Zircon as proxy of magma differentiation and mixing in the Tuscan Magmatic Province (Italy) [abstract only]

The 15-0.2 Ma-old Tuscan Magmatic Province comprises both plutonic and volcanic rocks that were emplaced/erupted in Tuscany and the Northern Tyrrhenian domain during regional extension following the subduction of the Adriatic plate below the Italian Peninsula. This work focuses on the Monte Capanne (MC) pluton (Elba) and the Capraia Volcano (the only volcanic edifice in the Tuscan Archipelago) using U-Pb geochronology, as well as detailed imaging, chemistry and isotopic (Hf) compositions of zircon. The Porto Azzurro (Eastern Elba) and Giglio island (South of Elba) intrusions were also investigated. Ion microprobe U-Pb zircon ages indicate 3 Ma of magmatic activity, i.e., from c. 8 Ma (MC pluton) to c. 5 Ma (Giglio). Eruption of Capraia Volcano (7.10-7.80 Ma) was essentially coeval with that of the MC pluton (7.04-8.08 Ma). Detailed BSE imaging and quantitative electron microprobe analyses have revealed a variety of textures associated with an extremely large range of trace to minor elements compositions in zircons from the MC pluton, which constrasts with relatively simple textures and zoning patterns from Capraia. Based on both inter- and intra-elemental data, it is suggested that both crystal fractionation and mixing between crustal and mantle-derived melts occurred, and was further complicated by reactions between other accessory phases. Magmatic grains in the MC pluton display a wide range of εHf(t) (-14.95 to -4.25) and two populations are found in almost every component of the pluton, which concurs with the magma mixing model. Other intrusions have a similar, albeit more restricted, range in εHf(t), suggesting a large extent of crustmantle interaction in the province, with a mantle component (represented by Capraia; εHf(t) = -4 to –7.5) largely modified by subduction-related metasomatic processes.