Magmatism and Geodynamics in the Tyrrhenian Sea Region

Abstract

The Tyrrhenian Sea region is the site of widespread Cenozoic igneous activity that shows extreme compositional variations in space and time, highlighting complex evolution history for magmas and their sources. Based on ages and volcanological-petrological-geochemical characteristics of mafic rocks, several magmatic provinces are distinguished, which are related to compositionally distinct sectors of the upper mantle beneath the Tyrrhenian Sea region. Rocks with MORB- and OIB-type geochemical signatures (i.e. low LILE/HFSE ratios, and EM1, FOZO, DMM isotopic compositions) originated from mantle rocks that were not affected by young subduction events. FOZO- and DMM-type magmas are best represented by the Sicily volcanics and may derive from an ascending plume head or from a metasomatised lithosphere-asthenosphere permeated by deep asthenospheric fluids. EM1-type rocks crop out in Sardinia and are unique in Europe. They could derive either from a mantle plume or from an ancient metasomatised lithosphere. The petrogenesis of arc-type magmas is related to contamination of various mantle rocks (MORB to OIB-type) by subducted upper crustal components. Four main types of subduction-related mantle metasomatic events are recognised in the Tyrrhenian Sea area, with a role of upper crustal components (sediments) increasing from Sardinia and the southern Tyrrhenian Sea to Central Italy. Metasomatism beneath Tuscany was Alpine in age, whereas mantle contamination beneath the Roman Province was provided by Miocene-Quaternary subduction of the Adriatic continental plate beneath the Northern Apennines. In contrast, subduction of the Ionian oceanic plate plus some sediments generated metasomatism and magmatism in Campania and the central-southern Tyrrhenian Sea.