Using thermal springs to quantify deep groundwater flow and its thermal footprint in the Alps and North American orogens

Abstract

The extent of deep groundwater flow in mountain belts and its thermal effects are uncertain. Here, we use a new database of discharge, temperature and composition of thermal springs in the Alps to estimate the extent of deep groundwater flow and its contribution to the groundwater and heat budget. The results indicate that springs are fed exclusively by meteoric water and make up 0.13% of the total groundwater budget. Spring water circulates on average to a depth of at least 2100 m. The net heat extracted from the subsurface equals 1.5% of the background heat flow, which equals an average thermal footprint for springs of 6 km2. Cooling by downward flow and heating by upward flow are estimated as approximately 6.5% and 5.0% of the background heat flow, respectively. Compared to orogens in North America the Alps have a relatively high amount of hydrothermal activity.

Deep Meteoric Water Circulation in Earth's Crust

“…The median circulation depth of the 38 springs compiled here was 2.6 km and this approach is thought to underestimate circulation depth due to isotopic re‐equilibration of waters as they interact with the rock mass as they rise toward the discharge area, and due to mixing of waters from different depths (Ferguson et al., 2009). The results presented here are similar to those found in the Alps (Diamond et al., 2018; Luijendijk et al., 2020). Very little is known about the permeability distribution of these systems from direct measurements, but numerical modeling indicates that country rock values on the order of 10 −16 m 2 are required to supply a sufficient amount of water to a fault to support the formation of thermal springs (Forster & Smith, 1989).…”

Long-wavelength late-Miocene thrusting in the north Alpine foreland: implications for late orogenic processes

“…After 10 Ma, but possibly as late as 5 Ma, the entire Molasse Basin was uplifted, resulting in basin-scale erosion (Baran et al, 2014;Cederbom et al, 2004Cederbom et al, , 2011Genser et al, 2007;Gusterhuber et al, 2012;von Hagke et al, 2012;Mazurek et al, 2006;Schlunegger and Mosar, 2011;Zweigel et al, 1998). Since 5 Ma, compressional thin-skinned tectonics in the wedge-top part of the basin and the Jura FTB are superseded by thick-skinned tectonics (Giamboni et al, 2004;Guellec et al, 1990;Madritsch et al, 2008;Mock and Herwegh, 2017;Mosar, 1999;Philippe et al, 1996;Ustaszewski and Schmid, 2007).…”

How biased are our models? – A Case Study of the Alpine Region

“…For the northern foreland, the data is derived from the Upper Rhine Graben data base provided in Freymark et al (2017) and references therein. The data of the Molasse Basin is retrieved from Przybycin et al (2015) and references therein, whereas the data from the Alps is compiled from Luijendijk et al (2020).…”