The late Miocene intrusive complex of Elba Island: two centuries of studies from Savi to Innocenti. Acta Vulcanologica, 20/21: 11-32

Elba Island represents a key site for the understanding of the tectono-magmatic evolution of the northern Tyrrhenian-Apennine system. Since xviii century the presence on the island of granites showing similarities with volcanic rocks of inland Tuscany attracted the interest of naturalists (G. Targioni Tozzetti). Textural and mineralogical analogies between Elba Late Miocene granites and Tuscan acidic Pliocene-Quaternary volcanites, coupled with the clear evidence of intrusion into ‘young’ sedimentary-ophiolitic rocks helped the earlier geologists (e.g., P. Savi and B. Lotti, xix century) to firmly discard the idea that all the granites are ‘old’. Lotti’s geological mapping at Elba Island defined the standard for geological surveys in Italy and provided the necessary geometrical detail of intrusions for the earlier interpretative model of the acidic magmatism. It is astonishing that at the dawn of granite geology in Tuscany those early pioneers correctly described the multilayer laccoliths of central Elba Island as well as the bannock-like shape of the Monte Capanne pluton. After this period of intensive investigations, about 40 years must be waited for new and innovative studies on Elba magmatism. The multidisciplinary project of L. Trevisan and G. Marinelli (1950-1960s) produced a new geological map of the magmatic complex, supported by accurate petrographic and geochemical data, and first isotope dating of intrusions. During the 1970- 2000s period, well-constrained petrological models were formulated, allowing a characterisation of the magmatic end members involved in the petrogenesis of magmatic rocks from Elba Island (mixing-mingling, mixing plus crystal fractionation). Although quite sophisticated, these models lack of any detailed field study devoted to define the geometry, internal variations and emplacement mechanisms of the intrusive bodies and their relationships with local tectonic evolution. Starting from the 1990’s, Fabrizio Innocenti and his research group did overcome the limits of standard granite petrology, understanding the importance of fieldwork, and stimulating an integrated investigation of the Elba Island granites. Such a multidisciplinary approach led to the definition of an integrated model for Elba Island magmatism that include understanding of melts generation at depth, transfer/emplacement mechanisms, magma modifications at emplacement level and interplay of magmatism with local/regional tectonics. The studies developed at Elba Island have potential to elucidate the geological evolution of granite intrusions throughout the Tuscan Magmatic Province.