## 3 Results
### The Sines Massif
#### 3.1.3 Petrography, Mineral Chemistry, and Geochemistry  
Two coarse-grained ultramafic to mafic samples from the Sines massif were collected for laboratory characterization and mineral carbonation experiments--a melanocratic cumulate gabbro at a cliff near Praia do Norte (Figures 5 and 6) and a gabbro-diorite at Montes de Chaos quarry (Figures 5 and 6). The cumulate gabbro sample displayed a medium to coarse igneous texture that preserved the ferromagnesian mineral phases. The mineral composition was found to be clinopyroxene (45-55%), olivine (15-20%), brown-amphibole (10-15%), plagioclase (5-10%), and primary ilmenite (5%) (Figure 8), although occasionally showed accessory alteration products (e.g., chlorite, actinolite, and serpentine). These secondary mineral phases occurred around the olivine, as well as around some pyroxene crystals. The enrichment in ferromagnesian minerals and their textural relations revealed cumulated textures, with amphibic crystals developing a poikilitic texture. The mineral chemistry (Table 4) indicated the presence of magnesium olivines (Fo = 0.52-0.67), Ca-Fe-Mg clinopyroxenes with diopside-augite compositions, Ti-rich amphiboles (tschermakite horneblende), and calcic plagioclase with bytownite-labradorite compositions (An = 0.67-0.79). Except for ilmenite, which was not detected in the XRD diffractogram where the presence of magnetite was revealed, suggesting equilibrium at low temperatures in the oxide phases, we confirmed all primary mineralogy by XRD analysis (Figure 9). The rock geochemistry data (Table 5) showed very low SiO\({}_{2}\) contents (42.3 wt %), compatible with an ultrabasic composition, and high MgO (12.90 wt %), CaO (12.7 wt %), Fe\({}_{2}\)O\({}_{3}\) (15.15 wt %), Cr (478 ppm), and Ni (117 ppm). This compositional spectrum, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & **Scanline 1** & **Scanline 2** & **Scanline 2\({}^{\star}\)** & **Scanline 3** \\ \hline \multirow{4}{*}{**Data**} & **Length (cm)** & 1275 & 1250 & 590 & 2630 \\ \cline{2-5}  & **Latitude** & 37.94978\({}^{\circ}\) & 37.9514\({}^{\circ}\) & 37.94924\({}^{\circ}\) \\ \cline{2-5}  & **Longitude** & \(-8.85078^{\circ}\) & \(-8.84634^{\circ}\) & \(-8.84187^{\circ}\) \\ \cline{2-5}  & **Azimuth** & 70\({}^{\circ}\) & 60\({}^{\circ}\) & 135\({}^{\circ}\) \\ \cline{2-5}  & **Number of** & & & \\  & **discontinuities** & 63 & 62 & 66 & 153 \\ \cline{2-5}  & **Discontinuities per m** & 4.9 & 5.0 & 11.2 & 5.8 \\ \hline \multirow{4}{*}{**Length of section between two**} & **Average** & 24.5 & 24.5 & 10.7 & 10.7 \\ \cline{2-5}  & **Standard deviation** & 20.7 & 23.2 & 11.0 & 11.0 \\ \cline{2-5}  & **Maximum value** & 103 & 120 & 57 & 57 \\ \cline{2-5}  & **Minimum value** & 4 & 3 & 1 & 1 \\ \cline{2-5}  & **Sum of sections \textgreater{} 10 cm** & 1167 & 1150 & 373 & 373 \\ \cline{2-5}  & **RQD (\%)** & 91.5 & 92.0 & 63.2 & 63.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Scanline data, RQD (Rock Quality Designation) index, and scanline statistics. Latitude and longitude refer to the starting point of each scanline. Scanline 2\({}^{\star}\) corresponds to the continuity of resuming observations along the same azimuth of scanline 2 after following 25 m of no collected data due to outcrop inaccessibility. coupled with a high value of TiO\({}_{2}\) (3.34 wt %), agrees with the observed enrichment in ferromagnesian mineral and denotes magmatic alkaline features.