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CO2和CH4渗漏在地球表面是一种普遍的地质现象,这些释放的温室气体不仅对全球气候变化和碳循环产生重要影响,而且可以示踪其来源及构造活动信息。对青藏公路沿线地表渗漏气体的组分、CO2和CH4碳同位素以及He同位素组成进行了分析,结果显示该区渗漏气体主要有N2型和CO2型2类。N2型渗漏气体主要分布在北麓河、布查湖和沱沱河东侧,N2含量均超过75%,CO2和CH4含量分别为3.45%~20.91%和0~3.58%。CO2型渗漏气体主要分布于二道沟南侧、沱沱河支流和唐古拉山兵站附近,CO2含量均超过96%。所分析的渗漏气体的CO2/3 He值、CH4/3 He值、δ13CCO2值和δ13C1值显示布查湖渗漏CO2和CH4均为生物成因,无幔源CO2和He;北麓河和沱沱河东侧渗漏CO2和CH4可能均为非生物成因,幔源CO2含量超过50%;二道沟南侧、沱沱河支流和唐古拉山兵站附近的CO2型气体中CO2主要为幔源无机成因,其中唐古拉山兵站渗漏气体中还伴有幔源CO2还原形成的微量非生物成因CH4。所有渗漏气体中He均是以壳源为主,幔源He仅占2.15%~5.66%。以上的结果表明研究区大量幔源无机CO2的释放,可能与班公湖—怒江缝合带和可可西里—金沙江缝合带这2条深大断裂带以及藏北新生代火山活动有关,但有限的幔源He输入可能与断裂带深部的开放性程度较低有关,反映了该区处于挤压的构造环境和地壳增厚的地质背景,或者是由于较高壳源放射性成因He的混入而“稀释”了幔源He所致。
Leakage of CO2 and CH4 on the Earth’s surface is a common geologic phenomenon that not only has a significant impact on global climate change and the carbon cycle, but also traces its origin and tectonic activity. The components of surface seepage gas, the carbon isotopes of CO2 and CH4 and the He isotope composition along the Qinghai-Tibet Highway were analyzed. The results show that there are mainly two types of gas leakage in this area, N2 and CO2. N2 gas leakages are mainly distributed in Beiluhe, Bucha Lake and the east of Tuotuo River with N2 content over 75% and CO2 and CH4 contents ranging from 3.45% to 20.91% and from 0 to 3.58% respectively. CO2-type gas leakage mainly located in the south of Erdaogou, Tuotuohe tributaries and the Tanggula station near the CO2 content of more than 96%. The CO2 / 3 He value, CH4 / 3 He value, δ13CCO2 value and δ13C1 value of the leaking gas indicated that both Leakage CO2 and CH4 in the Lake Bucha Lake were biogenic, with no mantle source CO2 and He; Beiluhe and Tuotuo Leakage of CO2 and CH4 on the east side of the river may be abiotic origin and mantle-derived CO2 content is over 50%. CO2 in the south of Erdaogou, Tuotuohe tributaries and nearby Tanggula station is mainly mantle-derived inorganic Among them, the trace gas of CH4 formed in the seepage gas of Tanggulashan station is accompanied by the reduction of mantle-derived CO2. In all the leaking gases, He is dominated by the crust, and mantle He is only 2.15% ~ 5.66%. The above results indicate that the release of a large amount of mantle-derived inorganic CO2 in the study area may be related to the two great fault zones of Banghu-Nujiang suture and Hoh Xil-Jinshajiang suture and Cenozoic volcanic activities in northern Tibet, but the limited mantle The source He input may be related to the lower degree of openness in the deep fault zone, reflecting the crustal tectonic setting and the crustal thickening of the geological setting, or due to the higher shell source He "Caused by the mantle source He.