## 5 Discussion
### Numerical Simulation and Correlation with Experimental Results  
Observations on fluid chemistry and pH changes over time indicate that, under similar conditions of P\({}_{\text{CO}_{2}}\) and temperature, the simulation with SSA = 120 cm\({}^{2}\)/g shows a relative agreement with the experimental data (Figures 7 and 8). The considered SSA is in the range of the specific area of olivine, plagioclase and pyroxene used in [53]. The predicted mobility of calcium is higher than for other components, with a slight increase in concentration for the first 24 days, before being incorporated within the secondary phases. As mentioned above, this increase is not reflected in Experiment 1. The model also shows that Ca\({}^{2+}\) has been consumed in Ca-zeolites and/or carbonates; for instance, mesolite and mordenite are the first phases to consume calcium at a low pH < 5.5. Moreover, the gradual increase in Mg concentration is justified by the progressive dissolution of diopside and forsterite, accompanied by a moderate precipitation of dolomite and later of magnesite. The results of the newly formed mineralogy (Table 9) indicate the presence of early neoformation phases (e.g., smectite) that can capture calcium within its structure. Nevertheless, no carbonates were observed or detected during the experiment. In CG specimens, most likely, the secondary phases might be local and covered by the considerable amount of salts lining the rock surface. The simulation also indicates that the \(\Delta\)(Mg/Si) and \(\Delta\)(Ca/Si) ratios are 1.45 and 0.35, respectively, and suggests that olivine, diopside and Ca-plagioclase (the main CG minerals) dissolve stoichiometrically [25]. Therefore, the high ratio between silicon in the simulation and the experiment (Si/Si\({}^{*}\) = 10) testify to the nonstoichiometric dissolution of CG in the experiment. Furthermore, (\(\Delta\)(Mg*/Si\({}^{*}\)) = 4) is significantly higher and denotes that magnesium dissolves faster than silica (incongruent dissolution). At pH > 5.5, Ca-Mg carbonates (namely, calcite and dolomite) start precipitating and continue up to a neutral/alkaline pH, consistent with the observations from other authors [25; 55]. Calcite remains the dominant carbonate phase at a high pH, indicating its stability under alkaline conditions. Iron displayed a similar trend to Mg\({}^{2+}\), showing a high release rate. Consequently, a tiny fraction of siderite and Fe-Mg-rich smectite was precipitated, concomitant with the dissolution of the primary Fe-rich minerals (fayalite) and followed by ankerite (Ca (Fe, Mg) (CO\({}_{3}\))\({}_{2}\)). The calculated silica and iron concentrations are significantly higher compared to Experiment 1. Besides the incongruent dissolution observed in the experiments, CG rocks are less reactive than basaltic rocks. As a matter of comparison, [PERSON] and [PERSON] [25] measured elevated P\({}_{\text{CO}_{2}}\)ion and Si values in glass basalts, in the same range of the simulations (2 mmol/kgw). Note that the brine used in Experiment 1 has a CO\({}_{2}\) concentration 1.5 times higher than that used previously by [PERSON] and [PERSON] [55], and thus, according to the those authors' results, further secondary phases are expected, since dissolved CO\({}_{2}\) is available during the time of the experiment. The limitation in secondary phases (in CG) is due to the rock reactivity. The experiment's duration is another factor influencing the secondary phases' precipitation. The total volume of secondary minerals predicted is 0.8 vol %, dominated mostly by zeolites (0.61% in rock volume), carbonates, especially calcite (0.172% in rock volume), and insignificant amount of clays. The small amounts of secondary phases render their identification in SEM very difficult, as reported in previous studies [62]. After 50 days, the \(\Delta\)(Ca) \(<\) 0 corresponds to a stage where zeolites and carbonates competed with a dominant volume of Ca-zeolites.