Development and evaluation of a thermodynamic dataset for phases of interest in CO2 mineral sequestration in basaltic rocks

A thermodynamic dataset describing 36 mineral reactions of interest for CO2–water–basalt interaction associated with CO2 mineral sequestration in basaltic formations is presented. Mineral selection for the dataset is based on extensive review of natural analogs of water–basalt interaction at low and elevated CO2 conditions. Widely used thermodynamic databases did not contain the mineral assemblage needed for successfully simulating the alteration processes observed in nature as important primary and secondary minerals were found to be missing.The EQ3/6 V7.2b database is the primary source for aqueous equilibrium constants in the developed dataset but reactions for four missing Al-hydroxy complexes were added. Recently published thermodynamic data were compiled for most of the minerals considered in this study. Mineral solubility constants obtained directly from measurements were compiled to the dataset without modification but SUPCRT was used for computing solubility constants when such data was not available.In order to verify that the presented dataset can capture alterations observed in nature, simulations of CO2–water–basalt interaction were carried out at low and elevated CO2 conditions and compared to observed basalt alteration in Iceland and Greenland. Overall simulated and observed alteration are in good agreement, both at low and elevated CO2 conditions, suggesting the dataset to be well suited for simulations of e.g. CO2–water–basalt interaction associated with CO2 mineral sequestration in basalts.

► A thermodynamic database describing CO2–water–basalt interaction is presented.
► Database validated by comparison to natural alteration at low and elevated CO2 levels.
► Important to critically review published data and widely used thermodynamic databases.
► Thermodynamic data for numerous important minerals are missing from the literature.