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Table 2 Dissolution reactions considered in the model

From: The element-release mechanisms of two pyrite-bearing siliciclastic rocks from the North German Basin at temperatures up to 90 °C under oxic and anoxic conditions

Phase

Reaction

Log K

∆H (KJ/mol)

Amorphous silica

SiO2(am) ↔ SiO2(aq)

− 2.71

20.05

Kaolinite

Al2Si2O5(OH)4 + 6H+ ↔ 2Al3+ + 2SiO2(aq) + 5H2O

6.81

− 151.8

Muscovite

KAl3Si3O10(OH)2 + 10H+ ↔ 3Al3+ + K+ + 3SiO2(aq) + 6H2O

13.6

− 243.2

Calcite

CaCO3 + H+ ↔ Ca2+ + HCO −3

1.85

− 25.71

Pyrite

FeS2 + 3.5O2 + H2O ↔ Fe2+ + 2SO 2−4  + 2H+

217.4

− 1412

FeS2 + 14Fe3+ + 8H2O ↔ 15Fe2+ + 2SO 2−4  + 16H+

98.5

− 50.69

Ferrihydrite

Fe(OH)3 + 3H+ ↔ Fe3+ + 3H2O

2.54

− 84.08

Amorphous aluminum hydroxide

Al(OH)3 + 3H+ ↔ Al3+ + 3H2O

9.7

–

Manganese oxo-hydroxide

MnOOH + 3H+ ↔ Mn3+ + 2H2O

− 0.16

–

  1. Data taken from the LLNL database, except log K of ferrihydrite (SIT database) and amorphous aluminum hydroxide (Kittrick 1969). Values for the standard enthalpy of formation ΔH for amorphous aluminum hydroxide and manganese oxohydroxide are not available in the databases
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