Abstract

The Neogene extension in the inner sector of the Northern Apennines has been accompanied, since Late Miocene, by the emplacement of anatectic plutonic bodies. The Campiglia Marittima monzogranite (K/Ar cooling age of 5.7 Ma), outcrops along the Southern Tuscany coast, on the western part of the mesozoic Campiglia Ridge. Field data were collected to study the role of regional tectonics on pluton emplacement. The data shows that N-S subvertical dextral faults border the western part of the mesozoic Campiglia Ridge. This fault zone is associated with NW-SE to N-S subvertical fracture cleavage, locally reactivated as N-S dextral faults. Pluton emplacement induced a N-S elongated thermal aureole. A sub-horizontal schistosity, due to the flattening induced by the rise of the pluton, is present within the aureole; structural data suggests that the development of such schistosity is coeval with strike-slip faulting. Semi-ductile shear zones in the pluton are kinematically compatible with the major N-S dextral shear recognized along the Campiglia Ridge. These evidences suggest that pluton emplacement was coeval with the N-S dextral shear. The sub-horizontal schistosity induced by the pluton culminates in correspondence with a major releasing bend formed by the N-S dextral faults along the western border of the Campiglia Ridge, where the thermal aureole widens. This suggests that pluton emplacement occurred in correspondence with the releasing bend as a consequence of the activity of the dextral faults. The lack of high-temperature shear within the intrusive body suggests a diapir-like ascent within the space created in the releasing bend. During Pliocene, regional extension reactivated the strike-slip faults at the borders of the Ridge and formed new sets of normal faults.

You do not currently have access to this article.