  Carbon capture and storage in basalt is being actively investigated as a
scalable climate change mitigation option. Accurate geochemical modeling
prediction of the extent and rate of CO2 mineralization is a critical component
in assessing the local and global feasibility and efficacy of this strategy. In
this study, we review basalt-CO2-water interaction experimental studies
conducted during the last two decades to determine whether they provide useable
information for geochemical modeling. Most of the cited experiments generate
data on the temporal evolution of water composition, and a few provide
identification of secondary precipitates and their compositions, offering
empirical and semi-quantitative information about the reactivity of basalts and
the likelihood of secondary carbonate mineralization at various temperatures,
pHs, and pCO2 conditions. However, most experiments provide insufficient
information on the properties and quantity of secondary minerals formed,
prohibiting accurate mass balance calculations and hence more quantitative
geochemical modeling studies. Primary Ca, Mg, and Fe-bearing minerals in basalt
control the availability of major ions released into aqueous solution for
carbonate precipitation, and many secondary minerals, i.e., smectites, Ca-Mg-Fe
carbonates, and zeolites, provide sinks for the same major ions, some of which
are difficult to quantify experimentally. Thus, we have a multi-source and
multi-sink inverse mass balance problem with insufficient constraints on the
bulk system in which the temporal evolution of major ions does not provide
sufficient information on which mineral(s) dissolve or the sequence of
dissolution and precipitation reactions. Going forward, we propose that future
experimental work should focus on trace elements and multiple isotopic tracers
and better characterize the solid reaction products with modern analytical
instruments.
