# Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems

Margaux Dupuy, Emilie Garel, Eliot Chatton, Thierry Labasque, Alexandra Mattei, Sébastien Santoni, Virginie Vergnaud, Luc Aquilina, Frédéric Huneau

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## To cite this version:

Margaux Dupuy, Emilie Garel, Eliot Chatton, Thierry Labasque, Alexandra Mattei, et al.. Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems. Journal of Hydrology, 2024, 634, pp.130956. 10.1016/j.jhydrol.2024.130956. insu-04481433

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Journal Pre-proofs

Research papers

Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems

M. Dupuy, E. Garel, E. Chatton, T. Labasque, A. Mattei, S. Santoni, V. Vergnaud, L. Aquilina, F. Huneau

PII: S0022-1694(24)00350-0

DOI: https://doi.org/10.1016/j.jhydrol.2024.130956

Reference: HYDROL 130956

To appear in: *Journal of Hydrology*

Received Date: 5 June 2023

Revised Date: 6 February 2024

Accepted Date: 9 February 2024

Please cite this article as: Dupuy, M., Garel, E., Chatton, E., Labasque, T., Mattei, A., Santoni, S., Vergnaud, V., Aquilina, L., Huneau, F., Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems, *Journal of Hydrology* (2024), doi: https://doi.org/10.1016/j.jhydrol.2024.130956

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2024 Published by Elsevier B.V.

<figure><img src="image_1.png" /></figure>
Journal Pre-proofs

Research papers

Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems

M. Dupuy, E. Garel, E. Chatton, T. Labasque, A. Mattei, S. Santoni, V. Vergnaud, L. Aquilina, F. Huneau

PII: S0022-1694(24)00350-0

DOI: https://doi.org/10.1016/j.jhydrol.2024.130956

Reference: HYDROL 130956

To appear in: *Journal of Hydrology*

Received Date: 5 June 2023

Revised Date: 6 February 2024

Accepted Date: 9 February 2024

Please cite this article as: Dupuy, M., Garel, E., Chatton, E., Labasque, T., Mattei, A., Santoni, S., Vergnaud, V., Aquilina, L., Huneau, F., Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems, *Journal of Hydrology* (2024), doi: https://doi.org/10.1016/j.jhydrol.2024.130956

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2024 Published by Elsevier B.V.

<figure><img src="image_3.png" /></figure>
1 Using natural gas content of groundwater to improve the understanding
2 of complex thermo-mineral spring systems

3 M. Dupuy$^{1,2,*}$, E. Garel$^{1,2}$, E. Chatton$^{3}$, T. Labasque$^{3}$, A. Mattei$^{1,2}$, S. Santoni$^{1,2}$, V. Vergnaud$^{3}$, L.

4 Aquilina³, F. Huneau¹,²

5 <sup>1</sup>Université de Corse Pascal Paoli, Département d'Hydrogéologie, Campus Grimaldi, BP 52, 20250 Corte, France.

6 CNRS UMR 6134 SPE, BP 52, 20250 Corte, France.

7 OSUR - Plateforme Condate Eau, CNRS - Univ Rennes, Géosciences Rennes UMR 6118, 35000 Rennes, France

8 * now at CSIRO, GPO BOX 2583, Brisbane, QLD 4102 Australia (Margaux Dupuy) [margauxdupuy@yahoo.fr](mailto:margauxdupuy@yahoo.fr)

9
1 Using natural gas content of groundwater to improve the understanding
2 of complex thermo-mineral spring systems

3 M. Dupuy$^{1,2,*}$, E. Garel$^{1,2}$, E. Chatton$^{3}$, T. Labasque$^{3}$, A. Mattei$^{1,2}$, S. Santoni$^{1,2}$, V. Vergnaud$^{3}$, L.

4 Aquilina³, F. Huneau¹,²

5 <sup>1</sup>Université de Corse Pascal Paoli, Département d'Hydrogéologie, Campus Grimaldi, BP 52, 20250 Corte, France.

6 CNRS UMR 6134 SPE, BP 52, 20250 Corte, France.

7 OSUR - Plateforme Condate Eau, CNRS - Univ Rennes, Géosciences Rennes UMR 6118, 35000 Rennes, France

8 * now at CSIRO, GPO BOX 2583, Brisbane, QLD 4102 Australia (Margaux Dupuy) [margauxdupuy@yahoo.fr](mailto:margauxdupuy@yahoo.fr)

9
10 Abstract

11 The varied gaseous composition of thermo-mineral waters emerging in a non-active
12 zone reflects the diversity and complexity of groundwater pathways and provides
13 important insights into their hydrogeological behaviours. The investigated geochemical
14 content of complex thermo-mineral springs revealed the need to use dissolved gas
15 contents as part of a multi-tracer approach to discriminate processes, geogenic (water-
16 gas-rock interactions), abiotic (geological confinement, flow paths) and biotic activity
17 influencing geochemical of groundwater along regional pathways. Irrespective of the
18 dissolved element content or the water type, examining the overall concentration of
19 dissolved gases enables an effective delineation of regional groundwater flow paths.
20 Using dissolved gas content further contributed to the circumvention of some analytical
21 challenges associated with conventional isotopic or geochemical techniques, often linked
22 to the high concentration of elements such as iron, sulfate, sulfide or other naturally
23 occurring elements content. The primary objectives are to analyse the gas composition of
24 individual springs, to identify the origin of these gases in the groundwater, and to use
25 this gas composition to improve the understanding of the flow patterns contributing to
26 the geochemical diversity observed at the surface of the groundwater. From field
27 investigations in a geologically and structurally complex area of Eastern Corsica (France),
28 three types of gas contents are identified: (type 1) CH₄ & H₂S-rich, (type 2) N₂-rich and
29 (type 3) CO₂-rich. The study of these dissolved gases highlights that the wide geochemical
30 diversity of thermo-mineral waters observed here is not only related to the mineralogical
31 composition of the local aquifer but also involves strong and cumulative interactions
32 along deep regional circulation pathways. This approach also reveals a common deep
33 crustal gaseous influence characterised by N₂ production, which interacts during up flow
34 with groundwater and then with the local metamorphic or sedimentary rock matrix. The
35 groundwater's isotopic and geochemical contents are then altered by local lithologies
36 encountered through both abiotic and biotic interactions. Finally, at shallow depths,
37 phreatic groundwater can add its geochemical and isotopic footprint and dilute this
38 complex mixture before groundwater emerges as mineral spring. This paper answers the
39 primary objectives yet further demonstrates that using dissolved gas as a tracer of
40 groundwater flow paths allows a deeper interpretation of surface geochemical and
41 isotopic observations, distinguishes local from regional flow paths, and provides
42 information about processes at the origin of groundwater diversity.

43 The combination of tools presented in this paper (i.e., geochemical, dissolved gas, and
44 isotopic tools) allows the establishment of a reliable regional groundwater flow scheme
45 for thermo-mineral waters in a non-active zone. This scheme is essential to improve
46 thermo-mineral water management, and protection to ensure their sustainable quality in
47 front of increasing anthropogenic and climatic pressures.
10 Abstract

11 The varied gaseous composition of thermo-mineral waters emerging in a non-active
12 zone reflects the diversity and complexity of groundwater pathways and provides
13 important insights into their hydrogeological behaviours. The investigated geochemical
14 content of complex thermo-mineral springs revealed the need to use dissolved gas
15 contents as part of a multi-tracer approach to discriminate processes, geogenic (water-
16 gas-rock interactions), abiotic (geological confinement, flow paths) and biotic activity
17 influencing geochemical of groundwater along regional pathways. Irrespective of the
18 dissolved element content or the water type, examining the overall concentration of
19 dissolved gases enables an effective delineation of regional groundwater flow paths.
20 Using dissolved gas content further contributed to the circumvention of some analytical
21 challenges associated with conventional isotopic or geochemical techniques, often linked
22 to the high concentration of elements such as iron, sulfate, sulfide or other naturally
23 occurring elements content. The primary objectives are to analyse the gas composition of
24 individual springs, to identify the origin of these gases in the groundwater, and to use
25 this gas composition to improve the understanding of the flow patterns contributing to
26 the geochemical diversity observed at the surface of the groundwater. From field
27 investigations in a geologically and structurally complex area of Eastern Corsica (France),
28 three types of gas contents are identified: (type 1) CH4 & H2S-rich, (type 2) N2-rich and
29 (type 3) CO2-rich. The study of these dissolved gases highlights that the wide geochemical
30 diversity of thermo-mineral waters observed here is not only related to the mineralogical
31 composition of the local aquifer but also involves strong and cumulative interactions
32 along deep regional circulation pathways. This approach also reveals a common deep
33 crustal gaseous influence characterised by N2 production, which interacts during up flow
34 with groundwater and then with the local metamorphic or sedimentary rock matrix. The
35 groundwater's isotopic and geochemical contents are then altered by local lithologies
36 encountered through both abiotic and biotic interactions. Finally, at shallow depths,
37 phreatic groundwater can add its geochemical and isotopic footprint and dilute this
38 complex mixture before groundwater emerges as mineral spring. This paper answers the
39 primary objectives yet further demonstrates that using dissolved gas as a tracer of
40 groundwater flow paths allows a deeper interpretation of surface geochemical and
41 isotopic observations, distinguishes local from regional flow paths, and provides
42 information about processes at the origin of groundwater diversity.

43 The combination of tools presented in this paper (i.e., geochemical, dissolved gas, and
44 isotopic tools) allows the establishment of a reliable regional groundwater flow scheme
45 for thermo-mineral waters in a non-active zone. This scheme is essential to improve
46 thermo-mineral water management, and protection to ensure their sustainable quality in
47 front of increasing anthropogenic and climatic pressures.
48 **Keywords**

49 Hydrogeology, thermo-mineral waters, water stable isotopes, water-rock interactions,
50 dissolved gases (CO₂, CH₄, H₂S, N₂, He)

51 **1. Introduction**

52 Abundant in thermo-mineral springs, dissolved gases discharged at the surface by
53 groundwaters provide important information about hydrogeological system functioning
54 (Giggenbach, 1991). Widely used as tracers in tectonically active zones in volcanic areas,
55 and seismically-active regions (Werner et al., 2022; Karolytè et al., 2019, 2017; Bräuer et al.,
56 2017; Benavente et al., 2016; Ruzié et al., 2013; Mörner and Etiope, 2002), gas emission
57 monitoring is underused as a basis for understanding the hydrogeological functioning of
58 complex hydro-systems that are not linked to an active zone. Some studies reveal that gas
59 discharge could not only be related to regional geotectonic settings but also the result of
60 water-rock interactions or biotic processes occurring through topographical and
61 hydrogeological discontinuities (Lee et al., 2021; Tassi et al., 2020; Kotowski et al., 2019,
62 Agnew and Halihan, 2018; Amaral et al., 2017).

63 As shown by Sacchi et al. (2022), to improve the sustainable management of mineral
64 water springs, it is necessary to identify processes occurring along the flow path of
65 valuable springs (i.e. exploited as spa or bottled). For this purpose, geochemical and
66 isotopic tools are the only two tools generally used to characterise mineral waters (Sacchi
67 et al., 2022; Lee et al., 2021; Lavrushin et al., 2018).

68 Nevertheless, the dissolved gas content can provide valuable information about the
69 subsurface flow system by significantly contributing to understanding the origin of flow
70 through the escape mechanisms of natural fluids. Preferential water flow through tectonic
71 structures is responsible for pressure variation, consequently triggering the progressive
72 release of gas at the surface as a function of their solubility. In the non-active zone, some
73 studies have revealed that gas-rich waters are only generated by meteoric water
74 infiltration and groundwater rocks interactions even in the shallowest part of the crust
75 (Agnew and Halihan, 2018). Subject to the natural increase in temperature with depth,
76 waters are warmed and, then flow through and between geotectonic units. The latter are
77 preferential pathways that allow water to quickly reach the surface before losing heat
78 (Goswami et al., 2022; Craw et al., 2013; Grasby et al., 2000). Physical and chemical
79 alterations due to depth associated with geological and geotectonic conditions can
80 increase water rock interactions and lead to gas release (Štrbački et al., 2020). From the
81 respective proportions of dissolved carbon dioxide (CO₂), methane (CH₄) or nitrogen (N₂)
82 combined with the proportion of reactive (H₂, H₂S, etc.) or noble (He, Ne, Ar) gases
83 measured in groundwater, processes causing their release could be identified (Agnew and
48 **Keywords**

49 Hydrogeology, thermo-mineral waters, water stable isotopes, water-rock interactions,
50 dissolved gases (CO₂, CH₄, H₂S, N₂, He)

51 **1. Introduction**

52 Abundant in thermo-mineral springs, dissolved gases discharged at the surface by
53 groundwaters provide important information about hydrogeological system functioning
54 (Giggenbach, 1991). Widely used as tracers in tectonically active zones in volcanic areas,
55 and seismically-active regions (Werner et al., 2022; Karolytè et al., 2019, 2017; Bräuer et al.,
56 2017; Benavente et al., 2016; Ruzié et al., 2013; Mörner and Etiope, 2002), gas emission
57 monitoring is underused as a basis for understanding the hydrogeological functioning of
58 complex hydro-systems that are not linked to an active zone. Some studies reveal that gas
59 discharge could not only be related to regional geotectonic settings but also the result of
60 water-rock interactions or biotic processes occurring through topographical and
61 hydrogeological discontinuities (Lee et al., 2021; Tassi et al., 2020; Kotowski et al., 2019,
62 Agnew and Halihan, 2018; Amaral et al., 2017).

63 As shown by Sacchi et al. (2022), to improve the sustainable management of mineral
64 water springs, it is necessary to identify processes occurring along the flow path of
65 valuable springs (i.e. exploited as spa or bottled). For this purpose, geochemical and
66 isotopic tools are the only two tools generally used to characterise mineral waters (Sacchi
67 et al., 2022; Lee et al., 2021; Lavrushin et al., 2018).

68 Nevertheless, the dissolved gas content can provide valuable information about the
69 subsurface flow system by significantly contributing to understanding the origin of flow
70 through the escape mechanisms of natural fluids. Preferential water flow through tectonic
71 structures is responsible for pressure variation, consequently triggering the progressive
72 release of gas at the surface as a function of their solubility. In the non-active zone, some
73 studies have revealed that gas-rich waters are only generated by meteoric water
74 infiltration and groundwater rocks interactions even in the shallowest part of the crust
75 (Agnew and Halihan, 2018). Subject to the natural increase in temperature with depth,
76 waters are warmed and, then flow through and between geotectonic units. The latter are
77 preferential pathways that allow water to quickly reach the surface before losing heat
78 (Goswami et al., 2022; Craw et al., 2013; Grasby et al., 2000). Physical and chemical
79 alterations due to depth associated with geological and geotectonic conditions can
80 increase water rock interactions and lead to gas release (Štrbački et al., 2020). From the
81 respective proportions of dissolved carbon dioxide (CO₂), methane (CH₄) or nitrogen (N₂)
82 combined with the proportion of reactive (H₂, H₂S, etc.) or noble (He, Ne, Ar) gases
83 measured in groundwater, processes causing their release could be identified (Agnew and
Halihan, 2018). Apart from atmospheric origin, the dissolved CO₂ has various origins such as deep-seated mantle (magmatic influence), thermogenic or biogenic (both occurring in sediments). Well known as anthropogenic emission (i.e. landfill, agricultural activities, etc.), the greenhouse gas CH₄ has multiple natural origins such as volcanic and, wetlands and or could be also the evidence of biotic processes from an anaerobic environment where microbial fermentation of organic matter occurs. The last major gas found is N₂, which may have an atmospheric origin, a magmatic origin, or can be caused by the intrusion of deep fluid. According to their potential origin and to their geochemical and isotopic composition, groundwater samples collected at the surface can provide information about fluid origin, up-flow paths and reservoir interactions with geological matrixes (D'amore et al., 1987). To ensure the sustainability of this mineral groundwater, gas monitoring was revealed to be a powerful and innovative tool to identify hydrochemical processes at the origin of springs, and to conceptualise the whole hydrogeological system as well as the aquifer conditions of flow paths. This study aims to use dissolved gases as integrative tracers of the water pathways within a non-active zone and regardless of the geological context or geological unit encountered (Marques et al., 2020; 2000 Tassi et al., 2020; Angelone et al., 2005; Minissale et al., 2019, 2004, 1999; Michard, 1990).

Corsica Island (France), and particularly its eastern part, highlights a wide hydrochemical diversity of thermo-mineral waters (Na-HCO₃, Ca-HCO₃, Ca-SO₄- HCO₃ and Na-Cl), not linked to any seismic- or tectonic activity (Dupuy et al., 2021). Emerging from a small mountain-plain continuum (<16 km), at the interface of sedimentary, metamorphic and igneous rocks, eastern Corsica thermo-mineral groundwater diversity is evidence of the existence of complex flow patterns and thus a perfect site for detailed investigations on groundwater gaseous content. To improve the gap in knowledge regarding the origin of the gas diversity observed, noble gases (He, Ne, Ar) and reactive gases (CO₂, N₂, H₂S, CH₄, H₂, O₂) were monitored to test the potential of dissolved gases to improve the hydrogeological understanding of 22 mineral springs.

The main aims were (1) to describe the gas composition of each spring; (2) to characterise the origin of these gas phases in groundwater and to differentiate geogenic from biotic influences. Then, using this gas composition (3) improves the description of the flow patterns involved in the groundwater diversity observed at the surface.

This work provides significant information regarding the major interest in investigating the gaseous phases of groundwaters in non-active zones, taking advantage of the complex hydrogeological model offered by Corsica Island geological conditions.

## 2. Study area
Halihan, 2018). Apart from atmospheric origin, the dissolved CO₂ has various origins such as deep-seated mantle (magmatic influence), thermogenic or biogenic (both occurring in sediments). Well known as anthropogenic emission (i.e. landfill, agricultural activities, etc.), the greenhouse gas CH₄ has multiple natural origins such as volcanic and, wetlands and or could be also the evidence of biotic processes from an anaerobic environment where microbial fermentation of organic matter occurs. The last major gas found is N₂, which may have an atmospheric origin, a magmatic origin, or can be caused by the intrusion of deep fluid. According to their potential origin and to their geochemical and isotopic composition, groundwater samples collected at the surface can provide information about fluid origin, up-flow paths and reservoir interactions with geological matrixes (D'amore et al., 1987). To ensure the sustainability of this mineral groundwater, gas monitoring was revealed to be a powerful and innovative tool to identify hydrochemical processes at the origin of springs, and to conceptualise the whole hydrogeological system as well as the aquifer conditions of flow paths. This study aims to use dissolved gases as integrative tracers of the water pathways within a non-active zone and regardless of the geological context or geological unit encountered (Marques et al., 2020; 2000 Tassi et al., 2020; Angelone et al., 2005; Minissale et al., 2019, 2004, 1999; Michard, 1990).

Corsica Island (France), and particularly its eastern part, highlights a wide hydrochemical diversity of thermo-mineral waters (Na-HCO₃, Ca-HCO₃, Ca-SO₄- HCO₃ and Na-Cl), not linked to any seismic- or tectonic activity (Dupuy et al., 2021). Emerging from a small mountain-plain continuum (<16 km), at the interface of sedimentary, metamorphic and igneous rocks, eastern Corsica thermo-mineral groundwater diversity is evidence of the existence of complex flow patterns and thus a perfect site for detailed investigations on groundwater gaseous content. To improve the gap in knowledge regarding the origin of the gas diversity observed, noble gases (He, Ne, Ar) and reactive gases (CO₂, N₂, H₂S, CH₄, H₂, O₂) were monitored to test the potential of dissolved gases to improve the hydrogeological understanding of 22 mineral springs.

The main aims were (1) to describe the gas composition of each spring; (2) to characterise the origin of these gas phases in groundwater and to differentiate geogenic from biotic influences. Then, using this gas composition (3) improves the description of the flow patterns involved in the groundwater diversity observed at the surface.

This work provides significant information regarding the major interest in investigating the gaseous phases of groundwaters in non-active zones, taking advantage of the complex hydrogeological model offered by Corsica Island geological conditions.

## 2. Study area
120 **Localisation and hydroclimatology**

121 In the Western Mediterranean Sea, Corsica Island (France) has a contrasted topography
122 (up to 2706 m. above sea level - asl.). The investigated area, located on the eastern part of
123 the island extends over 1,500 km². In the west of the study area, a mountainous zone, of
124 1034 km², rises to 2136 m, while in the east, the coastal part is a lowland plain extending
125 over 466 km². Despite the typical Mediterranean climate of the island, the mean
126 temperatures and precipitation vary significantly with the altitude (Fig. 1). According to
127 Bruno *et al.* (2001) average annual precipitation increases from about 600 mm near the
128 coast to more than 1600 mm at 1500 m asl, while the mean annual temperature decreases
129 from 16°C near the coast to 10°C at 1500 m asl (Mattei *et al.*, 2021; Bruno *et al.*, 2001). These
130 observations are confirmed by the ombrothermal diagrams displaying precipitation and
131 temperature observed on 3 cities of the study area, at Corte at 429 m asl (inland), Bastia
132 and Solenzara, two lowland stations respectively at 1 and 12 m asl. The inland part is
133 characterised by alpine climate conditions with high snowfall in winter and storm rain
134 events during the driest months from May to September for inland stations (Fig. 1) (Mattei
135 *et al.*, 2021; Rome and Giorgetti, 2007). While lowland stations saw their driest months
136 from April to September (Fig. 1). The study area is drained by four main rivers flowing
137 from West to East: the Solenzara River and the Travu River in the south part, the
138 Tavignanu River and the Golu River in the northern part (Fig. 2).

139 Geological and hydrogeological overview

140 The study area is located at the interface of 4 main geological units on the island (Fig.
141 2) (Caritg, 2009a, 2009b). The basement, mainly made of calc-alkaline granitoid rocks from
142 the Hercynian orogenesis, extends over the south-west. It is overlapped, along an N.NW-
143 S.SE axis, by two units from the Alpine orogenesis; the first unit is Eocene flysch, an
144 autochthonous sedimentary detrital unit and the second is lustrous schists, an
145 allochthonous metamorphic unit also called 'Alpine metamorphic unit', observed only in
146 the 'Castagniccia region'. The Neogene sedimentary basin of the Aleria plain is separated
147 from the allochthonous units by the Saint Antoine fault N.NE-S.SW oriented (N020°)
148 (Loče-Pilot et al., 2004). Geological and hydrogeological information of each unit
149 encountered in the study area is detailed in the paragraphs below.

150 In the study area, the Hercynian basement is mainly composed of biotite-rich
151 monzogranite, tonalo- or monzogranodiorite (Rossi *et al.*, 2015; Caritg, 2009a, 2009b). The
152 Pietrapola springs (Fig. 2) flow out of monzogranite in which alkaline feldspar [Na, K]
153 and plagioclase dominate [Na, Ca]. In the Travu valley, the Caldaniccia spring (Fig. 2)
154 flows out of tonalogranodiorite and monzogranodiorite, with plagioclase feldspars
155 dominant over alkaline feldspars, biotite [K, Mg, Fe, F] and amphibole [Ca, Mg, Fe]. The
156 granitic basement is intensively fractured by NE-SW faults (Caritg, 2009a). Only a few
120 **Localisation and hydroclimatology**

121 In the Western Mediterranean Sea, Corsica Island (France) has a contrasted topography
122 (up to 2706 m. above sea level - asl.). The investigated area, located on the eastern part of
123 the island extends over 1,500 km². In the west of the study area, a mountainous zone, of
124 1034 km², rises to 2136 m, while in the east, the coastal part is a lowland plain extending
125 over 466 km². Despite the typical Mediterranean climate of the island, the mean
126 temperatures and precipitation vary significantly with the altitude (Fig. 1). According to
127 Bruno *et al.* (2001) average annual precipitation increases from about 600 mm near the
128 coast to more than 1600 mm at 1500 m asl, while the mean annual temperature decreases
129 from 16°C near the coast to 10°C at 1500 m asl (Mattei *et al.*, 2021; Bruno *et al.*, 2001). These
130 observations are confirmed by the ombrothermal diagrams displaying precipitation and
131 temperature observed on 3 cities of the study area, at Corte at 429 m asl (inland), Bastia
132 and Solenzara, two lowland stations respectively at 1 and 12 m asl. The inland part is
133 characterised by alpine climate conditions with high snowfall in winter and storm rain
134 events during the driest months from May to September for inland stations (Fig. 1) (Mattei
135 *et al.*, 2021; Rome and Giorgetti, 2007). While lowland stations saw their driest months
136 from April to September (Fig. 1). The study area is drained by four main rivers flowing
137 from West to East: the Solenzara River and the Travu River in the south part, the
138 Tavignanu River and the Golu River in the northern part (Fig. 2).

