Fumarole gas geochemistry and tree-ring radiocarbon data at Mammoth Mountain, California (1989-2016)

Mammoth Mountain is a dacitic dome complex located on the southwestern rim of Long Valley Caldera, California. Mammoth Mountain has exhibited unrest over the past ~30 years, characterized by seismicity over a broad range of depths, elevated 3He/4He ratios in fumarolic gas and large-scale diffuse CO2 emissions. Monitoring of this unrest has included collection of fumarole gas samples for geochemical analysis and tree cores for radiocarbon analysis of annual growth rings. This report updates the long-term geochemical record at Mammoth Mountain, compiling the chemical and isotopic (d13C-CO2, 3He/4He) compositions of 59 gas samples collected from Mammoth Mountain fumarole from 1998 to 2016. In addition, we report radiocarbon compositions of 1989-2016 and 2013-2016 annual growth rings for the CTWP and HSL-1 lodgepole pines, respectively. The data sets are saved in spreadsheets in the *.csv format. The reader is referred to publications for details on sampling and analytical methods and data interpretations.