GNGTS 2013 - Atti del 32° Convegno Nazionale

enrichment in Lithium, Strontium, Fluorine and Boron is evident. Considering the deep struc- ture of the anticline as it has been reconstruct by previous works (Ghisetti and Vezzani, 2000; Mazzoli et al., 2002; Tozer et al., 2006; Scisciani, 2009), we believe that the high salt content and the minor elements mentioned above could be acquired by waters flowing through the underlying Triassic evaporites at the core of the anticline or through Messinian gypsum in the footwall of the Acquasanta thrust, while Madonna et al., 2005 hypothesized a contribution from volcanic fluids. In this framework, isotopic analyses of oxygen and deuterium provide useful results. In Fig. 2b, isotopic results of October and February sampling are represented. In October, cold springs C1 and C3 show high isotopic values, thermal waters (T1-T4) have the lowest ones, while C2 samples, from Rio Garrafo stream, shows intermediate values, closer to thermal ones. In February an evident shift of T2, T3 and T4 to values similar to Garrafo ones happens, probably due to a greater mixing. All these data are compatible with a meteoric origin of deep waters (Craig, 1961; Longinelli and Selmo, 2003) and the variation in oxygen seem to outline C2 as cold end-member and T1 as hot end-member of a possible mixing. Comparing these values with a correlation line δ 18 O/altitude, we can estimate an altitude of water infil- tration of approximately 1500 m a.s.l. (Zuppi et al., 1974; Conversini and Tazioli, 1993). This allows identifying possible recharge areas both to the west and to the south of the Acquasanta anticline. Fig. 3 – a) Schematic structural map of the Acquasanta area (modified from Menichetti, 2008); b) Contour plot from poles to fracture planes; c) DFN model; d) calculated porosity model; e) calculated permeability model. Legend: 1) Travertines; 2) Laga Formation; 3) Marly units, from Scaglia Variegata Formation to Marne a Pteropodi Formation; 4) Scaglia Rossa Formation; 5) Normal faults; 6) Detachment thrust; 7) Regional thrust; 8) Strike-slip fault; 9) Inferred fault; 10) Bedding attitude; C/T = Analyzed springs (C=cold, T=thermal). 254 GNGTS 2013 S essione 1.3