Abstract:

CO₂/³He ratio of the mantle-derived CO₂ gas pools ranges from 10⁷ to 10¹³ in petroliferous basins in East China.This differs greatly from the constant CO₂/³He ratio of 2?10⁹-7?10⁹ of the manile-derived CO₂ gas while Separatng from the basalt magma. The CO₂/³He ratio of Wanjingta CO₂ gas pool formed in Mesozoic in Sogliao Basin ranges from 10⁹-10¹³, but that of the mantle-derived CO₂ gas pools formed since Cenozoic in Huangha, Jiyang, Subei and Shanshui Basins is as low as 10⁷-10⁹. This indicates that CO₂/³He ratio of the mande-derived gas pools is controlled by release mechanism of the gases.The eruption and intrusion of the basalt magma provided a large number of gas sources for the formation of the mantle-derired gas pools; the CO₂ gas in the magma chamber would release directly along fault-passages which cut the chamber deeply. This played an important role in the formaion, the gas source supplies, the CO₂/³He ratio and geochemical properties of the pools. Meantime, characters of CO₂/³He ratio of the inomanic origin CO₂ gas pools provide a new evidence for its mantle-derived origin.

Key words: CO₂/³He ratio, mantle-derived gases, fault, formation mechanism