## 2 Materials and Methods
### Methods and Characterization Procedures  
The experiments were carried out in a steel reaction chamber, equipped with a pressure gauge and a thermocouple-controlled thermal heating jacket controlled by a thermocouple (Figure 2). The experimental suspensions were made by mixing 30 g of dry aggregates of different sizes of blue marl with 30 g of distilled deionized water (1:1 solid-water ratio). The pressure and temperature conditions required for the geological storage of supercritical CO\({}_{2}\) in deep formations must reach a pressure of 72 bar or more, with a temperature above 31 \({}^{\circ}\)C. CO\({}_{2}\), previously compressed in a pump to 100 bars to achieve the supercritical state, \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Original**} & \multicolumn{4}{c}{**120 h**} & \multicolumn{4}{c}{**240 h**} \\ \hline
**Minerals** & **wt\%** & \(\pm\sigma\) & **LOQ** & **LOD** & **wt\%** & \(\pm\sigma\) & **LOQ** & **LOD** & **wt\%** & \(\pm\sigma\) & **LOQ** & **LOD** \\ \hline Calcite & 35.4 & 0.9 & 1.2 & 0.6 & 38.0 & 1.4 & 1.9 & 0.9 & 39.3 & 1.8 & 2.4 & 1.2 \\ Dolomite & 3.3 & 0.6 & 0.8 & 0.4 & 5.3 & 0.8 & 1.1 & 0.6 & 6.3 & 0.9 & 1.2 & 0.6 \\ Quartz & 14.0 & 0.5 & 0.6 & 0.3 & 11.8 & 0.6 & 0.8 & 0.4 & 11.5 & 0.6 & 0.8 & 0.4 \\ Plagicolase (alphite) & 3.9 & 0.5 & 0.6 & 0.3 & 3.0 & 0.5 & 0.7 & 0.3 & 2.9 & 0.5 & 0.6 & 0.3 \\ Pyrite & 0.9 & 0.2 & 0.3 & 0.2 & 0.4 & 0.5 & 0.7 & 0.3 & 0.6 & 0.5 & 0.7 & 0.3 \\ Siderite & N.D. & – & – & – & 1.1 & 0.6 & 0.8 & 0.4 & 1.1 & 0.4 & 0.5 & 0.2 \\ Illite & 22.3 & 1.6 & 2.1 & 1.0 & 24.6 & 3.0 & 4.0 & 2.0 & 25.2 & 3.9 & 5.2 & 2.6 \\ Kaolinite & 5.2 & 0.8 & 1.1 & 0.6 & 5.4 & 0.8 & 1.1 & 0.6 & 6.0 & 1.0 & 1.3 & 0.7 \\ Smctite & 10.3 & 1.8 & 2.4 & 1.2 & 8.2 & 1.9 & 2.5 & 1.3 & 5.7 & 1.7 & 2.5 & 1.2 \\ I/Sm & 4.5 & 1.0 & 1.3 & 0.6 & 2.2 & 0.6 & 0.8 & 0.4 & 1.4 & 1.1 & 1.5 & 0.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mineralogical semi-quantification composition (wt%) of the original and treated samples after the reaction period of 120 and 240 h. \(\sigma\): 3 x Estimated standard deviation = 99.7% repeatability limit, normal distribution; LOQ: limit of quantification, LOD: limit of detection, N.D.: not detected. Figure 1: XRD-pattern of the raw blue marl. Cal: calcite; Q: quartz; Do: dolomite; I: illite; Kaol: kaolinite; Sm: smctite; I/Sm: mixed-layer illite-smctite. was then injected and maintained at constant pressure. Experimental tests were carried out at 120 h and 240 h at 35 \({}^{\circ}\) C, as was studied by [PERSON] et al. in previous studies [33; 34]. After the tests, the reaction chamber was depressurized by opening the gas outlet to allow CO2 to slowly escape. The resulting sample was collected and dried at 70 \({}^{\circ}\)C for 24 h. Previously, the slurries were filtered using fiberglass filters (0.7-\(\upmu\)m medium retention) and a vacuum pump. In this way, it was possible to separate a large part of the supernatant water from the solid sample. The mineralogical composition of the dry treated sample was determined by X-ray diffraction analysis (XRD), using a Bruker D8 Advance diffractometer with standard monochromatic Cu-K\(\upalpha\) radiation operating at 40 kV and 30 mA. Scanning was performed with a 0.015\({}^{\circ}\) 20 step size, and at 0.1 s per step from 3\({}^{\circ}\) to 70\({}^{\circ}\). Phylosi silicate identification was carried out on oriented specimens by clay fraction suspension. Three different states of the oriented samples were prepared: air dried (AD), saturated with ethylene glycol (EG), and heating at 550 \({}^{\circ}\)C. Oriented ADs were prepared when the suspension was dried at room temperature.