GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.3 179 mechanisms of magmatic replenishment and transfer that characterized the plumbing system of Etna since 2015, finally leading to the recent flank eruption of December 24-27, 2018. Combination of our petrologic and geodetic observations supports the idea that the violent paroxysmal activity affecting the VOR crater during December 2015 and May 2016 deeply changed the modes of magma supplying into the Etna plumbing system, enhancing episodes of deep replenishment and long-lasting storage at high pressure conditions, rather than shallow pressurization with frequent emissions of magma at the surface. References Aloisi M., Bonaccorso, A., Cannavò F., Gambino S., Mattia M., Puglisi G. and Boschi E.; 2009: A new dike intrusion style for the Mount Etna May 2008 eruption modelled through continuous tilt and GPS data . Terra Nova, 21 , 316– 321.  Cannata A., Di Grazia G., Giuffrida M., Gresta S., Palano M., Sciotto M., Viccaro M. and Zuccarello F.; 2018: Space- Time Evolution of Magma Storage and Transfer at Mt. Etna Volcano (Italy): The 2015–2016 Reawakening of Voragine Crater . Geochem. Geophys. Geosyst., 19 , 471-495. Costa F., Dohmen R. and Chakraborty, S.; 2008: Time scales of magmatic processes from modeling the zoning patterns of crystals. Rev. Mineral. Geochem., 69 , 545–594. Costa F. and Morgan D.J.; 2010: Time constraints from chemical equilibration in magmatic crystals. In: Dosseto A., Turner S.P., Van Orman J.A. (eds), Timescales of magmatic processes: from core to atmosphere, pp. 125–159 (Wiley, Oxford). Viccaro M., Giuffrida M., Zuccarello F., Scandura, M., Palano M. and Gresta S.; 2019: Violent paroxysmal activity drives self-feeding magma replenishment at Mt. Etna . Sci. Rep., 9 , 6717. RELATIONSHIP BETWEEN RESERVOIR PERMEABILITY, MAGMATISM AND THE DEVELOPMENT OF GEOTHERMAL RESOURCES IN CONTINENTAL SETTINGS G. Gola Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Pisa, Italy Introduction. Conductive heat transfer dominates in the middle-to-lower continental crust where the permeability of the metamorphic rocks limits an efficient convective heat transport (Ingebritsen and Manning 2003, Manning and Ingebritsen 1999). Instead, zones of crustal weakness and faulting allows efficient transport of fluids and also provides shallow magma storage space. Thanks to the high-temperature reservoir availability, the active or very recent magmatic fields represent the most interesting areas where geothermal exploration and exploitation focus. For this reason, the knowledge of the age of the last magmatic event as well as the emplacement depth and temperature of the magmatic intrusion are essential aspects in order to characterizing the geothermal system and assessing its potential. How long magma bodies persist in the middle-to-upper crust is a fundamental information to unravel also the relationship between magmatism and the development of conventional geothermal resources in continental settings. In this work, the results achieved by the numerical modelling of four geothermal fields in a magmatic setting are presented. The Ischia Island (southern Italy), the Long Valley caldera (eastern California), the Acoculco caldera complex (eastern Mexico) and the southern sector of the Larderello-Travale geothermal field (central Italy) have been matter of a multidisciplinary study in which an integrated approach has been applied in order to set-up numerical models able to simulate the conductive-convective thermal structure. The heat source has been parametrized both in space and time through an optimization procedure.