Anatectic-hybrid magmatism affected Tuscany (Italy) during Late Miocene, building up the Tuscan Magmatic Province (TMP) as the Apennine fold belt was thinned, heated and intruded by magmas. An intrusive complex was progressively built on Elba Island by emplacement of multiple laccoliths, a major pluton, and a final dyke swarm, all within the span from about 8 to 6.8 Ma. Several distinct magma sources, in both the crust and mantle, have been identified as contributing to the Elba magmatism as it evolved from crust-, to hybrid-, to mantle-dominated. However, a restricted number of components, geochemically similar to mafic K-andesites of the Island of Capraia and Cotoncello leucogranites at Elba, are sufficient to account for the generation by melt hybridization of the most voluminous magmas. Unusual magmas were emplaced at the beginning and end of the igneous activity, without contributing to the generation of these hybrid magmas. These are represented by early anatectic rocks (87Sr/86Sr from 0.7115 to 0.7146), and late mantle-derived magma strongly enriched in incompatible elements (87Sr/86Sr = 0.7114) with geochemical-isotopic characteristics intermediate between contemporaneous Capraia K-andesites and later lamproites from the TMP. The occurrence of such variety of rocks emphasizes the variable nature of crust and mantle sources that can be activated in a short time span during post-collisional magmatism.
The magmatic evolution of the Late Miocene laccolith-pluton-dyke granitic complex of Elba Island, Italy.
2002
Abstract
Anatectic-hybrid magmatism affected Tuscany (Italy) during Late Miocene, building up the Tuscan Magmatic Province (TMP) as the Apennine fold belt was thinned, heated and intruded by magmas. An intrusive complex was progressively built on Elba Island by emplacement of multiple laccoliths, a major pluton, and a final dyke swarm, all within the span from about 8 to 6.8 Ma. Several distinct magma sources, in both the crust and mantle, have been identified as contributing to the Elba magmatism as it evolved from crust-, to hybrid-, to mantle-dominated. However, a restricted number of components, geochemically similar to mafic K-andesites of the Island of Capraia and Cotoncello leucogranites at Elba, are sufficient to account for the generation by melt hybridization of the most voluminous magmas. Unusual magmas were emplaced at the beginning and end of the igneous activity, without contributing to the generation of these hybrid magmas. These are represented by early anatectic rocks (87Sr/86Sr from 0.7115 to 0.7146), and late mantle-derived magma strongly enriched in incompatible elements (87Sr/86Sr = 0.7114) with geochemical-isotopic characteristics intermediate between contemporaneous Capraia K-andesites and later lamproites from the TMP. The occurrence of such variety of rocks emphasizes the variable nature of crust and mantle sources that can be activated in a short time span during post-collisional magmatism.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
