Fig. 7
From: In-situ monitoring of 3He/4He in summit gases of Kilauea Volcano (Hawaii) prior to the 2020 eruption
Carbon dioxide (CO2) versus 3He/4He (R/RA, RC/RA) ratios for ground-truthing samples from data in Tables 2 and 3. All CO2 results from companion Giggenbach bottle samples were taken sequentially prior to copper tube samples taken for helium and isotopes. The one exception (green dot) was a CO2 analysis from the same copper tube sample (SB20-15, Table 2) analyzed by the USGS. The location of the sample sites is noted. Because low, air-like He isotope (R/RA) ratios for high CO2 content gas is unlikely, at least five fumarole-like gas samples (see left rectangle) were contaminated, either upon line flushing, tube crimping, storage or sample extraction. Partial vacuum loss (see right rectangle) refers to samples that may have lost part of their original vacuum. Samples labeled VGPS were vigorously pumped by an electric diaphragm pump; all others were manually pumped with a piston hand pump