腾冲新生代火山区CO_2气体释放通量及其成因  

Carbon dioxide emissions from Tengchong Cenozoic volcanic field,Yunnan Province,SW China

作　　者：成智慧[1] 郭正府[1] 张茂亮[1] 张丽红[1] 

机构地区：[1]中国科学院地质与地球物理研究所,新生代地质与环境重点实验室,北京100029

出　　处：《岩石学报》2014年第12期3657-3670,共14页Acta Petrologica Sinica

基　　金：中国科学院战略性先导科技专项(B类)(XDB03010600);国家自然科学基金重大国际合作研究项目(41020124002);国家自然科学重点基金项目(41130314)联合资助

摘　　要：许多研究结果表明,休眠期火山主要通过喷气孔、温泉以及土壤微渗漏三种方式向大气圈释放温室气体。腾冲是我国重要的新生代火山区之一,同时也是主要的水热活动区,但是关于温室气体释放通量的研究却鲜有报道。本文首次估算了该地区土壤微渗漏和温泉水的CO2释放通量,并根据气体成分的分析结果探讨了这些温室气体的来源。2012~2013年连续两年使用密闭气室法现场测量了土壤微渗漏CO2通量,结果表明,马站、热海-黄瓜箐和五合-蒲川-团田三个地区通量较高,其中,热海-黄瓜箐地区平均通量最高,马站次之,五合-蒲川-团田地区最低。较高的土壤微渗漏CO2释放地区同前人推断的岩浆囊的分布在空间上具有较好的一致性;三个地区气体的3He/4He比值较高,三端元模拟结果表明,它们均有较高含量的幔源He释放;根据气体CO2/3He与δ13CCO,CO2模拟计算,CO2主要来源于碳酸盐矿物的脱碳作用和岩浆脱气。由此推断2的释放同深部的岩浆囊具有重要的成因联系,它为碳酸盐矿物的脱碳作用提供了主要的热源,同时也是重要的物质来源。根据土壤微渗漏CO2平均通量及火山、地热异常区的分布面积估算出三个地区土壤微渗漏CO2的释放通量分别为1.8×106t/a（马站）,3.2×106t/a（热海-黄瓜箐）和2.0×106t/a（五合-蒲川-团田）。腾冲新生代火山区每年通过土壤微渗漏向大气圈释放CO2的量至少可达7.0×106t,为意大利Etna火山区释放CO2通量（1.4×107t/a）的二分之一。通过水岩相互作用计算温泉水中CO2气体的释放通量为4.9×104t/a。腾冲温泉气泡及温泉水向大气圈释放CO2气体的总通量为5.3×104t/a,远高于意大利Vulcano火山区温泉释放的CO2总通量（3.7×103t/a）。Recent researches have indicated that, beside volcanic eruption periods, dormant periods between the volcanic activities can emit a large amount of CO2 from the solid earth into atmosphere. In quiescent volcanoes, CO2 is released not only from fumaroles and hot springs but also from well-defined areas on the flanks and at the base of volcanoes, which has been called soil gases. Tengchong is one of the most important Cenozoic active volcanic fields, and a strong geothermal activity area in Southeast Tibet, while researches on flux of CO2 in Tengchong are poorly reported. During 2012 - 2013, using closed-chamber method widely applied abroad, soil CO2 flux surveys were performed on Mazhan, Daying mountain, Rehai-Huangguaqing, Wuhe-Puchuan-Tuantian and Banglazhang. It turns out that soil CO2 flux of Dayingshan and Banglazhang is very low （0.5 - 19. lgm-2d-l ）. However, 105, 133 and 97 measurements performed in Mazhan, Rehai-Huangguaqing and Wuhe-Puchuan-Tuantian are very high and show a wide range of values up to 6981.9gm-2d-1 and the average soil CO2 flux are 874. 5gm-2d-1, 42. 5gm-2d-1 and 25. lgm-2d-1 respectively. In order to elucidate its origin, gas samples of measured spots with high-CO2 flux were collected for compositional and isotopic analysis, and gases from hot springs nearby were also collected for comparison. Combined with the component and isotopic data of hot spring gases previously reported, we find a large range of 3He/4He ratios, 0. 22 - 5.92Ra. Mazhan-Qushi, Rehai-Huangguaqing and Wuhe- Puchuan-Tuantian present higher 3 He/4 He ratios and reveal their mantle origin. 813 Cco2 and CO2/3 He modeling indicates that CO2 may result from decarbonation of country rock and addition of carbon from mantle. Moreover, areas with high CO2 flux are consistent with the distribution of previously deduced magma chambers. The magma chambers are considered to be the major source of heat for decarbonation and a source of He and CO2. The total soil CO2 flux of Mazhan-Qushi, Tengchong-Rehai and Wuhe-Puchuan-Tuantian

关 键 词：土壤微渗漏 温泉 CO2 通量 成因 腾冲 

分 类 号：P317.3[天文地球—固体地球物理学]