These island arcs may be added to a continent during an orogenic event.
The processes of orogeny can take tens of millions of years and build mountains from plains or from the seabed.
The Pinhões orthogneiss yielded an age of 869 ± 9 Ma, interpreted as the emplacement age of the protolith during a late Tonian magmatic episode.
Samples CA-40 and CA-34 yielded U weighted mean ages of 652 ± 6 Ma and 636 ± 3 Ma, respectively, which are interpreted as dating emplacement and crystallization of the magmatic protoliths.
..that existed in the earlier part of the period comes from fossils found in North Africa, the central and western Sahara, and Egypt.
The event created the Variscan mountain belt, which includes the mountains of Portugal and western Spain, southwest Ireland, Cornwall, Devon, Pembrokeshire, the Gower Peninsula and the Vale of Glamorgan.
The main trend of the fold axes is E-W, indicating a N-S collision.
However, some samples plot in the intraplate field in tectonic discrimination diagrams and the Nd T model age of 1.36 Ga is unlike that of juvenile magmas in convergent settings.
The Altinho orthogneiss is quite similar in terms of trace elements geochemistry to the syenitic orthogneiss, which has a clearer intraplate affinity, and the dated samples have identical initial Sr isotope ratios (0.7047).