STUDY ON GEOCHEMICAL CHARACTERISTICS OF HOT SPRING GAS IN HAINAN ISLAND
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.
Nitrogen isotopesSpring gasGas geochemistryHainan Island