139 **Geological and hydrogeological overview**

140 The study area is located at the interface of 4 main geological units on the island (Fig.
141 2) (Caritg, 2009a, 2009b). The basement, mainly made of calc-alkaline granitoid rocks from
142 the Hercynian orogenesis, extends over the south-west. It is overlapped, along an N.NW-
143 S.SE axis, by two units from the Alpine orogenesis; the first unit is Eocene flysch, an
144 autochthonous sedimentary detrital unit and the second is lustrous schists, an
145 allochthonous metamorphic unit also called 'Alpine metamorphic unit', observed only in
146 the 'Castagniccia region'. The Neogene sedimentary basin of the Aleria plain is separated
147 from the allochthonous units by the Saint Antoine fault N.NE-S.SW oriented (N020°)
148 (Loče-Pilot et al., 2004). Geological and hydrogeological information of each unit
149 encountered in the study area is detailed in the paragraphs below.

150 In the study area, the Hercynian basement is mainly composed of biotite-rich
151 monzogranite, tonalo- or monzogranodiorite (Rossi *et al.*, 2015; Caritg, 2009a, 2009b). The
152 Pietrapola springs (Fig. 2) flow out of monzogranite in which alkaline feldspar [Na, K]
153 and plagioclase dominate [Na, Ca]. In the Travu valley, the Caldaniccia spring (Fig. 2)
154 flows out of tonalogranodiorite and monzogranodiorite, with plagioclase feldspars
155 dominant over alkaline feldspars, biotite [K, Mg, Fe, F] and amphibole [Ca, Mg, Fe]. The
156 granitic basement is intensively fractured by NE-SW faults (Caritg, 2009a). Only a few
reports from the French geological survey exist and they provide basic information on groundwater flows and aquifer capacity of this unit (Caritg, 2009a, 2009b). As in a mainly hard rock context, deep fractures associated with the superficial weathered horizon are the most favourable zones for the groundwater circulation and aquifer capacity (Lachassagne, 2011; Genevier et al., 2011; Dewandel et al., 2011; Caritg, 2009a; Caballero et al., 2006).

The Alpine metamorphic units are derived from the exhumation of oceanic and continental tectonic units involved in the Alpine orogeny (from the Late Cretaceous to the late Eocene, e.g., (Di Rosa et al., 2017). These tectonic units include metamorphic granitoids and metamorphic sedimentary rocks with metamorphic rocks derived from the oceanic crust (serpentinites, metagabbros and metabasalts). The observed so-called 'Lustrous schists' display a wide range of metamorphic facies from blueschist facies (mainly Inzecca series), eclogite facies (mainly Serra di Pigno and Castagniccia series) to greenschist facies (Piccoli et al., 2018; Gueydan et al., 2017; Di Rosa et al., 2017; Vitale Brovarone et al., 2013; Caritg, 2009b). These units are intensively folded and characterised by discontinuities displaying an NS orientation of schistosity, creating favourable hydrogeological conditions for many springs in the Castagniccia region (Fig. 2).

The Eocene autochthonous flysch is a vertical alternation of conglomerates, sandstones and dark clay, mainly made of arkose and pelite rocks. This formation rubs up against the Hercynian basement along the NE-SW contact and is overlapped by sedimentary deposits in the eastern part (Berthier et al., 1980; Amaudric, 1973). Vignola springs from the Travu Valley, Fontanella and Acqua acetosa are springs flowing out at the interface of this heterogeneous unit known as a low aquifer potential area (Caritg et al, 2009b).

The Neogene sedimentary formation is heterogeneous: from breccias and conglomerates to sands and marls. Due to basin subsidence, Neogene deposits dip to the east with an approximate thickness of 2 km at the coastline and up to 8.5 km in the middle of the Corsican channel. Covered by thin Quaternary alluvial deposits (Fig. 2), they are cut by N145-N155 and N20-N30 faults. These Neogene sediments present a few shallow local aquifers with very low productivity. However, their thickness and lithologic diversity suggest a noticeable hydrogeological potential as a deep multi-layer aquifer supported by the occurrence of artesian boreholes (Serrano et al., 2013; Loïe-Pilot et al., 2004).

## Hydrochemical background of springs in the study area

Twenty-four thermo-mineral springs flow out at the interface of the main geological formations described above (Fig. 2). Dupuy et al. (2021) the 6-month sampling campaign in 2018 provides a first overview of hydrochemical characteristics of 19 thermo-mineral
reports from the French geological survey exist and they provide basic information on groundwater flows and aquifer capacity of this unit (Caritg, 2009a, 2009b). As in a mainly hard rock context, deep fractures associated with the superficial weathered horizon are the most favourable zones for the groundwater circulation and aquifer capacity (Lachassagne, 2011; Genevier et al., 2011; Dewandel et al., 2011; Caritg, 2009a; Caballero et al., 2006).

The Alpine metamorphic units are derived from the exhumation of oceanic and continental tectonic units involved in the Alpine orogeny (from the Late Cretaceous to the late Eocene, e.g., (Di Rosa et al., 2017). These tectonic units include metamorphic granitoids and metamorphic sedimentary rocks with metamorphic rocks derived from the oceanic crust (serpentinites, metagabbros and metabasalts). The observed so-called 'Lustrous schists' display a wide range of metamorphic facies from blueschist facies (mainly Inzecca series), eclogite facies (mainly Serra di Pigno and Castagniccia series) to greenschist facies (Piccoli et al., 2018; Gueydan et al., 2017; Di Rosa et al., 2017; Vitale Brovarone et al., 2013; Caritg, 2009b). These units are intensively folded and characterised by discontinuities displaying an NS orientation of schistosity, creating favourable hydrogeological conditions for many springs in the Castagniccia region (Fig. 2).

The Eocene autochthonous flysch is a vertical alternation of conglomerates, sandstones and dark clay, mainly made of arkose and pelite rocks. This formation rubs up against the Hercynian basement along the NE-SW contact and is overlapped by sedimentary deposits in the eastern part (Berthier et al., 1980; Amaudric, 1973). Vignola springs from the Travu Valley, Fontanella and Acqua acetosa are springs flowing out at the interface of this heterogeneous unit known as a low aquifer potential area (Caritg et al., 2009b).

The Neogene sedimentary formation is heterogeneous: from breccias and conglomerates to sands and marls. Due to basin subsidence, Neogene deposits dip to the east with an approximate thickness of 2 km at the coastline and up to 8.5 km in the middle of the Corsican channel. Covered by thin Quaternary alluvial deposits (Fig. 2), they are cut by N145-N155 and N20-N30 faults. These Neogene sediments present a few shallow local aquifers with very low productivity. However, their thickness and lithologic diversity suggest a noticeable hydrogeological potential as a deep multi-layer aquifer supported by the occurrence of artesian boreholes (Serrano et al., 2013; Loïe-Pilot et al., 2004).

## Hydrochemical background of springs in the study area

Twenty-four thermo-mineral springs flow out at the interface of the main geological formations described above (Fig. 2). Dupuy et al. (2021) the 6-month sampling campaign in 2018 provides a first overview of hydrochemical characteristics of 19 thermo-mineral
193 groundwaters and results are summarised below.

194 The Pietrapola and Caldaniccia sites show springs flowing out respectively from
195 potassium feldspar-rich- monzogranite and tonalograniodiorite. Thereby a high-altitude
196 recharge (>800 m asl) supplies the springs emerging through major faults providing
197 thermal-alkaline-water, fully equilibrated with rock. Their low mineralisation (<300
198 µS/cm) associated with a Na-HCO₃ water type and high SiO₂ content confirms that this
199 water is provided by the hydrolysis of Hercynian granitoids at depth (Dupuy *et al.*, 2021).

200 All other springs are cold resulting from a local recharge at a shallower depth. Acqua
201 acetosa, Vignola and Fontanella flow out at the interface between Eocene Flyschs and
202 Hercynian basement or Neogene sediments (Table 1). These 3 springs are highly
203 mineralised (from 2100 and up to 12 000 µS/cm²), contain high levels of chlorine, boron
204 and fluorine and display respectively a Ca-Na-HCO₃ for Acqua acetosa and a Na-Cl water
205 type for the latter two. Their high mineralisation comes partly from the dissolution of
206 interstitial-residual-brines (Aquilina et al., 2011). This geochemical diversity translates to
207 the importance of tectonics in the complexity of the flow pattern involved at the interface
208 of the different geological units (Martín-Loeches et al., 2020).

209 The Puzzichellu springs group flows out along the Saint Antoine fault, aligned on a
210 N20-N30 axis (Fig. 2), where the Puzzichellu and the Campo-Favajo springs emerge from
211 sandstones including rhyolite conglomerates covered by deposits of organic matter-rich
212 marls (Caritg et al., 2009a, 2009b). This group is characterised by Na-HCO3, Ca-Na-HCO3
213 and Ca-SO4- HCO3 water types. Here, deep groundwaters are influenced during the
214 upflow process by mixing with more carbonated groundwaters of sedimentary origin
215 (Dupuy et al., 2021). The sulfur isotopes performed on the artesian borehole of the
216 Puzzichellu site (PUZ-F, Table 1) have shown the presence of bacterial activity, explaining
217 the high sulfate and sulfite content recorded in the groundwater (Dupuy et al., 2021;
218 Dominici et al., 1986).

219 **3. Sampling and analytical procedures**

220 **3.1. Sampling strategy and rainfall data**

221 Based on their legal accessibility, geology and spatial coverage 22 thermo-mineral
222 waters, located at 15 different sites and flowing out at low altitudes (<554 m asl) were
223 sampled. The location, name and exact geographical coordinates are provided in Table 1.

224 To identify altitude recharge of precipitation at a regional scale, δ¹⁸O and δ²H extracts
225 from a monthly sampled precipitation observation network at 5 stations [Aleria (9 m),
226 Bastia (1 m), Bonifacio (99 m), Corte (486 m), Campana (760 m), and Palneca (785 m)] were
193 groundwaters and results are summarised below.

194 The Pietrapola and Caldaniccia sites show springs flowing out respectively from
195 potassium feldspar-rich- monzogranite and tonalograniodiorite. Thereby a high-altitude
196 recharge (>800 m asl) supplies the springs emerging through major faults providing
197 thermal-alkaline-water, fully equilibrated with rock. Their low mineralisation (<300
198 µS/cm) associated with a Na-HCO₃ water type and high SiO₂ content confirms that this
199 water is provided by the hydrolysis of Hercynian granitoids at depth (Dupuy *et al.*, 2021).

200 All other springs are cold resulting from a local recharge at a shallower depth. Acqua
201 acetosa, Vignola and Fontanella flow out at the interface between Eocene Flyschs and
202 Hercynian basement or Neogene sediments (Table 1). These 3 springs are highly
203 mineralised (from 2100 and up to 12 000 µS/cm²), contain high levels of chlorine, boron
204 and fluorine and display respectively a Ca-Na-HCO₃ for Acqua acetosa and a Na-Cl water
205 type for the latter two. Their high mineralisation comes partly from the dissolution of
206 interstitial-residual-brines (Aquilina et al., 2011). This geochemical diversity translates to
207 the importance of tectonics in the complexity of the flow pattern involved at the interface
208 of the different geological units (Martín-Loeches et al., 2020).

209 The Puzzichellu springs group flows out along the Saint Antoine fault, aligned on a
210 N20-N30 axis (Fig. 2), where the Puzzichellu and the Campo-Favajo springs emerge from
211 sandstones including rhyolite conglomerates covered by deposits of organic matter-rich
212 marls (Caritg et al., 2009a, 2009b). This group is characterised by Na-HCO3, Ca-Na-HCO3
213 and Ca-SO4- HCO3 water types. Here, deep groundwaters are influenced during the
214 upflow process by mixing with more carbonated groundwaters of sedimentary origin
215 (Dupuy et al., 2021). The sulfur isotopes performed on the artesian borehole of the
216 Puzzichellu site (PUZ-F, Table 1) have shown the presence of bacterial activity, explaining
217 the high sulfate and sulfite content recorded in the groundwater (Dupuy et al., 2021;
218 Dominici et al., 1986).

219 **3. Sampling and analytical procedures**

220 **3.1. Sampling strategy and rainfall data**

221 Based on their legal accessibility, geology and spatial coverage 22 thermo-mineral
222 waters, located at 15 different sites and flowing out at low altitudes (<554 m asl) were
223 sampled. The location, name and exact geographical coordinates are provided in Table 1.

224 To identify altitude recharge of precipitation at a regional scale, δ¹⁸O and δ²H extracts
225 from a monthly sampled precipitation observation network at 5 stations [Aleria (9 m),
226 Bastia (1 m), Bonifacio (99 m), Corte (486 m), Campana (760 m), and Palneca (785 m)] were
used to calculate the isotopic altitudinal gradient from data extracted from Nlend B. et al. (2023) and Mattei et al. (2021). By calculating the linear regression relating the rainwater stable isotope values to their sampling altitude, a regional isotopic elevation gradient can be obtained; here considered equal to $δ^2H = -0.019 * altitude (m asl) + (-34.876)$. This equation can be used to estimate the recharge altitude of springs out on the eastern part of the island.

## 3.2. Groundwater sampling procedures

The 22 springs were sampled monthly from January 2018 to March 2019. Physical and chemical parameters were simultaneously measured in the field. Electrical conductivity (EC), temperature (T), redox potential (Eh) and pH were measured with a WTW multi 3410 (WTW gmbH, Weilheim, Germany). Bicarbonates concentration ($HCO_3$) was also determined, in the field, using a HACH digital titrator (HACH Company, Loveland, USA). Samples were filtered through 0.45 µm nitrocellulose membranes for determination of major ions and stored in two 50 mL polyethylene bottles before storage at 4°C. One bottle was acidified using ultrapure nitric acid for cation analysis. A Dionex ICS 1100 chromatograph (Thermo FischerScientific, Waltham, USA) was used to determine ionic concentrations at the Hydrogeology Dept. of the University of Corsica (CNRS UMR SPE 6134). The analysis was checked and validated for ionic balance under 10%.

For the stable isotopes of the water molecule analysis ($δ^{18}O/^{2}H$), 20 mL amber glass bottles were filled without filtration and no headspace to ensure perfect conservation then were stored at 4 °C. They were determined using a Liquid-Water stable isotope analyser DLT-100 (Los Gatos Research, San Jose, CA, USA) at the Hydrogeology Department of the University of Corsica (CNRS UMR 6134), France, following the analytical scheme recommended by the IAEA (Penna et al., 2010). The analytical precision was better than 0.5‰ for $^{2}H$ and 0.2‰ for $^{18}O$.

For tritium ($^{3}H$) analysis, 500 ml polyethylene bottles were filled and then stored at 4°C until analysis. The $^{3}H$ activity was measured by a liquid scintillation analyser (DL > 0.2 UT) following the protocol of Thatcher et al (1977). These analyses were carried out at the Hydrosys Labor Kft. in Budapest, Hungary.

## 3.4. Gas sampling procedures

During four campaigns in 2018 (April, July, September, and December), springs were also sampled for the analysis of dissolved gases in 500 ml glass bottles by over-flushing, after rinsing three times the bottle volume with the spring water. Bottles were closed with rubber caps and sealed with a metal ring, then sent within 48 hours for analyses at the
used to calculate the isotopic altitudinal gradient from data extracted from Nlend B. et al. (2023) and Mattei et al. (2021). By calculating the linear regression relating the rainwater stable isotope values to their sampling altitude, a regional isotopic elevation gradient can be obtained; here considered equal to $δ^2H = -0.019 * altitude (m asl) + (-34.876)$. This equation can be used to estimate the recharge altitude of springs out on the eastern part of the island.

## 3.2. Groundwater sampling procedures

The 22 springs were sampled monthly from January 2018 to March 2019. Physical and chemical parameters were simultaneously measured in the field. Electrical conductivity (EC), temperature (T), redox potential (Eh) and pH were measured with a WTW multi 3410 (WTW gmbH, Weilheim, Germany). Bicarbonates concentration ($HCO_3$) was also determined, in the field, using a HACH digital titrator (HACH Company, Loveland, USA). Samples were filtered through 0.45 µm nitrocellulose membranes for determination of major ions and stored in two 50 mL polyethylene bottles before storage at 4°C. One bottle was acidified using ultrapure nitric acid for cation analysis. A Dionex ICS 1100 chromatograph (Thermo Fischer Scientific, Waltham, USA) was used to determine ionic concentrations at the Hydrogeology Dept. of the University of Corsica (CNRS UMR SPE 6134). The analysis was checked and validated for ionic balance under 10%.

For the stable isotopes of the water molecule analysis ($δ^{18}O/^{2}H$), 20 mL amber glass bottles were filled without filtration and no headspace to ensure perfect conservation then were stored at 4 °C. They were determined using a Liquid-Water stable isotope analyser DLT-100 (Los Gatos Research, San Jose, CA, USA) at the Hydrogeology Department of the University of Corsica (CNRS UMR 6134), France, following the analytical scheme recommended by the IAEA (Penna et al., 2010). The analytical precision was better than 0.5‰ for $^{2}H$ and 0.2‰ for $^{18}O$.

For tritium ($^{3}H$) analysis, 500 ml polyethylene bottles were filled and then stored at 4°C until analysis. The $^{3}H$ activity was measured by a liquid scintillation analyser (DL > 0.2 UT) following the protocol of Thatcher et al (1977). These analyses were carried out at the Hydrosys Labor Kft. in Budapest, Hungary.

## 3.4. Gas sampling procedures

During four campaigns in 2018 (April, July, September, and December), springs were also sampled for the analysis of dissolved gases in 500 ml glass bottles by over-flushing, after rinsing three times the bottle volume with the spring water. Bottles were closed with rubber caps and sealed with a metal ring, then sent within 48 hours for analyses at the
Geosciences Rennes laboratory (CNRS UMR 6118) as detailed in Chatton et al., 2017. Noble and reactive gases (Ne, He, Ar, N₂, O₂, CO₂) were extracted by headspace and measured by gas chromatography equipped with a catharometer detector (µGC 3000 – SRA) at the Condate Eau platform (OSUR CNRS - Univ Rennes, France). Uncertainty is estimated at +/- 5% for [CO₂] and [CH₄] and +/- 3% for other gases.

The anthropogenic gases (CFCs and SF₆) were sampled in stainless-steel ampoules after washing through at least three volumes of the ampoule and before closing it to ensure no air contamination. Their concentrations in groundwater were obtained through a methodology of purge-and-trap inspired by Busenberg et Plummer (1992). Water was degassed by N₂ stripping and gases were trapped in a stainless-steel tube filled with HayesepD® and maintained at -100 °C in an ethanol bath. After 6 (CFCs) or 10 (SF₆) min of pre-concentration, the gases were injected into a Gas Chromatograph equipped with an Electron Capture Detector (GC-ECD, Perkin Elmer) by immersing the trap into boiling water. The analytical uncertainty is estimated to be 1-3% for CFCs and near 5% for SF₆. Analyses were performed at the Condate Eau Platform (OSUR CNRS-Univ Rennes, France).

## 3.5 Recharge condition modelling

Dissolved gases, such as argon (Ar), nitrogen (N₂) and neon (Ne), were used to model recharge conditions, using an inverse model developed from the methods described by Aeschbach-Hertig *et al.* (1999). This model has been adapted to use the available dissolved Ne, Ar and N₂ concentrations in cm³STP/g (Standard Temperature and Pressure) to model the Temperature (NGT) and the amount of excess air (EA) as already applied on hydrogeological systems by Chatton *et al.* (2017). Limited by the low quantity of available dissolved gases (Ne, N₂ and Ar) and their related analytical uncertainty, this study considers a simple model of excess air formation to determine the recharge conditions (NGT and EA). The established inverse model is established considers an Unfractionated Air model (UA model), which assumes a total dissolution of unfractionated excess air during the recharge. That means that the reverse model will consider that dissolved noble gas concentrations depend on different parameters: the recharge temperature (so-called noble gas temperature, NGT), the volume of unfractionated excess air (EA), the altitude of recharge and the recharge salinity. The two latter field parameters being known, only two free parameters (NGT and EA) remain to be determined using the inverse model with a degree of freedom v = 1. Because absolute NGT values were not conclusive, only the Excess Air (EA) concentration was used in this paper and results are displayed in Table 3.

## 3.6 Statistical analysis: Principal component analysis (PCA) and Hierarchical clustering (HCA)
Geosciences Rennes laboratory (CNRS UMR 6118) as detailed in Chatton et al., 2017. Noble and reactive gases (Ne, He, Ar, N₂, O₂, CO₂) were extracted by headspace and measured by gas chromatography equipped with a catharometer detector (µGC 3000 – SRA) at the Condate Eau platform (OSUR CNRS - Univ Rennes, France). Uncertainty is estimated at +/- 5% for [CO₂] and [CH₄] and +/- 3% for other gases.

The anthropogenic gases (CFCs and SF₆) were sampled in stainless-steel ampoules after washing through at least three volumes of the ampoule and before closing it to ensure no air contamination. Their concentrations in groundwater were obtained through a methodology of purge-and-trap inspired by Busenberg et Plummer (1992). Water was degassed by N₂ stripping and gases were trapped in a stainless-steel tube filled with HayesepD® and maintained at -100 °C in an ethanol bath. After 6 (CFCs) or 10 (SF₆) min of pre-concentration, the gases were injected into a Gas Chromatograph equipped with an Electron Capture Detector (GC-ECD, Perkin Elmer) by immersing the trap into boiling water. The analytical uncertainty is estimated to be 1-3% for CFCs and near 5% for SF₆. Analyses were performed at the Condate Eau Platform (OSUR CNRS-Univ Rennes, France).

## 3.5 Recharge condition modelling

Dissolved gases, such as argon (Ar), nitrogen (N₂) and neon (Ne), were used to model recharge conditions, using an inverse model developed from the methods described by Aeschbach-Hertig *et al.* (1999). This model has been adapted to use the available dissolved Ne, Ar and N₂ concentrations in cm³STP/g (Standard Temperature and Pressure) to model the Temperature (NGT) and the amount of excess air (EA) as already applied on hydrogeological systems by Chatton *et al.* (2017). Limited by the low quantity of available dissolved gases (Ne, N₂ and Ar) and their related analytical uncertainty, this study considers a simple model of excess air formation to determine the recharge conditions (NGT and EA). The established inverse model is established considers an Unfractionated Air model (UA model), which assumes a total dissolution of unfractionated excess air during the recharge. That means that the reverse model will consider that dissolved noble gas concentrations depend on different parameters: the recharge temperature (so-called noble gas temperature, NGT), the volume of unfractionated excess air (EA), the altitude of recharge and the recharge salinity. The two latter field parameters being known, only two free parameters (NGT and EA) remain to be determined using the inverse model with a degree of freedom v = 1. Because absolute NGT values were not conclusive, only the Excess Air (EA) concentration was used in this paper and results are displayed in Table 3.

## 3.6 Statistical analysis: Principal component analysis (PCA) and Hierarchical clustering (HCA)
A Principal Component Analysis (PCA) is a statistical technique used for a dimensionality reduction of input data in order to simplify data visualisation. In our study, PCA is applied to identify patterns and relationships within complex datasets of variables such as physicochemical parameters (pH, Eh, T, E.C), geochemical components ($HCO_3$) and gas contents ($O_2$, $CO_2$, $CH_4$, $H_2S$, $N_2$, He, Ne, Ar, $H_2$) and displaying it by springs. It allows us to represent the data in a lower-dimensional space, facilitating the interpretation of underlying patterns (Everitt, B.S., 2001, Kim, K.-H, 2020).

A heatmap generated by Hierarchical Cluster Analysis (HCA) visually represents the results of clustering analysis. In the context of HCA, a heatmap displays a matrix of colours where each cell corresponds to a pair of variables or observations. The intensity of the colour in each cell indicates the degree of similarity or dissimilarity between the paired variables or observations. Clusters of similar entities are visually apparent as contiguous blocks of similar colours, providing a clear representation of hierarchical relationships within the dataset. Heatmaps are valuable for identifying patterns, trends, or groupings in complex datasets analysed through HCA. In our study, according to the methodology displayed by Tarvainen (2019), HCA is employed to categorise gas abundance in springs into hierarchical structures, aiding in the identification of distinct groups within the dataset.

# 4. Results and discussion

## 4.1. Water type diversity

During the sampling period, the groundwater temperature ranges from 11 to 54°C distinguishing thermal waters (T>20°C), such as at the Pietrapola site and the Travu valley (N = 8), from cold waters (T<20°C) which concerns all the other springs (N = 14, Table 1). A wide range of mineralisation levels and pH values are observed ranging from 150 µS/cm (CALD) to 12 620 µS/cm (FONT) with pH ranging between 4.45 (S-SUP) to 9.7 (P-LAV) (Table 2). In order to discriminate water types, major element proportions were displayed on a Piper diagram (Fig. 3). Three main water types are observed Na-Cl, $NaHCO_3$ and $CaHCO_3$, also with two intermediate facies $Na-Ca-HCO_3$ and $Ca-SO_4-HCO_3$. Thermal waters at the Pietrapola site and CALD, show a typical $NaHCO_3$ water type affirming their geothermal origin from granitoid rocks (Fig. 2) (Martín-Loeches et al., 2020). The thermal spring VIGN and the cold spring FONT, have a Na-Cl water type; this mature water (Giggenbach, 1988) shows long-time interaction with detrital rocks. The $CaHCO_3$ water type is observed for all the Castagniccia Region springs (Fig. 2, 3) except S-SUP, which displays an intermediate $Ca-SO_4-HCO_3$ water type, PORT and FAJO-G displaying another intermediate facies $Na-Ca-HCO_3$.

