摘要
为了查明海南岛温泉气体的起源,探讨海南岛温泉与琼北新生代火山活动的关系,通过对海南岛温泉气体成分和氮(N)同位素组成进行分析研究.结果表明:海南岛温泉气体以N2为主,含量都在87％以上,个别样品达到90％以上,且均有CO2共存.海南岛温泉气体δ15N值均大于0,且断裂带集中地区的样品,其δ15N值普遍偏大,而断裂带相对稀疏地区的样品,其δ15N值相对较低,说明温泉气体主要受断裂带控制,主要来源为地壳和大气.此外,海南岛温泉气体不论是气体组合还是氦同位素特征,都与腾冲、长白山及五大连池活动火山区地热流体逸出气体明显不同,前者气体组合以N2为主,后者主要以CO2为主,前者He含量高,3He/4He低,而后者He含量低,3He/4He高.综合温泉气体成分和同位素特征,认为海南岛温泉气体主要为地壳和大气来源,少量为幔源混入,其温泉气体释放活动属于正常的断层气体活动,与琼北新生代火山活动关系不大.
Abstract
In order to find out the origin of spring gas in Hainan Island and explore the relationship between springs in Hainan Island and Cenozoic volcanic activity in northern Hainan,the gas compo-sition and nitrogen(N)isotope composition of hot springs in Hainan Island were analyzed.The re-sults show that the hot spring gas in Hainan Island is dominated by N2,with a content of more than 87％,and individual samples reach more than 90％,and CO2 coexists.The 815 values of the hot spring gas in Hainan Island are all greater than 0,and the 615 values of the samples in the fault zone concentration area are generally larger,while the 815 values of the samples in the relatively sparse fault zone area are relatively low,indicating that the hot spring gas is mainly controlled by the fault zone,and the main source is the crust and atmosphere.In addition,the gas composition and helium isotope characteristics of hot spring gases in Hainan Island are obviously different from those of geo-thermal fluids in Tengchong,Changbai Mountain and Wudalianchi active volcanic areas.The former is mainly composed of N2,while the latter is mainly composed of CO2.The former has high He con-tent and low 3He/4He ratio,while the latter has low He content and high 3He/4He ratio.Based on the composition and isotope characteristics of hot spring gas,it is considered that the hot spring gas in Hainan Island is mainly derived from the crust and atmosphere,and a small amount is mixed with mantle source.The release activity of hot spring gas is a normal fault gas activity,which is not relat-ed to the Cenozoic volcanic activity in northern Hainan Island.
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