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Understanding how the lithosphere accommodates deformation along oblique convergent plate boundaries is an important issue for unveiling orogenic belt exhumation. The Variscan belt exposed in Sardinia represents an area where it is possible to investigate the inner part of this orogen and a km-scale transpressive shear zone, i.e. the Posada-Asinara shear zone, that drove the exhumation of the metamorphic core of the belt. Even though the Asinara island offers very good exposure of main tectonic units building up the Variscan belt of Sardinia, a detailed geological map of the island is still lacking, due to a former limitation of access that lasted for many years. In this contribution, we compile a new 1:25.000 geological-structural map of the entire Asinara island useful to better understand this key sector of the Variscan belt in Sardinia.

ABSTRACTThis paper presents the structural map of the Barrabisa Complex, an E-W ribbon-like migmatitic massif exposed in the northern part of Sardinia. The migmatites consist of metatexites and diatexites with variable melt proportion, grading in the central part of the complex to a foliated peraluminous granodiorite. Xenotime/monazite dating indicates that the foliated granodiorite pluton emplaced in upper Carboniferous times (≈307–313 Ma) within a narrow E-W ductile top-to-the east shear zone cutting through a Variscan high-grade metamorphic basement composed of orthogneisses, metasedimentary-derived migmatites and subordinate amphibolites. Field geological mapping, coupled with structural and micro-structural analysis, allowed us to distinguish the granodioritic pluton and three metamorphic units characterized by variable melt to protholith ratio, that represent a continuous transition from metatexite to diatexite with high melt concentration, to foliated granodiorite.

This paper deals with the geological mapping of the late-Variscan Sàrrabus pluton, (south-eastern Sardinia), a shallow multiple and composite igneous complex dominated by several generations of granodiorites, metaluminous and peraluminous granites and repeated pulses of mantle-derived mafic magmas. The map has been compiled based on geological surveys at 1:10,000 and 1:5,000 scales, assisted by in situ gamma-ray spectrometry and detailed petrographic investigations. Granite-related ore deposits have been also reported. The emplacement age of the pluton can be constrained by U/Pb dating on zircons of Cala Regina granodiorite, yielding an age of 286 ± 9 Ma. The resulting scenario documents a bimodal magmatism controlled by an EW trending shear zone, followed by the shallower emplacement of several pulses of independent granite magmas.