Fluid flow paths in fossil and active geothermal fields: the Plio-Pleistocene Boccheggiano-Montieri and the Larderello areas

This one-day excursion aims to illustrate the similarieties between fossil and Present hydrothermal fluid paths, comparing the structural setting of the Plio-Pleistocene Boccheggiano-Montieri mineralized area and the Present Larderello geothermal field. Both areas are characterized by fluid flow throw cataclasites hosted within the Pliocene-Present normal faults. From these structural channels, fluids migrated toward structural traps predominantly located the Upper Triassic Anidriti di Burano Fm., one of the main detachment levels for the tectonic evolution of the Northern Apennines. Both areas are located in Southern Tuscany, where a diffuse intra-crustal magmatism developed contemporaneously to extensional tectonics. Magmatism, extensional structures and dominated meteoric water circulation enhanced hydrothermal fluid flow both in the Boccheggiano area and in the Larderello field. During this field trip we like to stress the importance to study the Past, i.e. the fossil geothermal systems, in order to better understand the Present, i.e. the Larderello field. The first part of this field trip is dedicated to the relationships between mineralization and structures in the Boccheggiano-Montieri mining area, whereas the second part of the day is addressed to the visit of the Larderello geothermal area and to its natural manifestations. Furthermore, data from the subsurface will be illustrated and discussed.

DOI 10.3301/GFT.2011.03

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