Springs located on the sedimentary plain show diversified water types: CAM-F with a
A Principal Component Analysis (PCA) is a statistical technique used for a dimensionality reduction of input data in order to simplify data visualisation. In our study, PCA is applied to identify patterns and relationships within complex datasets of variables such as physicochemical parameters (pH, Eh, T, E.C), geochemical components ($HCO_3$) and gas contents ($O_2$, $CO_2$, $CH_4$, $H_2S$, $N_2$, He, Ne, Ar, $H_2$) and displaying it by springs. It allows us to represent the data in a lower-dimensional space, facilitating the interpretation of underlying patterns (Everitt, B.S., 2001, Kim, K.-H, 2020).

A heatmap generated by Hierarchical Cluster Analysis (HCA) visually represents the results of clustering analysis. In the context of HCA, a heatmap displays a matrix of colours where each cell corresponds to a pair of variables or observations. The intensity of the colour in each cell indicates the degree of similarity or dissimilarity between the paired variables or observations. Clusters of similar entities are visually apparent as contiguous blocks of similar colours, providing a clear representation of hierarchical relationships within the dataset. Heatmaps are valuable for identifying patterns, trends, or groupings in complex datasets analysed through HCA. In our study, according to the methodology displayed by Tarvainen (2019), HCA is employed to categorise gas abundance in springs into hierarchical structures, aiding in the identification of distinct groups within the dataset.

# 4. Results and discussion

## 4.1. Water type diversity

During the sampling period, the groundwater temperature ranges from 11 to 54°C distinguishing thermal waters (T>20°C), such as at the Pietrapola site and the Travu valley (N = 8), from cold waters (T<20°C) which concerns all the other springs (N = 14, Table 1). A wide range of mineralisation levels and pH values are observed ranging from 150 µS/cm (CALD) to 12 620 µS/cm (FONT) with pH ranging between 4.45 (S-SUP) to 9.7 (P-LAV) (Table 2). In order to discriminate water types, major element proportions were displayed on a Piper diagram (Fig. 3). Three main water types are observed Na-Cl, $NaHCO_3$ and $CaHCO_3$, also with two intermediate facies $Na-Ca-HCO_3$ and $Ca-SO_4-HCO_3$. Thermal waters at the Pietrapola site and CALD, show a typical $NaHCO_3$ water type affirming their geothermal origin from granitoid rocks (Fig. 2) (Martín-Loeches et al., 2020). The thermal spring VIGN and the cold spring FONT, have a Na-Cl water type; this mature water (Giggenbach, 1988) shows long-time interaction with detrital rocks. The $CaHCO_3$ water type is observed for all the Castagniccia Region springs (Fig. 2, 3) except S-SUP, which displays an intermediate $Ca-SO_4-HCO_3$ water type, PORT and FAJO-G displaying another intermediate facies $Na-Ca-HCO_3$.

Springs located on the sedimentary plain show diversified water types: CAM-F with a
335 Na-HCO₃ water type is close to waters flowing through granitic rocks; ACQ has an
336 intermediate facies Na-Ca-HCO₃ characteristic of groundwaters flowing at the interface
337 of magmatic and sedimentary rocks (Martín-Loeches et al., 2020); then the Puzzichellu site
338 shows two springs with another intermediate Ca-SO₄-HCO₃ water type.

339 Thus, the geochemical signature of the thermo-mineral springs highlights five different
340 groundwater types, representing a high diversity of springs for a small area. These five
341 water types (Fig. 3) and their spatial distribution (Fig. 2) are not correlated with the
342 geological unit from which they spring out.

343 **4.2. Water gas composition**

344 **4.2.1. Multi-criteria classification of gaseous discharge**

345 To improve the understanding of groundwater flows and to discriminate the origin of
346 the various geochemical signatures, a multi-criteria classification of gaseous discharge
347 composition was carried out by applying hierarchical cluster analysis (HCA) on chemical
348 abundance gas measured in April, September and December 2018 (Table 3). In Fig. 4, the
349 average gas concentration by spring is depicted according to colour from low
350 concentration (dark blue) to high concentration (deep red). Hierarchical cluster analysis
351 is performed on the 13 thermo-mineral groundwater samples, based on 9 dissolved gas
352 components (Ne, He, Ar, N₂, H₂, CO₂, O₂, CH₄, H₂S) and indicates the existence of only
353 three clusters with three distinct gaseous types: Type I (CH₄ and H₂S), Type II (N₂) and
354 Type III (CO₂). Visual inspection of the vertical dendrogram reveals that cluster 1 is linked
355 to the remaining two other cluster types at a great distance, indicating that the gaseous
356 origin of Type I differs strongly from the rest of the analysed groundwater. Each related
357 cluster and main gas composition is detailed below.

358 **4.2.1.1 Type I: CH₄ and H₂S rich springs**

359 Cluster 1 concerns a borehole (PUZ-F) and a natural water spring (CAM-F) flowing
360 out from the Neogene sedimentary depositions (Fig. 2). These groundwaters are
361 intermediately mineralised (1041< E.C.<1592 µS/cm), neutral to alkaline (6.9<pH<8, mean
362 value 7.3), with varying water types due to major ions showing natural variations (Fig. 3):
363 from Ca-HCO₃-SO₄ in PUZ-F to Na-HCO₃ in CAM-F. Temperatures are below 20°C (13.5<
364 T(°C) <17.5) and a typical smell of hydrogen sulfide (rotten egg) is very strong at both
365 sites. Springs concerned by the Cluster I are characterised by the highest concentration in
366 CH₄ and H₂S measured in the study area with an average CH₄ concentration of 9*10⁻⁴ mol/l
367 (PUZ-F) up to 2*10⁻³ mol/l (CAM-F) and an average H₂S concentration of 1*10⁻⁴ mol/L
368 (PUZ-F) to 4*10⁻⁵ mol/l (CAM-F) (Table 3, Fig. 4). The average H₂ content (1*10⁻⁸ mol/l)
369 measured in CAM-F is noticeable. The average CO₂ content varies from 1*10⁻³ to 3*10⁻⁴
335 Na-HCO₃ water type is close to waters flowing through granitic rocks; ACQ has an
336 intermediate facies Na-Ca-HCO₃ characteristic of groundwaters flowing at the interface
337 of magmatic and sedimentary rocks (Martín-Loeches et al., 2020); then the Puzzichellu site
338 shows two springs with another intermediate Ca-SO₄-HCO₃ water type.

339 Thus, the geochemical signature of the thermo-mineral springs highlights five different
340 groundwater types, representing a high diversity of springs for a small area. These five
341 water types (Fig. 3) and their spatial distribution (Fig. 2) are not correlated with the
342 geological unit from which they spring out.

343 **4.2. Water gas composition**

344 **4.2.1. Multi-criteria classification of gaseous discharge**

345 To improve the understanding of groundwater flows and to discriminate the origin of
346 the various geochemical signatures, a multi-criteria classification of gaseous discharge
347 composition was carried out by applying hierarchical cluster analysis (HCA) on chemical
348 abundance gas measured in April, September and December 2018 (Table 3). In Fig. 4, the
349 average gas concentration by spring is depicted according to colour from low
350 concentration (dark blue) to high concentration (deep red). Hierarchical cluster analysis
351 is performed on the 13 thermo-mineral groundwater samples, based on 9 dissolved gas
352 components (Ne, He, Ar, N₂, H₂, CO₂, O₂, CH₄, H₂S) and indicates the existence of only
353 three clusters with three distinct gaseous types: Type I (CH₄ and H₂S), Type II (N₂) and
354 Type III (CO₂). Visual inspection of the vertical dendrogram reveals that cluster 1 is linked
355 to the remaining two other cluster types at a great distance, indicating that the gaseous
356 origin of Type I differs strongly from the rest of the analysed groundwater. Each related
357 cluster and main gas composition is detailed below.

358 **4.2.1.1 Type I: CH₄ and H₂S rich springs**

359 Cluster 1 concerns a borehole (PUZ-F) and a natural water spring (CAM-F) flowing
360 out from the Neogene sedimentary depositions (Fig. 2). These groundwaters are
361 intermediately mineralised (1041< E.C.<1592 µS/cm), neutral to alkaline (6.9<pH<8, mean
362 value 7.3), with varying water types due to major ions showing natural variations (Fig. 3):
363 from Ca-HCO₃-SO₄ in PUZ-F to Na-HCO₃ in CAM-F. Temperatures are below 20°C (13.5<
364 T(°C) <17.5) and a typical smell of hydrogen sulfide (rotten egg) is very strong at both
365 sites. Springs concerned by the Cluster I are characterised by the highest concentration in
366 CH₄ and H₂S measured in the study area with an average CH₄ concentration of 9*10⁻⁴ mol/l
367 (PUZ-F) up to 2*10⁻³ mol/l (CAM-F) and an average H₂S concentration of 1*10⁻⁴ mol/L
368 (PUZ-F) to 4*10⁻⁵ mol/l (CAM-F) (Table 3, Fig. 4). The average H₂ content (1*10⁻⁸ mol/l)
369 measured in CAM-F is noticeable. The average CO₂ content varies from 1*10⁻³ to 3*10⁻⁴
370 mol/l, for CAM-F and PUZ-F respectively, and it is associated with the very low amount 371 of O₂ (respectively from 3*10⁻⁷ to 5*10⁻⁷ mol/l) these concentrations suggests that the water 372 flows mainly through anoxic environment. Type I also highlights the occurrence of 373 significant content in Ne, Ar and N₂ respectively up to 9*10⁻⁹, 2*10⁻⁵ and 7*10⁻⁴ mol/l, which 374 are characteristic of the next cluster (Type II: N₂-rich springs) (Fig. 4).

### 4.2.1.2 Type II: N₂-rich springs

376 This second cluster concerns thermal springs (CALD, P-SOA, P-LAV, P-B), 377 characterised by alkaline pH above 8.7 up to 9.7, very low mineralisation (mean value 378 ≈330 µS/cm) and temperatures ranging from 30.4 to 54.7°C (Table 2) with Na and HCO₃ 379 as dominant ions in all samples. This type is mainly represented by a high content in N₂ 380 between 4*10⁻⁴ and 6*10⁻⁴ mol/l associated with noble gas occurrence Ne (up to 8*10⁻⁹ 381 mol/l), Ar (up to 2*10⁻⁵ mol/l) and He (up to 8*10⁻⁷ mol/l) (Fig. 4).

### 4.2.1.3 Type III: CO₂-rich springs

383 The third cluster corresponds to the cold carbonated waters of Castagniccia and to two 384 springs (FONT and ACQ) emerging in the sedimentary plain. These springs show 385 temperatures ranging from 11°C (AMPU) to 22°C (ACQ), with a wide range of 386 mineralisation from 230 µS/cm (S-SUP) to 2 890 µS/cm (ACQ) and up to 12 620 µS/cm 387 (FONT) (Table 1). The Ca-HCO₃ water type is the dominant feature, even if a Na-Cl water 388 type is observed at (FONT). This type presents a very high content in CO₂ with 389 concentrations varying between 2*10⁻² and 4*10⁻² mol/l associated with N₂ occurrence up 390 to 4*10⁻⁴ mol/l (Fig. 4).

### 4.2.2. Abundance classification

392 Three main gaseous provinces have been identified from the multi-criteria 393 classification of gaseous discharge performed on the thermo-mineral groundwaters: CH₄ 394 and H₂S-rich (Type I), N₂-rich (Type II), and CO₂-rich (Type III). According to Faramawy 395 et al. (2016), natural gas flux may have multiple origins and come from different processes 396 such as, thermogenic processes forming CO₂, H₂S, H₂ and N₂, abiogenic processes forming 397 CH₄ from mantle degassing or CO₂-reduction (Sherwood Lollar et al., 2002; Rojey, 1997), 398 but also from biogenic processes forming CH₄, CO₂ and H₂. In addition, two processes 399 could also participate at the same time and provide the same gas content, as has already 400 been observed in different regions (Štrbački et al., 2020; Barros et al., 2020; Moritz et al., 401 2015; Angelone et al., 2005; Sherwood Lollar et al., 2002).

402 As shown in Fig. 4, each type representing the major gas released is also associated 403 with minor gases that are also released at the same time. The relative occurrence between
370 mol/l, for CAM-F and PUZ-F respectively, and it is associated with the very low amount 371 of O₂ (respectively from 3*10⁻⁷ to 5*10⁻⁷ mol/l) these concentrations suggests that the water 372 flows mainly through anoxic environment. Type I also highlights the occurrence of 373 significant content in Ne, Ar and N₂ respectively up to 9*10⁻⁹, 2*10⁻⁵ and 7*10⁻⁴ mol/l, which 374 are characteristic of the next cluster (Type II: N₂-rich springs) (Fig. 4).

### 4.2.1.2 Type II: N₂-rich springs

376 This second cluster concerns thermal springs (CALD, P-SOA, P-LAV, P-B), 377 characterised by alkaline pH above 8.7 up to 9.7, very low mineralisation (mean value 378 ≈330 µS/cm) and temperatures ranging from 30.4 to 54.7°C (Table 2) with Na and HCO₃ 379 as dominant ions in all samples. This type is mainly represented by a high content in N₂ 380 between 4*10⁻⁴ and 6*10⁻⁴ mol/l associated with noble gas occurrence Ne (up to 8*10⁻⁹ 381 mol/l), Ar (up to 2*10⁻⁵ mol/l) and He (up to 8*10⁻⁷ mol/l) (Fig. 4).

### 4.2.1.3 Type III: CO₂-rich springs

383 The third cluster corresponds to the cold carbonated waters of Castagniccia and to two 384 springs (FONT and ACQ) emerging in the sedimentary plain. These springs show 385 temperatures ranging from 11°C (AMPU) to 22°C (ACQ), with a wide range of 386 mineralisation from 230 µS/cm (S-SUP) to 2 890 µS/cm (ACQ) and up to 12 620 µS/cm 387 (FONT) (Table 1). The Ca-HCO₃ water type is the dominant feature, even if a Na-Cl water 388 type is observed at (FONT). This type presents a very high content in CO₂ with 389 concentrations varying between 2*10⁻² and 4*10⁻² mol/l associated with N₂ occurrence up 390 to 4*10⁻⁴ mol/l (Fig. 4).

### 4.2.2. Abundance classification

392 Three main gaseous provinces have been identified from the multi-criteria 393 classification of gaseous discharge performed on the thermo-mineral groundwaters: CH₄ 394 and H₂S-rich (Type I), N₂-rich (Type II), and CO₂-rich (Type III). According to Faramawy 395 et al. (2016), natural gas flux may have multiple origins and come from different processes 396 such as, thermogenic processes forming CO₂, H₂S, H₂ and N₂, abiogenic processes forming 397 CH₄ from mantle degassing or CO₂-reduction (Sherwood Lollar et al., 2002; Rojey, 1997), 398 but also from biogenic processes forming CH₄, CO₂ and H₂. In addition, two processes 399 could also participate at the same time and provide the same gas content, as has already 400 been observed in different regions (Štrbački et al., 2020; Barros et al., 2020; Moritz et al., 401 2015; Angelone et al., 2005; Sherwood Lollar et al., 2002).

402 As shown in Fig. 4, each type representing the major gas released is also associated 403 with minor gases that are also released at the same time. The relative occurrence between
major and minor gas occurrence gives information about the processes involved, flow
patterns or combination processes occurring along flow paths. Indeed, the occurrence of
dissolved gases in groundwater is often the result of flow pattern mixing (Lee *et al.*, 2021;
Hiscock, 2009; Kipfer *et al.*, 2002). Influenced by physical degassing processes, these minor
gases appear in relative proportions as follows: N₂, Ar and Ne for Type I (CH₄ and H₂S-
rich), Ne and Ar with He for Type II (N₂-rich) and N₂ for Type III (CO₂-rich) (Fig. 4). This
observation highlights a minimal proportion of N₂ in each Type and the occurrence of Ar
and Ne in Type I and II. However, further study of the amount of dissolved gas is needed
to determine their origin.

4.2.3. Gas origin

To relate the composition of gases with their potential genesis processes, the 100*N₂-
CO₂-10000*Ar and the N₂-1 000*He-100*Ar ternary diagrams, proposed by Giggenbach *et
al*. (1983) and established from Powell and Cumming (2010), are shown in Fig. 5. This
figure displays groundwater dissolved gas content according to their relative content in
N₂, Ar, CO₂ (Fig. 5.A) and N₂, Ar, He (Fig 5.B).

In Figure 5.A, the trend towards the CO₂-vertex highlights the high amount of CO₂
contained in Type III springs and shows its seasonal degassing processes. The gas content
varies according to the month of sampling. This trend also shows that CO₂ content is not
linked to volcanic or to magmatic phenomena.

The literature highlights that the thermal decomposition of organic matter involves
alteration of the ¹³C-CH₄ isotopic signal varying from -60‰ to -20‰ (Faramawy et al.,
2016; Whiticar et al., 1986; Berndt et al., 1996). In contrast to abiogenic processes
responsible for the reduction of CO₂ into CH₄, mainly observed in hydrothermal water-
rock interactions and serpentinization of ultramafic rocks (Sherwood 2002), which shows
an enriched signal ¹³C-CH₄ > -60‰ (Agnew and Halihan, 2018; Faramawy et al., 2016).
Biogenic processes due to biotic activity are responsible for gas production and show a
depleted ¹³C-CH₄ <-60‰ signature. In the regional literature, the δ¹³C-CH₄ signature was
performed on 3 carbo-gaseous springs of Castagniccia (Type III) and revealed an accurate
δ¹³C-CH₄ isotopic ratios of -26.1 (AMPU), -24.9 (PORT) and -21.6‰ (MOIT) (Berthier et al.,
1980). This signature is usually indicative of thermogenic processes corresponding to a
slow decomposition of organic material with depth because of an increase in pressure and
temperature on sedimentary rocks (Barros et al., 2021, Faramawy et al., 2016; Berndt et al.,
1996; Whiticar et al., 1986). As observed in thermo-mineral waters from Italy by Minissale
(2004), a CO₂ content which comes from mantle degassing is added, along the
groundwater pathway, thermogenic- CO₂ coming from the remobilisation of
metamorphic decarbonation reactions of carbonated rocks (Barros et al., 2021; Lavrushin
et al., 2018; Petrović et al., 2010; Thiébaud et al., 2010). During the metamorphism of
major and minor gas occurrence gives information about the processes involved, flow
patterns or combination processes occurring along flow paths. Indeed, the occurrence of
dissolved gases in groundwater is often the result of flow pattern mixing (Lee *et al.*, 2021;
Hiscock, 2009; Kipfer *et al.*, 2002). Influenced by physical degassing processes, these minor
gases appear in relative proportions as follows: N₂, Ar and Ne for Type I (CH₄ and H₂S-
rich), Ne and Ar with He for Type II (N₂-rich) and N₂ for Type III (CO₂-rich) (Fig. 4). This
observation highlights a minimal proportion of N₂ in each Type and the occurrence of Ar
and Ne in Type I and II. However, further study of the amount of dissolved gas is needed
to determine their origin.

4.2.3. Gas origin

To relate the composition of gases with their potential genesis processes, the 100*N₂-
CO₂-10000*Ar and the N₂-1 000*He-100*Ar ternary diagrams, proposed by Giggenbach *et
al*. (1983) and established from Powell and Cumming (2010), are shown in Fig. 5. This
figure displays groundwater dissolved gas content according to their relative content in
N₂, Ar, CO₂ (Fig. 5.A) and N₂, Ar, He (Fig 5.B).

In Figure 5.A, the trend towards the CO₂-vertex highlights the high amount of CO₂
contained in Type III springs and shows its seasonal degassing processes. The gas content
varies according to the month of sampling. This trend also shows that CO₂ content is not
linked to volcanic or to magmatic phenomena.

The literature highlights that the thermal decomposition of organic matter involves
alteration of the ¹³C-CH₄ isotopic signal varying from -60‰ to -20‰ (Faramawy et al.,
2016; Whiticar et al., 1986; Berndt et al., 1996). In contrast to abiogenic processes
responsible for the reduction of CO₂ into CH₄, mainly observed in hydrothermal water-
rock interactions and serpentinization of ultramafic rocks (Sherwood 2002), which shows
an enriched signal ¹³C-CH₄ > -60‰ (Agnew and Halihan, 2018; Faramawy et al., 2016).
Biogenic processes due to biotic activity are responsible for gas production and show a
depleted ¹³C-CH₄ <-60‰ signature. In the regional literature, the δ¹³C-CH₄ signature was
performed on 3 carbo-gaseous springs of Castagniccia (Type III) and revealed an accurate
δ¹³C-CH₄ isotopic ratios of -26.1 (AMPU), -24.9 (PORT) and -21.6‰ (MOIT) (Berthier et al.,
1980). This signature is usually indicative of thermogenic processes corresponding to a
slow decomposition of organic material with depth because of an increase in pressure and
temperature on sedimentary rocks (Barros et al., 2021, Faramawy et al., 2016; Berndt et al.,
1996; Whiticar et al., 1986). As observed in thermo-mineral waters from Italy by Minissale
(2004), a CO₂ content which comes from mantle degassing is added, along the
groundwater pathway, thermogenic- CO₂ coming from the remobilisation of
metamorphic decarbonation reactions of carbonated rocks (Barros et al., 2021; Lavrushin
et al., 2018; Petrović et al., 2010; Thiébaud et al., 2010). During the metamorphism of
sedimentary rocks, calcite reacts with SiO₂-rich fluids to produce wollastonite rock and CO₂. The latter is then trapped by the schistosities of the rocks (Chiodini et al., 2020). Some wollastonite deposits were identified in Castagniccia and allow confirmation that the high CO₂ content here is an addition of thermogenic CO₂ to mantle-degassing CO₂ (Vitale Brovarone et al., 2013; Malvoisin et al., 2012; Ravna et al., 2010).

The two figures (Fig 5.A and 5.B) highlight that all thermo-mineral groundwaters encountered have an N₂/Ar ratio ranging between air and air-saturated water (ASW) ratios. This ratio suggests that the N₂ component comes from trapped air, due to atmospheric gases solubilised during rain infiltration (Fig. 5.B) (Epstein et al., 2021, Powell and Cumming, 2010; Minissale, 2004; Rojey, 1997; Giggenbach et al., 1983). The relatively higher content in Argon can be explained by radiogenic decay accumulating along flow paths and translating long residence times, confirming previous isotopic dating results (Dupuy et al., 2021). Moreover, some studies also reveal that Ar could be also produced by bacterial consumption of oxygen stock in an organic-rich environment. This process added to water with a relatively shorter residence time could explain why the highest Ar-content is observed during September, in PUZ-N and CAM-F springs, both emerging from a rich organic matter environment (Faramawy et al., 2016, Rojey et al., 1997). As observed on neighbouring Sardinia island, N₂-rich waters are aligned along the ASW - Crust axis suggesting a general increase in crustal He produced by radioactive decay (Fig 5.B), mostly observable during the winter period (Amaral et al., 2017; Minissale, 2004; 1999; Paternoster et al., 2017). Helium is a radiogenic gas, produced from the radioactive decay of U and Th present in weathered rocks from Earth's crust. Low in the atmosphere, He is widely used as a tracker of volcanic activity, translating gases' deep origin from mantle or crust degassing (Amaral et al., 2017). Therefore, according to Hiscock (2009), its accumulation in groundwater could also be due to long interaction time in U-Th-rich rocks. N₂, associated with the He amount provides unequivocal evidence for a contribution of deep non-atmospheric gas to these groundwater samples and a long residence time (Casillas-Trasvina et al., 2023, Zippa et al., 2019, Kulongoski et al., 2008).

## 4.3. Reactional processes

### 4.3.1. Processes identification

Principal component analysis (PCA) was performed from in-situ physical and chemical parameters (T, pH, Eh, O₂, HCO₃), combined with gas abundance in April 2018, to confirm the different processes occurring (Figure 6, Table 1). The first two components explain 50.35% of the total variance of the population. The component F1 is negatively correlated with high CO₂ content, showing the CO₂ degassing (Type III), and positively correlated with N₂, Ar and Ne characterising a crustal influence (Type I and Type II) (Mikhail and Sverjensky, 2014). This last observation highlights the occurrence of deep influence also
sedimentary rocks, calcite reacts with SiO₂-rich fluids to produce wollastonite rock and CO₂. The latter is then trapped by the schistosities of the rocks (Chiodini et al., 2020). Some wollastonite deposits were identified in Castagniccia and allow confirmation that the high CO₂ content here is an addition of thermogenic CO₂ to mantle-degassing CO₂ (Vitale Brovarone et al., 2013; Malvoisin et al., 2012; Ravna et al., 2010).

