The studied sections across the metamorphic basement of northern Sardinia show evidence for the tectonic behaviour of a large part of an orogen, with a change from crustal thickening with tectonic transport perpendicular to the belt to a transpression with displacement parallel to the belt. D2 deformation in NE Sardinia has been related to the activity of a crustal-scale transpressional deformation, causing slow rate of exhumation and telescoped isograds in the low- to medium- grade metamorphic rocks.
Hitherto the exhumation of metamorphic rocks in the Variscan belt has been largely attributed to extensional tectonics and to the development of metamorphic core complexes. The D2 tectonic evolution of northern Sardinia, together with petrographic and geochronological data, suggests that metamorphic rocks were exhumed in different ways in different sectors of the Variscan belt. The exhumation of the metamorphic rocks of northern Sardinia during D2 was controlled by the activity of a crustal-scale transpressional deformation zone testifying to a progressive change from frontal (D1: 330-340 Ma;) to oblique convergence at 315-320 Ma (D2).
The exhumation started early during collision and during the development of amphibolite facies metamorphism. In the early stages, during frontal collision, exhumation was rapid and the velocity of exhumation decreased as collision became more and more oblique and the displacement of the metamorphic rocks switched in predominant horizontal component of movement.
The overall change of the displacement direction affecting a large sector of a belt, such as the exposed section in Sardinia, has been tentatively related to the progressive development of indentation tectonics of the Ibero-Armorican arc during the Upper Paleozoic.
The Variscan basement in Sardinia clearly shows how displacement parallel to the belt may deeply affect the tectono-metamorphic evolution of wide portions of an orogen.