| Abstract: | Central and southern Tuscany contain all the presently exploited geothermal fields of Italy, and accordingly were chosen to test the geothermal resource assessment methodology described by Muffler and Cataldi (this issue). Using new compilations at 1:200,000 of all available drill-hole, geological, gravity, and thermal-gradient data, the region was divided into 31 zones, each of reasonably homogenous geology and thermal regime. The upper 3 km of each area was then divided by horizontal surfaces into three volumes consisting of (1) the impermeable cover (Neoautochthon, Ligurids, and the upper terrigenous part of the Tuscan Series), (2) the Jurassic and Triassic rocks that form the main reservoir complex (the lower carbonate part of the Tuscan Series) and (3) the underlying Triassic and Paleozoic quartzite and phyllite of low porosity, thus allowing calculation of geothermal energy in both rock and pore water. The aggregate of these values is the “accessible geothermal resource base” of central and southern Tuscany. |