The two figures (Fig 5.A and 5.B) highlight that all thermo-mineral groundwaters encountered have an N₂/Ar ratio ranging between air and air-saturated water (ASW) ratios. This ratio suggests that the N₂ component comes from trapped air, due to atmospheric gases solubilised during rain infiltration (Fig. 5.B) (Epstein et al., 2021, Powell and Cumming, 2010; Minissale, 2004; Rojey, 1997; Giggenbach et al., 1983). The relatively higher content in Argon can be explained by radiogenic decay accumulating along flow paths and translating long residence times, confirming previous isotopic dating results (Dupuy et al., 2021). Moreover, some studies also reveal that Ar could be also produced by bacterial consumption of oxygen stock in an organic-rich environment. This process added to water with a relatively shorter residence time could explain why the highest Ar-content is observed during September, in PUZ-N and CAM-F springs, both emerging from a rich organic matter environment (Faramawy et al., 2016, Rojey et al., 1997). As observed on neighbouring Sardinia island, N₂-rich waters are aligned along the ASW - Crust axis suggesting a general increase in crustal He produced by radioactive decay (Fig 5.B), mostly observable during the winter period (Amaral et al., 2017; Minissale, 2004; 1999; Paternoster et al., 2017). Helium is a radiogenic gas, produced from the radioactive decay of U and Th present in weathered rocks from Earth's crust. Low in the atmosphere, He is widely used as a tracker of volcanic activity, translating gases' deep origin from mantle or crust degassing (Amaral et al., 2017). Therefore, according to Hiscock (2009), its accumulation in groundwater could also be due to long interaction time in U-Th-rich rocks. N₂, associated with the He amount provides unequivocal evidence for a contribution of deep non-atmospheric gas to these groundwater samples and a long residence time (Casillas-Trasvina et al., 2023, Zippa et al., 2019, Kulongoski et al., 2008).

## 4.3. Reactional processes

### 4.3.1. Processes identification

Principal component analysis (PCA) was performed from in-situ physical and chemical parameters (T, pH, Eh, O₂, HCO₃), combined with gas abundance in April 2018, to confirm the different processes occurring (Figure 6, Table 1). The first two components explain 50.35% of the total variance of the population. The component F1 is negatively correlated with high CO₂ content, showing the CO₂ degassing (Type III), and positively correlated with N₂, Ar and Ne characterising a crustal influence (Type I and Type II) (Mikhail and Sverjensky, 2014). This last observation highlights the occurrence of deep influence also
on springs from the sedimentary plain (Type I). The component F2 is positively correlated with O₂ content, highlighting mixing with surface waters concerning mainly one Type III spring (AMPU). The component F3 is positively correlated with H₂S and CH₄-content and negatively with He and Temperature; this axis differentiates biotic processes observed in Type I from water with long residence times (Type II) (Dupuy *et al.*, 2021).

### 4.3.2. Biogenic gas evidence

The determination of recharge conditions allows the determination of the excess air (EA) contribution. This value reflects the difference between groundwater gas concentration observed in water and modelled concentration at the recharge area (Table 3). A positive EA reflects a gas supply within the aquifer while a negative value means the involvement of degassing processes, which can be also associated with dilution processes (mixing or pressure variation due to the tectonic structure). EA determined on CO₂-free sources only, Type I and Type II, shows values ranging between $-6.24*10^{-3}$ (CAM-F) and $1.28*10^{-3}$ (PUZ-F). All springs show negative EA suggesting the involvement of dilution processes, except for PUZ-F (Type II), which shows a positive value during the whole of the sampling period. As suggested in the literature, the combination of CH₄ with a high amount of H₂S in groundwater suggests the involvement of biotic processes (Tassi *et al.*, 2020; Lavrushin *et al.*, 2018; Etiope, 2017; Gilhooly *et al.*, 2014; Dupalová *et al.*, 2012; Machel *et al.*, 2001). Associated with the ³⁴S-SO₄ and ³⁴S-H₂S data measured at the same mineral spring from Dupuy *et al.* (2021), this positive EA value confirms that those biotic processes are responsible for the increase of gas content in the aquifer, due to the biological degradation of organic matter. This spring emerges from Miocene sediments known to contain thick organic matter-rich marls (Aghione deposits of the Miocene). However, negative EA values found on other Type I groundwaters (CAM-F & PUZ-N) also emerging from the Miocene sediments are correlated with ³⁴S values measured in a previous study, which does not show significant biotic activity (Dupuy *et al.*, 2021). The EA seems therefore to be a good tracer of high biotic processes, showing equivalent results to ³⁴S analyses (Table 3).

### 4.3.3. Groundwater equilibration

Dissolved gas prevalence in groundwater is linked to physical and chemical parameters and element equilibration state; a pH-Eh diagram was used to characterise reservoir conditions affecting the gas content (Fig. 7, Table 2). Considering a stable pH value, the variation of Eh ranging from -238 to 401 mV represents the water equilibrium state and allows identifying equilibration with gas prevalence. All springs studied flow mainly under confined reducing conditions (Fig. 7). The CO₂ and N₂-rich springs (Type II and III) plot in the prevalence state of their predominant gas phases. Type I waters do not plots either in the CH₄ or in the H₂S prevalence area, and highlight a higher Eh value than
on springs from the sedimentary plain (Type I). The component F2 is positively correlated with O₂ content, highlighting mixing with surface waters concerning mainly one Type III spring (AMPU). The component F3 is positively correlated with H₂S and CH₄-content and negatively with He and Temperature; this axis differentiates biotic processes observed in Type I from water with long residence times (Type II) (Dupuy *et al.*, 2021).

### 4.3.2. Biogenic gas evidence

The determination of recharge conditions allows the determination of the excess air (EA) contribution. This value reflects the difference between groundwater gas concentration observed in water and modelled concentration at the recharge area (Table 3). A positive EA reflects a gas supply within the aquifer while a negative value means the involvement of degassing processes, which can be also associated with dilution processes (mixing or pressure variation due to the tectonic structure). EA determined on CO₂-free sources only, Type I and Type II, shows values ranging between $-6.24*10^{-3}$ (CAM-F) and $1.28*10^{-3}$ (PUZ-F). All springs show negative EA suggesting the involvement of dilution processes, except for PUZ-F (Type II), which shows a positive value during the whole of the sampling period. As suggested in the literature, the combination of CH₄ with a high amount of H₂S in groundwater suggests the involvement of biotic processes (Tassi *et al.*, 2020; Lavrushin *et al.*, 2018; Etiope, 2017; Gilhooly *et al.*, 2014; Dupalová *et al.*, 2012; Machel *et al.*, 2001). Associated with the ³⁴S-SO₄ and ³⁴S-H₂S data measured at the same mineral spring from Dupuy *et al.* (2021), this positive EA value confirms that those biotic processes are responsible for the increase of gas content in the aquifer, due to the biological degradation of organic matter. This spring emerges from Miocene sediments known to contain thick organic matter-rich marls (Aghione deposits of the Miocene). However, negative EA values found on other Type I groundwaters (CAM-F & PUZ-N) also emerging from the Miocene sediments are correlated with ³⁴S values measured in a previous study, which does not show significant biotic activity (Dupuy *et al.*, 2021). The EA seems therefore to be a good tracer of high biotic processes, showing equivalent results to ³⁴S analyses (Table 3).

### 4.3.3. Groundwater equilibration

Dissolved gas prevalence in groundwater is linked to physical and chemical parameters and element equilibration state; a pH-Eh diagram was used to characterise reservoir conditions affecting the gas content (Fig. 7, Table 2). Considering a stable pH value, the variation of Eh ranging from -238 to 401 mV represents the water equilibrium state and allows identifying equilibration with gas prevalence. All springs studied flow mainly under confined reducing conditions (Fig. 7). The CO₂ and N₂-rich springs (Type II and III) plot in the prevalence state of their predominant gas phases. Type I waters do not plots either in the CH₄ or in the H₂S prevalence area, and highlight a higher Eh value than
expected for CH₄ and H₂S rich springs. Figure 7 shows that the CH₄ prevalence area is close to the NH₄⁺ predominance area.

To identify springs influenced by abiotic processes, the simple NH₄⁺ occurrence in groundwater was used as a witness of the water flowing through very reducing conditions. Indeed, the NH₄⁺ is naturally released from the degradation of organic nitrogen under highly reducing conditions. Its occurrence in groundwater, especially when the physicochemical parameters of springs do not align with the NH₄⁺ prevalence conditions, underscores water flowing through strong geologic confinement, as observed for Type I and some springs of Type II. The NH₄⁺ values ranged from 0.01 (PUZ-N) to 2.17 mg/L (CAM-F) for Type I and ranged from 0.09 (MOIT) to 1.56 mg/L (FONT) for Type III. The spring CAM-F displays the highest concentration in NH₄⁺.

The fact that very reducing conditions are reached may cause a secondary production of CH₄ from CO₂, by processes referred to here as abiotic, and explain the high CH₄, CO₂ and H₂S gas content measured in some groundwaters (Fig. 8) (Tassi et al., 2020; Marques et al., 2018; Minissale et al., 2000; Paull et al., 2000). Indeed, results from Figure 7 associated which the binary diagrams (Fig. 8), allow to distinguish the gas variation involved by the biotic activity from abiotic production with the example of the CAM-F springs (Chelnokov et al., 2018; Jenden et al., 2015). Then, the re-equilibration of water during the up-flow under oxidative conditions explains the Eh value observed at the discharge.

## 4.4. Flowpath

### 4.4.1 From degassing to local flow information

As suggested by the high dissolved gas content and confirmed by the negative EA (Table 3), degassing processes are important in these thermo-mineral groundwaters. The degassing process can result from factors such as dilution, mixing, or the local tectonic structure. This latter can lead to variations in pressure, which, in turn, influence the release of gases depending on the solubility conditions of each gas. To discriminate dilution at one side, with modern water at another side, from mixing between two different aquifer units during upwelling, anthropogenic gas (CFC and SF₆) analyses were initially performed (Table 4). Results show that SF₆ values ranged from 0.89 (P-B) to 8.33 (FONT) pptv, 19 (PUZ-F) to 166.82 (S-SOT) pptv for CFC-12, from 88.03 (FORC) to 283.04 pptv (P-B) for CFC-11 and from 3.78(P-LAV) to 18.27 pptv (PUZ-F) for CFC-113 (Table 4). These values show a low of SF₆, CFC-12 and CFC-113 with an uncorrelated high amount of CFC-11. To explain this, it is acquired that if atmospheric contamination occurs all CFCs gases should be impacted in the same proportions (Cartwright et al., 2017; Darling et al., 2012). So only a few natural processes could explain the relative amount of variation between CFCs as microbial breakdown or sorption, but neither of these can explain the
expected for CH₄ and H₂S rich springs. Figure 7 shows that the CH₄ prevalence area is close to the NH₄⁺ predominance area.

To identify springs influenced by abiotic processes, the simple NH₄⁺ occurrence in groundwater was used as a witness of the water flowing through very reducing conditions. Indeed, the NH₄⁺ is naturally released from the degradation of organic nitrogen under highly reducing conditions. Its occurrence in groundwater, especially when the physicochemical parameters of springs do not align with the NH₄⁺ prevalence conditions, underscores water flowing through strong geologic confinement, as observed for Type I and some springs of Type II. The NH₄⁺ values ranged from 0.01 (PUZ-N) to 2.17 mg/L (CAM-F) for Type I and ranged from 0.09 (MOIT) to 1.56 mg/L (FONT) for Type III. The spring CAM-F displays the highest concentration in NH₄⁺.

The fact that very reducing conditions are reached may cause a secondary production of CH₄ from CO₂, by processes referred to here as abiotic, and explain the high CH₄, CO₂ and H₂S gas content measured in some groundwaters (Fig. 8) (Tassi et al., 2020; Marques et al., 2018; Minissale et al., 2000; Paull et al., 2000). Indeed, results from Figure 7 associated which the binary diagrams (Fig. 8), allow to distinguish the gas variation involved by the biotic activity from abiotic production with the example of the CAM-F springs (Chelnokov et al., 2018; Jenden et al., 2015). Then, the re-equilibration of water during the up-flow under oxidative conditions explains the Eh value observed at the discharge.

## 4.4. Flowpath

### 4.4.1 From degassing to local flow information

As suggested by the high dissolved gas content and confirmed by the negative EA (Table 3), degassing processes are important in these thermo-mineral groundwaters. The degassing process can result from factors such as dilution, mixing, or the local tectonic structure. This latter can lead to variations in pressure, which, in turn, influence the release of gases depending on the solubility conditions of each gas. To discriminate dilution at one side, with modern water at another side, from mixing between two different aquifer units during upwelling, anthropogenic gas (CFC and SF₆) analyses were initially performed (Table 4). Results show that SF₆ values ranged from 0.89 (P-B) to 8.33 (FONT) pptv, 19 (PUZ-F) to 166.82 (S-SOT) pptv for CFC-12, from 88.03 (FORC) to 283.04 pptv (P-B) for CFC-11 and from 3.78(P-LAV) to 18.27 pptv (PUZ-F) for CFC-113 (Table 4). These values show a low of SF₆, CFC-12 and CFC-113 with an uncorrelated high amount of CFC-11. To explain this, it is acquired that if atmospheric contamination occurs all CFCs gases should be impacted in the same proportions (Cartwright et al., 2017; Darling et al., 2012). So only a few natural processes could explain the relative amount of variation between CFCs as microbial breakdown or sorption, but neither of these can explain the
proportion obtained here, from springs in different geological contexts (Chambers et al., 2019; Kotowski et al., 2019). Moreover, according to Beyerle et al. (1999), these anthropogenic gases are responsive to Excess Air formation and degassing processes. Degassing processes could then explain the relative proportions observed which are inversely proportional to their AE sensitivity (Cartwright et al., 2017). Even if degassing processes influence the anthropogenic gas content in groundwater, their occurrence in groundwater highlights a dilution process with modern water and should be confirmed by the ³H content (Table 3).

Tritium measured in groundwater ranges from 0 (P-X) to 2.3 TU (PARD); knowing that the average ³H content in Corsican rainwater is about 8 TU (Juhlke et al., 2020) it can be concluded that Type I are old water diluted by modern surface waters or shallow groundwaters (characterised by the presence of anthropogenic gases, negative EA and with noticeable ³H amount). By comparison, the negative EA combined with groundwater deprived of ³H characterises Type II as composed of old groundwater only. Type III groundwater shows the widest diversity of flow path contributions. In this category (CO₂-rich springs) some springs are mainly composed of old water while many other springs result from mixing processes between old water diluted with an actual water fraction (Table 3) containing anthropogenic gases and ³H.

### 4.4.2 Influence of regional flow

Noble gases found in groundwater reveal the recharge conditions history. It is usually admitted that the higher the concentration of noble gases in the water, the colder is the recharge temperatures observed (Hiscock, 2009; Kipfer et al., 2002). The Ar and N₂ concentrations are displayed in Fig. 9. Carbogaseous waters (Type III) show the lowest amount of noble gas, due to their intensive degassing. Fig. 9 highlights the CH₄-rich waters (Type I) springing out from the sedimentary plain and show a higher or equivalent amount of noble gas than thermal springs (Type II). However, this observation is different from the recharge altitude estimation calculated from δ²H and δ¹⁸O data measured in this study (Table 2). These values show a differentiated recharge altitude ranging from 764 to 900 m asl for Type II and from 78 to 290 m asl for Type I. The noble gas concentration suggests that, even if most groundwater flow in the sedimentary plain comes from a local recharge, some springs from the plain (Type I) can also be supplied by a deeper up-flow coming from a higher altitude.

As detailed by Elena et al. (2020), helium is a highly volatile radiogenic gas, its accumulation in groundwater is usually proportional to the increasing depth or residence time at the contact with source-rocks (Werner et al., 2022; Casillas-Trasvina et al., 2022; Karolyté et al., 2019; Kulongoski et al., 2008). The measure of He excess is therefore significant (analytical threshold ≈ 10⁻⁹ cm3STP/g) due to accumulation along the flow line
proportion obtained here, from springs in different geological contexts (Chambers et al., 2019; Kotowski et al., 2019). Moreover, according to Beyerle et al. (1999), these anthropogenic gases are responsive to Excess Air formation and degassing processes. Degassing processes could then explain the relative proportions observed which are inversely proportional to their AE sensitivity (Cartwright et al., 2017). Even if degassing processes influence the anthropogenic gas content in groundwater, their occurrence in groundwater highlights a dilution process with modern water and should be confirmed by the ³H content (Table 3).

Tritium measured in groundwater ranges from 0 (P-X) to 2.3 TU (PARD); knowing that the average ³H content in Corsican rainwater is about 8 TU (Juhlke et al., 2020) it can be concluded that Type I are old water diluted by modern surface waters or shallow groundwaters (characterised by the presence of anthropogenic gases, negative EA and with noticeable ³H amount). By comparison, the negative EA combined with groundwater deprived of ³H characterises Type II as composed of old groundwater only. Type III groundwater shows the widest diversity of flow path contributions. In this category (CO₂-rich springs) some springs are mainly composed of old water while many other springs result from mixing processes between old water diluted with an actual water fraction (Table 3) containing anthropogenic gases and ³H.

### 4.4.2 Influence of regional flow

Noble gases found in groundwater reveal the recharge conditions history. It is usually admitted that the higher the concentration of noble gases in the water, the colder is the recharge temperatures observed (Hiscock, 2009; Kipfer et al., 2002). The Ar and N₂ concentrations are displayed in Fig. 9. Carbogaseous waters (Type III) show the lowest amount of noble gas, due to their intensive degassing. Fig. 9 highlights the CH₄-rich waters (Type I) springing out from the sedimentary plain and show a higher or equivalent amount of noble gas than thermal springs (Type II). However, this observation is different from the recharge altitude estimation calculated from δ²H and δ¹⁸O data measured in this study (Table 2). These values show a differentiated recharge altitude ranging from 764 to 900 m asl for Type II and from 78 to 290 m asl for Type I. The noble gas concentration suggests that, even if most groundwater flow in the sedimentary plain comes from a local recharge, some springs from the plain (Type I) can also be supplied by a deeper up-flow coming from a higher altitude.

As detailed by Elena et al. (2020), helium is a highly volatile radiogenic gas, its accumulation in groundwater is usually proportional to the increasing depth or residence time at the contact with source-rocks (Werner et al., 2022; Casillas-Trasvina et al., 2022; Karolyté et al., 2019; Kulongoski et al., 2008). The measure of He excess is therefore significant (analytical threshold ≈ 10⁻⁹ cm3STP/g) due to accumulation along the flow line
and indicates very long circulatory processes. All (non-carbogaseous) springs show an excess of He. The greatest excess (from $10^{-5}$ and $10^{-6}$ cm3STP/g) is observed for Type III, however, the amount of He excess in the sedimentary plain springs (Type I) confirms their supply by the deep flow, having a long residence time.

### 4.4.3 Conceptual model of groundwater flow towards thermo-mineral springs

From the geochemical, the water stable isotopic and gases dataset obtained a conceptual hydrogeological model of the region is proposed (Fig. 10). It shows that meteoric water infiltrated at high altitudes (>800 m asl) infiltrates into granitic rocks through major faults and deep fractures. Water is then warmed by the natural geothermal gradient until the shallower part of the crust where water is enriched with high amounts of $N_2$, He, and low amounts of $CO_2$. The local geostructure allows the release of dissolved gases up to the near surface (Type II). However, this study reveals that the type II ($N_2$-rich) also supplies trough depth all other thermal and mineral springs emerging in the sedimentary plain (Fig. 11). Depending on waters and rocks encountered along the gaseous up-flow, this regional gaseous signature is locally modified by abiotic and biotic processes. During the flow path through metamorphic rocks, the deep gaseous flux is mixed with carbonated waters coming from a local recharge. The water circulation through these rocks allows the mobilisation of thermogenic $CO_2$ coming from metamorphosed schists (Type III). This high amount of $CO_2$ increases the degassing process of low soluble gases as noble gas originating from the regional gaseous flux.

Carbogaseous water also springs out in the southern part of the sedimentary plain, at the interface of the different geological units, where the metamorphosed rocks are overlapped by an impermeable geological layer of Eocene flyschs. Here also metamorphosed rocks supply the sedimentary plain at depth with $N_2$ and $CO_2$ gases which are subsequently influenced along their pathway through deep anoxic and very reducing conditions. This abiotic process is responsible for the $N_2$ reduction into $NH_4^+$ and $CO_2$ into $CH_4$ increasing $NH_4^+$ and $CH_4$ content in groundwater (Fig. 11). Then, still supplied by a local recharge, the water flows in contact with the organic material contained in the Miocene sediments. Biotic processes alter the sulfate isotopic and geochemical composition of those waters and increase the $H_2S$ amount in surface waters (Type I) (Fig. 10 and 11).

Using this innovative and complex combination of tools, investigations highlight the occurrence of a regional gas supply observed in all thermo-mineral waters of the eastern part of Corsica Island, even in a non-tectonically active zone. The geological structural complexity of the island is responsible for a wide variety of processes affecting gas and water composition and explains the high diversity of thermo-mineral water observed, as shown in Fig. 10. The complexity and the diversity of processes accumulating along the regional path confirm the
and indicates very long circulatory processes. All (non-carbogaseous) springs show an excess of He. The greatest excess (from $10^{-5}$ and $10^{-6}$ cm3STP/g) is observed for Type III, however, the amount of He excess in the sedimentary plain springs (Type I) confirms their supply by the deep flow, having a long residence time.

### 4.4.3 Conceptual model of groundwater flow towards thermo-mineral springs

From the geochemical, the water stable isotopic and gases dataset obtained a conceptual hydrogeological model of the region is proposed (Fig. 10). It shows that meteoric water infiltrated at high altitudes (>800 m asl) infiltrates into granitic rocks through major faults and deep fractures. Water is then warmed by the natural geothermal gradient until the shallower part of the crust where water is enriched with high amounts of $N_2$, He, and low amounts of $CO_2$. The local geostructure allows the release of dissolved gases up to the near surface (Type II). However, this study reveals that the type II ($N_2$-rich) also supplies trough depth all other thermal and mineral springs emerging in the sedimentary plain (Fig. 11). Depending on waters and rocks encountered along the gaseous up-flow, this regional gaseous signature is locally modified by abiotic and biotic processes. During the flow path through metamorphic rocks, the deep gaseous flux is mixed with carbonated waters coming from a local recharge. The water circulation through these rocks allows the mobilisation of thermogenic $CO_2$ coming from metamorphosed schists (Type III). This high amount of $CO_2$ increases the degassing process of low soluble gases as noble gas originating from the regional gaseous flux.

Carbogaseous water also springs out in the southern part of the sedimentary plain, at the interface of the different geological units, where the metamorphosed rocks are overlapped by an impermeable geological layer of Eocene flyschs. Here also metamorphosed rocks supply the sedimentary plain at depth with $N_2$ and $CO_2$ gases which are subsequently influenced along their pathway through deep anoxic and very reducing conditions. This abiotic process is responsible for the $N_2$ reduction into $NH_4^+$ and $CO_2$ into $CH_4$ increasing $NH_4^+$ and $CH_4$ content in groundwater (Fig. 11). Then, still supplied by a local recharge, the water flows in contact with the organic material contained in the Miocene sediments. Biotic processes alter the sulfate isotopic and geochemical composition of those waters and increase the $H_2S$ amount in surface waters (Type I) (Fig. 10 and 11).

Using this innovative and complex combination of tools, investigations highlight the occurrence of a regional gas supply observed in all thermo-mineral waters of the eastern part of Corsica Island, even in a non-tectonically active zone. The geological structural complexity of the island is responsible for a wide variety of processes affecting gas and water composition and explains the high diversity of thermo-mineral water observed, as shown in Fig. 10. The complexity and the diversity of processes accumulating along the regional path confirm the
involvement of gas and water mixing processes between the different geological units. To achieve a more sustainable use of thermo-mineral springs on the island of Corsica, quantifying the interplay between regional and local flows must be considered for future research. Indeed, due to the complexity of the flow paths involving, deep upwelling, interactions with the local geological matrix and mixing with phreatic waters, quantification of mixing ratios will be helpful in a further attempt to contribute to a more sustainable exploitation of the island's thermo-mineral springs.

## 5. Conclusion

These investigations aimed to provide new information on the accumulation of hydrogeological processes along groundwater flow-paths within tectonically non-active zones. Our findings demonstrate that groundwater gas contents can provide an almost complete assessment of hydrogeological processes (abiotic and biotic) occurring on both regional and local scales. This approach reveals not easily discernible insights by using more conventional hydrogeochemical and isotopic tools.

The use of dissolved gases as tracers circumvents the methodological constraints often encountered with classic tools, due to the presence of CO₂, iron, or sulfur, which can constrain the water analyses. This unconventional method enables us to identify the flow paths irrespective of water type or encountered geological units making analysis possible independently of water intrinsic properties (conductivity, pH, carbon or sulfide content).

