Until recently, the age of wrench or transpressional tectonics in Sardinia was not very well constrained. Undeformed granitoids, cross-cutting the main structures, were dated at 290-310 Ma (Del Moro et al., 1975) constraining only the upper limit of the Variscan deformation events. This age is also confirmed from Permian basins that sealed the Variscan deformed complexes at 300 Ma. The lower limit age was deduced by the consideration that D2 deformation started during lower amphibolite facies metamorphism dated by the Rb/Sr whole-rock at 344±7 Ma in migmatites that underwent amphibolite facies metamorphism (Ferrara et al., 1978) and 330 Ma (Palmeri et al., 1997).
In situ 40Ar/39Ar laserprobe analysis on white mica allowed Di Vincenzo et al., (2004), to constrain the age of S1 and S2 foliation in the grt+bt zone of the Baronie area and to better constrain the age of collisional (D1) and transpressional (D2) deformation phases. Using microstructural relations, microchemical composition and age they have characterized a deformed celadonite-rich mica flakes that define the D1 phase (both inside garnet and plagioclase porphyroblasts and in the core of large white micas in the matrix) and a celadonite-poor white mica aligned along the S2 foliation. The resulting ages span from 345 Ma to 300-310 Ma from D1 to D2 (Di Vincenzo et al., 2004). D1 ages concentrate in the 330-340 Ma interval, whereas D2 ages have been constrained between 315 and 320 Ma (Di Vincenzo et al., 2004). Moreover, these results do not confirm the hypothesis proposed by Helbing & Tiepolo, (2005), regarding the existence of a pre-Variscan metamorphic basement represented by the micaschists and gneisses of the low- to medium grade metamorphic complex of Baronie.