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During the lower and middle Miocene the western Anatolia and the eastern Aegean Sea were dominated by a calcalkaline volcanism associated with minor acid and basic volcanics. The basic subcrustal volcanics consist mainly of alkali basalts and hawaiites (9.7-11.9 m.y.), nepheline hawaiites and nepheline trachyandesites (Kula area from 1.1 m.y. to the recent times). The rhyolitic volcanics (12.5 m.y.) derived by a partial melting process in the upper crust (Sr/Sr=0.7121). The calcalkaline suite (16.2-21.5 m.y., mean valueSr/Sr=0.708) shows a trend from latite-andesites to dacites and rhyodacites; a latite andesite system related to a sinking slab of lithosphere and constituted by a mixing of oceanic crust (tholeiite), oceanic sediments and/or tectonic fragments of sialic crust is envisaged. [ABSTRACT FROM AUTHOR]

Exploration of endogenous fluids in the Carboli area has been conducted in two stages: the first comprised 3 shallow test-wells drilled in 1938 and 1939; the second comprised 9 deep wells drilled between 1962 and 1966. This paper describes the development and the results of geothermal research in the Carboli area, which represents the southern-most part of the Larderello region. Prior to the beginning of exploration (1938), the area was characterized by a large number of active thermal manifestations, such as hot springs, fumaroles, mud-pools, etc. Subsequently, after drilling had been started, the manifestations gradually disappeared, to the point of complete extinction. Hydrothermal activity in the Carboli area thus showed that it had undergone an evolution relating both to the depth of the wells and their distance from the manifestations. The series of geochemical, hydrological and structural data, together with the inter-action ascertained as between deep wells, shallow testwells and manifestations, enable the reconstruction of the progressive evolution of the local geothermal phenomenon. There follow some remarks regarding the circulation of the water in the main reservoir. This circulation develops according to a complex « spiral » pattern, which is the resultant of the convective and the laminar mouvement of the water. At a certain distance from the absorption areas, the convective cells therefore assume an extremely oblique attitude. In conclusion, the relative simplicity of the Carboli area enables the construction of a model of the water circulation and of the evolution of the geothermal phenomenon, a model which, although representative of a marginal area, is also partly representative of the situations existing in other parts of the Larderello geothermal basin. [ABSTRACT FROM AUTHOR]