In conclusion, studying dissolved gas content is an unconventional yet valuable tool, providing qualitative information about aquifer hydrogeological functioning such as the recharge conditions, the regional flow paths, hydrogeological compartments mixing (deep versus phreatic) and the impact of bacterial activity on water composition.

However, it is important to acknowledge several limitations, which can be categorised into two: practical and technical aspects, as well as more generalised data interpretation. Practical and technical limitations include the need for careful sampling, rapid gas sample analysis (< 48H) and cautious transportation (avoiding sudden pressure changes). To respectively avoid, atmospheric contamination, gas consumption or production by biotic activity, or artificial degassing which could introduce results bias, especially for carbonaceous samples. The limitations of the methodology and data interpretation arise from the high diversity of dissolved gases measured in this study. Resulting in contrasting gas signatures that are easy to identify and differ significantly from the uncertainties associated with our analytical tools. Further studies are needed to evaluate the applicability and effectiveness of this methodology when applied to springs with lower geochemical and gas diversity.
involvement of gas and water mixing processes between the different geological units. To achieve a more sustainable use of thermo-mineral springs on the island of Corsica, quantifying the interplay between regional and local flows must be considered for future research. Indeed, due to the complexity of the flow paths involving, deep upwelling, interactions with the local geological matrix and mixing with phreatic waters, quantification of mixing ratios will be helpful in a further attempt to contribute to a more sustainable exploitation of the island's thermo-mineral springs.

## 5. Conclusion

These investigations aimed to provide new information on the accumulation of hydrogeological processes along groundwater flow-paths within tectonically non-active zones. Our findings demonstrate that groundwater gas contents can provide an almost complete assessment of hydrogeological processes (abiotic and biotic) occurring on both regional and local scales. This approach reveals not easily discernible insights by using more conventional hydrogeochemical and isotopic tools.

The use of dissolved gases as tracers circumvents the methodological constraints often encountered with classic tools, due to the presence of CO₂, iron, or sulfur, which can constrain the water analyses. This unconventional method enables us to identify the flow paths irrespective of water type or encountered geological units making analysis possible independently of water intrinsic properties (conductivity, pH, carbon or sulfide content).

In conclusion, studying dissolved gas content is an unconventional yet valuable tool, providing qualitative information about aquifer hydrogeological functioning such as the recharge conditions, the regional flow paths, hydrogeological compartments mixing (deep versus phreatic) and the impact of bacterial activity on water composition.

However, it is important to acknowledge several limitations, which can be categorised into two: practical and technical aspects, as well as more generalised data interpretation. Practical and technical limitations include the need for careful sampling, rapid gas sample analysis (< 48H) and cautious transportation (avoiding sudden pressure changes). To respectively avoid, atmospheric contamination, gas consumption or production by biotic activity, or artificial degassing which could introduce results bias, especially for carbonaceous samples. The limitations of the methodology and data interpretation arise from the high diversity of dissolved gases measured in this study. Resulting in contrasting gas signatures that are easy to identify and differ significantly from the uncertainties associated with our analytical tools. Further studies are needed to evaluate the applicability and effectiveness of this methodology when applied to springs with lower geochemical and gas diversity.
To pave the way for further research, it remains to be seen whether the dissolved gas content can be used to mathematically quantify groundwater mixing along the flow path. Quantifying flow paths at the origin of mineral water genesis is imperative for the effective protection and management of exploited spa or bottled springs. Understanding processes involved in gases and water release is essential to ensure the sustainability and quality of these valuable resources. It would allow the identification of potential sources of contamination, monitor the influence of biotic factors, and assess the impact of external forces, such as climate change and anthropogenic activities. By quantifying flow paths, we gain insights into the hydrogeological dynamics that shape mineral water composition, enabling us to make informed decisions for resource preservation. This knowledge empowers stakeholders to safeguard the integrity of spa and bottled springs, ensuring their long-term availability and benefit to society. This significance is heightened when considering that currently remote regions in Europe, such as those hosting UNESCO World Heritage sites, have their economies dependent solely on the spa tourism and social appeal of these historically renowned mineral springs since the 18th century.

## DECLARATION OF COMPETING INTEREST

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## ACKNOWLEDGEMENT

This research was supported by the *Culletività di Corsica* through the GERHYCO interdisciplinary project dedicated to water management, ecology and hydro-ecosystem services in an island context.

## DATA AVAILABILITY

Data will be made available on request.
To pave the way for further research, it remains to be seen whether the dissolved gas content can be used to mathematically quantify groundwater mixing along the flow path. Quantifying flow paths at the origin of mineral water genesis is imperative for the effective protection and management of exploited spa or bottled springs. Understanding processes involved in gases and water release is essential to ensure the sustainability and quality of these valuable resources. It would allow the identification of potential sources of contamination, monitor the influence of biotic factors, and assess the impact of external forces, such as climate change and anthropogenic activities. By quantifying flow paths, we gain insights into the hydrogeological dynamics that shape mineral water composition, enabling us to make informed decisions for resource preservation. This knowledge empowers stakeholders to safeguard the integrity of spa and bottled springs, ensuring their long-term availability and benefit to society. This significance is heightened when considering that currently remote regions in Europe, such as those hosting UNESCO World Heritage sites, have their economies dependent solely on the spa tourism and social appeal of these historically renowned mineral springs since the 18th century.

## DECLARATION OF COMPETING INTEREST

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## ACKNOWLEDGEMENT

This research was supported by the *Culletività di Corsica* through the GERHYCO interdisciplinary project dedicated to water management, ecology and hydro-ecosystem services in an island context.

## DATA AVAILABILITY

Data will be made available on request.
685 List of Figures

686 Figure 1: Ombrothermal diagrams displaying low-land and in-land mean climatic conditions at 3 stations of the study area (Bastia and Solenzara for the low-land and Corte for the in-land climatic conditions). Data is collected by the French weather forecast office and it' is available online. Data displayed here is compiled from 1950 to 2020. This diagram displays the total monthly precipitation in mm and the monthly minimum, maximum, and mean temperatures express in degree centigrade and gives relative expression of summer drought. The intensity and duration of the dry season based on the intersections of the Temperature curves and the Precipitation one.

693 Figure 2: Location and simplified geology of the studied area. Location and typology of the thermo-mineral springs. The spring symbols describe gas type; spring name colour refers to the geochemical water type.

696 Figure 3: Piper diagram of Eastern Corsica thermo-mineral water samples (N=259). Circle around spring symbols represents quantitative information on the total dissolved solids (T.D.S.) in groundwaters. For more accurate representation, the TDS values are proportionally magnified by 5.

700 Figure 4: Multi-criteria classification and characterisation of thermal and mineral water samples were carried out applying hierarchical type analysis (HCA) on gas chemical composition obtained in April on 9 springs. This heatmap is a graphic representation of data where gas abundances (Ne, He, Ar, N₂, H₂, CO₂, O₂, CH₄, H₂S) are depicted by colour, from low concentration (dark blue) to high concentration (deep red).

705 Figure 5: Ternary diagrams displaying dissolved gas content in thermo-mineral waters after Giggenbach *et al.* (1983). All springs are displayed by code name then by the number of the sampling month. The ternary diagram (A) displays N₂-CO₂-Ar to illustrate the relative CO₂ contribution of magmatic, meteoric and volcanic sources of gases in Corsican thermo-mineral springs. The meteoric component is limited by the air ratio (N₂/Ar=84) and the air saturated water (ASW) ratio (N₂/Ar=38), the volcanic component by (CO₂/N₂=200), and it confirms the predominantly meteoric origin of these compounds. The lines between CO₂ apex, ASW and Air points indicate the effect of shallow contamination on dissolved gases. The ternary diagram (B) displays N₂-He-Ar to illustrate the relative contribution from magmatic, meteoric or crustal sources of gases in thermo-mineral springs. The meteoric component is limited by the air ratio (N₂/Ar=84) and the air saturated water (ASW) ratio (N₂/Ar=38) and it confirms the predominantly meteoric origin of these compounds. (*) Sampling air contamination.

717 Figure 6: Principal Component Analysis (PCA) discriminating processes and flows involved in spring water composition.

719 Figure 7: Pourbaix diagram explaining the predominance of CO₂, N₂ and CH₄ gases. Eh vs. pH values of thermomineral springs were plotted to determine waters influenced by reductive conditions.

721 Figure 8: Binary diagram of CH₄, H₂S and CO₂ abundances observed in waters. Biogenic influence is evidenced with the line 1:1 due to bacterial activity (Chelnokov *et al.*, 2018)

723 Figure 9: Binary diagram of N₂ and Ar in mol/L in thermo-mineral waters. Regression lines are displayed
685 List of Figures

686 Figure 1: Ombrothermal diagrams displaying low-land and in-land mean climatic conditions at 3 stations of the study area (Bastia and Solenzara for the low-land and Corte for the in-land climatic conditions). Data is collected by the French weather forecast office and it' is available online. Data displayed here is compiled from 1950 to 2020. This diagram displays the total monthly precipitation in mm and the monthly minimum, maximum, and mean temperatures express in degree centigrade and gives relative expression of summer drought. The intensity and duration of the dry season based on the intersections of the Temperature curves and the Precipitation one.

693 Figure 2: Location and simplified geology of the studied area. Location and typology of the thermo-mineral springs. The spring symbols describe gas type; spring name colour refers to the geochemical water type.

696 Figure 3: Piper diagram of Eastern Corsica thermo-mineral water samples (N=259). Circle around spring symbols represents quantitative information on the total dissolved solids (T.D.S.) in groundwaters. For more accurate representation, the TDS values are proportionally magnified by 5.

700 Figure 4: Multi-criteria classification and characterisation of thermal and mineral water samples were carried out applying hierarchical type analysis (HCA) on gas chemical composition obtained in April on 9 springs. This heatmap is a graphic representation of data where gas abundances (Ne, He, Ar, N₂, H₂, CO₂, O₂, CH₄, H₂S) are depicted by colour, from low concentration (dark blue) to high concentration (deep red).

705 Figure 5: Ternary diagrams displaying dissolved gas content in thermo-mineral waters after Giggenbach *et al.* (1983). All springs are displayed by code name then by the number of the sampling month. The ternary diagram (A) displays N₂-CO₂-Ar to illustrate the relative CO₂ contribution of magmatic, meteoric and volcanic sources of gases in Corsican thermo-mineral springs. The meteoric component is limited by the air ratio (N₂/Ar=84) and the air saturated water (ASW) ratio (N₂/Ar=38), the volcanic component by (CO₂/N₂=200), and it confirms the predominantly meteoric origin of these compounds. The lines between CO₂ apex, ASW and Air points indicate the effect of shallow contamination on dissolved gases. The ternary diagram (B) displays N₂-He-Ar to illustrate the relative contribution from magmatic, meteoric or crustal sources of gases in thermo-mineral springs. The meteoric component is limited by the air ratio (N₂/Ar=84) and the air saturated water (ASW) ratio (N₂/Ar=38) and it confirms the predominantly meteoric origin of these compounds. (*) Sampling air contamination.

717 Figure 6: Principal Component Analysis (PCA) discriminating processes and flows involved in spring water composition.

719 Figure 7: Pourbaix diagram explaining the predominance of CO₂, N₂ and CH₄ gases. Eh vs. pH values of thermomineral springs were plotted to determine waters influenced by reductive conditions.

721 Figure 8: Binary diagram of CH₄, H₂S and CO₂ abundances observed in waters. Biogenic influence is evidenced with the line 1:1 due to bacterial activity (Chelnokov *et al.*, 2018)

723 Figure 9: Binary diagram of N₂ and Ar in mol/L in thermo-mineral waters. Regression lines are displayed
724 by colour according to each type: CO₂, N₂ or CH₄ rich water.

725 Figure 10. Hydrogeological conceptual model of thermo-mineral waters from the eastern part of Corsica.

726 Established from gas composition in order to discriminate flow and processes involved along the

727 regional continuous flow path from mountains to plain.

728 Figure 11. Major gas-related processes according to each spring type. Type I : CH₄ & H₂S rich, Type II : N₂

729 rich and Type III : CO₂ rich. Oxi. Proc. : Oxidation process ; Red. Proc. : Reduction process.

730 List of tables

731 Table 1: Information about sites, spring localities, code name, type and altitude.

732 Table 2: Field parameters, hydrochemical and isotopic contents of thermo-mineral groundwaters.

733 Table 3: Concentration of dissolved gas sampled with analytical error. Helium and excess air calculation results.

734 (<LOD) limit of detection, (n.m) non-measured, (-) calculation not realisable due to high CO₂ degassing.

735 Table 4: CFC and SF₆ concentrations measured in water in pmol/L and pptv

736
724 by colour according to each type: CO₂, N₂ or CH₄ rich water.

725 Figure 10. Hydrogeological conceptual model of thermo-mineral waters from the eastern part of Corsica.

726 Established from gas composition in order to discriminate flow and processes involved along the

727 regional continuous flow path from mountains to plain.

728 Figure 11. Major gas-related processes according to each spring type. Type I : CH₄ & H₂S rich, Type II : N₂

729 rich and Type III : CO₂ rich. Oxi. Proc. : Oxidation process ; Red. Proc. : Reduction process.

730 List of tables

731 Table 1: Information about sites, spring localities, code name, type and altitude.

732 Table 2: Field parameters, hydrochemical and isotopic contents of thermo-mineral groundwaters.

733 Table 3: Concentration of dissolved gas sampled with analytical error. Helium and excess air calculation results.

734 (<LOD) limit of detection, (n.m) non-measured, (-) calculation not realisable due to high CO₂ degassing.

735 Table 4: CFC and SF₆ concentrations measured in water in pmol/L and pptv

736
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759 Berndt, M.E., Allen, D.E., Seyfried Jr, W.E., 1996. Reduction of CO₂ during serpentinization of olivine at 300 C and 500 bar. Geology 24, 351-354.

761 Berthier, F., Demange, J., Desplan, A., 1980. Etude préliminaire des ressources géothermiques de la Corse (Rapport final No. 80SGN784GTH). BRGM.

763 Beyerle, U., Aeschbach-Hertig, W., Hofer, M., Imboden, D.M., Baur, H., Kipfer, R., 1999. Infiltration of river water to a shallow aquifer investigated with 3H/3He, noble gases and CFCs. Journal of Hydrology 220, 169-185.

765 Bräuer, K., Kämpf, H., Niedermann, S., Wetzel, H.-U., 2017. Regional distribution pattern of carbon and helium isotopes from different volcanic fields in the French Massif Central: Evidence for active mantle degassing and water transport. Chemical Geology, Progress in the Application of Gas Geochemistry to Geothermal, Tectonic and Magmatic Studies 469, 4-18. https://doi.org/10.1016/j.chemgeo.2017.04.004.

769 Bruno, C., Dupré, G., Giorgetti, G., Giorgetti, J.P., Alesandri, J., 2001. Chi tempu face?: météorologie, climat et microclimats de la Corse., CRDP de Corse.

771 Busenberg, E., Plummer, L.N., 1992. Use of chlorofluorocarbons (CCl3F and CCl2F2) as hydrologic tracers and age-dating tools: The alluvium and terrace system of central Oklahoma. Water Resources Research 28, 2257-2283. https://doi.org/10.1029/92WR01263.

774 Caballero, Y., Lachassagne, P., Ladouche, B., 2006. Contribution à l'évaluation de la ressource en eau des aquifères de
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759 Berndt, M.E., Allen, D.E., Seyfried Jr, W.E., 1996. Reduction of CO₂ during serpentinization of olivine at 300 C and 500 bar. Geology 24, 351-354.

761 Berthier, F., Demange, J., Desplan, A., 1980. Etude préliminaire des ressources géothermiques de la Corse (Rapport final No. 80SGN784GTH). BRGM.

763 Beyerle, U., Aeschbach-Hertig, W., Hofer, M., Imboden, D.M., Baur, H., Kipfer, R., 1999. Infiltration of river water to a shallow aquifer investigated with 3H/3He, noble gases and CFCs. Journal of Hydrology 220, 169-185.

765 Bräuer, K., Kämpf, H., Niedermann, S., Wetzel, H.-U., 2017. Regional distribution pattern of carbon and helium isotopes from different volcanic fields in the French Massif Central: Evidence for active mantle degassing and water transport. Chemical Geology, Progress in the Application of Gas Geochemistry to Geothermal, Tectonic and Magmatic Studies 469, 4-18. https://doi.org/10.1016/j.chemgeo.2017.04.004.

769 Bruno, C., Dupré, G., Giorgetti, G., Giorgetti, J.P., Alesandri, J., 2001. Chi tempu face?: météorologie, climat et microclimats de la Corse., CRDP de Corse.

771 Busenberg, E., Plummer, L.N., 1992. Use of chlorofluorocarbons (CCl3F and CCl2F2) as hydrologic tracers and age-dating tools: The alluvium and terrace system of central Oklahoma. Water Resources Research 28, 2257-2283. https://doi.org/10.1029/92WR01263.

774 Caballero, Y., Lachassagne, P., Ladouche, B., 2006. Contribution à l'évaluation de la ressource en eau des aquifères de
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783 Casillas-Trasvina, A., B. Rogiers, K. Beerten, J. Pärn, L. Wouters, and K. Walraevens. 2022. 'Using Helium-4, Tritium, 784 Carbon-14 and Other Hydrogeochemical Evidence to Evaluate the Groundwater Age Distribution: The Case of the 785 Neogene Aquifer, Belgium'. Journal of Hydrology X 17:100132. https://doi.org/10.1016/j.hydroa.2022.100132.

786 Chambers, L.A., Gooddy, D.C., Binley, A.M., 2019. Use and application of CFC-11, CFC-12, CFC-113 and SF6 as 787 environmental tracers of groundwater residence time: A review. Geoscience Frontiers 10, 1643-1652.

788 Chatton, E., Labasque, T., de La Bernardie, J., Guihéneuf, N., Bour, O., Aquilina, L., 2017. Field Continuous 789 Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics and Biogeochemistry of 790 Groundwater Flow. Environ. Sci. Technol. 51, 846-854. https://doi.org/10.1021/acs.est.6b03706.

791 Chelnokov, G.A., Bragin, I.V., Kharitonova, N.A., 2018. Geochemistry of mineral waters and associated gases of the 792 Sakhalin Island (Far East of Russia). Journal of Hydrology 559, 942-953. https://doi.org/10.1016/j.jhydrol.2018.02.049.

793 Chiodini, G., Cardellini, C., Caliro, S., Avino, R., Donnini, M., Granieri, D., Morgantini, N., Sorrenti, D., Frondini, F., 794 2020. The hydrothermal system of Bagni San Filippo (Italy): fluids circulation and CO₂ degassing. Italian Journal of 795 Geosciences 139, 383-397. https://doi.org/10.3301/IJG.2020.12.

796 Craw, D., Upton, P., Horton, T., Williams, J., 2013. Migration of hydrothermal systems in an evolving collisional orogen, 797 New Zealand. Miner Deposita 48, 233-248. https://doi.org/10.1007/s00126-012-0421-8.

798 D'Amore, F., Fancelli, R., Caboi, R., 1987. Observations on the application of chemical geothermometers to some 799 hydrothermal systems in Sardinia. Geothermics 16, 271-282. https://doi.org/10.1016/0375-6505(87)90006-X.

800 Darling, W. G., D. C. Gooddy, A. M. MacDonald, and B. L. Morris. 2012. 'The Practicalities of Using CFCs and SF6 for 801 Groundwater Dating and Tracing'. Applied Geochemistry, 13th International Symposium on Water-Rock 802 Interaction (WRI-13), 27 (9): 1688-97. https://doi.org/10.1016/j.apgeochem.2012.02.005.

803 Dewandel, B., Lachassagne, P., Zaidi, F.K., Chandra, S., 2011. A conceptual hydrodynamic model of a geological 804 discontinuity in hard rock aquifers: Example of a quartz reef in granitic terrain in South India. Journal of Hydrology 805 405, 474-487. https://doi.org/10.1016/j.jhydrol.2011.05.050.

806 Di Rosa, M., De Giorgi, A., Marroni, M., Vidal, O., 2017. Syn-convergence exhumation of continental crust: evidence 807 from structural and metamorphic analysis of the Monte Cecu area, Alpine Corsica (Northern Corsica, France). 808 Geological Journal 52, 919-937. https://doi.org/10.1002/gj.2857

809 Dominici, R., Iundt, F., Juncy, G., Mickaelly, B., 1986. Prospection des anomalies gazeuses liées a l'hydrothermalisme 810 de Puzzichellu - commune d'Aghione (Haute Corse) (No. 86SGN002CSC), BRGM. Bastia.

811 Dupalová, T., Sracek, O., Vencelides, Z., Žák, K., 2012. The origin of thermal waters in the northeastern part of the Eger 812 Rift, Czech Republic. Applied geochemistry 27, 689-702.
775 socle des roches granitiques de Corse (Rapport final No. BRGM/RP-54541-FR).

776 Caritg, S., 2009a. Carte géologique harmonisée du département de la Corse du sud : Notice explicative (Rapport final
777 No. brgm/rp-57749-FR). BRGM.

778 Caritg, S., 2009b. Carte géologique harmonisée du département de la haute-Corse : Notice explicative (Rapport final
779 No. BRGM/RP-57748-FR). BRGM.

780 Cartwright, Ian, D. Cendón, M. Currell, and K. Meredith. 2017. 'A Review of Radioactive Isotopes and Other Residence
781 Time Tracers in Understanding Groundwater Recharge: Possibilities, Challenges, and Limitations'. Journal of
782 Hydrology 555 (December): 797-811. https://doi.org/10.1016/j.jhydrol.2017.10.053.

783 Casillas-Trasvina, A., B. Rogiers, K. Beerten, J. Pärn, L. Wouters, and K. Walraevens. 2022. 'Using Helium-4, Tritium, 784 Carbon-14 and Other Hydrogeochemical Evidence to Evaluate the Groundwater Age Distribution: The Case of the 785 Neogene Aquifer, Belgium'. Journal of Hydrology X 17:100132. https://doi.org/10.1016/j.hydroa.2022.100132.

786 Chambers, L.A., Gooddy, D.C., Binley, A.M., 2019. Use and application of CFC-11, CFC-12, CFC-113 and SF6 as 787 environmental tracers of groundwater residence time: A review. Geoscience Frontiers 10, 1643-1652.

788 Chatton, E., Labasque, T., de La Bernardie, J., Guihéneuf, N., Bour, O., Aquilina, L., 2017. Field Continuous 789 Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics and Biogeochemistry of 790 Groundwater Flow. Environ. Sci. Technol. 51, 846-854. https://doi.org/10.1021/acs.est.6b03706.

791 Chelnokov, G.A., Bragin, I.V., Kharitonova, N.A., 2018. Geochemistry of mineral waters and associated gases of the 792 Sakhalin Island (Far East of Russia). Journal of Hydrology 559, 942-953. https://doi.org/10.1016/j.jhydrol.2018.02.049.

793 Chiodini, G., Cardellini, C., Caliro, S., Avino, R., Donnini, M., Granieri, D., Morgantini, N., Sorrenti, D., Frondini, F., 794 2020. The hydrothermal system of Bagni San Filippo (Italy): fluids circulation and CO₂ degassing. Italian Journal of 795 Geosciences 139, 383-397. https://doi.org/10.3301/IJG.2020.12.

796 Craw, D., Upton, P., Horton, T., Williams, J., 2013. Migration of hydrothermal systems in an evolving collisional orogen, 797 New Zealand. Miner Deposita 48, 233-248. https://doi.org/10.1007/s00126-012-0421-8.

798 D'Amore, F., Fancelli, R., Caboi, R., 1987. Observations on the application of chemical geothermometers to some 799 hydrothermal systems in Sardinia. Geothermics 16, 271-282. https://doi.org/10.1016/0375-6505(87)90006-X.

800 Darling, W. G., D. C. Gooddy, A. M. MacDonald, and B. L. Morris. 2012. 'The Practicalities of Using CFCs and SF6 for 801 Groundwater Dating and Tracing'. Applied Geochemistry, 13th International Symposium on Water-Rock 802 Interaction (WRI-13), 27 (9): 1688-97. https://doi.org/10.1016/j.apgeochem.2012.02.005.

803 Dewandel, B., Lachassagne, P., Zaidi, F.K., Chandra, S., 2011. A conceptual hydrodynamic model of a geological 804 discontinuity in hard rock aquifers: Example of a quartz reef in granitic terrain in South India. Journal of Hydrology 805 405, 474-487. https://doi.org/10.1016/j.jhydrol.2011.05.050.

806 Di Rosa, M., De Giorgi, A., Marroni, M., Vidal, O., 2017. Syn-convergence exhumation of continental crust: evidence 807 from structural and metamorphic analysis of the Monte Cecu area, Alpine Corsica (Northern Corsica, France). 808 Geological Journal 52, 919-937. https://doi.org/10.1002/gj.2857

809 Dominici, R., Iundt, F., Juncy, G., Mickaelly, B., 1986. Prospection des anomalies gazeuses liées a l'hydrothermalisme 810 de Puzzichellu - commune d'Aghione (Haute Corse) (No. 86SGN002CSC), BRGM. Bastia.

