The Present Therrnal State of the Alpine Region: Influence of Fluid Circulation

Abstract

There is a good correlation between the Swiss heat flow density (HFD) map (Medici & Rybach, 1995) with the uplift map, the topographic map and the high-grade metamorphic rocks distribution (Wenk & Wenk, 1984; Steck & Hunziker, 1994). It suggests that there are relationships between the geology, the tectonics and the presence of geothermal resources (anomalies). Areas with the lowest heat flow values correspond to the Alps, where the higher uplifl values are found. 1D thermal simulations demonstrate that the exhumation of metamorphic rocks, and consequently the HFD values, should be higher than those observed, as already proposed by Oxburgh and England (1980). Therefore, low HFD values in the alpine region might reflect large amounts of cold groundwaters circulating into the massifs that decrease the internal temperatures. On the other hand, ascending warm waters with relatively high flowrates can heat the surrounding rocks and consequently induce local positive geothermal anomalies (a 5OoC/km, e.g. Gotthard highway tunnel).