## 3 Results
### The Sines Massif  
#### Geological Setting  
The Sines massif (Figure 5) is located on the west Portuguese coast (southwest Iberia). Onshore it has a relatively small area (\(\approx\)10 km\({}^{2}\)), largely covered by Plio-Quaternary sediments, mainly outcropping along the seacoast and in the Montes de Chaos quarry (Figure 6). It exhibits an elliptical shape that is elongated into the continental shelf and has been interpreted by Teixeira (2011) and Ribeiro et al. (2013) as a subvolcanic ring structure. Carvalho et al. (2013), resorting to geophysical data (magnetic, gravimetric, and seismic reflection), were able to model the offshore of the massif, along a NE-SW trend, and covering an area of \(\approx\)300 km\({}^{2}\).  
\begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline
**Geological Formation** & **C1** & **C2** & **C3** & **C4** & **C5** & **C6** & **C7** & **C8** & **C9** & \(\sum\) \\ \hline
**1—Sines massif** & 6 & 3 & 6 & 0 & 6 & 9 & 0 & 0 & 0 & 30 \\ \hline
**2—Diabases from Iberian** & 1 & 2 & 3 & 3 & 9 & 6 & 3 & 0 & 0 & 27 \\
**Pyrite Belt** & 6 & 3 & 6 & 3 & 1 & 6 & 3 & 0 & 0 & 28 \\ \hline
**3—Gabbros of** & 6 & 3 & 6 & 0 & 1 & 1 & 3 & Elim & 0 & — \\ \hline
**4—Beja gabbros** & 6 & 3 & 6 & 0 & 1 & 1 & 3 & Elim & 0 & — \\ \hline
**5—Ophiolitic sequences** & 9 & 1 & Elim & 0 & 9 & 6 & 3 & 0 & 0 & — \\ \hline
**6—Alter do Chao/Cabeco** & 9 & 3 & 6 & 0 & 6 & 1 & 3 & Elim & 0 & — \\
**Vide massif** & 6 & 1 & Elim & 0 & 1 & 1 & 3 & 0 & 0 & — \\ \hline
**8—Vale de Maceiras massif** & 6 & 2 & 3 & 0 & 1 & 1 & 3 & 0 & 0 & 16 \\ \hline
**9—Campo Maior massif** & 6 & 3 & 6 & 0 & 6 & 1 & 3 & 0 & 0 & 25 \\ \hline
**10—Elvas massif** & 6 & 2 & 3 & 0 & 6 & 1 & 0 & 0 & 0 & 18 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Ranking of ultrabasic and basic geological formations in the Alentejo region. A massif with an ideal condition would have a total score of 45.  
Figure 5: Geological map of Sines massif (adapted from Inverno et al. [34]) with sampling localities.  
Figure 6: Mesoscopic features of Sines massif at seacoast near Praia do Norte (**a**) and Montes de Cháos quarry (**b**). Detail of sampled cumulate gabbro at a cliff near Praia do Norte (**c**) and gabbro-diorite at Montes de Cháos quarry (**d**).  
Together with the Sintra and Monchique massifs, the volcanic complex of Lisbon, and several other minor intrusions, the Sines Massif is part of a Late Cretaceous alkaline magmatic cycle dated to ca. 22 Ma (94-72 Ma) [35].  
The Sines massif is mainly formed of gabbros, diorites, and svenites, with a profusion of dykes of variable composition (basalts, microgabbros, microdorites, trachybasalts, lamprophyres, trachytes, and microsyenites [34; 36]). Despite the Cenozoic sedimentary cover, the geological map of Portugal at 1/50,000 scale (sheet 42-C, Santiago de Cacem [34]) shows that these intrusive rocks cut the Carboniferous flysch at the south (Mira Formation) and Lower Jurassic carbonate rocks at the north. A model of multiphase emplacement is accepted for the genesis of the Sines massif, with the intrusion of gabbro-diorite, followed by the intrusion of svenite, and finally the net of dykes that cut the intrusive massif rocks and the surrounding country rocks.