811 Dupalová, T., Sracek, O., Vencelides, Z., Žák, K., 2012. The origin of thermal waters in the northeastern part of the Eger 812 Rift, Czech Republic. Applied geochemistry 27, 689-702.
813 Dupuy, M., Garel, E., Huneau, F., Santoni, S., Di Rosa, M., Mattei, A., 2021. Geochemical and isotope characterisation of thermo-mineral springs of Corsica Island: from geological complexity to groundwater singularity. Water 13, 2413.
815 https://doi.org/10.3390/w13172413.

816 Elena, F., Vasiliy, L., Natalia, K., Arslan, S., Elena, M., Ekaterina, B., Anna, K., Alexey, M., Elena, B., 2020. Hydrogeology and hydrogeochemistry of mineral sparkling groundwater within Essentuki area (Caucasian mineral water region).
818 Environmental Earth Sciences 79, 1–12.

819 Epstein, Gabe S., Gray E. Bebout, B.W. Christenson, H. Sumino, I. Wada, C. Werner, and D.R. Hilton. 2021. 'Cycling of CO2 and N2 Along the Hikurangi Subduction Margin, New Zealand: An Integrated Geological, Theoretical, and Isotopic Approach'. Geochemistry, Geophysics, Geosystems 22 (9): e2021GC009650.
822 https://doi.org/10.1029/2021GC009650.

823 Etiope, G., 2017. Abiotic Methane in Continental Serpentinization Sites: An Overview. Procedia Earth and Planetary Science, 15th Water-Rock Interaction International Symposium, WRI-15 17, 9–12.
825 https://doi.org/10.1016/j.proeps.2016.12.006.

826 Everitt, B.S., Dunn, G., 2001. Principal Components Analysis, in: Applied Multivariate Data Analysis. John Wiley & Sons, Ltd, pp. 48–73. https://doi.org/10.1002/9781118887486.ch3

828 Faramawy, S., Zaki, T., Sakr, A.A.-E., 2016. Natural gas origin, composition, and processing: A review. Journal of Natural Gas Science and Engineering 34, 34–54. https://doi.org/10.1016/j.jngse.2016.06.030

830 Genevier, M., Mardhel, V., Frissant, N., 2011. Actualisation de la synthèse hydrogéologique de la région Corse (Rapport final No. BRGM/RP-59924-FR). BRGM.

832 Giggenbach, W.F., 1991. Chemical techniques in geothermal exploration. Application of geochemistry in geothermal reservoir development 119–144.

834 Giggenbach, W.F., 1988. Geothermal solute equilibria. Derivation of Na-K-Mg-Ca geoindicators. Geochimica et Cosmochimica Acta 52, 2749–2765. https://doi.org/10.1016/0016-7037(88)90143-3.

836 Giggenbach, W.F., Gonfiantini, R., Jangi, B.L., Truesdell, A.H., 1983. Isotopic and chemical composition of parbati valley geothermal discharges, North-West Himalaya, India. Geothermics 12, 199–222. https://doi.org/10.1016/0375-6505(83)90030-5.

839 Gilhooly, W.P., Fike, D.A., Druschel, G.K., Kafantaris, F.-C.A., Price, R.E., Amend, J.P., 2014. Sulfur and oxygen isotope insights into sulfur cycling in shallow-sea hydrothermal vents, Milos, Greece. Geochem Trans 15, 12.
841 https://doi.org/10.1186/s12932-014-0012-y.

842 Goswami, S., AK. Rai, and S. Tripathy. 2022. 'Re-Visiting Geothermal Fluid Circulation, Reservoir Depth and Temperature of Geothermal Springs of India'. Journal of Hydrology 612 (September): 128131.
844 https://doi.org/10.1016/j.jhydrol.2022.128131.

845 Grasby, S.E., Hutcheon, I., Krouse, H.R., 2000. The influence of water-rock interaction on the chemistry of thermal springs in western Canada. Applied Geochemistry 15, 439–454. https://doi.org/10.1016/S0883-2927(99)00066-9.

847 Gueydan, F., Brun, J.-P., Phillippon, M., Noury, M., 2017. Sequential extension as a record of Corsica Rotation during Apennines slab roll-back. Tectonophysics, Evolution of fore-arc and back-arc sedimentary basins with focus on the Japan subduction system and its analogues 710–711, 149–161. https://doi.org/10.1016/j.tecto.2016.12.028.

850 Hiscock, K.M., 2009. Hydrogeology: principles and practice. John Wiley & Sons.
813 Dupuy, M., Garel, E., Huneau, F., Santoni, S., Di Rosa, M., Mattei, A., 2021. Geochemical and isotope characterisation of thermo-mineral springs of Corsica Island: from geological complexity to groundwater singularity. Water 13, 2413.
814 https://doi.org/10.3390/w13172413.
815

816 Elena, F., Vasiliy, L., Natalia, K., Arslan, S., Elena, M., Ekaterina, B., Anna, K., Alexey, M., Elena, B., 2020. Hydrogeology and hydrogeochemistry of mineral sparkling groundwater within Essentuki area (Caucasian mineral water region).
817
818 Environmental Earth Sciences 79, 1–12.

819 Epstein, Gabe S., Gray E. Bebout, B.W. Christenson, H. Sumino, I. Wada, C. Werner, and D.R. Hilton. 2021. 'Cycling of CO2 and N2 Along the Hikurangi Subduction Margin, New Zealand: An Integrated Geological, Theoretical, and Isotopic Approach'. *Geochemistry, Geophysics, Geosystems* 22 (9): e2021GC009650.
820
821
822 https://doi.org/10.1029/2021GC009650.

823 Etiope, G., 2017. Abiotic Methane in Continental Serpentinization Sites: An Overview. Procedia Earth and Planetary Science, 15th Water-Rock Interaction International Symposium, WRI-15 17, 9–12.
824
825 https://doi.org/10.1016/j.proeps.2016.12.006.

826 Everitt, B.S., Dunn, G., 2001. Principal Components Analysis, in: Applied Multivariate Data Analysis. John Wiley & Sons, Ltd, pp. 48–73. https://doi.org/10.1002/9781118887486.ch3

828 Faramawy, S., Zaki, T., Sakr, A.A.-E., 2016. Natural gas origin, composition, and processing: A review. Journal of Natural Gas Science and Engineering 34, 34–54. https://doi.org/10.1016/j.jngse.2016.06.030

830 Genevier, M., Mardhel, V., Frissant, N., 2011. Actualisation de la synthèse hydrogéologique de la région Corse (Rapport final No. BRGM/RP-59924-FR). BRGM.

832 Giggenbach, W.F., 1991. Chemical techniques in geothermal exploration. Application of geochemistry in geothermal reservoir development 119–144.

834 Giggenbach, W.F., 1988. Geothermal solute equilibria. Derivation of Na-K-Mg-Ca geoindicators. Geochimica et Cosmochimica Acta 52, 2749–2765. https://doi.org/10.1016/0016-7037(88)90143-3.

836 Giggenbach, W.F., Gonfiantini, R., Jangi, B.L., Truesdell, A.H., 1983. Isotopic and chemical composition of parbati valley geothermal discharges, North-West Himalaya, India. Geothermics 12, 199–222. https://doi.org/10.1016/0375-6505(83)90030-5.

839 Gilhooly, W.P., Fike, D.A., Druschel, G.K., Kafantaris, F.-C.A., Price, R.E., Amend, J.P., 2014. Sulfur and oxygen isotope insights into sulfur cycling in shallow-sea hydrothermal vents, Milos, Greece. Geochem Trans 15, 12. https://doi.org/10.1186/s12932-014-0012-y.

842 Goswami, S., AK. Rai, and S. Tripathy. 2022. 'Re-Visiting Geothermal Fluid Circulation, Reservoir Depth and Temperature of Geothermal Springs of India'. Journal of Hydrology 612 (September): 128131.
843
844 https://doi.org/10.1016/j.jhydrol.2022.128131.

845 Grasby, S.E., Hutcheon, I., Krouse, H.R., 2000. The influence of water-rock interaction on the chemistry of thermal springs in western Canada. Applied Geochemistry 15, 439–454. https://doi.org/10.1016/S0883-2927(99)00066-9.

847 Gueydan, F., Brun, J.-P., Phillippon, M., Noury, M., 2017. Sequential extension as a record of Corsica Rotation during Apennines slab roll-back. Tectonophysics, Evolution of fore-arc and back-arc sedimentary basins with focus on the Japan subduction system and its analogues 710–711, 149–161. https://doi.org/10.1016/j.tecto.2016.12.028.

850 Hiscock, K.M., 2009. Hydrogeology: principles and practice. John Wiley & Sons.
851 Jenden, P.D., Titley, P.A., Worden, R.H., 2015. Enrichment of nitrogen and 13C of methane in natural gases from the Khuff Formation, Saudi Arabia, caused by thermochemical sulfate reduction. Organic Geochemistry 82, 54–68.

853 Juhlke, T.R., Sültenfuß, J., Trachte, K., Huneau, F., Garel, E., Santoni, S., Barth, J.A., Geldern, R. van, 2020. Tritium as a hydrological tracer in Mediterranean precipitation events. Atmospheric Chemistry and Physics 20, 3555–3568.

855 Karolytė, R., Johnson, G., Györe, D., Serno, S., Flude, S., Stuart, F.M., Chivas, A.R., Boyce, A., Gilfillan, S.M.V., 2019. Tracing the migration of mantle in gas fields and mineral water springs in south-east Australia using noble gas and stable isotopes. Geochimica et Cosmochimica Acta 259, 109–128. https://doi.org/10.1016/j.gca.2019.06.002.

858 Karolytė, R., Serno, S., Johnson, G., Gilfillan, S.M.V., 2017. The influence of oxygen isotope exchange between CO 2 and H 2 O in natural CO 2 -rich spring waters: Implications for geothermometry. Applied Geochemistry 84, 173–186. https://doi.org/10.1016/j.apgeochem.2017.06.012.

861 Kim, K.-H., Yun, S.-T., Yu, S., Choi, B.-Y., Kim, M.-J., Lee, K.-J., 2020. Geochemical pattern recognitions of deep thermal groundwater in South Korea using self-organizing map: Identified pathways of geochemical reaction and mixing. Journal of Hydrology 589, 125202. https://doi.org/10.1016/j.jhydrol.2020.125202

864 Kipfer, R., Aeschbach-Hertig, W., Peeters, F., Stute, M., 2002. Noble gases in lakes and ground waters. Reviews in mineralogy and geochemistry 47, 615–700.

866 Kotowski, T., L. Chudzik, and J. Najman. 2019. 'Application of Dissolved Gases Concentration Measurements, Hydrochemical and Isotopic Data to Determine the Circulation Conditions and Age of Groundwater in the Central Sudetes Mts'. Journal of Hydrology 569 (February): 735–52. https://doi.org/10.1016/j.jhydrol.2018.12.013.

869 Kulongoski, Justin T., David R. Hilton, Richard G. Cresswell, Stephen Hostetler, and Gerry Jacobson. 2008. 'Helium-4 Characteristics of Groundwaters from Central Australia: Comparative Chronology with Chlorine-36 and Carbon-14 Dating Techniques'. Journal of Hydrology 348 (1): 176–94. https://doi.org/10.1016/j.jhydrol.2007.09.048.

872 Lachassagne, P., 2011. The fracture permeability of Hard Rock Aquifers is due neither to tectonics, nor to unloading, but to weathering processes. Terra Nova 145–161. https://doi.org/10.1111/j.1365-3121.2011.00998.x.

874 Lavrushin, V.Y., Israfailov, Y.G., Polyak, B.G., Pokrovsky, B.G., Bujakaite, M.I., Kamensky, I.L., 2018. Conditions of the formation of thermomineral waters in the Talysh fold zone of the Lesser Caucasus (Azerbaijan) based on isotope-geochemical data (3He/4He, δ13C co2, δ13Cch4, δ15N-N2, 87Sr/86Sr, δD-H2O, and δ18O-H2O). Lithology and Mineral Resources 53, 53–75. https://doi.org/10.1134/S0024490217060050.

878 Lee, J.M., Koh, D.-C., Chae, G.-T., Kee, W.-S., Ko, K.-S., 2021. Integrated assessment of major element geochemistry and geological setting of traditional natural mineral water sources in South Korea at the national scale. Journal of Hydrology 598, 126249. https://doi.org/10.1016/j.jhydrol.2021.126249.

881 Loče-Pilot, M.-D., Durand-Delga, M., Feinberg, H., Gourinard, Y., Magné, J., 2004. Les formations burdigaliennes de Corse orientale dans leur cadre géodynamique. Comptes Rendus Geoscience 336, 919–930. https://doi.org/10.1016/j.crte.2004.02.011.

884 Machel, H.G., 2001. Bacterial and thermochemical sulfate reduction in diagenetic settings of old and new insights. Sedimentary Geology 33.

886 Malvoisin, B., Chopin, C., Brunet, F., Galvez, M.E., 2012. Low-temperature Wollastonite Formed by Carbonate Reduction: a Marker of Serpentinite Redox Conditions. Journal of Petrology 53, 159–176. https://doi.org/10.1093/petrology/egr060.

889 Marques, J.M., Eggenkamp, H.G.M., Carreira, P.M., Antunes da Silva, M., 2020. Origin and evolution of Cl in CO2-rich
851 Jenden, P.D., Titley, P.A., Worden, R.H., 2015. Enrichment of nitrogen and 13C of methane in natural gases from the Khuff Formation, Saudi Arabia, caused by thermochemical sulfate reduction. Organic Geochemistry 82, 54–68.

853 Juhlke, T.R., Sültenfuß, J., Trachte, K., Huneau, F., Garel, E., Santoni, S., Barth, J.A., Geldern, R. van, 2020. Tritium as a hydrological tracer in Mediterranean precipitation events. Atmospheric Chemistry and Physics 20, 3555–3568.

855 Karolytė, R., Johnson, G., Györe, D., Serno, S., Flude, S., Stuart, F.M., Chivas, A.R., Boyce, A., Gilfillan, S.M.V., 2019. Tracing the migration of mantle in gas fields and mineral water springs in south-east Australia using noble gas and stable isotopes. Geochimica et Cosmochimica Acta 259, 109–128. https://doi.org/10.1016/j.gca.2019.06.002.

858 Karolytė, R., Serno, S., Johnson, G., Gilfillan, S.M.V., 2017. The influence of oxygen isotope exchange between CO 2 and H 2 O in natural CO 2 -rich spring waters: Implications for geothermometry. Applied Geochemistry 84, 173–186. https://doi.org/10.1016/j.apgeochem.2017.06.012.

861 Kim, K.-H., Yun, S.-T., Yu, S., Choi, B.-Y., Kim, M.-J., Lee, K.-J., 2020. Geochemical pattern recognitions of deep thermal groundwater in South Korea using self-organizing map: Identified pathways of geochemical reaction and mixing. Journal of Hydrology 589, 125202. https://doi.org/10.1016/j.jhydrol.2020.125202

864 Kipfer, R., Aeschbach-Hertig, W., Peeters, F., Stute, M., 2002. Noble gases in lakes and ground waters. Reviews in mineralogy and geochemistry 47, 615–700.

866 Kotowski, T., L. Chudzik, and J. Najman. 2019. 'Application of Dissolved Gases Concentration Measurements, Hydrochemical and Isotopic Data to Determine the Circulation Conditions and Age of Groundwater in the Central Sudetes Mts'. Journal of Hydrology 569 (February): 735–52. https://doi.org/10.1016/j.jhydrol.2018.12.013.

869 Kulongoski, Justin T., David R. Hilton, Richard G. Cresswell, Stephen Hostetler, and Gerry Jacobson. 2008. 'Helium-4 Characteristics of Groundwaters from Central Australia: Comparative Chronology with Chlorine-36 and Carbon-14 Dating Techniques'. Journal of Hydrology 348 (1): 176–94. https://doi.org/10.1016/j.jhydrol.2007.09.048.

872 Lachassagne, P., 2011. The fracture permeability of Hard Rock Aquifers is due neither to tectonics, nor to unloading, but to weathering processes. Terra Nova 145–161. https://doi.org/10.1111/j.1365-3121.2011.00998.x.

874 Lavrushin, V.Y., Israfailov, Y.G., Polyak, B.G., Pokrovsky, B.G., Bujakaite, M.I., Kamensky, I.L., 2018. Conditions of the formation of thermomineral waters in the Talysh fold zone of the Lesser Caucasus (Azerbaijan) based on isotope-geochemical data (3He/4He, δ13C co2, δ13Cch4, δ15N-N2, 87Sr/86Sr, δD-H2O, and δ18O-H2O). Lithology and Mineral Resources 53, 53–75. https://doi.org/10.1134/S0024490217060050.

878 Lee, J.M., Koh, D.-C., Chae, G.-T., Kee, W.-S., Ko, K.-S., 2021. Integrated assessment of major element geochemistry and geological setting of traditional natural mineral water sources in South Korea at the national scale. Journal of Hydrology 598, 126249. https://doi.org/10.1016/j.jhydrol.2021.126249.

881 Loče-Pilot, M.-D., Durand-Delga, M., Feinberg, H., Gourinard, Y., Magné, J., 2004. Les formations burdigaliennes de Corse orientale dans leur cadre géodynamique. Comptes Rendus Geoscience 336, 919–930. https://doi.org/10.1016/j.crte.2004.02.011.

884 Machel, H.G., 2001. Bacterial and thermochemical sulfate reduction in diagenetic settings of old and new insights. Sedimentary Geology 33.

886 Malvoisin, B., Chopin, C., Brunet, F., Galvez, M.E., 2012. Low-temperature Wollastonite Formed by Carbonate Reduction: a Marker of Serpentinite Redox Conditions. Journal of Petrology 53, 159–176. https://doi.org/10.1093/petrology/egr060.

889 Marques, J.M., Eggenkamp, H.G.M., Carreira, P.M., Antunes da Silva, M., 2020. Origin and evolution of Cl in CO2-rich
890 thermal and mineral waters from northern Portugal. Applied Geochemistry 116, 104569.

891 https://doi.org/10.1016/j.apgeochem.2020.104569.

892 Marques, J.M., Etiope, G., Neves, M.O., Carreira, P.M., Rocha, C., Vance, S.D., Christensen, L., Miller, A.Z., Suzuki, S.,

893 2018. Linking serpentinization, hyperalkaline mineral waters and abiotic methane production in continental

894 peridotites: an integrated hydrogeological-bio-geochemical model from the Cabeço de Vide CH4-rich aquifer

895 (Portugal). Applied Geochemistry 96, 287–301. https://doi.org/10.1016/j.apgeochem.2018.07.011.

896 Marques, J.M., Carreira, P.M.M., Aires-Barros, L., Graça, R.C., 2000. Nature and role of CO2 in some hot and cold HCO

897 3 /Na/CO 2 -rich Portuguese mineral waters: a review and reinterpretation. Environmental Geology 40, 53–63.

898 https://doi.org/10.1007/s002540000151.

899 Martín-Loeches, M., Pavón-García, J., Molina-Navarro, E., Martínez-Santos, P., Almeida, C., Reyes-López, J.,

900 Cienfuegos-Hevia, I., Sastre-Merlín, A., 2020. Hydrogeochemistry of granitic mountain zones and the influence of

901 adjacent sedimentary basins at their tectonic borders: the case of the Spanish Central System batholith. Hydrogeol

902 J. https://doi.org/10.1007/s10040-020-02202-1.

903 Mattei, A., Huneau, F., Garel, E., Santoni, S., Vystavna, Y., 2021. Evaporation in Mediterranean conditions: estimations

904 based on isotopic approaches at the watershed scale. Hydrological Processes n/a. https://doi.org/10.1002/hyp.14085

905 Michard, G., 1990. Behaviour of major elements and some trace elements (Li, Rb, Cs, Sr, Fe, Mn, W, F) in deep hot waters

906 from granitic areas. Chemical Geology 89, 117–134.

907 Mikhail, S., Sverjensky, D.A., 2014. Nitrogen speciation in upper mantle fluids and the origin of Earth’s nitrogen-rich

908 atmosphere. Nature Geoscience 7, 816–819. https://doi.org/10.1038/ngeo2271.

909 Minissale, A., 2004. Origin, transport and discharge of CO₂ in central Italy. Earth-Science Reviews 66, 89–141.

910 https://doi.org/10.1016/j.earscirev.2003.09.001.

911 Minissale, A., Donato, A., Procesi, M., Pizzino, L., Giammanco, S., 2019. Systematic review of geochemical data from

912 thermal springs, gas vents and fumaroles of Southern Italy for geothermal favourability mapping. Earth-Science

913 Reviews 188, 514–535. https://doi.org/10.1016/j.earscirev.2018.09.008.

914 Minissale, A., Magro, G., Martinelli, G., Vaselli, O., Tassi, G.F., 2000. Fluid geochemical transect in the Northern

915 Apennines (central-northern Italy): fluid genesis and migration and tectonic implications. Tectonophysics 319, 199–

916 222. https://doi.org/10.1016/S0040-1951(00)00031-7.

917 Minissale, A., Magro, G., Tassi, F., Frau, F., Vaselli, O., 1999. The origin of natural gas emissions from Sardinia island,

918 Italy. Geochemical journal 33, 1–12.

919 Moritz, A., Hélie, J.-F., Pinti, D.L., Larocque, M., Barnetche, D., Retailleau, S., Lefebvre, R., Gélinas, Y., 2015. Methane

920 Baseline Concentrations and Sources in Shallow Aquifers from the Shale Gas-Prone Region of the St. Lawrence

921 Lowlands (Quebec, Canada). Environ. Sci. Technol. 49, 4765–4771. https://doi.org/10.1021/acs.est.5b00443.

922 Mörner, N.-A., Etiope, G., 2002. Carbon degassing from the lithosphere. Global and Planetary Change 33, 185–203.

923 Nlend, B., Huneau, F., Garel, E., Santoni, S., Mattei, A., 2023. Precipitation isoscapes in areas with complex topography:

924 Influence of large-scale atmospheric dynamics versus microclimatic phenomena. Journal of Hydrology 617, 128896.

925 https://doi.org/10.1016/j.jhydrol.2022.128896.

926 Paternoster, M., Oggiano, G., Sinisi, R., Caracausi, A., Mongelli, G., 2017. Geochemistry of two contrasting deep fluids

927 in the Sardinia microplate (western Mediterranean): Relationships with tectonics and heat sources. Journal of

928 Volcanology and Geothermal Research 336, 108–117. https://doi.org/10.1016/j.jvolgeores.2017.02.011.
890 thermal and mineral waters from northern Portugal. Applied Geochemistry 116, 104569.

891 https://doi.org/10.1016/j.apgeochem.2020.104569.

892 Marques, J.M., Etiope, G., Neves, M.O., Carreira, P.M., Rocha, C., Vance, S.D., Christensen, L., Miller, A.Z., Suzuki, S.,

893 2018. Linking serpentinization, hyperalkaline mineral waters and abiotic methane production in continental

894 peridotites: an integrated hydrogeological-bio-geochemical model from the Cabeço de Vide CH4-rich aquifer

895 (Portugal). Applied Geochemistry 96, 287-301. https://doi.org/10.1016/j.apgeochem.2018.07.011.

896 Marques, J.M., Carreira, P.M.M., Aires-Barros, L., Graça, R.C., 2000. Nature and role of CO2 in some hot and cold HCO

897 3 /Na/CO 2 -rich Portuguese mineral waters: a review and reinterpretation. Environmental Geology 40, 53-63.

898 https://doi.org/10.1007/s002540000151.

899 Martín-Loeches, M., Pavón-García, J., Molina-Navarro, E., Martínez-Santos, P., Almeida, C., Reyes-López, J.,

900 Cienfuegos-Hevia, I., Sastre-Merlín, A., 2020. Hydrogeochemistry of granitic mountain zones and the influence of

901 adjacent sedimentary basins at their tectonic borders: the case of the Spanish Central System batholith. Hydrogeol

902 J. https://doi.org/10.1007/s10040-020-02202-1.

903 Mattei, A., Huneau, F., Garel, E., Santoni, S., Vystavna, Y., 2021. Evaporation in Mediterranean conditions: estimations

904 based on isotopic approaches at the watershed scale. Hydrological Processes n/a. https://doi.org/10.1002/hyp.14085

905 Michard, G., 1990. Behaviour of major elements and some trace elements (Li, Rb, Cs, Sr, Fe, Mn, W, F) in deep hot waters

906 from granitic areas. Chemical Geology 89, 117-134.

907 Mikhail, S., Sverjensky, D.A., 2014. Nitrogen speciation in upper mantle fluids and the origin of Earth's nitrogen-rich

908 atmosphere. Nature Geoscience 7, 816-819. https://doi.org/10.1038/ngeo2271.

