geothermal gas / gas state / noble gas analyses / Chemical geology / gas bottles / gas isotope analysis / gas falls / gas chromatography / stable gas isotope results / Chemical and isotopic compositions / gas isotope analyses / geothermal systems / gas concentrations / low gas concentrations / gas chemistry / gas isotope / sampled gas / stable gas isotope analyses / gas isotope composition / chemical characteristics / rubber-stoppered glass phials / present gas concentrations / calculated gas ratios / gas phase / /