Tuscany Magmatic Province

The Tuscany Magmatic Province (Fig. 2.1) comprises several mafic to silicic intrusive and extrusive centres scattered through southern Tuscany and the Tuscan archipelago. The silicic rocks of the Tolfa-Manziana-Cerite area, north-west of Rome, and a mafic ultrapotassic dyke from Sisco (Corsica) are also traditionally included into the Tuscany Province (Poli et al. 2003). 

Fig. 2.1. Location of intrusive and extrusive rocks of the Tuscany Magmatic Province. Numbers in parentheses indicate ages (in Ma).

The Tuscany Magmatic Province consists of an association of calc-alkaline to lamproitic mafic to intermediate magmas and silicic intrusive and effusive rocks. Silicic melts have been formed by crustal melting, with an important role of mixing with mantle-derived magmas. Mafic melts are of mantle origin but resemble closely some upper crustal rocks, such as metapelites, in terms of incompatible trace elements and radiogenic isotope... 

Fig. 2.2. A) TAS classification diagram of Tuscany magmatic rocks. Note that TAS nomenclature applies to volcanic rocks only. The dashed line divides the subalkaline and alkaline fields (Irvine and Baragar 1971). B) AQ vs. K20/Na20 diagram for mafic rocks (MgO > 3 wt%) of the Tuscany Province. For definition of AQ see Chap. 1.

Fig. 2.4. Sr, Nd (A) and Pb (B) isotopic composition of Tuscany magmatic rocks. Symbols as in Fig. 2.2. Composition of other Italian magmatic provinces are shown or comparison.

Southern Italy. There is a pronounced northward decrease in He/ He ratios between the Aeolian Islands of southern Italy and the region of Mt. Vesuvius known as the Campanian Magmatic Province or the Neopolitan volcanic region. Mt. Etna on Sicily can be included in this trend as recent work (e.g., Schiano et al. 2001) indicates a progressive transition from a plume-related to a typical island-arc source for this volcano. The trend or step function in the helium isotope systematics of southern Italy was first pointed out by Sano et al. (1989) and ascribed to shallow crustal contamination effects. However, subsequent work (Marty et al. 1994) has shown the combined He-O-Sr-C isotope systematics are consistent with the progressive involvement of Africa continental crust which has been subducted beneath the southern Tyrrhenian Sea. The influence of the African plate increases in a northerly direction (Marty et al. 1994)—towards Mt. Vesuvius (see data of Graham et al. 1993) and possibly as far north as the Roman and South Tuscany volcanic provinces (see Tedesco 1997). 

Table 2.1. Petrological characteristics and ages (in Ma) of magmatism in the Tuscany Province.

Fig. 2.3. Variation diagrams of MgO vs. selected major and trace elements and 87Sr/86Sr for magmatic rocks of the Tuscany Province. Symbols as in Fig. 2.2.

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