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Vercellino, A.
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Vercellino, A.
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- PublicationOpen AccessVolcanic spreading forcing and feedback in geothermal reservoir development, Amiata Volcano, Italia(2014)
; ; ; ; ; ; ; ; ;Borgia, A.; EDRA ;Mazzoldi, A.; UMSNH-IIM, Instituto de Investigaciones en Ciencias de la Tierra, Edif. "U" Ciudad Universitaria CP 58060, Morelia, Mich., México ;Brunori, C. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Allocca, C.; EDRA via di Fioranello 31, 00134 Roma, Italia ;Delcroix, C.; EDRAvia di Fioranello 31, 00134 Roma, Italia ;Micheli, L.; Regione Toscana, via di Novoli 26, Firenze, 50127 Italia. ;Vercellino, A.; Dipartimento di Scienze della Terra, Università degli Studi di Milano, via Botticelli 23, Milano, 20133 Italia. ;Grieco, G.; Dipartimento di Scienze della Terra, Università degli Studi di Milano, via Botticelli 23, Milano, 20133 Italia.; ; ; ; ; ; ; We made a stratigraphic, structural and morphologic study of Amiata Volcano in Italy. We find that the edifice is dissected by intersecting grabens that accommodate the collapse of the higher sectors of the volcano. In turn, a number of compressive structures and diapirs exist all around the margin of the volcano. These structures create an angular drainage pattern, with stream damming and captures, and a set of lakes within and around the volcano. We interpret these structures as the result of volcanic spreading of the edifice of Amiata onto its weak substratum, formed by the late Triassic evaporites (Anidriti of Burano) and the Middle-Jurassic to Early-Cretaceous clayey chaotic complexes (Ligurian Complex). Regional doming created a slope in the basement forcing the outward flow and spreading of the ductile layers below the volcano. We model the dynamics of spreading with a scaled lubrication approximation of the Navier Stokes equations, and numerically study a solution. In the model we include simple functions for volcanic deposition and surface erosion that change the topography over time. Scaling indicates that spreading at Amiata could still be active. The numerical solution shows that, as the central part of the edifice sinks into the weak basement, diapiric structures of the underlying formations form around the base of the volcano. Deposition of volcanic rocks within the volcano and surface erosion away from it both enhance spreading. In addition, a sloping basement may constitute a trigger for the formation of trains of adjacent diapirs. Finally, we observe that volcanic spreading has created ideal heat traps that constitute todays’ exploited geothermal fields at Amiata. Normal faults generated by volcanic spreading, volcanic conduits, and direct contact between volcanic rocks (which host an extensive fresh-water aquifer) and the rocks of the geothermal field, constitute ideal pathways for water recharge during vapour extraction for geothermal energy production. We think that volcanic spreading could maintain faults in a critically stressed state, facilitating the occurrence of triggered seismicity.243 613