Mafic magmas

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... 

Felsic Describes an igneous rock, lava, or magma that is relatively enriched in silica (>66wt% as Si02) and is generally more depleted in magnesium and iron than intermediate and mafic rocks (Hyndman, 1985), 42 (Press and Siever, 2001), 74. 

Petrological and geochemical signatures of mafic enclaves match quite closely those of the Tuscany mafic rocks. However, some of the observed geochemical characteristics may have been modified by interaction with host silicic magmas and could not represent pristine compositions of mafic melts. 

There is little doubt that the Tuscany mafic magmas have been subject to fractional crystallisation, mixing and crustal assimilation (e.g. Conticelli 1998). However, their high MgO, Ni and Cr concentrations, whose values are close to those of primary mantle melts, exclude that the mafic magmas with different enrichments in potassium and incompatible elements can be derived from each other by any common evolution process. Therefore, it has been concluded that the variable petrological and geochemical compositions of mafic rocks in Tuscany basically result from anomalous and heterogeneous mantle sources (Peccerillo et al. 1987). 

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