In-situ monitoring of 3He/4He in summit gases of Kilauea Volcano (Hawaii) prior to the 2020 eruption

Table 2 Conventional Helium Isotope Data, Sulfur Banks, Kilauea, December 2020 Deployment†

Conventional Sample ID	Collection Date	Location Type	R/R_a	R_c/R_a	⁴He/²⁰Ne	X-value*	⁴He (cm³STP/ cm³)	²⁰Ne (cm³STP/ cm³)	⁴⁰Ar (%)**	Comments
SB 20-1	12/10/20	VGPS Exhaust	1.0	n.d.	0.3	0.9	4.06E-06	1.35E-05	0.6936	OK
SB 20-2	12/10/20	Tee near fumarole	1.0	n.d.	0.3	0.8	4.20E-06	1.56E-05	0.8015	Sample Lost***
SB 20-3	12/12/20	VGPS Exhaust	1.0	n.d.	0.3	0.9	4.00E-06	1.37E-05	0.7038	OK
SB 20-4	12/12/20	Tee near fumarole	1.0	n.d.	0.3	0.9	3.68E-06	1.32E-05	0.6782	Sample Lost?
SB20-5	12/13/20	VGPS Exhaust	1.0	n.d.	0.3	1.0	4.99E-06	1.62E-05	0.8323	OK
SB20-6	12/13/20	Tee near fumarole	0.8	n.d.	0.2	0.7	3.49E-06	1.55E-05	0.7963	Sample Lost***
SB20-7	12/15/20	VGPS Exhaust	1.1	n.d.	0.3	0.9	4.50E-06	1.56E-05	0.8015	OK
SB20-8	12/15/20	Tee near fumarole	0.9	n.d.	0.3	0.9	4.11E-06	1.52E-05	0.7809	Sample Lost***
SB20-9	12/17/20	VGPS Exhaust	10.4	14.3 ± 0.34	1.1	3.4	6.44E-06	5.88E-06	0.3021	OK
SB20-10	12/17/20	Tee near fumarole	14.6	14.8 ± 0.52	18.9	59.5	4.78E-06	2.52E-07	0.0129	OK
SB20-11	12/19/20	VGPS Exhaust	0.9	n.d.	0.3	0.9	4.83E-06	1.63E-05	0.8374	Sample Lost***
SB20-12	12/19/20	Tee near fumarole	1.0	n.d.	0.3	0.9	4.76E-06	1.62E-05	0.8323	Sample Lost***
SB20-13	12/20/20	VGPS Exhaust	11.2	16.0 ± 0.67	1.0	3.1	4.94E-06	4.95E-06	0.2543	OK
SB20-14	12/20/20	Tee near fumarole	14.8	15.0 ± 0.53	31.5	98.9	4.48E-06	1.42E-07	0.0073	OK
SB20-15	12/20/20	Tee near fumarole	15.0	15.1 ± 0.20	35.6	124	6.06E-06	1.70E-07	0.0088	OK

† All samples were collected in crimped copper tubes after pumping gas through them, either automatically or by hand. Samples SB20-1 through SB20-14 were analyzed in the Barry Lab at WHOI. Replicate sample SB20-15 was analyzed by A. Hunt, USGS Denver Isotope Lab; this sample was 99.0% CO₂. Detailed analysis procedures can be found in Hunt (2015)
* X value is calculated as the ⁴He/²⁰Ne of the sample over the ⁴He/²⁰Ne of air
** Calculated using ²⁰Ne/⁴⁰Ar and assuming ²⁰Ne and ⁴⁰Ar concentrations of 0.00001818 and 0.00934 mol/mol for pure dry air, respectively
*** Air compositions are due to sample gases being overwhelmed by air contamination. Air corrections (R_C/R_A) are not included for samples with ⁴He/²⁰Ne values below 1.0, because the correction breaks down (P. Barry, pers. comm., 2022)

ISSN: 2191-5040