The exhumation of the Variscan High Grade Metamorphic Complex of Sardinia has been driven by a wide dextral shearing which reached middle crustal levels at 325 ±1.3 Ma and caused partial melting. The migmatization process has been followed by the emplacement of syn-tectonic granites dated at 316 ±2 Ma, 318 ±3 Ma and 317 ±2 Ma which produced contact metamorphism at 315 ±1.3 Ma in mylonitic Silurian orthogneiss. The NW-SE dextral shear zone of the Capo Ferro area (NE Sardinia) shows remarkable petro-tectonic analogies and can thus be related to the East Variscan Shear Zone, a major intra-continental shear zone which was active in the southern European Variscides from 325 Ma to 315 Ma and that is precisely dated with the U-Pb monazite system. The emplacement of migmatitic gneisses along large shear zones within this time interval is not restricted to Sardinia, but has also been observed in southern Corsica, in the French Massif Central, in the Western Alps and in central Spain. This pattern of shear zones is related to a complex geodynamic scenario, linked to the oblique convergence between Gondwana and Laurussia plates during the Middle-Upper Carboniferous.
The East Variscan Shear Zone:geochronological constraints from the Capo Ferro area (NE Sardinia, Italy)
PADOVANO, MATTEO;ELTER, FRANCO;
2014-01-01
Abstract
The exhumation of the Variscan High Grade Metamorphic Complex of Sardinia has been driven by a wide dextral shearing which reached middle crustal levels at 325 ±1.3 Ma and caused partial melting. The migmatization process has been followed by the emplacement of syn-tectonic granites dated at 316 ±2 Ma, 318 ±3 Ma and 317 ±2 Ma which produced contact metamorphism at 315 ±1.3 Ma in mylonitic Silurian orthogneiss. The NW-SE dextral shear zone of the Capo Ferro area (NE Sardinia) shows remarkable petro-tectonic analogies and can thus be related to the East Variscan Shear Zone, a major intra-continental shear zone which was active in the southern European Variscides from 325 Ma to 315 Ma and that is precisely dated with the U-Pb monazite system. The emplacement of migmatitic gneisses along large shear zones within this time interval is not restricted to Sardinia, but has also been observed in southern Corsica, in the French Massif Central, in the Western Alps and in central Spain. This pattern of shear zones is related to a complex geodynamic scenario, linked to the oblique convergence between Gondwana and Laurussia plates during the Middle-Upper Carboniferous.
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