The Guadiana traverse along the south and central part of the OMZ clearly shows a strong polarity on the deformation and metamorphism. In the vicinity of the suture zone, in the southernmost sector of this traverse, the regional metamorphic peak reaches the amphibolitic facies, having a few local units in the granulitic (metagabbros in BAOC) and eclogitic facies (in the MPC). The high grade and high pressure metamorphic rocks are almost completed retrograded by a later tectonometamorphic event, in the greenschists facies. Towards the NE, the metamorphism decreases and in the EZBD there are no evidences of metamorphism higher than the greenschists facies. In this domain, towards the NE, the metamorphism still decreases and the schists are gradually replaced by slates.
Concerning the deformation, the three deformation phases displayed in the southern region, contrast with the EZBD, progressively less deformed towards the NE. In fact, along this traverse, the tectonic style range from refolded mylonitic foliations in the vicinity of the suture, to large sectors with only one slaty cleavage, in the northern part of the EZBD.
The tectonic complexity of the suture zone and the EBD probably result form a near synchronous process of obduction/subduction during the two first events, as showed in Figure 20. In fact, a few outcrops in the EBD, seems to present contradictory interference patterns between D1 and D2 events. In these scarce situations, structures showing top to the north or northeast shearing, congruent with D1 kinematics, are superposed on D2 structures. Moreover, the strong obliquity between de trending of the D2 fold axes and the related stretching lineation (indicating top to the NW or NNW) seems to be also an evidence of a synchronous process of subduction and obduction. According to this interpretation, towards the NE, these earlier deformation events become weaker and progressively later and they are not present in the northern part of the EZBD.
Figure 20. Schematic representation
Schematic representation of the near contemporaneous D1 related obduction and D2 related subduction, affecting autochthonous and alochthonous units in the southern boundary of OMZ. BAOC – Beja-Acebuches Ophiolitic Complex; MPC – Moura Philonitic Complex;
Évora-Beja Domain;
Estremoz-Barrancos Domain.
The general structure of the fully described Guadiana traverse is represented on Figure 21. D1 related obduction structures are only present in the Beja-Acebuches Ophiolitic Complex, in the MPC and in the related alochthonous units. Concerning the last deformation event (D3 in the suture zone and EBD and D2 in EZBD), the vergence change in the northern part of the studied sector (towards NE), could be an evidence of a latter pulse related with obduction kinematics.
