Abstract
Understanding hydrogeological processes at the origin of thermal and mineral groundwater are necessary to ensure their sustainable management. However, many processes are involved in their genesis and often only one or two processes are investigated at the same time. Here, we propose to use an innovative combination of geochemical, isotopic (34S, 14C, 18O, 2H) and geothermometry tools to identify, for the first time in a multi-composite geological context, all processes at the origin of diversified thermo-mineral waters. 19 springs covering a wide range of temperature and chemical composition emerging on a restricted area of Corsica Island (France) were selected. Geochemical results highlight five geochemical provinces, suggesting a common origin for some of them. Geothermometry tools show the unexpected involvement of a common deep groundwater reservoir within this non-active zone. Water stable isotopes highlight a contrasted altitude in recharge areas supplying lowland springs. This suggests that different flow patterns have to be involved to explain the wide geochemical diversity observed and to allow the design of a very first conceptual groundwater-flow model. This paper demonstrates the efficiency of the combination of the selected tools as tracers of water–rock interaction, independently of flow depth, intrinsic water properties, geological conditions and interaction time disparities.
Highlights
Mineral and thermal groundwaters are very special water resources characterised by stable and specific geochemical characteristics in terms of dissolved ions and gaseous contents as well as stable, and most of the time, relatively high temperatures
We propose to use an innovative combination of geochemical, isotopic (34S, 14C, 18O, 2H) and geothermometry tools to identify, for the first time in a multi-composite geological context, all processes at the origin of diversified thermo-mineral waters. 19 springs covering a wide range of temperature and chemical composition emerging on a restricted area of Corsica Island (France) were selected
This paper demonstrates the efficiency of the combination of the selected tools as tracers of water–rock interaction, independently of flow depth, intrinsic water properties, geological conditions and interaction time disparities
Summary
Mineral and thermal groundwaters are very special water resources characterised by stable and specific geochemical characteristics in terms of dissolved ions and gaseous contents as well as stable, and most of the time, relatively high temperatures. Groundwater circulation in-depth increases the complexity and the multiplicity of groundwater pathways and provides a high diversity of water qualities with potential health benefits such as for thermal, alkaline, CO2-rich, brines, ferruginous or sulphurous waters [1,2] These processes can be even more complex in the case of long-residence-time groundwater [3,4,5,6]. Many regions with a complex and a multi-composite geological structure, such as Corsica, have a wide mineral and thermal water diversity Their origin and the hydrogeological processes responsible for the thermomineral specificity and diversity are too complex to be clearly understood [1,5,14,15]. The potential evapotranspiration is estimated about 2590 mm in the coastal regions of Corsica and the aquifer recharge rate is around 127 mm/y (about 16% of yearly rainfall) [24,25]
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