青藏高原乌丽冻土区二氧化碳成因探讨

Discussion about the CO_2 Origins of Wuli Permafrost Zone in Qinghai-Tibetan Plateau

为了查明青藏高原乌丽冻土区天然气的组分与成因,对采集自乌丽水合物试验孔ZK1井及其周边钻孔的岩心顶空气、岩心解析气以及湖水气进行了组分和碳同位素测试分析,同时对ZK1井及其周边钻孔岩心中的碳酸盐岩碳同位素进行了测试分析。测试结果显示:该区天然气主要成分为二氧化碳,其含量在98%以上,烃类气体(主要为甲烷)含量很少;二氧化碳碳同位素主频在-4‰^-6‰(VPDB)之间,少量富烃样品的甲烷碳同位素主频介于-32.38‰^-27.82‰(VPDB)之间,碳酸盐岩的碳同位素平均值为-3.87‰(VPDB)。综合分析认为,研究区二氧化碳主要为幔源成因,可能与该区强烈的构造运动和岩浆活动有关。

In order to understand the component and origin of gases from gas-hydrate drillhole （ZK1）in Wuli permafrost zone,Qinghai-Tibetan Plateau,the gas components and the carbon isotopes of headspace gas samples and resolving gas samples from hole ZK1 and its adjacent drillholes and gas samples from lake water are ana-lyzed.At the same time,the carbon isotopes of carbonate rocks from cores are also analyzed.The results show that more than 98% natural gas is composed of carbon dioxide with a little hydrocarbon gas（mainly methane）, the main maximum values of δ13 CCOδ13 CCH 4 2 are between -4‰ and -6‰（VPDB）,the main maximum values of from a few rich-methane samples are between -32.38‰ and -27.82‰（VPDB）,while the mean val-ue of δ13 CCaCO 3 is -3.87‰（VPDB）.Integrated with regional geology,it could be drawn a conclusion that the CO2 of Wuli permafrost zone is mainly of volcanic mantle type,which is related with strong tectonic movement and magma activities.