The Tyrrhenian margin geological setting: from the Apennine orogeny to the K-rich volcanism

We present an up-to-date review of the existing data on the evolution of the Apennine – Tyrrhenian basin system and of the tectonic models developed to interpret the complex evolution of magmatism and volcanism along the Tyrrhenian margins of peninsular Italy from Miocene to the Present. The Tyrrhenian margin volcanic belt lies within a back-arc basin located on top of the NW-dipping Adriatic – Ionian slab, active along the convergent boundary between the Africa and Eurasia plates. It is characterized by significant crustal thinning, high thermal flow and huge production of mantle fluids. Seismic activity is very low and clusters in geothermal and volcanic areas. The structural architecture of the extensional Tyrrhenian margin is mainly controlled by NW – SE oriented normal faults, which are presently active along the Apennine water shade. This volcanism can be divided on the basis of time – space and petrographic criteria into four different provinces: the Corsica Magmatic Province, the Tuscan Magmatic Province, the Roman Magmatic Province and the Lucanian Magmatic Province. Inside each of these magmatic regions, igneous rocks with different petrochemical affinities are found in the same timespan beside the main magmatic association. The structural control over the Roman Magmatic Province volcano locations and spacing can be divided into two main components: the geometry of the mantle source, which defines the general trend of the volcanic chain, and the structure of the crust, which defines zones of preferential permeability to magmatic fluids. On a crustal scale, the localization of volcanoes is ubiquitously related to cross-cutting NW-trending and NE-trending transverse extensional structures. Volcanoes of the Tyrrhenian margin show a variety of mor- phologies and eruption styles. In particular, Middle – Upper Pleistocene volcanoes of the Roman Magmatic Province display both effusive and explosive activity. Highly explosive volcanoes have erupted several intermediate- to large-volume ignimbrites and are characterized by large, polyphased calderas and vast ignimbrite plateaus. Volcanoes characterized by intermittent effusive and explosive activity have formed stratovolcanoes and also erupted intermediate-volume ignimbrites that generally formed small summit collapse composite calderas