Lower crustal granite genesis connected with chemical fractionation in the continental crust of Calabria (Southern Italy)
Caggianelli, Alfredo; Del Moro, Aldo; Paglionico, Antonio; Piccarreta, Giuseppe; Pinarelli, Laura; Rottura, Alessandro
European Journal of Mineralogy Volume 3 Number 1 (1991), p. 159 - 180
published: Feb 21, 1991
manuscript accepted: Sep 17, 1990
manuscript received: Nov 21, 1989
ArtNo. ESP147050301014, Price: 29.00 €
Abstract Granulite-facies rocks, of metasedimentary and metaigneous type are exposed in the Serre (Southern Calabria). They are representative of the intermediate - lower crust remaining after the Hercynian orogeny and exhumed during the Alpine orogeny. Huge masses of calc-alkaline and peraluminous granitoids intrude both the lower crust and the overlying shallower crustal levels. In this paper, we deal with the composition of the lower crust and its relationship with granitoids along the Serre section, on the basis of major, minor, trace elements, REE and Sr, Pb, Nd isotope systematics. The metapelites, which make up a large part of the lower crust section, have a restite character due to the extraction both of in situ crystallized leucosomes and of some of the late-Hercynian peraluminous granites which intrude the upper crust. The dominant calc-alkaline granitoids seem to require the contribution of hydrated basic lower crust and/or mantle-derived magmas for their genesis. As a result it appears that the melting processes which affected the lower crust about 300 Ma ago, at the same time as decompression, produced a crustal differentiation contributing to the generation of granitoids which migrated toward high crustal levels. The occurrence of some gabbroic rocks and microgranular mafic enclaves associated with the calc-alkaline plutonic rocks indicates that the mantle contributed both thermally and chemically to granitoid genesis. Nd model ages in granitoids (1.0 - 2.4 Ga) indicate significant addition of juvenile material in late Proterozoic - early Palaeozoic times.