Chemical and isotope composition of light hydrocarbons gases in hydrothermal systems: preliminary results from three Italian thermal areas

摘要

CO_2 and light C_1-C_4 saturated hydrocarbons were analysed for chemical and C-isotope composition in some gas samples coming from three hydrothermal systems with different deep temperatures and geological settings. The chemical data indicate that the total amount of light alkanes increases with decreasing temperature, and C_2-C_4 concentrations relative to CH_4 follow distinct patterns which discriminate between abiogenic and thermogenic gases. The δ~(13)C values indicate that inorganic synthesis predominates in high-T settings, and particularly in volcanic-hydrothermal systems.