Dinamiche di differenziazione magmatica lungo il vulcano di retro-arco Marsili, Tirreno Meridionale
Tutor: Teresa Trua
Co-tutors: Andrea Marzoli; Michael Marani
The volcano Marsili, centre of Marsili back-arc basin in southern Tyrrhenian Sea, may be said as the biggest volcano in Europe, elongated 60km NNE-SSW, 20km of maximum width and 3000m of high, with a volume resembling Etna’s. During the last years, it has been a point of great attention for Italy due to the tsunami hazard related with a future eruption and consequent flank collapse, which could affect all the south-western sector of the country. Marsili is also a point of great interest for scientific matters such as geodynamics of subduction-related volcanism and back-arc systems and for magmatic processes. Its super inflated structure may be a consequence lateral boundaries confining the spreading rate of the basin and OIB African mantle input in the IAB magmatic system, increasing magma production and thus vertical accretion of the volcano. The similarity with MOR (mid ocean ridge) features turns Marsili into a “living laboratory” close to the shore, allowing then the comparison with its processes and MOR’s. Former studies identified the mush zone at the depth of the Moho (10km in this basin). Plagioclase and clinopyroxene crystals may show this reservoir as the main fractionation reservoir where also magma mixing processes are documented. Plagioclase Ab-rich crystals point for shallow-crust reservoirs. Only few samples were analysed, limiting the characterisation of these reservoirs.
This PhD aims to study and model Marsili’s plumbing system by identifying the main reservoirs and all the differentiation processes occurring there. Ascent rates and residence times will also be estimated to better understand chronologically the system. Phenocrysts (olivine, clinopyroxene and plagioclase) from Marsili’s lavas will be analysed for major (Electron Microprobe – University of Padova, Italy) and trace elements (LA-ICP-MS – University of Calabria, Italy) in order to document possible chemical disequilibrium profiles or else to provide data for modelling P, T and X conditions during crystallisation in the different reservoirs. MELTS and Petrolog3 will be used as modelling software for reservoir physical and chemical conditions and Matlab will serve for model residence times and ascent rates by using diffusion coefficients.
Modelling Marsili’s plumbing system will allow to identify which magmatic processes and respective rates may be acting under this great volcano, thus giving further clues on understanding back-arc systems and MOR magmatic structures.