Structural analyses performed in the low-grade metamorphic Variscan basament, outcropping in Southern Nurra (NW Sardinia), pointed out the presence of brittle-ductile shear zones. These shear zones deform F1 folds, developed during the first D1 tectonic event, and are later deformed by the second D2 tectonic phase. These overprinting criteria indicate that the development of shear zones can be confined during the final stages of D1 tectonic phase, but before respect to the D2 event. The recognized kinematic indicators point out to a top to the SW sense of shear, coherently with the tectonic transport associated to the D1 event. Preliminary data from fluid inclusions trapped during the development of shear zones highlight the presence of a retrograde metamorphic pattern, respect to the main M1 metamorphic event sincronous with the D1 tectonic phase (Franceschelli et al., 1990). The geometry, the kinematics and the data on the thermo-baric evolution suggest that the shear zones developed in a compressive tectonic setting and played an important role during the exhumation of low grade metamorphic rocks of Northwestern Sardinia.
Zone di taglio fragili-duttili nel basamento Varisico metamorfico di basso grado della Nurra meridionale (Sardegna nord-occidentale)
MONTOMOLI, CHIARA
2002-01-01
Abstract
Structural analyses performed in the low-grade metamorphic Variscan basament, outcropping in Southern Nurra (NW Sardinia), pointed out the presence of brittle-ductile shear zones. These shear zones deform F1 folds, developed during the first D1 tectonic event, and are later deformed by the second D2 tectonic phase. These overprinting criteria indicate that the development of shear zones can be confined during the final stages of D1 tectonic phase, but before respect to the D2 event. The recognized kinematic indicators point out to a top to the SW sense of shear, coherently with the tectonic transport associated to the D1 event. Preliminary data from fluid inclusions trapped during the development of shear zones highlight the presence of a retrograde metamorphic pattern, respect to the main M1 metamorphic event sincronous with the D1 tectonic phase (Franceschelli et al., 1990). The geometry, the kinematics and the data on the thermo-baric evolution suggest that the shear zones developed in a compressive tectonic setting and played an important role during the exhumation of low grade metamorphic rocks of Northwestern Sardinia.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
