Weak hydrothermal carbonation of the Ongeluk volcanics: evidence for low CO2 concentrations in seawater and atmosphere during the Paleoproterozoic global glaciation

Progress in Earth and Planetary Science

Table 1 Isotopic compositions of calcites and CO₂ content in the Ongeluk basaltic andesites and hydrothermal jaspilites

Sample no.	Rock type	Classification of calcite	CO₂ (wt%)	δ¹³C (VPDB, ‰)	δ¹⁸O (VPDB, ‰)	Temperature (°C)^a
GU033	Basaltic andesite	Disseminated	0	− 14.2	− 15.2	123
GU034	Basaltic andesite	Disseminated	0	− 15.6	− 13.8	109
GU035	Basaltic andesite	Disseminated	0	− 13.2	− 14.6	117
GU036	Basaltic andesite	Disseminated	0.01	− 15.8	− 15.8	130
GU037	Basaltic andesite	Disseminated	0.01	− 16.1	− 14.3	114
GU038	Basaltic andesite	Disseminated	0	− 15.9	− 12.9	100
GU041	Basaltic andesite	Disseminated	0	− 18.9	− 14.1	112
GU045	Basaltic andesite	Disseminated	0	− 18.3	− 13.3	104
GU048	Basaltic andesite	Disseminated	0	− 15.7	− 13.2	103
GU049	Basaltic andesite	Disseminated	0	− 14.9	− 14.6	117
GU054	Basaltic andesite	Disseminated	0	− 23.5	− 14.3	114
GU055	Basaltic andesite	Disseminated	0.01	− 24.9	− 15	121
GU063	Basaltic andesite	Disseminated	0	− 22.3	− 12.3	94
GU110	Pillowed basaltic andesite (core)	Disseminated	0	− 15.6	− 10.2	77
GU172	Basaltic andesite	Disseminated	0	− 18.0	− 10.8	82
GU174	Basaltic andesite with calcite veins	Disseminated/vein	0.060	− 16.1	− 17.1	147
GU144	Interpillow jaspilite	–	0	− 17.0	− 17.6	153
GU149	Interpillow jaspilite	–	0	− 21.3	− 13.4	105
GU151	Interpillow jaspilite	–	0.01	− 31.9	− 17.9	158
GU150	Interpillow jaspilite with calcite/quartz veins	–	0.1	− 15.4	− 17.7	155
GU158	Brecciated interpillow jaspilite	–	0.05	− 12.5	− 17.8	156

^aFormation temperature was estimated from the reported oxygen fractionation factor (O’Neil et al. 1969; Friedman and O’Neil 1977; Chacko et al. 2001) assuming a fluid with δ18O = 0‰ (SMOW)