Study of the Simplon area geothermal anomaly in the frame of a transalpine deep railway tunnel feasibility project

The crossing of huge mountain chains by very deep tunnel excavations, such as in the transalpine railway project across the Simplon area, poses the big question of the high temperatures within the interested rock massif. The local geothermal situations along the Alpine chain are not yet adequately known, but because of the few available data, they are suspected to be very complex. Due to such uncertainties and on account of the great depths implied and the peculiarity of the problem, as a basic approach to understand the actual situation in the Simplon area we have adopted a multidisciplinary procedure, including surface geology lineaments, dipole geoelectric and magnetotelluric deep soundings and physical, chemical and isotope analyses of water samples. In this paper, at first we outline the details of the methods and then disclose the obtained results. The combined interpretation of the whole set of data has allowed to outline a preliminary geothermal model of the explored massif. The study of some geoelectric dispersion effects has finally allowed to predict the range of temperatures referred to the local geothermal anomaly.