PROTOCOLS FOR GAS AND VAPOR SAMPLING IN HYDROTHERMAL DISCHARGE AREAS

Hydrothermal features such as hot springs, fumeroles, mud volcanos, and so-called “frying pans” are the surface expressions of complex subsurface systems of heat and mass transfer. Geochemical techniques are commonly used to obtain information on reservoir characteristics such as reservoir temperature, fluid-rock interactions, fluid pathways, the presence or absence of phase separation, and hydrothermal fluid origins.

Aqueous geochemical samples may be unreliable, because fluids interact with surrounding rocks, have variable pH and redox states, and collected samples may be easily contaminated. To circumvent these difficulties, bulk gas samples and isotopic evaluations are desireable, but the protocols for obtaining gas samples are typically more demanding than those for aqueous samples; in addition, the physical act of sampling may be more hazardous. As with any geochemical sampling program an understanding of proper collection techniques, sample handling procedures, and careful identification of on-site hazards is important. Here we present an overview of published methods for the safe and reliable collection of gas and vapor samples in hydrothermal systems that is specifically targeted towards sampling by undergraduate researchers.