Genesis of Miocene-Pliocene intrusive rocks from Tuscan Magmatic Province: implication on the structure of Apeninic litosphere

Extensive petrological and geochemical investigations carried out in the last years revealed a complex magmatic setting for the Tuscan Magmatic Province given by the occurrence of a large variety of rock types closely associated in space and time. The main rock associations are represented by: i) ultrapotassic rocks with lamproitic (LMP) affinity; ii) high-potassium calcalkaline and shoshonitic rocks; iii) hybrid rocks between LMP and Roman-type potassic and highly potassic magmas; iv) acid volcanics and intrusives. Petrological and geochemical data on mafic magmas from the Tuscany province reveal a complex evolutionary history of mantle sources. Acid volcanites and intrusives has been traditionally considered as typical crustal anatectic rocks; new data suggest a more complex genesis. A process of interaction between basic and salic end-members is, in fact, responsible for the evolution of the Tuscan Magmatic Province Intrusive magmatism. Major and trace elements and isotopic systematics helps to recognize the basic end-member as compositionally akin to mafic rocks from the Capraia Island, whereas the leucocratic endmember is a crustal anatectic melt derived by partial melting at ca 4- 6 Kbar of garnet micaschists of the Tuscany basement. Data obtained by CROP 03 profile indicate a superposition of upper crust of both the European and Adriatic plates in westermost Tuscany. This fits well the petrological model reported in this work.