Magmatic Signature in Submarine Hydrothermal Fluids Vented Offshore Ventotene and Zannone Islands (Pontine Archipelago, Central Italy)

Table 4

Helium and carbon isotopic composition of the dissolved (D) and bubbling gases (B). The ³He/⁴He ratios are normalized to the atmospheric helium isotopic composition and expressed as R/Ra where R is the isotopic ratio of the sample and Ra the atmospheric one.

Sample ID	Site	Depth (m)	Type	Sampling method	R/Ra	He/Ne	R/Rac	Error	δ^13CCO2	δ^13CCH4	δ^13CTDIC	CO2/^3He
5	Z1	134	D	Niskin	0.91	0.283	—	0.0152	—	n.a.	-0.52
9	Z2	127	D	Niskin	0.91	0.316	—	0.0143	—	n.a.	-1.51
13	ZDA	120	D	Niskin	0.80	0.344	—	0.0140	—	n.a.	-0.35
14	ZDA	147	D	Niskin	0.87	0.511	—	0.0178	—	n.a.	-0.53
17	Z2	127	B	ROV	3.72	92.19	3.73	0.0325	-0.71	-45.50	—
18	Z2	125	B	ROV	3.75	51.78	3.76	0.0302	-6.16	-44.28	—
19	VEN	80	B	Two-way glass bottle	1.33	25.26	1.34	0.0230	1.93	n.a	—
11-BT1	ZGP	129	B	ROV	3.49	7.71	3.60	0.02420	n.a.	-43.70	—
12-BT1	ZGP	129	B	ROV	3.50	7.11	3.62	0.02434	n.a.	n.a.	—
13-BT4	ZGP	127	B	ROV	3.41	5.47	3.56	0.02395	n.a.	n.a.	—

R/Ra_c is the ³He/⁴He ratio corrected for the atmospheric contamination (see text for details). n.a. = not analyzed; Data and labels after Martorelli et al. [27].