The geothermal ranking of Italian territory to 3 km depth proposed in
this paper is based on qualitative assessments of: (1) the hydrogeolog
ical characteristics of the different rock complexes (including litho-
stratigraphic sequence and structural setting), in order to identify m
ajor regional aquifers within a depth of 3 km. Clastic aquifers have n
ot been considered in this study; (2) the temperature range within the
regional aquifers, and the impermeable rock complexes, based on avail
able temperature, heat-flow data and geodynamic and structural conditi
ons. Figures 1 and 2, and Plates 1-6, illustrate the different geother
mal situations in Italy in terms of geodynamic, hydrogeological and th
ermal conditions to a maximum depth of 3 km. Italian territory has bee
n divided into four main categories, A-D (in decreasing order of geoth
ermal interest), each category being subdivided into classes, accordin
g to the estimated maximum temperature. of the regional aquifer or of
the impermeable formations within the reference depth, and according t
o the different potential use of the geothermal resource. The geotherm
al ranking of Italy shown in Plate 6 summarizes the objectives and lim
its of this work, and represents a reference base for identifying the
priority areas for more detailed local studies and exploratory drillin
g.