Reactions between komatiite and CO2-rich seawater at 250 and 350 °C, 500 bars: implications for hydrogen generation in the Hadean seafloor hydrothermal system

Progress in Earth and Planetary Science

Table 2 Composition of the sampled fluids in the experiments (mmol/kg)

Experiment	Time (h)	pH₂₅ _°C ^a	ΣCO₂ ^b	pH_{25 °C} ^c	pH_in-situ ^d	H₂	ΣCO₂	Cl	Na	K	Mg	Ca	Si	Fe	Mn
250 °C	0	n.a.	n.a.	4.9	6.0	0.003	396	1128	1036	0.08	n.d.	0.073	n.d.	n.d.	n.d.
	43	6.3	0.9	3.7	4.1	0.010	161	1174	939	0.94	36.2	46.5	6.1	0.49	0.19
	119	5.8	1.9	4.1	4.5	0.014	67	1168	951	0.89	40.4	39.7	4.4	0.56	0.15
	452	6.6	1.0	4.3	4.7	0.004	35	1186	948	0.85	38.4	39.2	2.4	0.77	0.23
	859	6.4	2.3	4.6	5.0	0.007	36	1178	937	1.24	37.2	48.7	2.1	0.85	0.24
	1771	7.1	1.0	4.4	4.8	0.021	35	1186	820	0.88	36.4	43.6	1.6	0.93	0.24
	2760	6.8	1.2	4.5	4.8	0.024	33	1175	949	0.95	36.4	48.8	3.5	0.97	0.25
350 °C	0	n.a.	n.a.	4.9	7.2	n.d.	396	966	946	0.10	0.03	0.078	n.d.	n.d.	n.d.
	90	6.1	1.9	3.8	5.6	6.0	176	971	902	0.78	1.2	39.4	3.7	1.53	0.71
	258	6.4	1.7	3.9	5.6	2.8	163	968	882	0.86	1.2	38.0	3.7	1.80	0.73
	594	6.4	1.7	3.9	5.6	2.9	179	963	877	0.98	1.1	42.2	3.6	1.65	0.67
	1146	6.5	1.8	3.9	5.7	2.7	174	969	900	1.08	1.0	41.1	3.8	1.61	0.63
	1530	6.6	1.7	3.9	5.7	2.2	171	953	884	0.81	1.0	37.3	4.1	1.55	0.60