渭河盆地地热水水溶氦气成因与来源研究

Origin and Source of Soluble Helium Gas in Geothermal Water,Weihe Basin

渭河盆地地热水中含有丰富的水溶氦气,通过采集分析渭河盆地地热水水溶氦气成分和He同位素研究了氦气的成因与来源。分析结果表明,渭河盆地地热水水溶氦气体积分数普遍超过0.1%,最高达到3.395%。地热水水溶氦气的3He/4He比值介于(3.61±0.29)×10-8～(7.80±0.23)×10-7之间,氦气的R/Ra值小于1.00。天然气的4He/20Ne比值研究一致表明,渭河盆地地热水水溶氦气主要为壳源成因,混有微量的幔源氦。区域地质资料分析表明,富铀花岗岩放射性成因的氦气是渭河盆地地热水水溶氦气的主要来源,大面积出露于秦岭造山带以及隐伏于渭河盆地南缘新生代沉积层下的富铀花岗岩体为渭河盆地地热水水溶氦气的主要气源岩。

Helium gas is a kind of strategic rare resources. Helium gas abundance for industrial development in natural gas is 0.1%. The geothermal water of Weihe Basin contains abundant soluble helium gas whose relative content is more than 0.1% with the highest of 3. 395 %. Isotope analysis of the helium gas from this geothermal water shows that ^3He/^4He values are between （3.61±0.29） × 10^-8-（7. 80±0.23） × 10^-7. Its helium R/R, value of the helium gas is less than 1.0. ^4He/^20Ne ratio indicates that helium gas from the geothermal water in the basin is mainly the kind of crust-derived helium mixed with trace of mantle source. Regional geological data analysis shows that granite abundant in radioactive uranium, exposed in Qinling Orogenic Belt and distributed in large areas under Cenozoic sedimentary in South margin of Weihe Basin is the main source rock of soluble helium of the geothermal water.