO2. The mass balance model shows that 11±6% of the DIC is sourced from the dissolution of shallow carbonate minerals, 9±8% formed by pyrolysis of sedimentary organic matter, 80±9% derived from deep metamorphic origin and mantle-derived CO2. Among them, the deep-sourced CO2in Anninghe fault zones (ANHFZ) is merely metamorphic carbon, whereas ca. 12% and ca. 88% of the deep-sourced CO2in the XSHFZ are derived from the mantle and metamorphic carbon, respectively. The average deep-sourced CO2flux in the Kangding geothermal field is estimated to be 160 t a−1. If all the hot springs in various fault zones in the southeastern margin of the Tibetan Plateau are taken into account, the regional deep-sourced CO2flux would reach ca. 105t a−1. These results show that the deep-sourced CO2released from non-volcanic areas might account for a considerable proportion of the total amount of global deep-sourced carbon degassing, which should be paid more attention to.