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The Variscan migmatite complex of Sardinia (Italy) is characterized by two deformation phases that could be subdivided in eight deformational events (Elter 2007, Elter & Padovano 2008). A particolar attention has been directed to D2 event. The D2 event is characterized by penetrative planar anisotropy (S2) in granulitic to amphibolitic conditions (350-344 M.y.). Structural data allow to define a composite frame. A lot of calc-silicate and quarzitic nodules (46 nodules on XZ plane, 15 on YZ plane and 7 on the three planes) are recognizable. They are mainly simmetrically boudinated whereas some shearband boudins could be also recognizable. They show a prolate ellipsoid size (in the apparent constriction field), with the major axis (X) parallel to the mineralogic lineation. The angle between major axis (X) and S2 schistosity is mainly 0°, but locally it reaches angles between -35° to +30°.
The Rigid Grain Net method (RGN, Jessup et al., 2007) applied to σ porphyroclasts of k-feldspar, garnet, amphiboles and nodules of sillimanite+quartz allow to define the Vorticity Number (Wm) variable between: k-feldspar 0.28-0.93; garnet 0.28-0.60; amphiboles 0.17-0.71; sillimanite+quartz 0.38-0.83. This kind of values suggest that the deformation is in the field of general shear (0Wm1, Bailey et al., 2004), generated by the interaction between pure shear and simple shear, where pure shear could be dominant with respect to simple shear. σ k-feldspar, garnet and amphiboles are recognizable on S2 schistosity and coeval with the apparent constriction deformation of calc-silicate nodules, on XZ plane. All these data are also in agreement with the presence of synshearing flow folds (Alsop & Holdsworth, 2004) and sheath folds. The analyses of sheath folds (Alsop & Holdsworth, 2006) previously allow to define these ones like analogous eye-fold on YZ plane and like cat's eye fold on XZ plane. This composite sheath folds configuration could be in agreement with a general shear deformation, syntectonic with the D2 event. All these structural data could be representative of a transpressive deformation coeval with the migmatization process. Elter & Padovano (2008) suggest that the emplacement of the Variscan migmatitic complex of Sardinia could be related with a mantle gneiss dome generated by a N-S shortening that develops in the time span of 350-300 M.y.
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