909 Minissale, A., 2004. Origin, transport and discharge of CO₂ in central Italy. Earth-Science Reviews 66, 89-141.

910 https://doi.org/10.1016/j.earscirev.2003.09.001.

911 Minissale, A., Donato, A., Procesi, M., Pizzino, L., Giammanco, S., 2019. Systematic review of geochemical data from

912 thermal springs, gas vents and fumaroles of Southern Italy for geothermal favourability mapping. Earth-Science

913 Reviews 188, 514-535. https://doi.org/10.1016/j.earscirev.2018.09.008.

914 Minissale, A., Magro, G., Martinelli, G., Vaselli, O., Tassi, G.F., 2000. Fluid geochemical transect in the Northern

915 Apennines (central-northern Italy): fluid genesis and migration and tectonic implications. Tectonophysics 319, 199-

916 222. https://doi.org/10.1016/S0040-1951(00)00031-7.

917 Minissale, A., Magro, G., Tassi, F., Frau, F., Vaselli, O., 1999. The origin of natural gas emissions from Sardinia island,

918 Italy. Geochemical journal 33, 1-12.

919 Moritz, A., Hélie, J.-F., Pinti, D.L., Larocque, M., Barnetche, D., Retailleau, S., Lefebvre, R., Gélinas, Y., 2015. Methane

920 Baseline Concentrations and Sources in Shallow Aquifers from the Shale Gas-Prone Region of the St. Lawrence

921 Lowlands (Quebec, Canada). Environ. Sci. Technol. 49, 4765-4771. https://doi.org/10.1021/acs.est.5b00443.

922 Mörner, N.-A., Etiope, G., 2002. Carbon degassing from the lithosphere. Global and Planetary Change 33, 185-203.

923 Nlend, B., Huneau, F., Garel, E., Santoni, S., Mattei, A., 2023. Precipitation isoscapes in areas with complex topography:

924 Influence of large-scale atmospheric dynamics versus microclimatic phenomena. Journal of Hydrology 617, 128896.

925 https://doi.org/10.1016/j.jhydrol.2022.128896.

926 Paternoster, M., Oggiano, G., Sinisi, R., Caracausi, A., Mongelli, G., 2017. Geochemistry of two contrasting deep fluids

927 in the Sardinia microplate (western Mediterranean): Relationships with tectonics and heat sources. Journal of

928 Volcanology and Geothermal Research 336, 108-117. https://doi.org/10.1016/j.jvolgeores.2017.02.011.
929 Paull, C., Lorenson, T., Borowski, W., Ussler, B., Olsen, K., Rodriguez, N., 2000. Isotopic composition of CH₄, CO₂
930 species, and sedimentary organic matter within samples from the Blake Ridge: Gas source implications. Proceedings
931 of the Ocean Drilling Program: Scientific Results 164. https://doi.org/10.2973/odp.proc.sr.164.207.2000.

932 Penna, D., Stenni, B., Šanda, M., Wrede, S., Bogaard, T. A., Gobbi, A., Borga, M., Fischer, B. M. C., Bonazza, M., and
933 Chárová, Z., 2010. On the reproducibility and repeatability of laser absorption spectroscopy measurements for δ2H
934 and δ18O isotopic analysis, Hydrol. Earth Syst. Sci., 14, 1551–1566, https://doi.org/10.5194/hess-14-1551-2010.

935 Petrović, T., Zlokolica-Mandić, M., Veljković, N., Vidojević, D., 2010. Hydrogeological conditions for the forming and
936 quality of mineral waters in Serbia. Journal of Geochemical Exploration 107, 373–381.

937 Piccoli, F., Vitale Brovarone, A., Ague, J.J., 2018. Field and petrological study of metasomatism and high-pressure
938 carbonation from lawsonite eclogite-facies terrains, Alpine Corsica. Lithos 304–307, 16–37.
939 https://doi.org/10.1016/j.lithos.2018.01.026.

940 Powell, T., Cumming, W., 2010. Spreadsheets for geothermal water and gas geochemistry, in: Proceedings. pp. 1–3.

941 Ravna, E.J.K., Andersen, T.B., Jolivet, L., Capitani, C.D., 2010. Cold subduction and the formation of lawsonite eclogite
942 – constraints from prograde evolution of eclogitized pillow lava from Corsica. Journal of Metamorphic Geology 28,
943 381–395. https://doi.org/10.1111/j.1525-1314.2010.00870.x.

944 Rojey, A., 1997. Technological innovations in gas field operations; L'innovation technique dans l'exploitation des
945 ressources gazieres. Gaz d'Aujourd'hui (Paris), 121 : 404-407, ISSN : 0016-5328.

946 Rome, S., Giorgetti, J.-P., 2007. Corsican mountains and its climatic features [WWW Document]. URL
947 https://doi.org/10.4267/2042/14846.

948 Rossi, P., Cocherie, A., Fanning, C.M., 2015. Evidence in Variscan Corsica of a brief and voluminous Late Carboniferous
to Early Permian volcanic-plutonic event contemporaneous with a high-temperature/low-pressure metamorphic
949 peak in the lower crust. Bulletin de la Société Géologique de France 186, 171–192.
950

951 Ruzié, L., Aubaud, C., Moreira, M., Agrinier, P., Dessert, C., Gréau, C., Crispi, O., 2013. Carbon and helium isotopes in
952 thermal springs of La Soufrière volcano (Guadeloupe, Lesser Antilles): implications for volcanological monitoring.
953 Chemical Geology 359, 70–80.

954 Sacchi, E., Cuoco, E., Oster, H., Paolucci, V., Tedesco, D., Viaroli, S., 2022. Tracing groundwater circulation in a valuable
955 mineral water basin with geochemical and isotopic tools: the case of FERRARELLE, Riardo basin, Southern Italy.
956 Environ Geochem Health 44, 1–28. https://doi.org/10.1007/s10653-021-00845-x.

957 Serrano, O., Allanic, C., Magar, M., 2013. Synthèse géologique du bassin tertiaire de la Plaine orientale Corse - Liaison
Terre-Mer entre San Nicolao et Solenzara (Rapport final No. BRGM/RP-62303-FR).

959 Sherwood Lollar, B., Westgate, T.D., Ward, J.A., Slater, G.F., Lacrampe-Couloume, G., 2002. Abiogenic formation of
960 alkanes in the Earth's crust as a minor source for global hydrocarbon reservoirs. Nature 416, 522–524.
961 https://doi.org/10.1038/416522a.

962 Štrbački, J., Živanović, V., Ćuk Đurović, M., Atanacković, N., Dragišić, V., 2020. Origin, diversity and geothermal
963 potentiality of thermal and mineral waters in Vrnjačka Banja, Serbia. Environ Earth Sci 79, 309.
964 https://doi.org/10.1007/s12665-020-09050-y.

965 Tarvainen, T., Sapon, S., Jarva, J., 2019. Applying heatmaps in interpretation of geochemical baseline data on urban soils
966 in Finland. Journal of Geochemical Exploration 205, 106345. https://doi.org/10.1016/j.gexplo.2019.106345
929 Paull, C., Lorenson, T., Borowski, W., Ussler, B., Olsen, K., Rodriguez, N., 2000. Isotopic composition of CH$_{4}$, CO$_{2}$
930 species, and sedimentary organic matter within samples from the Blake Ridge: Gas source implications. Proceedings
931 of the Ocean Drilling Program: Scientific Results 164. https://doi.org/10.2973/odp.proc.sr.164.207.2000.

932 Penna, D., Stenni, B., Šanda, M., Wrede, S., Bogaard, T. A., Gobbi, A., Borga, M., Fischer, B. M. C., Bonazza, M., and
933 Chárová, Z., 2010. On the reproducibility and repeatability of laser absorption spectroscopy measurements for δ2H
934 and δ18O isotopic analysis, Hydrol. Earth Syst. Sci., 14, 1551–1566, https://doi.org/10.5194/hess-14-1551-2010.

935 Petrović, T., Zlokolica-Mandić, M., Veljković, N., Vidojević, D., 2010. Hydrogeological conditions for the forming and
936 quality of mineral waters in Serbia. Journal of Geochemical Exploration 107, 373–381.

937 Piccoli, F., Vitale Brovarone, A., Ague, J.J., 2018. Field and petrological study of metasomatism and high-pressure
938 carbonation from lawsonite eclogite-facies terrains, Alpine Corsica. Lithos 304–307, 16–37.
939 https://doi.org/10.1016/j.lithos.2018.01.026.

940 Powell, T., Cumming, W., 2010. Spreadsheets for geothermal water and gas geochemistry, in: Proceedings. pp. 1–3.

941 Ravna, E.J.K., Andersen, T.B., Jolivet, L., Capitani, C.D., 2010. Cold subduction and the formation of lawsonite eclogite
942 – constraints from prograde evolution of eclogitized pillow lava from Corsica. Journal of Metamorphic Geology 28,
943 381–395. https://doi.org/10.1111/j.1525-1314.2010.00870.x.

944 Rojey, A., 1997. Technological innovations in gas field operations; L'innovation technique dans l'exploitation des
945 ressources gazieres. Gaz d'Aujourd'hui (Paris), 121 : 404-407, ISSN : 0016-5328.

946 Rome, S., Giorgetti, J.-P., 2007. Corsican mountains and its climatic features [WWW Document]. URL
947 https://doi.org/10.4267/2042/14846.

948 Rossi, P., Cocherie, A., Fanning, C.M., 2015. Evidence in Variscan Corsica of a brief and voluminous Late Carboniferous
to Early Permian volcanic-plutonic event contemporaneous with a high-temperature/low-pressure metamorphic
949 peak in the lower crust. Bulletin de la Société Géologique de France 186, 171–192.
950

951 Ruzié, L., Aubaud, C., Moreira, M., Agrinier, P., Dessert, C., Gréau, C., Crispi, O., 2013. Carbon and helium isotopes in
952 thermal springs of La Soufrière volcano (Guadeloupe, Lesser Antilles): implications for volcanological monitoring.
953 Chemical Geology 359, 70–80.

954 Sacchi, E., Cuoco, E., Oster, H., Paolucci, V., Tedesco, D., Viaroli, S., 2022. Tracing groundwater circulation in a valuable
955 mineral water basin with geochemical and isotopic tools: the case of FERRARELLE, Riardo basin, Southern Italy.
956 Environ Geochem Health 44, 1–28. https://doi.org/10.1007/s10653-021-00845-x.

957 Serrano, O., Allanic, C., Magar, M., 2013. Synthèse géologique du bassin tertiaire de la Plaine orientale Corse - Liaison
958 Terre-Mer entre San Nicolao et Solenzara (Rapport final No. BRGM/RP-62303-FR).

959 Sherwood Lollar, B., Westgate, T.D., Ward, J.A., Slater, G.F., Lacrampe-Couloume, G., 2002. Abiogenic formation of
960 alkanes in the Earth's crust as a minor source for global hydrocarbon reservoirs. Nature 416, 522–524.
961 https://doi.org/10.1038/416522a.

962 Štrbački, J., Živanović, V., Ćuk Đurović, M., Atanacković, N., Dragišić, V., 2020. Origin, diversity and geothermal
963 potentiality of thermal and mineral waters in Vrnjačka Banja, Serbia. Environ Earth Sci 79, 309.
964 https://doi.org/10.1007/s12665-020-09050-y.

965 Tarvainen, T., Sapon, S., Jarva, J., 2019. Applying heatmaps in interpretation of geochemical baseline data on urban soils
966 in Finland. Journal of Geochemical Exploration 205, 106345. https://doi.org/10.1016/j.gexplo.2019.106345
967 Tassi, F., Feyzullayev, A.A., Bonini, M., Sani, F., Aliyev, C.S., Darrah, T.H., Vaselli, O., Baghirli, R.J., 2020. Mantle vs. crustal fluid sources in the gas discharges from Lesser Caucasus and Talysh Mountains (Azerbaijan) in relation to the regional geotectonic setting. Applied Geochemistry 118, 104643. https://doi.org/10.1016/j.apgeochem.2020.104643.

971 Thatcher, L.L., Janzer, V.J., Edwards, K.W., 1977. Methods for Determination of Radioactive Substances in Water and Fluvial Sediments. U.S. Government Printing Office.

973 Thiébaud, E., Dzikowski, M., Gasquet, D., Renac, C., 2010. Reconstruction of groundwater flows and chemical water evolution in an amagmatic hydrothermal system (La Léchère, French Alps). Journal of Hydrology 381, 189–202. https://doi.org/10.1016/j.jhydrol.2009.11.041.

976 Vitale Brovarone, A., Beyssac, O., Malavieille, J., Molli, G., Beltrando, M., Compagnoni, R., 2013. Stacking and metamorphism of continuous segments of subducted lithosphere in a high-pressure wedge: The example of Alpine Corsica (France). Earth-Science Reviews 116, 35–56. https://doi.org/10.1016/j.earscirev.2012.10.003

979 Werner, C., C. I. Schipper, S. J. Cronin, P. H. Barry, and M. K. Stewart. 2022. ‘Magmatic Carbon and Helium in Springs Reveals the Vitality of a Dormant Volcano, Taranaki, New Zealand’. Geophysical Research Letters 49 (18): e2022GL099273. https://doi.org/10.1029/2022GL099273.

982 Whiticar, M.J., Faber, E., Schoell, M., 1986. Biogenic methane formation in marine and freshwater environments: CO2 reduction vs. acetate fermentation—Isotope evidence. Geochimica et Cosmochimica Acta 50, 693–709. https://doi.org/10.1016/0016-7037(86)90346-7.

985 Zippa, E., Plyusnin, A., Shvartsev, S., 2019. The chemical and isotopic compositions of thermal waters and gases in the Republic of Buryatia, Russia. E3S Web Conf. 98, 01055. https://doi.org/10.1051/e3sconf/20199801055.
967 Tassi, F., Feyzullayev, A.A., Bonini, M., Sani, F., Aliyev, C.S., Darrah, T.H., Vaselli, O., Baghirli, R.J., 2020. Mantle vs. crustal fluid sources in the gas discharges from Lesser Caucasus and Talysh Mountains (Azerbaijan) in relation to the regional geotectonic setting. Applied Geochemistry 118, 104643. https://doi.org/10.1016/j.apgeochem.2020.104643.

971 Thatcher, L.L., Janzer, V.J., Edwards, K.W., 1977. Methods for Determination of Radioactive Substances in Water and Fluvial Sediments. U.S. Government Printing Office.

973 Thiébaud, E., Dzikowski, M., Gasquet, D., Renac, C., 2010. Reconstruction of groundwater flows and chemical water evolution in an amagmatic hydrothermal system (La Léchère, French Alps). Journal of Hydrology 381, 189–202. https://doi.org/10.1016/j.jhydrol.2009.11.041.

976 Vitale Brovarone, A., Beyssac, O., Malavieille, J., Molli, G., Beltrando, M., Compagnoni, R., 2013. Stacking and metamorphism of continuous segments of subducted lithosphere in a high-pressure wedge: The example of Alpine Corsica (France). Earth-Science Reviews 116, 35–56. https://doi.org/10.1016/j.earscirev.2012.10.003

979 Werner, C., C. I. Schipper, S. J. Cronin, P. H. Barry, and M. K. Stewart. 2022. ‘Magmatic Carbon and Helium in Springs Reveals the Vitality of a Dormant Volcano, Taranaki, New Zealand’. Geophysical Research Letters 49 (18): e2022GL099273. https://doi.org/10.1029/2022GL099273.

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Tables

Table 1: Information about sites, springs localities, code name, type and altitude.
Tables

