Structure of a Variscan migmatite-granite transition zone (N Sardinia, Italy)

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.