Geology and microstructural evolution of syn-to late-Tectonic granitoids from Capo Vaticano Promontory (southern Calabria, Italy)

Abstract

This study presents new field and microstructural constraints into the batholith architecture and supra-to subsolidus evolution of late Variscan granitoids at Capo Vaticano Promontory, part of the ∼13 km-Thick Serre Batholith in southern Italy. A field survey, assisted by petrographic analyses, produced the first geological map of the area (1:140,000 scale), detailing magmatic unit relationships and their petro-structural features. A migmatitic border zone (MBZ) marks the transition from lower-crustal paragneisses to the deepest emplaced granitoids. The oldest, deepest granitoids are strongly to moderately foliated amphibole-biotite tonalites and quartz diorites, transitioning to biotite tonalites and quartz-diorites (BT), which can be subdivided into strongly to moderately foliated (BTs) and weakly foliated to unfoliated (BTw). Clear intrusive contacts mark the passage from BTw to overlying weakly foliated-unfoliated porphyritic muscovite-biotite granodiorites and granites (PMBG). The study also revealed: A) a northern sector with a continuous batholith cross-section and b) a southern sector with an irregular distribution of the magmatic units due to post-Variscan tectonics. Microstructures document late Variscan deformation starting at suprasolidus conditions (e.g., quartz chessboard patterns and submagmatic fractures in plagioclase) and evolving through progressively high-to low-Temperature subsolidus stages (e.g., feldspar bulging, quartz recrystallization, mica kinking) for all the magmatic units. Continuous supra-to subsolidus deformation associated with a well-developed fabric suggests tectonic control on the emplacement and cooling of early tonalites/quartz diorites, while the emplacement of the porphyritic granitoids has occurred during waning tectonic activity stages in the framework of the post-collisional evolution of the south-western Variscan Belt.