Table A1.
Summary of the geochemical characteristics of fluid samples collected in the SMT.
| Sampling site | Snail (2861 m) |
Pika (2773 m) |
Archaean (2986 m) |
Deep seawater | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Sample type | Borehole | Natural vent |
Fe–H2S available* |
Borehole | Natural vent |
Natural vent |
||||
| H2S-type | Fe-type | <150°C | >150°C | <150°C | >150°C | |||||
| T ave. | 25 | 55 | 54 | 41 | 10 | 28 | 265 | 101 | 251 | 3 |
| (Range; °C) | (3–40) | (15–116) | (15–81) | (18–59) | (3–50) | (230–330) | (75–117) | (153–343) | ||
| pH | 6.69 | 6.65 | 5.85 | 6.38 | 7.57 | 6.59 | 3.33 | 5.61 | 3.60 | 7.73 |
| Alk. (meq) | 2.22 | 2.09 | 2.16 | 1.94 | 2.37 | 2.28 | −0.95 | 0.95 | −0.63 | 2.48 |
| Mg (mM) | 46.2 | 45.6 | 40.9 | 45.5 | 50.0 | 49.8 | 8.5 | 41.3 | 13.3 | 50.8 |
| Ca (mM) | 10.7 | 11.2 | 12.9 | 11.1 | 9.7 | 10.2 | 34.4 | 10.7 | 16.0 | 9.6 |
| Sr (μM) | 85.0 | 89.7 | 82.4 | 91.6 | 83.5 | 87.5 | 123 | 100 | 102 | 84.8 |
| Na (mM) | 460 | 455 | 450 | 463 | 469 | 460 | 457 | 424 | 370 | 457 |
| K (mM) | 10.8 | 11.4 | 13.0 | 11.7 | 9.7 | 9.7 | 24.9 | 13.5 | 25.6 | 9.6 |
| Li (mM) | 0.046 | 0.076 | 0.118 | 0.081 | 0.028 | 0.044 | 0.530 | 0.158 | 0.391 | 0.033 |
| B (μM) | 388 | 401 | 353 | 481 | n.d. | 362 | 695 | 524 | 984 | 375 |
| C1 (mM) | 540 | 545 | 542 | 539 | n.d. | 548 | 576 | 533 | 461 | 542 |
| Br (mM) | 0.85 | 0.85 | 0.83 | 0.85 | 0.84 | 0.84 | 0.93 | n.d. | 0.77 | 0.86 |
| SO4 (mM) | 25.3 | 25.0 | 22.9 | 23.9 | 25.7 | 26.9 | 3.5 | 23.0 | 7.6 | 27.4 |
| Si (mM) | 1.05 | 1.60 | 2.98 | 1.97 | 0.21 | 0.49 | 14.2 | 3.47 | 12.6 | 0.17 |
| NH4 (μM) | 14.3 | 7.9 | 5.2 | 7.3 | n.d. | 3.5 | 36.3 | 8.4 | 31.1 | 11.0 |
| NO3 (μM) | 4.4 | 13.2 | 2.8 | 0.0 | n.d. | 25.1 | 6.8 | 20.7 | 8.3 | 33.8 |
| H2S (μM) | 0.41 | 57.1 | 229 | 6.6 | n.d. | 34.6 | 6001 | 572 | 4313 | 0.04 |
| Mn (mM) | 0.15 | 0.23 | 0.32 | 0.20 | 0.12 | 0.02 | 0.99 | 0.23 | 0.89 | 0.0018 |
| Fe (μM) | 62.4 | 57.0 | 19.5 | 119 | 115 | 82.8 | 6494 | 244 | 2056 | 8.9 |
| Ba (μM) | 1.67 | 22.1 | n.d. | 33.4 | n.d. | 4.60 | 46.2 | 44.7 | 40.2 | 1.66 |
| O2 (μM) | 286 | 164 | n.d. (164) | n.d. | 98 | 18 | 16 | 18 | 100** | |
| N2 (μM) | 1630 | 1771 | n.d. | n.d. | n.d. | n.d. | 1099 | 1358 | 967 | n.d. |
| CO2 (mM) | 7.20 | 7.76 | n.d. (7.76) | 3.11 | n.d. | 8.42 | 36.2 | 16.8 | 16.6 | 2.3** |
| CH4 (μM) | 0.86 | 1.37 | n.d. (1.37) | 0.22 | n.d. | 1.46 | 14.9 | 20.9 | 15.8 | 0.0003** |
| H2 (μM) | 0.10 | 6.62 | n.d. (6.62) | n.d. | 0.69 | 23.8 | 67.8 | 33.2 | 0.0004** | |
Average values for each sample type at each sampling site, i.e., boreholes, low-temperature (<150°C) natural vents and high temperature (>150°C) natural vents are shown. These data were obtained from the samples collected in 2003, 2004, 2005, and 2010. *The chemical data for the samples of the Snail site with iron and sulfide concentrations, which are shown in italic, were divided into H2S-type (high H2S/Fe) and Fe-type (high Fe/H2S). For thermodynamic calculation, the average values in parentheses were used. **Concentrations of O2, CO2, CH4, and H2 in deep seawater were obtained previously (McCollom, 2007).