Table 1 Formation ages and the QMS gas composition data from 12 drilling mud gas samples from IODP Expeditions 338 and 348 covering the depth range 950–3050 mbsf. Analytical errors are ± 20% for helium and ± 5% for all other gases. Formation ages from nannofossils, C0002F: Strasser et al. 2014c; C0002N/P: Tobin et al., 2014
From: Mantle-derived fluids in the Nankai Trough Kumano forearc basin
Sample # [mbsf] | Expedition/ Hole | Formation age [Ma]a | He (ppmv) | Ar (vol.%) | N2 (vol.%) | O2 (vol.%) | CH4 (vol.%) |
|---|---|---|---|---|---|---|---|
950 | 338/C0002F | 3.79–5.59 | 6.8 | 0.93 | 74.8 | 19.2 | 4.98 |
1400 | 338/C0002F | > 5.59 | 6.9 | 0.98 | 77.9 | 20.5 | 0.50 |
1700 | 338/C0002F | > 5.59 | 6.7 | 1.00 | 78.2 | 20.3 | 0.43 |
1800 | 338/C0002F | > 5.59 | 6.7 | 0.96 | 78.6 | 20.3 | 0.19 |
1850 | 338/C0002F | > 5.59 | 6.6 | 1.01 | 78.2 | 20.4 | 0.22 |
2050 | 348/C0002N | ≤ 7.362–7.424 | 8.1 | 0.93 | 78.8 | 20.1 | 0.07 |
2200 | 348/C0002N | ≤ 9.35 | 8.0 | 0.92 | 80.0 | 19.8 | 0.12 |
2349.5 A | 348/C0002P | ≤ 10.541 | 7.9 | 0.93 | 78.8 | 20.1 | 0.20 |
2349.5 B | 348/C0002P | ≤ 10.541 | n.a. | n.a. | n.a. | n.a. | n.a. |
2850 | 348/C0002P | ≤ 10.72 | 8.3 | 0.91 | 79.3 | 19.5 | 0.25 |
2968.5 | 348/C0002P | ≤ 10.72 | 8.5 | 0.90 | 78.2 | 18.9 | 1.91 |
3050 | 348/C0002P | ≤ 10.72 | 8.0 | 0.92 | 79.3 | 19.5 | 0.23 |