Recharge and Geochemical Evolution of Groundwater in Fractured Basement Aquifers (NW India): Insights from Environmental Isotopes (δ18O, δ2H, and 3H) and Hydrogeochemical Studies
Abstract:Considering water as a limiting factor for socio-economic development, especially in arid/semi-arid regions, both scientific communities and policymakers are interested in groundwater recharge-related data. India is fast moving toward a crisis of groundwater due to intense abstraction and contamination. There is a lack of understanding regarding the occurrence, movement, and behaviors of groundwater in a fractured basement terrane. Therefore, integrated environmental isotopes (δ18O, δ2H, and 3H) and hydrogeoch… Show more
“…It is possible to determine the geochemical evolution pattern by identifying water chemistry types (Pradhan et al 2022). Piper diagrams are widely used as a graphical means of showing linear trends of major ions within a groundwater system (Piper 1944); therefore, it is important to first define the hydrochemical facies before attempting to determine the hydrogeochemical controls on groundwater.…”
Tamborine Mountain, Queensland (Australia), is a prime example of a basalt fractured-rock aquifer. Yet very little is known about the hydrochemistry of this groundwater system. Both analytical (major ions and stable isotopes) and multivariate (hierarchical cluster analysis, principal component analysis and factor analysis) analyses were used in this study to investigate the factors that interact within this aquifer system, in order to determine groundwater hydrogeochemistry. A new approach was applied to the data by classifying hydrographs by water type to clearly identify differing aquifer zones. Three distinct groundwater chemistry types were identified, and they were differentiated by variations in depth. Shallow bores were dominated by Na–Cl waters, deep bores were dominated by Na–HCO3 and Ca–HCO3 waters, and the two deepest bores were dominated by mixed water types. The evaluation of hydrogeochemical data has determined that both mineral weathering processes and groundwater/surface-water interaction had a strong influence on the hydrogeochemistry. Seasonal effects were minimal in the study area based on physicochemical parameters and ion chemistry. However, stable isotopic data show temporal trends. Increased rainfall events during the wet season produced a depletion in δ18O and increased d-excess values. The opposite is found during the dry season as a result of higher evaporation rates that are not hindered by intense rainfall events.
“…It is possible to determine the geochemical evolution pattern by identifying water chemistry types (Pradhan et al 2022). Piper diagrams are widely used as a graphical means of showing linear trends of major ions within a groundwater system (Piper 1944); therefore, it is important to first define the hydrochemical facies before attempting to determine the hydrogeochemical controls on groundwater.…”
Tamborine Mountain, Queensland (Australia), is a prime example of a basalt fractured-rock aquifer. Yet very little is known about the hydrochemistry of this groundwater system. Both analytical (major ions and stable isotopes) and multivariate (hierarchical cluster analysis, principal component analysis and factor analysis) analyses were used in this study to investigate the factors that interact within this aquifer system, in order to determine groundwater hydrogeochemistry. A new approach was applied to the data by classifying hydrographs by water type to clearly identify differing aquifer zones. Three distinct groundwater chemistry types were identified, and they were differentiated by variations in depth. Shallow bores were dominated by Na–Cl waters, deep bores were dominated by Na–HCO3 and Ca–HCO3 waters, and the two deepest bores were dominated by mixed water types. The evaluation of hydrogeochemical data has determined that both mineral weathering processes and groundwater/surface-water interaction had a strong influence on the hydrogeochemistry. Seasonal effects were minimal in the study area based on physicochemical parameters and ion chemistry. However, stable isotopic data show temporal trends. Increased rainfall events during the wet season produced a depletion in δ18O and increased d-excess values. The opposite is found during the dry season as a result of higher evaporation rates that are not hindered by intense rainfall events.
“…These faults and fractures have served as the pathways for mineral-rich fluids to percolate into the low-grade schistose rocks (< 0.76 Ga) giving rise to hydrothermal Cu, Pb, and Zn mineralization (Sharma and Biswal, 2020;Sharma et al, 2022) and U mineralization in the albitite veins (Ray, 1987). Further, the fractures acted as suitable waterways for aquifers (Pradhan et al, 2021(Pradhan et al, , 2022.…”
Section: Southwestern Sdtmentioning
confidence: 99%
“…In the process, sulfide minerals are also deposited (Sharma and Biswal, 2020;Sharma et al, 2022). Groundwater flow through brittle fractures created structural aquifers bringing rock-water interaction (Pradhan et al, 2021(Pradhan et al, , 2022. These low to medium temperature alterations probably reset the geochronological ages (monazite ages) of the older terrane.…”
Section: Structural Distinction Between Terranesmentioning
“…The elevation ranges from 215 to 810 m above Mean Sea Level (MSL). The average temperature ranges from 35 to 42 °C and the annual average precipitation is 805 mm mostly received through the southwest monsoon 15 , 35 , 36 . Figure 1 Geological and structural map of the study area with major shear zones, fracture, faults, and litho-units.…”
Crystalline basement rock aquifers underlie more than 20% of the earth’s surface. However, owing to an inadequate understanding of geological structures, it is challenging to locate the groundwater resources in crystalline hard rock terranes. In these terranes, faults, fractures, and shear zones play an important role in bedrock weathering and ultimately groundwater storage. This study integrates important geological structures with 2D high-resolution subsurface resistivity images in understanding the factors that influenced bedrock weathering and groundwater. The results reveal the variability of weathered zone depth in different structural zones (Zone-I to Zone-IV). This is due to the presence of foliations, fractures, and faults. A thicker weathered zone develops when a fracture/fault overprints a pre-existing planar pervasive structure like foliations (Zone-II) as compared to zones only with faults/fractures (Zone-III). Further, the transmissivity of boreholes also shows relatively higher in Zone-II than Zone-III, which implies a good pact between different structural features and possible groundwater storage. The study also demonstrates the role of paleostress and different tectonic structures influencing the depth of the “Critical Zone”. While the geology may vary for different structural terranes, the approach presented in this paper can be readily adopted in mapping bedrock weathering and groundwater resources in crystalline basement terranes globally.
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