Contact metamorphism-related deformation mechanisms of radiolarites and skarns at the Monte Capanne pluton, Elba Island, Italy

During Late Miocene magmatic activity, Elba Island was intruded by multiple magmatic complexes. In the north-eastern part of Western Elba, the rocks have undergone pyroxene hornfels metamorphism and ductile deformation due to the intrusion and following uplift of the 6.9 Ma Mt. Capanne monzogranitic pluton. Objectives of this study are preliminary detailed microfabric analyses of a metalimestone (diopside-bearing marble), a metacalc-silicate (wollastonite-bearing skarn) and a metachert from the contact aureole at the Spartaia and Paolina beach to present a first insight into the contact metamorphism-related deformation mechanisms. X-ray diffraction, electron backscatter diffraction, scanning electron and optical cathodoluminescence microscopy were applied, to quantify microstructures and crystallographic preferred orientations (textures). It was found that the metalimestones and metachert show significant microstructural deformation and strong texture that is correlated to the intrusion, uplift and exhumation of the Mt. Capanne pluton. The metalimestones show intensive simple shear deformation by grain shape preferred orientations, deformation bands, twinning, recrystallisation and textures. Some of the deformation features in the skarn cannot only be correlated to the intruding pluton but also to the metamorphic reactions by growth of the thermometamorphic mineral wollastonite. The very fine-grained metachert shows a polygonal microstructure and a homogenous texture throughout the fold hinge and limbs. From these first results, further detailed studies can be deduced and defining now a systematic sampling considering e.g. sample orientation related to folds, the metamorphic gradient within the contact aureole and non-metamorphic pendants in Eastern Elba to refine the metamorphic and deformation history at different scales.