## 4 Results
### Petrographic and Chemical Characterisation of Rocks before and after SC CO\({}_{2}\) Exposure
Moreover, XRD performed on the surface of CG and GD 64-days specimens, through grazing incidence (Figure 4), additionally reveals the presence of smectite and gypsum, which were not detected in 0-day specimens. Figure 4: Diffractograms obtained through grazing apparatus on specimens after 64 days within brine: (**a**) cumulate gabbro; and (**b**) gabbro-diorite. For each we present diffractograms obtained at two distances, where the highest value is nearest the surface of the specimen. Figure 3: Stereo-zoom image that displays the effect of minerals dissolution (arrow) on the surface of a gabbro-diorite specimen after 64 days within brine. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline  & **Sample/Days** & **Clinopyroxene** & **Amphilable** & **Pigigelcase** & **Clinochiver** & **Verniculite** & **Talc** & **Mica** & **Olivene** & **Halite** & **Ratile** & **Imentie** & **Magnetic** \\ \hline  & CC\({}_{0}\) & 32 & 24 & 13 & 4 & & & 2 & 5 & & & 2 \\  & CC\({}_{1}\) & 38 & 28 & 17 & 4 & & Tr & 3 & 8 & 1 & & 2 \\
**Experiment 1** & CC\({}_{4}\) & 26 & 29 & 24 & 4 & Tr & Tr & 3 & 10 & 1 & & 2 \\  & CC\({}_{1}\) & 37 & 21 & 21 & 3 & Tr & 2 & 12 & 1 & & 2 \\  & CC\({}_{6}\) & 34 & 24 & 28 & 3 & Tr & 2 & 8 & 1 & & 2 \\ \hline  & CD\({}_{0}\) & 16 & 4 & 69 & Tr & & & & 6 & 3 & & 3 \\  & CD\({}_{1}\) & 12 & 4 & 73 & 1 & Tr & 5 & 1 & 1 & 2 & \\
**Experiment 2** & CD\({}_{4}\) & 12 & 4 & 73 & 1 & Tr & 5 & 1 & 1 & 2 & \\  & CD\({}_{1}\) & 10 & 5 & 73 & 1 & Tr & 5 & 1 & 1 & 1 & 1 \\  & CD\({}_{6}\) & 16 & 4 & 69 & 2 & & Tr & 4 & 2 & 1 & 1 \\ \hline \end{tabular}
\end{table} 
Table 4: Mineralogical composition obtained through powder XRD. Tr: trace amount. As described for the CG [60], the SEM images obtained before and after each experiment on GD (Figure 5a,b) essentially show an increase in ferromagnetism minerals' dissolution, reflected in the higher surface roughness, as reported by other authors [61]. The added phases show different reflectance on backscattered electron (BSE) images and, according to EDS elemental map distribution (Figure 5c,d), correspond to significant enrichment in chlorine (Cl), sodium (Na), sulfur (S) and carbon (C). The precipitation of salts in the form of efflorescence covers a large part of the surface of the specimens and the cavities generated by the dissolution. The carbon enrichment observed on the edge of 64-day specimens (CG and GD) and associated with salts (Figures 5d and 6a) corresponds to organic material, which accumulates due to runoff during the drying process at 40 \({}^{\circ}\)C. The origin of this material remains to be identified, but is probably related to the presence of organic material (hydrocarbon) within the original brine. In fact, the carbon particles observed at the surface (Figure 6a) are not related to the crystallization of carbonates or any other mineral phase [60]. The ATR-FTIR spectra of these carbon-enriched areas present infrared fingerprints pointing to the presence of triglyceride-enriched areas whose origin is still to be determined [58]. In addition, the analysis by ATR-FTIR of CG and GD after 16 days (Figure 6b) of interaction with CO\({}_{2}\) revealed a decrease in the intensity of the absorption band  
Whole-rock geochemistry data for CG and GD before and after 64 days within a SC CO\({}_{2}\)-prime solution are shown in Table 5. For CG the most significant variations after a six-day run were an increase in CaO (+0.4 wt. %) and a decrease in Fe\({}_{2}\)O\({}_{3}\) (-0.4 wt. %), whereas in GD CaO and Fe\({}_{2}\)O\({}_{3}\) decreased ((-0.4 wt. % and (-0.3 wt. %, respectively). The enrichment in sodium was more evident in GD specimens after 64 days within SC CO\({}_{2}\)-prime (+0.13 wt. % vs. 0.04 wt. % for CG). Sulfur increased in both samples after 64 days (+0.05 wt. % and +0.08 wt. % for GB and GD, respectively).