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

Geothermal Energy

Science – Society – Technology

Table 1 Minerals and exchangers considered in the model

Phase	Composition	Mass fraction, %		Reactive surface, m²/g
Phase	Composition	Sample I	Sample II	Sample I	Sample II
Quartz	SiO ₂	95	39	0.002	0.02
Amorphous silica	SiO_{2 (amorph)}	0.0001	0.0009	300	300
Potassium feldspar	KAlSi₃ O ₈	2	8	0.0023	0.023
Kaolinite	Al₂Si₂O₅(OH)₄	1	37	3.6	3.6
Muscovite	KAl₃Si₃O₁₀(OH)₂	1	12	1.2	1.2
Calcite	CaCO₃	0	0.2	0	0.0001
Pyrite	FeS₂	0.005	0.29	0.003	0.001
Ferrihydrite	Fe(OH)_{3 (amorph)}	0.007	0.26	n.a.	n.a.
Aluminum hydroxide	Al(OH)_{3 (amorph)}	0.0013	0.02	n.a.	n.a.
Manganese oxohydroxide	MnOOH	0.0007	0.0004	n.a.	n.a.
Al exchange	AlX₃	7.3 × 10⁻⁵	2.6 × 10⁻⁴	n.a.	n.a.
Ca exchange	CaX₂	3.8 × 10⁻³	0.3	n.a.	n.a.
Mn exchange	MnX₂	8.4 × 10⁻⁵	6.4 × 10⁻⁴	n.a.	n.a.

Phases printed in italics were excluded after sensitivity analysis or initial simulations. Mass fractions were taken from Müller et al. (2017), except amorphous aluminum hydroxide, which was calculated from sequential extraction data (ibid.). Reactive surfaces were calculated from specific surface values collected in the RES³T database
Phases printed in italics were excluded after sensitivity analysis or initial simulations