Degassing thermal features at Yellowstone National Park include spectacular geysers, roiling hot springs, bubbling mud pots, fumaroles, frying pans, and areas of passive degassing characterized by steaming ground. Most of these features are readily identified by visible clouds of steam that are occasionally accompanied by a strong “rotten egg” odor from emissions of hydrogen sulfide gas. Gas compositions typically are greater than 90% carbon dioxide with lesser amounts of helium, hydrogen, hydrogen sulfide, methane, nitrogen and other trace components. The composition of the gas and relative amounts of gas and steam relate both to the type of feature as well as the geographic location within the park. In 2003 we began a long-term field study of Yellowstone gases with a goal of obtaining complete chemical analyses from a variety of features from all areas of the park.
Results from samples collected through 2012 are published in numerous journal articles and reports (Bergfeld et al., 2012, 2014; Chiodini et al., 2012; Evans et al., 2010; Lowenstern et al., 2012, 2014, 2015; and Werner et al., 2008). Synthesis of these data allow us to delineate areas within Yellowstone that are dominated by magmatic versus crustal gas sources and to tease out additional information regarding sedimentary and metamorphic sources for crustal gas. This report compiles our published gas and water data with new gas data from samples collected through September, 2018 and includes some previously unpublished carbon isotope data from waters collected during 2011. Some of the analyses represent replicate samples collected in different bottles on the same day, others are samples collected from the same location in different years, and some sites were only sampled once. A companion data release focused on water chemistry and discharge for 2017-18 waters is planned be published in a separate report. The data herein are organized by sample type: Tables 1 and 2 include bulk chemistry and isotope data for 199 gas samples collected in evacuated bottles containing sodium hydroxide and 41 gas samples collected in dry evacuated bottles, respectively; Table 3 presents chemical and isotope data for 62 water samples from thermal and non-thermal features; Table 4 contains helium and carbon isotope data for 10 water samples and 1 gas sample. Each sample is assigned a group number linked to a particular area within the park (figure 1). Samples in groups 2 through 10 and 12 through 22 tend to be in close proximity. Group 11 includes samples from general locations across Eastern Yellowstone. Samples keyed to group 1 (miscellaneous) are not co-located.
The analytical results include major and trace element chemistry for the gases and waters, and isotope values for carbon dioxide (d13C-CO2), dissolved inorganic carbon (d13C-DIC), helium (3He/4He), steam (d18O, dD), neon (20Ne/22Ne and 21Ne/22Ne), and argon (38Ar/36Ar and 40Ar/36Ar). All data in this report supersede previously published analyses. The reader is directed to early publications for details on sampling and analytical methods and for in depth discussions regarding interpretations of the gas data.