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Metamorphism and kinematics of the early deformation in the Variscan suture of SW Iberia
Author(s) -
PONCE C.,
SIMANCAS J. F.,
AZOR A.,
MARTÍNEZ POYATOS D. J.,
BOOTHREA G.,
EXPÓSITO I.
Publication year - 2012
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.2012.00988.x
Subject(s) - geology , metamorphism , mylonite , fibrous joint , lineation , schist , subduction , geochemistry , devonian , context (archaeology) , metamorphic rock , petrology , geomorphology , seismology , shear zone , paleontology , tectonics , medicine , anatomy
The early (Devonian) collisional stage in SW Iberia has been investigated through the analysis of deformation in the Cubito‐Moura schists, the main lithology of an Allochthonous Complex putatively rooted in the suture between the Ossa‐Morena and South Portuguese zones. The first deformation in these schists (D 1 ) is recorded as a S 1 ‐L 1 mylonitic fabric well preserved in early quartz veins. Subsequent D 2 deformation caused the main folds and the main (S 2 ) foliation. After restoration, the stretching lineation (L 1 ) trends at a small angle with the Ossa‐Morena/South Portuguese suture. This trend, together with the top‐to‐the‐east kinematics determined from quartz microfabric is indicative of an oblique left‐lateral collisional scenario in SW Iberia. Chlorite–white K‐mica–quartz ± chloritoid multi‐equilibrium calculations yield P–T conditions in the range 0.9–1.2 GPa and 300–400 °C, during the first collisional stage. P–T conditions during D 2 were 0.3–0.8 GPa and 400–450 °C, thus indicating an important stage of exhumation of the Allochthonous Complex during these two collisional events, after subduction of the Ossa‐Morena Zone margin under the South Portuguese Zone continental crust. In the general context of the Variscan orogen, dominated by dextral collision, the left‐lateral convergence in SW Iberia can be explained in terms of the Avalonian salient represented by the South Portuguese Zone, which would impinge between Iberia and Morocco.