Electrical Resistivity Structure and Helium Isotopes around Naruko Volcano, Northeastern Japan and Its Implication for the Distribution of Crustal Magma

Table 1

Chemical and isotopic compositions of hot spring gases sampled observed in this study. The analytical error for ⁴He/²⁰Ne is ~15% of the values given. Abbreviation: ND: not determined.

No.	1	2	3	4	5
Site Name	Nakayamadaira	Onikobe	Wakuya	Sendai-Atago	Sendai-Atago
Latitude	38.723	38.813	38.541	38.245	38.245
Longitude	140.677	140.667	141.149	140.879	140.879
Phase	Gas	Gas	Dissolved	Gas	Dissolved
^3He/^4He (×10^−6) [±1𝜎]	4.86±0.17	3.62±0.10	0.78±0.03	0.46±0.01	0.41±0.01
^3He/^4He (R/RA)	3.47	2.59	0.56	0.33	0.29
^4He/^20Ne	6.3	1.3	2.6	591	410
CO2 (%)	88	76.1	ND	6.1	ND
N2 (%)	2	12	ND	92	ND
CH4 (%)	0.23	0.048	ND	0.83	ND
O2 (%)	0.02	0.11	ND	0.76	ND
He (%)	0.0001	0.0001	ND	0.042	ND
Ar (%)	0.058	0.22	ND	0.16	ND
𝛿^18O (‰)	−9.3	−10.4	−9.1	−6.7	−6.5
𝛿D (‰)	−65	−68	−59	−36	−35
Temp. (^∘C)	99.4	99.3	21.6	16.7	18.6
pH	9.0	8.8	9.0	8.8	8.7