Geochemical modelling of granitoid magma diversity at Capo Vaticano Promontory (Serre Batholith, southern Italy)

Late-Variscan metaluminous/weakly peraluminous (quartz-diorites and tonalites) and strongly peraluminous (two mica porphyritic granodiorites and granites) granitoids represent two magmatic associations making up the Capo Vaticano Promontory (central Calabria, Italy). They characterize a portion of a complete continental crustal section exposed in continuity from NW to SE in the adjacent Serre Batholith. In this paper, we deal with geochemical modelling trying to understand the evolutionary processes responsible for the CVP granitoid genesis. We have investigated the main processes such as fractional crystallization, variable entrainment of peritectic mineral phases in the melt (Stevens et al., 2007; Clemens and Stevens, 2012), restite-unmixing (White and Chappell, 1977) and magma mixing to explain the geochemical variability in major and trace elements of these magmatic suites. The quartz-diorites and tonalites, representing the deepest seated rocks, are constituted by various amount of Pl+Bt+Amph+Qtz. Bt-rich and Pl-rich quartz-diorite are characterized by cumulus of Bt and Pl, respectively. A multi-step articulated fractional crystallization process was able to reproduce the quartzdiorite/ tonalitic trends. Starting from a tonalitic parental magma, three different cumulates were produced: a mafic (Bt-rich) cumulate (75 % Bt, 10 % Pl and 5 % Ap) after F=10 %, a second cumulate composed by Pl (45 %), Bt (30 %) and Amph (5 %) after F=20 % and Pl-rich quartz-diorite (60 % Pl, 20 % Bt and 20 % Amph) as the third cumulates, after F=30 %. Among the source-related models, restitic unmixing could have played a minor role in the quartz-diorite and tonalite genesis, defining them as products derived from partial melting of Itype sources. Pl+Kfs+Qtz+Bt+Ms are the main phases constituting the porphyritic granodiorites and granites. A simple fractional crystallization from less evolved granodiorites sample (KA2) has reproduced the more evolved liquid composition (PA27), after F=27 %. In addition, PAE modelling is consistent with partial melting of a metapelitic source with entrainment of 20 to 5 % vol. of a peritectic assemblage made of orthopyroxene and garnet. Magma mixing modelling with mafic end-members (a basalt, a basaltic andesite and the MME of CVP) excluded any additional contribution from the mantle. Finally, geochemical modelling highlights the fractional crystallization as the main responsible process in the CVP granitoids differentiation, whereas PAE and restite unmixing processes do not provide evidence about source contributions. This study supports the idea that granitoid rocks represent recycled crustal material in the Capo Vaticano Promontory.