Relationships of geothermal conditions to structural and hydrogeological features in the Roccamonfina region (Northern Campania, Italy)

Abstract

On the basis of data available until June 1967, the geological situation of the Roccamonfina region seemed to have some interest as far as geothermal research is concerned. No direct element other than the general indication of a recent volcanic activity pointed, however, to the existence of anomalous thermal conditions at depth. With a view to ascertaining the existence of such anomaly and of the other geological conditions required for the formation of an industrial geothermal field, a series of studies and prospections was carried out. They consisted of geological and photogeological investigations, chemical and isotopic analyses on gas and water, hydrogeological studies, gravimetrical surveys, shallow and deep geo-electrical prospections and some shallow test-wells for the determination of geothermal gradient and heat flow. The Roccamonfina region represents an extensive volcanotectonic depression, prevailingly filled-in by volcanic terrains and containing clastic, varyingly coarse-grained, sediments at the bottom. Below these terrains, the pre-Pliocene basement (Mesozoic carbonate and overlying flysch-facies complexes) is characterized by overthrust and doubling of series. Thus, marked thinning and shearing-out affected shaly and marly members of flyschoid terrains. As a result, at some points two potential reservoirs exist; whereas, impervious cap-rock is absolutely missing in other areas within the Roccamonfina depression. The whole depression is featured by rapid and active water-circulation, whose feeding areas are mainly represented by the volcanic edifice and the outcropping calcareous structures bordering the depression itself.