Combined field mapping, structural analysis and Neogene stratigraphy were used to define the tectonic evolution of the Gavorrano-Capanne Vecchie area, located in the southern sector of the Colline Metallifere region (Tuscany). A particular aim of this study was to constrain the deformation pattern accompanying the genesis and the emplacement of the Pliocene (4.9-4.4 Ma) Gavorrano monzogranite intrusion. A N-S trending right-lateral strike-slip fault zone, constituted by an array of discontinuous fault segments arranged en-echelon was recognised as the main brittle deformation event in the study area. These fault segments are constituted by straight or sinuous segments having lengths in the order of a hundred to a thousand meters, usually associated with cataclasite zones several meters in width. They constitute a network of faults up to 20 kilometers long, which may be followed almost continuously in the field from Caldana village in the south, to the Capanne Vecchie area in the north. The N-S trending fault segments control the relationships among the different tectono-stratigraphic units exposed in the study area. The N-S dextral transcurrent faulting has been found to control, along a NE-SE trending extensional accommodation zone, the Lower Pliocene subsidence and deposition of the Fosso dei Noni basinal area. A late Messinian-Early Pliocene age of the N-S right-lateral strike-slip episode is thus proposed. The strike slip faulting has been consequently demonstrated to be coeval with the cooling and emplacement of the Gavorrano intrusion. Late NW-SE normal faulting fragmented the original intrusive contacts, controlling the late uplift history of the Gavorrano-Capanne Vecchie area.

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