Nova Terra 52

c . 566 Ma (U-Pb in zircon), and the main metamorphic event at c . 590 Ma (U-Pb in garnet), with a probable secondary tectonothermal event at c . 540 Ma (later event of zircon growth in granites). With regard to the ophiolitic nature proposed for the intermediate mafic unit, a critical problem is whether this unit should be considered a different terrane in the Mérida Massif, or whether it can be considered part of the same tectonostratigraphic unit that would include at least the upper unit (Upper Schist-Metagranitoid Unit). The latter is the previous interpretation of the Mérida Massif, where different terranes have not been differen- tiated, and the entire group is thought to represent a single peri-Gondwanan arc, in which the mafic unit is the base of the arc itself (Bandrés et al . 2004). A discussion of this point is important since it affects the geological interpretation of the SW Iberian Massif and the equivalent regions throughout the Variscan Orogen. It is also a key question in the reconstruction of the Ediacaran margin of Gondwana, the possible geo- dynamic domains of which are little known. The discus- sion is less relevant when it comes to classifying the Figure 14. P-T pseudosection calculated with Theriak-Domino software (De Capitani and Brown 1987; De Capitani and Petrakakis 2010) for sample 117,350. System MnNCFMASHTO (MnO-Na 2 O-CaO-FeO-Fe 2 O 3 -MgO-Al 2 O 3 -SiO 2 -TiO 2 -H 2 O), considering H 2 O saturation. Stability domains for some of the most significant mineral phases and the reference field for garnet amphibolites (green star) are also shown. The colours assigned to the different stability fields represent thermodynamic variance, with increasing variance from lighter to darker color. 22 R. ARENAS ET AL. &KDSWHU