Magmatism in the Tyrrhenian Sea Region: An Introductory Overview

Abstract

Cenozoic magmatism in the Tyrrhenian Sea region exhibits a wide range of major, trace element, and radiogenic isotope characteristics. Based on petrological and trace element signatures, especially LILE/HFSE ratios of mafic rocks, two main families of magmas are recognised respectively showing arc-type (orogenic) and intraplate (anorogenic) compositional features. Orogenic magmas have calcalkaline, shoshonitic and potassic alkaline affinities, and are spread over the entire Tyrrhenian region becoming younger eastward, from the Oligo-Miocene volcanic belt of Sardinia to the young to active calcalkaline to potassic alkaline volcanoes of the Italian peninsula and the southeastern Tyrrhenian Sea. Large volumes of Quaternary potassic and ultrapotassic rocks in central Italy represent the most important magma types of young orogenic activity. Anorogenic rocks include tholeiites to Na-alkaline compositions and occur in Sardinia, in the Tyrrhenian Sea basin and Sicily. No clear age polarity is observed for anorogenic rocks. Areal distribution, ages, and major, trace element and radiogenic isotope compositions allow recognising several distinct volcanic provinces. Except for a few rhyolites and granitoid rocks from Tuscany, the bulk of magmas is of mantle origin, testifying to extremely heterogeneous upper mantle sources. Geochronological, petrological and isotopic data suggest that multiple metasomatic events over compositionally variable pre-metasomatic mantle rocks are responsible for this heterogeneity.