Groundwater-driven temperature changes at thermal springs in response to recent glaciation: Bormio hydrothermal system, Central Italian Alps

Volpi, Giorgio; Magri, Fabien; Frattini, Paolo; Crosta, Giovanni B.; Riva, Federico

Groundwater-driven temperature changes at thermal springs in response to recent glaciation: Bormio hydrothermal system, Central Italian Alps | Changements de température liés aux eaux souterraines au droit des sources thermales en réponse à la glaciation récente: système hydrothermal de Bormio, Alpes Centrales italiennes Cambios de temperatura del agua subterránea en los manantiales termales en respuesta a la glaciación reciente: sistema hidrotermal de Bormio, Alpes italianos centrales 针对意大利中部阿尔卑斯山脉博尔米奥水热系统近期的冰川作用所发生的地下水-驱使的温度变化 Mudanças de temperatura forçado pelas águas subterrâneas em nascentes termais em resposta a glaciação recente: sistema hidrotermal Bormio, Alpes Italianos Centrais

2017

Volpi, Giorgio | Magri, Fabien | Frattini, Paolo | Crosta, Giovanni B. | Riva, Federico

Thermal springs are widespread in the European Alps, with hundreds of geothermal sites known and exploited. The thermal circulation and fluid outflows were examined in the area around Bormio (Central Italian Alps), where ten geothermal springs discharge from dolomite bodies located close to the regional Zebrù thrust. Water is heated in deep circulation systems and upwells vigorously at a temperature of about 40 °C. Heat and fluid transport is explored by steady and transient three-dimensional finite-element simulations taking into account the effect of the last glaciation, which in the study area was recognized to end around 11,000–12,000 years ago. The full regional model (ca. 700 km²) is discretized with a highly refined triangular finite-element planar grid. Numerical simulations suggest a reactivation of the system following the end of the Last Glacial Maximum. Results correctly simulate the observed discharge rate of ca. 2,400 L/min and the spring temperatures after ca. 13,000 years from deglaciation, and show a complete cooling of the aquifer within a period of approximately 50,000 years. Groundwater flow and temperature patterns suggest that thermal water flows through a deep system crossing both sedimentary and metamorphic lithotypes along a fracture network associated with the thrust system. This example gives insights into the influences of deep alpine structures and glaciations on groundwater circulation that control the development of many hydrothermal systems not necessarily associated with convective heat flow.

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