Table 1 Concentrations of selected aqueous species in M-vent and L-vent fluids and seawater

Temperature

35 °C

231 °C

2 °C

pH (25 °C)

4.8

5.2

7.8

K⁺ (mmol/kg)

10.7

18.9

9.95

Ca²⁺ (mmol/kg)

18.5

19.7

9.98

Mg²⁺ (mmol/kg)

39.2

0

53.0

Cl⁻ (mmol/kg)

549

528

537

SO₄²⁻ (mmol/kg)

22.2

0

27.7

∑H₂S (mmol/L)

0.00042

6.3

–

∑CO₂ (mmol/kg)

21.6

11.5

2.3

CH₄ (μmol/L)

24

83

–

H₂ (mmol/L)

< 0.002

0.83

–