Table 1: Information about sites, springs localities, code name, type and altitude.
<table><thead><tr><th rowspan="3">Spring name</th><th rowspan="3">CODE</th><th rowspan="3">Type</th><th colspan="4">Geographic Coordinates</th></tr><tr><th rowspan="2">Altitude (m asl)</th><th colspan="2">in " Lambert 93"</th><th rowspan="2">Municipality</th></tr><tr><th>X (m)</th><th>Y (m)</th></tr></thead><tbody><tr><td>Acqua Acetosa</td><td>ACQ</td><td>Spring</td><td>47</td><td>1,227,704.289</td><td>6,119,785.550</td><td>Serra di Fiumorbo</td></tr><tr><td>Caldaniccia Travu</td><td>CALD</td><td>Spring</td><td>284</td><td>1,220,620.598</td><td>6,111,725.565</td><td>Chisa</td></tr><tr><td>Vignola Travu</td><td>VIGN</td><td>Spring</td><td>190</td><td>1,223,000.993</td><td>6,112,347.655</td><td>Chisa</td></tr><tr><td>Fontanella</td><td>FONT</td><td>Spring</td><td>1</td><td>1,231,781.421</td><td>6,107,000.355</td><td>Solaro</td></tr><tr><td rowspan="7">Pietrapola</td><td>P-MUR3</td><td>Spring</td><td rowspan="7">190</td><td rowspan="7">1,222,833.837</td><td rowspan="7">6,119,744.012</td><td rowspan="7">Isolaccio-di-Fiumorbo</td></tr><tr><td>P-LAV</td><td>Spring</td></tr><tr><td>P-LEC</td><td>Spring</td></tr><tr><td>P-LUC</td><td>Spring</td></tr><tr><td>P-MUR1</td><td>Spring</td></tr><tr><td>P-ESC</td><td>Spring</td></tr><tr><td>P-RAST</td><td>Spring</td></tr></tbody></table>
<table><thead><tr><th rowspan="3">Spring name</th><th rowspan="3">CODE</th><th rowspan="3">Type</th><th colspan="4">Geographic Coordinates</th></tr><tr><th rowspan="2">Altitude (m asl)</th><th colspan="2">in " Lambert 93"</th><th rowspan="2">Municipality</th></tr><tr><th>X (m)</th><th>Y (m)</th></tr></thead><tbody><tr><td>Acqua Acetosa</td><td>ACQ</td><td>Spring</td><td>47</td><td>1,227,704.289</td><td>6,119,785.550</td><td>Serra di Fiumorbo</td></tr><tr><td>Caldaniccia Travu</td><td>CALD</td><td>Spring</td><td>284</td><td>1,220,620.598</td><td>6,111,725.565</td><td>Chisa</td></tr><tr><td>Vignola Travu</td><td>VIGN</td><td>Spring</td><td>190</td><td>1,223,000.993</td><td>6,112,347.655</td><td>Chisa</td></tr><tr><td>Fontanella</td><td>FONT</td><td>Spring</td><td>1</td><td>1,231,781.421</td><td>6,107,000.355</td><td>Solaro</td></tr><tr><td rowspan="7">Pietrapola</td><td>P-MUR3</td><td>Spring</td><td rowspan="7">190</td><td rowspan="7">1,222,833.837</td><td rowspan="7">6,119,744.012</td><td rowspan="7">Isolaccio-di-Fiumorbo</td></tr><tr><td>P-LAV</td><td>Spring</td></tr><tr><td>P-LEC</td><td>Spring</td></tr><tr><td>P-LUC</td><td>Spring</td></tr><tr><td>P-MUR1</td><td>Spring</td></tr><tr><td>P-ESC</td><td>Spring</td></tr><tr><td>P-RAST</td><td>Spring</td></tr></tbody></table>
<table><tr><td></td><td>P-SOA</td><td>Spring</td><td></td><td></td><td></td><td></td></tr><tr><td>Campo-Favajo</td><td>CAM-F</td><td>Spring</td><td>25</td><td>1,231,884.619</td><td>6,137,973.405</td><td>Antisanti</td></tr><tr><td rowspan="3">Puzzichellu</td><td>PUZ-F</td><td>Borehole</td><td>60</td><td>1,230,383.109</td><td>6,135,227.581</td><td>Aghione</td></tr><tr><td>PUZ-N</td><td>Spring</td><td></td><td></td><td></td><td></td></tr><tr><td>PUZ-G</td><td>Spring</td><td></td><td></td><td></td><td></td></tr><tr><td rowspan="2">Fajo-Quarcio</td><td>QUAR-D</td><td>Spring</td><td>110</td><td>1,228,744.504</td><td>6,142,058.466</td><td>Giuncaggio</td></tr><tr><td>QUAR-G</td><td>Spring</td><td>110</td><td></td><td></td><td></td></tr><tr><td>Vadina</td><td>VAD</td><td>Spring</td><td>18</td><td>1,234,334.584</td><td>6,129,574.738</td><td>Ghisonaccia</td></tr><tr><td>Pardina</td><td>PARD</td><td>Spring</td><td>554</td><td>1,228,492.188</td><td>6,158,708.617</td><td>Tarrano</td></tr><tr><td>Moïta</td><td>MOIT</td><td>Spring</td><td>442</td><td>1,228,931.829</td><td>6,152,106.468</td><td>Moïta</td></tr><tr><td>Forcione</td><td>FORC</td><td>Spring</td><td>177</td><td>1,227,838.685</td><td>6,169,146.731</td><td>Scata</td></tr><tr><td>La Porta</td><td>PORT</td><td>Spring</td><td>369</td><td>1,223,782.856</td><td>6,169,454.126</td><td>Poggio Marinaccio</td></tr><tr><td>Piana</td><td>PIAN</td><td>Spring</td><td>370</td><td>1,225,496.502</td><td>6,164,172.761</td><td>Stazzona</td></tr><tr><td>Surgente Sottana</td><td>SSOT</td><td>Borehole</td><td>415</td><td>1,225,544.676</td><td>6,163,060.865</td><td>Rappaggio</td></tr></table>
<table><tr><td></td><td>P-SOA</td><td>Spring</td><td></td><td></td><td></td><td></td></tr><tr><td>Campo-Favajo</td><td>CAM-F</td><td>Spring</td><td>25</td><td>1,231,884.619</td><td>6,137,973.405</td><td>Antisanti</td></tr><tr><td rowspan="3">Puzzichellu</td><td>PUZ-F</td><td>Borehole</td><td>60</td><td>1,230,383.109</td><td>6,135,227.581</td><td>Aghione</td></tr><tr><td>PUZ-N</td><td>Spring</td><td></td><td></td><td></td><td></td></tr><tr><td>PUZ-G</td><td>Spring</td><td></td><td></td><td></td><td></td></tr><tr><td rowspan="2">Fajo-Quarcio</td><td>QUAR-D</td><td>Spring</td><td>110</td><td>1,228,744.504</td><td>6,142,058.466</td><td>Giuncaggio</td></tr><tr><td>QUAR-G</td><td>Spring</td><td>110</td><td></td><td></td><td></td></tr><tr><td>Vadina</td><td>VAD</td><td>Spring</td><td>18</td><td>1,234,334.584</td><td>6,129,574.738</td><td>Ghisonaccia</td></tr><tr><td>Pardina</td><td>PARD</td><td>Spring</td><td>554</td><td>1,228,492.188</td><td>6,158,708.617</td><td>Tarrano</td></tr><tr><td>Moïta</td><td>MOIT</td><td>Spring</td><td>442</td><td>1,228,931.829</td><td>6,152,106.468</td><td>Moïta</td></tr><tr><td>Forcione</td><td>FORC</td><td>Spring</td><td>177</td><td>1,227,838.685</td><td>6,169,146.731</td><td>Scata</td></tr><tr><td>La Porta</td><td>PORT</td><td>Spring</td><td>369</td><td>1,223,782.856</td><td>6,169,454.126</td><td>Poggio Marinaccio</td></tr><tr><td>Piana</td><td>PIAN</td><td>Spring</td><td>370</td><td>1,225,496.502</td><td>6,164,172.761</td><td>Stazzona</td></tr><tr><td>Surgente Sottana</td><td>SSOT</td><td>Borehole</td><td>415</td><td>1,225,544.676</td><td>6,163,060.865</td><td>Rappaggio</td></tr></table>
<table><tr><td>Surgente Supprana</td><td>SSUP</td><td>Spring</td><td>477</td><td>1,225,594.739</td><td>6,163,049.761</td><td>Rappaggio</td></tr><tr><td>Caldane d'Ampugnani</td><td>AMPU</td><td>Spring</td><td>159</td><td>1,229,540.988</td><td>6,168,923.534</td><td>San Gavino d'Ampugnani</td></tr></table>
<table><tr><td>Surgente Supprana</td><td>SSUP</td><td>Spring</td><td>477</td><td>1,225,594.739</td><td>6,163,049.761</td><td>Rappaggio</td></tr><tr><td>Caldane d'Ampugnani</td><td>AMPU</td><td>Spring</td><td>159</td><td>1,229,540.988</td><td>6,168,923.534</td><td>San Gavino d'Ampugnani</td></tr></table>
<table><caption>Table 2: Field parameters, hydrochemical and isotopic content of thermo-mineral groundwaters.</caption><thead><tr><th rowspan="2">SPRINGS CODE</th><th rowspan="2">DATE</th><th rowspan="2">T. °C</th><th rowspan="2">pH</th><th rowspan="2">E.C. μS/cm²</th><th rowspan="2">Eh mV</th><th rowspan="2">O₂ mg/L</th><th rowspan="2">HCO₃⁻ mg/L</th><th rowspan="2">CO₃²⁻ mg/L</th><th rowspan="2">NH₄ mg/L</th><th rowspan="2">3H mg/L</th><th rowspan="2">TU</th><th rowspan="2">STD</th><th rowspan="2">²H ‰</th><th rowspan="2">¹⁸O ‰</th><th rowspan="2">Estimated recharge altitude (m.a.s.l.) Ave.</th><th rowspan="2">STD</th></tr><tr><th>STD</th><th>STD</th><th>STD</th><th>STD</th><th>STD</th><th>STD</th><th>STD</th></tr></thead><tbody><tr><td rowspan="2">ACQ</td><td>Apr-18</td><td>15.7</td><td>5.93</td><td>2150</td><td>310</td><td>0.85</td><td>8.7</td><td>1437</td><td>1.3E-03</td><td>0.27</td><td></td><td></td><td>-40.03</td><td>0.10</td><td>-7.22</td><td>0.03</td><td rowspan="2">263</td><td rowspan="2">34</td></tr><tr><td>Dec-18</td><td>17.9</td><td>6.01</td><td>2120</td><td>228</td><td>0.28</td><td>2.9</td><td>1291</td><td>1.4E-03</td><td>0.08</td><td>1.1</td><td>0.2</td><td>-38.69</td><td>0.38</td><td>-6.88</td><td>0.00</td></tr><tr><td rowspan="2">AMPU</td><td>Apr-18</td><td>13.5</td><td>5.99</td><td>1126</td><td>319</td><td>3.85</td><td>37.9</td><td>798</td><td>8.3E-04</td><td></td><td></td><td></td><td>-43.52</td><td>0.09</td><td>-7.63</td><td>0.05</td><td rowspan="2">458</td><td rowspan="2">32</td></tr><tr><td>Dec-18</td><td>12.9</td><td>5.83</td><td>1237</td><td>356</td><td>3.40</td><td>32.8</td><td>836</td><td>6.0E-04</td><td>1.63</td><td></td><td></td><td>-43.04</td><td>0.34</td><td>-7.86</td><td>0.03</td></tr><tr><td rowspan="2">CALD</td><td>Apr-18</td><td>33</td><td>9.58</td><td>150</td><td>2</td><td>2.11</td><td>0.3</td><td>63</td><td>2.6E-01</td><td>1.59</td><td></td><td></td><td>-52.11</td><td>0.07</td><td>-8.17</td><td>0.02</td><td>1035</td><td>115</td></tr><tr><td>Dec-18</td><td>16.5</td><td>7.83</td><td>1405</td><td>196</td><td>0.25</td><td>2.5</td><td>468</td><td>3.4E-02</td><td></td><td></td><td></td><td>-39.64</td><td>0.27</td><td>-7.13</td><td>0.04</td><td></td><td></td></tr><tr><td rowspan="2">CAM-F</td><td>Sep-18</td><td>17.1</td><td>7.78</td><td>1429</td><td>-90</td><td>0.01</td><td>0.1</td><td>494</td><td>3.2E-02</td><td>0.0</td><td></td><td></td><td>-39.21</td><td>0.24</td><td>-7.05</td><td>0.05</td><td>228</td><td>17</td></tr><tr><td>Dec-18</td><td>16.6</td><td>7.67</td><td>1381</td><td>-111</td><td>0.16</td><td>1.6</td><td>461</td><td>2.3E-02</td><td></td><td></td><td></td><td>-39.05</td><td>0.10</td><td>-6.83</td><td>0.16</td><td></td><td></td></tr><tr><td>FAJO-D</td><td>Apr-18</td><td>15.7</td><td>7.35</td><td>698</td><td>-25</td><td>25.00</td><td>2.45</td><td>503</td><td>1.3E-02</td><td></td><td></td><td></td><td>-41.18</td><td>0.18</td><td>-7.44</td><td>0.02</td><td>292</td><td>35</td></tr></tbody></table>
<table><caption>Table 2: Field parameters, hydrochemical and isotopic content of thermo-mineral groundwaters.</caption><thead><tr><th rowspan="2">SPRINGS CODE</th><th rowspan="2">DATE</th><th>T.</th><th>pH</th><th>E.C.</th><th>Eh</th><th>O<sub>2</sub></th><th>HCO<sub>3</sub><sup>-</sup></th><th>CO<sub>3</sub><sup>2-</sup></th><th>NH<sub>4</sub></th><th>3H</th><th rowspan="2">2H</th><th rowspan="2">18O</th><th colspan="2">Estimated recharge altitude (m.a.s.l.)</th></tr><tr><th>°C</th><th></th><th>µS/cm<sup>2</sup></th><th>mV</th><th>mg/L</th><th>%</th><th>mg/L</th><th>mg/L</th><th>mg/L</th><th>TU</th><th>STD</th><th>‰</th><th>STD</th><th>Ave.</th><th>STD</th></tr></thead><tbody><tr><td rowspan="2">ACQ</td><td>Apr-18</td><td>15.7</td><td>5.93</td><td>2150</td><td>310</td><td>0.85</td><td>8.7</td><td>1437</td><td>1.3E-03</td><td>0.27</td><td></td><td>-40.03</td><td>0.10</td><td>-7.22</td><td>0.03</td><td rowspan="2">263</td><td rowspan="2">34</td></tr><tr><td>Dec-18</td><td>17.9</td><td>6.01</td><td>2120</td><td>228</td><td>0.28</td><td>2.9</td><td>1291</td><td>1.4E-03</td><td>0.08</td><td>1.1</td><td>0.2</td><td>-38.69</td><td>0.38</td><td>-6.88</td><td>0.00</td></tr><tr><td rowspan="2">AMPU</td><td>Apr-18</td><td>13.5</td><td>5.99</td><td>1126</td><td>319</td><td>3.85</td><td>37.9</td><td>798</td><td>8.3E-04</td><td></td><td></td><td></td><td>-43.52</td><td>0.09</td><td>-7.63</td><td>0.05</td><td rowspan="2">458</td><td rowspan="2">32</td></tr><tr><td>Dec-18</td><td>12.9</td><td>5.83</td><td>1237</td><td>356</td><td>3.40</td><td>32.8</td><td>836</td><td>6.0E-04</td><td>1.63</td><td></td><td></td><td>-43.04</td><td>0.34</td><td>-7.86</td><td>0.03</td></tr><tr><td rowspan="2">CALD</td><td>Apr-18</td><td>33</td><td>9.58</td><td>150</td><td>2</td><td>2.11</td><td>0.3</td><td>63</td><td>2.6E-01</td><td>1.59</td><td></td><td></td><td>-52.11</td><td>0.07</td><td>-8.17</td><td>0.02</td><td>1035</td><td>115</td></tr><tr><td>Dec-18</td><td>16.5</td><td>7.83</td><td>1405</td><td>196</td><td>0.25</td><td>2.5</td><td>468</td><td>3.4E-02</td><td></td><td></td><td></td><td>-39.64</td><td>0.27</td><td>-7.13</td><td>0.04</td><td></td><td></td></tr><tr><td rowspan="2">CAM-F</td><td>Sep-18</td><td>17.1</td><td>7.78</td><td>1429</td><td>-90</td><td>0.01</td><td>0.1</td><td>494</td><td>3.2E-02</td><td>0.0</td><td></td><td></td><td>-39.21</td><td>0.24</td><td>-7.05</td><td>0.05</td><td>228</td><td>17</td></tr><tr><td>Dec-18</td><td>16.6</td><td>7.67</td><td>1381</td><td>-111</td><td>0.16</td><td>1.6</td><td>461</td><td>2.3E-02</td><td></td><td></td><td></td><td>-39.05</td><td>0.10</td><td>-6.83</td><td>0.16</td><td></td><td></td></tr><tr><td>FAJO-D</td><td>Apr-18</td><td>15.7</td><td>7.35</td><td>698</td><td>-25</td><td>25.00</td><td>2.45</td><td>503</td><td>1.3E-02</td><td></td><td></td><td></td><td>-41.18</td><td>0.18</td><td>-7.44</td><td>0.02</td><td>292</td><td>35</td></tr></tbody></table>
<table><tbody><tr><td></td><td>Sep-18</td><td>16.8</td><td>7.03</td><td>693</td><td>67</td><td>-</td><td>-</td><td>538</td><td>6.1E-03</td><td>1.3</td><td>0.2</td><td>-41.30</td><td>0.50</td><td>-7.37</td><td>0.03</td></tr><tr><td></td><td>Dec-18</td><td>16.2</td><td>7.11</td><td>700</td><td>-4</td><td>2.34</td><td>22.9</td><td>405</td><td>5.5E-03</td><td></td><td></td><td>-39.79</td><td>0.34</td><td>-7.19</td><td>0.09</td></tr><tr><td></td><td>Apr-18</td><td>15.5</td><td>7.30</td><td>704</td><td>-34</td><td>28.60</td><td>2.81</td><td>438</td><td>9.3E-03</td><td></td><td></td><td>-40.69</td><td>0.56</td><td>-7.26</td><td>0.04</td></tr><tr><td>FAJO-G</td><td>Sep-18</td><td>16.7</td><td>7.16</td><td>694</td><td>39</td><td>-</td><td>-</td><td>400</td><td>6.2E-03</td><td>1.1</td><td>0.2</td><td>-41.19</td><td>0.69</td><td>-7.51</td><td>0.12</td><td>277</td><td>25</td></tr><tr><td></td><td>Dec-18</td><td>16.3</td><td>7.02</td><td>711</td><td>9</td><td>1.90</td><td>19.5</td><td>372</td><td>4.1E-03</td><td></td><td></td><td>-39.98</td><td>0.14</td><td>-7.23</td><td>0.07</td><td></td><td></td></tr><tr><td></td><td>Apr-18</td><td>17.5</td><td>6.13</td><td>12150</td><td>190</td><td>0.02</td><td>0.2</td><td>1696</td><td>2.4E-03</td><td></td><td></td><td>-41.30</td><td>0.47</td><td>-7.39</td><td>0.04</td><td></td><td></td></tr><tr><td>FONT</td><td>Sep-18</td><td>19.5</td><td>6.06</td><td>12200</td><td>222</td><td>0.20</td><td>2</td><td>1764</td><td>2.2E-03</td><td>1.2</td><td>0.2</td><td>-42.70</td><td>0.55</td><td>-7.07</td><td>0.03</td><td>334</td><td>45</td></tr><tr><td></td><td>Dec-18</td><td>18.9</td><td>6.46</td><td>12070</td><td>178</td><td>0.77</td><td>8.1</td><td>1787</td><td>5.5E-03</td><td></td><td></td><td>-41.01</td><td>0.12</td><td>-6.94</td><td>0.02</td><td></td><td></td></tr><tr><td></td><td>Apr-18</td><td>15.2</td><td>5.77</td><td>1002</td><td>275</td><td>0.08</td><td>0.8</td><td>676</td><td>4.3E-04</td><td></td><td></td><td>-46.08</td><td>0.31</td><td>-7.91</td><td>0.12</td><td></td><td></td></tr><tr><td>FORC</td><td>Sep-18</td><td>15.4</td><td>5.79</td><td>1026</td><td>290</td><td>0.75</td><td>7.6</td><td>665</td><td>4.4E-04</td><td>0.0</td><td></td><td>-46.66</td><td>0.07</td><td>-8.23</td><td>0.07</td><td>580</td><td>17</td></tr><tr><td></td><td>Dec-18</td><td>15.4</td><td>5.80</td><td>1022</td><td>298</td><td>0.17</td><td>1.7</td><td>689</td><td>4.6E-04</td><td></td><td></td><td>-46.03</td><td>0.10</td><td>-8.23</td><td>0.10</td><td></td><td></td></tr><tr><td>MOIT</td><td>Sep-18</td><td>13.5</td><td>5.99</td><td>1149</td><td>311</td><td>0.70</td><td>7</td><td>781</td><td>8.1E-04</td><td></td><td></td><td>-47.40</td><td>0.44</td><td>-8.37</td><td>0.01</td><td>650</td><td>24</td></tr><tr><td></td><td>Sep-18</td><td>14.9</td><td>5.89</td><td>1216</td><td>279</td><td>-</td><td>-</td><td>856</td><td>7.1E-04</td><td>0.24</td><td>0.0</td><td>-47.05</td><td>0.34</td><td>-8.15</td><td>0.04</td><td></td><td></td></tr></tbody></table>
<table><tbody><tr><td></td><td>Sep-18</td><td>16.8</td><td>7.03</td><td>693</td><td>67</td><td>-</td><td>-</td><td>538</td><td>6.1E-03</td><td>1.3</td><td>0.2</td><td>-41.30</td><td>0.50</td><td>-7.37</td><td>0.03</td></tr><tr><td></td><td>Dec-18</td><td>16.2</td><td>7.11</td><td>700</td><td>-4</td><td>2.34</td><td>22.9</td><td>405</td><td>5.5E-03</td><td></td><td></td><td>-39.79</td><td>0.34</td><td>-7.19</td><td>0.09</td></tr><tr><td></td><td>Apr-18</td><td>15.5</td><td>7.30</td><td>704</td><td>-34</td><td>28.60</td><td>2.81</td><td>438</td><td>9.3E-03</td><td></td><td></td><td>-40.69</td><td>0.56</td><td>-7.26</td><td>0.04</td></tr><tr><td rowspan="2">FAJO-G</td><td>Sep-18</td><td>16.7</td><td>7.16</td><td>694</td><td>39</td><td>-</td><td>-</td><td>400</td><td>6.2E-03</td><td>1.1</td><td>0.2</td><td>-41.19</td><td>0.69</td><td>-7.51</td><td>0.12</td><td>277</td><td>25</td></tr><tr><td>Dec-18</td><td>16.3</td><td>7.02</td><td>711</td><td>9</td><td>1.90</td><td>19.5</td><td>372</td><td>4.1E-03</td><td></td><td></td><td>-39.98</td><td>0.14</td><td>-7.23</td><td>0.07</td><td></td><td></td></tr><tr><td></td><td>Apr-18</td><td>17.5</td><td>6.13</td><td>12150</td><td>190</td><td>0.02</td><td>0.2</td><td>1696</td><td>2.4E-03</td><td></td><td></td><td>-41.30</td><td>0.47</td><td>-7.39</td><td>0.04</td><td></td><td></td></tr><tr><td rowspan="2">FONT</td><td>Sep-18</td><td>19.5</td><td>6.06</td><td>12200</td><td>222</td><td>0.20</td><td>2</td><td>1764</td><td>2.2E-03</td><td>1.2</td><td>0.2</td><td>-42.70</td><td>0.55</td><td>-7.07</td><td>0.03</td><td>334</td><td>45</td></tr><tr><td>Dec-18</td><td>18.9</td><td>6.46</td><td>12070</td><td>178</td><td>0.77</td><td>8.1</td><td>1787</td><td>5.5E-03</td><td></td><td></td><td>-41.01</td><td>0.12</td><td>-6.94</td><td>0.02</td><td></td><td></td></tr><tr><td></td><td>Apr-18</td><td>15.2</td><td>5.77</td><td>1002</td><td>275</td><td>0.08</td><td>0.8</td><td>676</td><td>4.3E-04</td><td></td><td></td><td>-46.08</td><td>0.31</td><td>-7.91</td><td>0.12</td><td></td><td></td></tr><tr><td rowspan="2">FORC</td><td>Sep-18</td><td>15.4</td><td>5.79</td><td>1026</td><td>290</td><td>0.75</td><td>7.6</td><td>665</td><td>4.4E-04</td><td>0.0</td><td></td><td>-46.66</td><td>0.07</td><td>-8.23</td><td>0.07</td><td>580</td><td>17</td></tr><tr><td>Dec-18</td><td>15.4</td><td>5.80</td><td>1022</td><td>298</td><td>0.17</td><td>1.7</td><td>689</td><td>4.6E-04</td><td></td><td></td><td>-46.03</td><td>0.10</td><td>-8.23</td><td>0.10</td><td></td><td></td></tr><tr><td rowspan="2">MOIT</td><td>Sep-18</td><td>13.5</td><td>5.99</td><td>1149</td><td>311</td><td>0.70</td><td>7</td><td>781</td><td>8.1E-04</td><td></td><td></td><td>-47.40</td><td>0.44</td><td>-8.37</td><td>0.01</td><td>650</td><td>24</td></tr><tr><td>Dec-18</td><td>14.9</td><td>5.89</td><td>1216</td><td>279</td><td>-</td><td>-</td><td>856</td><td>7.1E-04</td><td>0.24</td><td>0.0</td><td>-47.05</td><td>0.34</td><td>-8.15</td><td>0.04</td><td></td><td></td></tr></tbody></table>
<table><tbody><tr><td></td><td>Dec-18</td><td>13.8</td><td>5.99</td><td>1010</td><td>279</td><td>0.52</td><td>5.3</td><td>694</td><td>7.2E-04</td><td>0.25</td><td>-46.81</td><td>0.58</td><td>-8.16</td><td>0.08</td></tr><tr><td></td><td>Apr-18</td><td>12</td><td>5.44</td><td>516</td><td>402</td><td>1.52</td><td>15.3</td><td>265</td><td>7.8E-05</td><td>0.17</td><td>-48.36</td><td>0.31</td><td>-8.50</td><td>0.06</td></tr><tr><td rowspan="2">PARD</td><td>Sep-18</td><td>12.5</td><td>5.53</td><td>556</td><td>233</td><td>0.55</td><td>5.6</td><td>314</td><td>1.1E-04</td><td>0.06</td><td>2.3</td><td>0.3</td><td>-48.57</td><td>0.40</td><td>-8.40</td><td>0.02</td><td>702</td><td>41</td></tr><tr><td>Dec-18</td><td>12.1</td><td>5.20</td><td>497</td><td>373</td><td>1.61</td><td>16</td><td>275</td><td>4.7E-05</td><td>0.01</td><td></td><td></td><td>-47.84</td><td>0.40</td><td>-8.28</td><td>0.02</td><td></td><td></td></tr><tr><td rowspan="2">P-B</td><td>Sep-18</td><td>44</td><td>8.89</td><td>372</td><td>-185</td><td>0.54</td><td></td><td>128</td><td>1.1E-01</td><td></td><td>0.0</td><td></td><td>-54.81</td><td>0.30</td><td>-9.22</td><td>0.06</td><td></td><td></td></tr><tr><td>Dec-18</td><td>43.2</td><td>9.67</td><td>338</td><td>-61</td><td>4.04</td><td>67.1</td><td>100</td><td>5.0E-01</td><td></td><td></td><td></td><td>-55.06</td><td>0.20</td><td>-9.10</td><td>0.04</td><td></td><td></td></tr><tr><td></td><td>Apr-18</td><td>48.6</td><td>9.18</td><td>336</td><td>189</td><td>0.53</td><td>9.8</td><td>122</td><td>1.9E-01</td><td></td><td></td><td></td><td>-54.65</td><td>0.22</td><td>-9.09</td><td>0.05</td><td></td><td></td></tr><tr><td rowspan="2">P-LAV</td><td>Sep-18</td><td>48.9</td><td>9.00</td><td>376</td><td>-174</td><td>2.43</td><td></td><td>118</td><td>1.3E-01</td><td></td><td>0.0</td><td></td><td>-54.47</td><td>0.03</td><td>-8.96</td><td>0.02</td><td>1045</td><td>21</td></tr><tr><td>Dec-18</td><td>49.9</td><td>9.63</td><td>340</td><td>-123</td><td>0.55</td><td>9.8</td><td>110</td><td>4.9E-01</td><td>0.56</td><td></td><td></td><td>-55.26</td><td>0.28</td><td>-9.35</td><td>0.07</td><td></td><td></td></tr><tr><td></td><td>Apr-18</td><td>31.3</td><td>9.32</td><td>334</td><td>202</td><td>3.89</td><td>48.4</td><td>110</td><td>2.4E-01</td><td>0.46</td><td></td><td></td><td>-54.96</td><td>0.24</td><td>-9.33</td><td>0.05</td><td></td><td></td></tr><tr><td rowspan="2">P-LUC</td><td>Sep-18</td><td>34.5</td><td>9.36</td><td>338</td><td>19</td><td>1.42</td><td>20.4</td><td>132</td><td>3.2E-01</td><td>0.32</td><td>0.0</td><td></td><td>-51.63</td><td>0.13</td><td>-8.62</td><td>0.06</td><td>1031</td><td>43</td></tr><tr><td>Dec-18</td><td>32.5</td><td>9.60</td><td>336</td><td>-82</td><td>1.17</td><td>16.5</td><td>109</td><td>4.6E-01</td><td>0.43</td><td></td><td></td><td>-54.97</td><td>0.16</td><td>-8.85</td><td>0.06</td><td></td><td></td></tr><tr><td>P-MUR3</td><td>Dec-18</td><td>50.1</td><td>9.38</td><td>338</td><td>-98</td><td>2.06</td><td>37.1</td><td>112</td><td>1.8E-01</td><td>0.47</td><td></td><td></td><td>-54.10</td><td>0.31</td><td>-8.89</td><td>0.08</td><td>1036</td><td>24</td></tr></tbody></table>
<table><tbody><tr><td></td><td>Dec-18</td><td>13.8</td><td>5.99</td><td>1010</td><td>279</td><td>0.52</td><td>5.3</td><td>694</td><td>7.2E-04</td><td>0.25</td><td>-46.81</td><td>0.58</td><td>-8.16</td><td>0.08</td><td></td><td></td></tr><tr><td></td><td>Apr-18</td><td>12</td><td>5.44</td><td>516</td><td>402</td><td>1.52</td><td>15.3</td><td>265</td><td>7.8E-05</td><td>0.17</td><td>-48.36</td><td>0.31</td><td>-8.50</td><td>0.06</td><td></td><td></td></tr><tr><td rowspan="2">PARD</td><td>Sep-18</td><td>12.5</td><td>5.53</td><td>556</td><td>233</td><td>0.55</td><td>5.6</td><td>314</td><td>1.1E-04</td><td>0.06</td><td>2.3</td><td>0.3</td><td>-48.57</td><td>0.40</td><td>-8.40</td><td>0.02</td><td>702</td><td>41</td></tr><tr><td>Dec-18</td><td>12.1</td><td>5.20</td><td>497</td><td>373</td><td>1.61</td><td>16</td><td>275</td><td>4.7E-05</td><td>0.01</td><td></td><td></td><td>-47.84</td><td>0.40</td><td>-8.28</td><td>0.02</td><td></td><td></td></tr><tr><td rowspan="2">P-B</td><td>Sep-18</td><td>44</td><td>8.89</td><td>372</td><td>-185</td><td>0.54</td><td></td><td>128</td><td>1.1E-01</td><td></td><td>0.0</td><td></td><td>-54.81</td><td>0.30</td><td>-9.22</td><td>0.06</td><td></td><td></td></tr><tr><td>Dec-18</td><td>43.2</td><td>9.67</td><td>338</td><td>-61</td><td>4.04</td><td>67.1</td><td>100</td><td>5.0E-01</td><td></td><td></td><td></td><td>-55.06</td><td>0.20</td><td>-9.10</td><td>0.04</td><td>1045</td><td>17</td></tr><tr><td rowspan="2">P-LAV</td><td>Sep-18</td><td>48.9</td><td>9.00</td><td>376</td><td>-174</td><td>2.43</td><td></td><td>118</td><td>1.3E-01</td><td></td><td>0.0</td><td></td><td>-54.47</td><td>0.03</td><td>-8.96</td><td>0.02</td><td>1045</td><td>21</td></tr><tr><td>Dec-18</td><td>49.9</td><td>9.63</td><td>340</td><td>-123</td><td>0.55</td><td>9.8</td><td>110</td><td>4.9E-01</td><td>0.56</td><td></td><td></td><td>-55.26</td><td>0.28</td><td>-9.35</td><td>0.07</td><td></td><td></td></tr><tr><td rowspan="2">P-LUC</td><td>Sep-18</td><td>34.5</td><td>9.36</td><td>338</td><td>19</td><td>1.42</td><td>20.4</td><td>132</td><td>3.2E-01</td><td>0.32</td><td>0.0</td><td></td><td>-51.63</td><td>0.13</td><td>-8.62</td><td>0.06</td><td>1031</td><td>43</td></tr><tr><td>Dec-18</td><td>32.5</td><td>9.60</td><td>336</td><td>-82</td><td>1.17</td><td>16.5</td><td>109</td><td>4.6E-01</td><td>0.43</td><td></td><td></td><td>-54.97</td><td>0.16</td><td>-8.85</td><td>0.06</td><td></td><td></td></tr><tr><td>P-MUR3</td><td>Dec-18</td><td>50.1</td><td>9.38</td><td>338</td><td>-98</td><td>2.06</td><td>37.1</td><td>112</td><td>1.8E-01</td><td>0.47</td><td></td><td></td><td>-54.10</td><td>0.31</td><td>-8.89</td><td>0.08</td><td>1036</td><td>24</td></tr></tbody></table>