GEOCHEMICAL CHARACTERS, CARBON AND HELIUM ISOTOPIC COMPOSITIONS OF NATURAL-GAS FROM HAT SPRINGS OF SOME AREAS IN CHINA

The main components of hot spring gases in some areas of China are CO2 or N-2, and they have no or trace alkanes and very lower quantity of He. The delta(13)C(1) values of hot spring gases mainly range from -20 parts per thousand to -22 parts per thousand, which suggest the metha ne mainly be the inorganic origin in these gases. The delta(13)C(CO2) values of hot spring gases are mainly from -4% to -8%, so these carbon dioxides are also the inorganic origin. delta(13)C(CO2), values posit ively correlate with CO2 contents, their regression equation is delta( 13)C(CO2)(parts per thousand)approximate to 0.966 log-CO2-6.354; delta (13)C(CO2), values negatively correlate with N-2 contents, their regre ssion equation is delta(13)C(CO2)(parts per thousand)approximate to-0. 109N(2)-3.193. According to the helium isotopic compositions, we can d istinguish mantle-derived hot spring gases from crustal hot spring gas es, the former with R/Ra>1 and the latter with R/Ra<1.