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Robert Wyns - One of the best experts on this subject based on the ideXlab platform.
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respective roles of the Weathering Profile and the tectonic fractures in the structure and functioning of crystalline thermo mineral carbo gaseous aquifers
Journal of Hydrology, 2017Co-Authors: Benoit Dewandel, M Alazard, Patrick Lachassagne, Vincent Baillycomte, Renaud Coueffe, Sandrine Grataloup, Bernard Ladouche, Sandra Lanini, Jeanchristophe Marechal, Robert WynsAbstract:Crystalline thermo-mineral and carbo-gaseous (CTMCG) hydrosystems are well known for their economic importance in fields such as thermal, spa activities and natural mineral water (NMW) bottling. Such systems are usually associated with strong structural complexity, which is rarely characterised in detail or robustly. This research focuses on a CTMCG hydrosystem associated with a peri-alpine graben. A multidisciplinary approach with a very large set of data and methods – geological modelling with geophysics and geological data from outcrops and several boreholes, hydrodynamic data, hydrochemistry, hydrogeological and geochemical modelling – reveals very novel results and allows a robust conceptual model to be constructed. The aquifer at the origin of the carbo-gaseous natural mineral water is the 100–125 m-thick fractured stratiform layer of the Weathering Profile of the crystalline rock (granite). It forms a rather large and thick inertial aquifer that can be numerically modelled, in a similar fashion to a porous medium. The majority of tectonic faults length act as impervious boundaries that divide this aquifer into around ten elongated compartments that were precisely delineated. These tectonic faults are permeable only along two small areas that were also precisely located. These permeable zones feed some aquifer compartments with deep, highly mineralised carbo-gaseous water, which mixes with “fresher” water and forms the exploited NMW. These results can be generalised and in particular show a strong opposition between low-inertia CTMCG hydrosystems without a subsurface reservoir, as the Weathering Profile was eroded, and high-inertia hydrosystems such as the one studied.
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a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase Weathering
Journal of Hydrology, 2006Co-Authors: Benoit Dewandel, Patrick Lachassagne, Jeanchristophe Marechal, Robert Wyns, N S KrishnamurthyAbstract:Summary The weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas. These Weathering Profiles generally develop under both stable geodynamic conditions (Weathering rate ≫ erosion rate) and a hydrolysing climate. They are composed of thick stratiform layers that follow the paleo-landscape (paleotopography) and thus present a gently dipping sequence at a regional scale. The structure and the hydrodynamic properties of the Weathering Profile of a granitic area (53 km 2 Maheshwaram catchment, state of Andhra Pradesh, India) were characterized in detail and mapped from observations on outcrops, 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones. The structure of the Weathering Profile results from a multiphase process: an ancient Weathering Profile was partly eroded, down to its fissured layer. It was later re-weathered more or less parallel to the current topographic surface. This peculiar structure is linked to the geodynamic history of the Indian Peninsula that underwent alternate Weathering and erosion-dominated phases. The Profile is thus composed, from top to bottom, up to a total depth of 35 m, of sandy regolith saprolite (1–3 m), 10–15 m of laminated saprolite containing unusual preserved fissures and a 15–20 m thick fissured layer. By comparing various case studies in similar terrain, a generalized 3-D geological and hydrogeological conceptual model of granite-type aquifers (granites, gneisses, etc.) is proposed. In granite-type rocks, single Weathering or multiphase Weathering and erosion processes induce similar geological structures. A few main geological differences arise from the comparison of single phase and multiphase Weathering Profiles: (i) in the later, the respective thicknesses of the various layers can be deeply modified, (ii) the ancient fissured layer can be re-weathered, and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures, and (iii) the upper part of the fissured layer is more densely fissured. As a result of the same Weathering processes, the fissures from the fissured layer of single phase or multi-phase Profiles exhibit very similar hydraulic conductivities, and show both a higher density of conductive fissures at the top of the layer. The preserved ancient fissures within the laminated layer of a multiphase Profile are partly obliterated by the recent Weathering; their hydraulic conductivity is thus significantly reduced. Nevertheless, they do significantly contribute to borewell yield. These Weathering-induced fissures provide most of the aquifer permeability. The use of such a conceptual model for the precise geological mapping of the Weathering structure appears to be a prerequisite for groundwater development and management in hard-rock areas as it answers to several key issues.
Benoit Dewandel - One of the best experts on this subject based on the ideXlab platform.
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respective roles of the Weathering Profile and the tectonic fractures in the structure and functioning of crystalline thermo mineral carbo gaseous aquifers
Journal of Hydrology, 2017Co-Authors: Benoit Dewandel, M Alazard, Patrick Lachassagne, Vincent Baillycomte, Renaud Coueffe, Sandrine Grataloup, Bernard Ladouche, Sandra Lanini, Jeanchristophe Marechal, Robert WynsAbstract:Crystalline thermo-mineral and carbo-gaseous (CTMCG) hydrosystems are well known for their economic importance in fields such as thermal, spa activities and natural mineral water (NMW) bottling. Such systems are usually associated with strong structural complexity, which is rarely characterised in detail or robustly. This research focuses on a CTMCG hydrosystem associated with a peri-alpine graben. A multidisciplinary approach with a very large set of data and methods – geological modelling with geophysics and geological data from outcrops and several boreholes, hydrodynamic data, hydrochemistry, hydrogeological and geochemical modelling – reveals very novel results and allows a robust conceptual model to be constructed. The aquifer at the origin of the carbo-gaseous natural mineral water is the 100–125 m-thick fractured stratiform layer of the Weathering Profile of the crystalline rock (granite). It forms a rather large and thick inertial aquifer that can be numerically modelled, in a similar fashion to a porous medium. The majority of tectonic faults length act as impervious boundaries that divide this aquifer into around ten elongated compartments that were precisely delineated. These tectonic faults are permeable only along two small areas that were also precisely located. These permeable zones feed some aquifer compartments with deep, highly mineralised carbo-gaseous water, which mixes with “fresher” water and forms the exploited NMW. These results can be generalised and in particular show a strong opposition between low-inertia CTMCG hydrosystems without a subsurface reservoir, as the Weathering Profile was eroded, and high-inertia hydrosystems such as the one studied.
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a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase Weathering
Journal of Hydrology, 2006Co-Authors: Benoit Dewandel, Patrick Lachassagne, Jeanchristophe Marechal, Robert Wyns, N S KrishnamurthyAbstract:Summary The weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas. These Weathering Profiles generally develop under both stable geodynamic conditions (Weathering rate ≫ erosion rate) and a hydrolysing climate. They are composed of thick stratiform layers that follow the paleo-landscape (paleotopography) and thus present a gently dipping sequence at a regional scale. The structure and the hydrodynamic properties of the Weathering Profile of a granitic area (53 km 2 Maheshwaram catchment, state of Andhra Pradesh, India) were characterized in detail and mapped from observations on outcrops, 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones. The structure of the Weathering Profile results from a multiphase process: an ancient Weathering Profile was partly eroded, down to its fissured layer. It was later re-weathered more or less parallel to the current topographic surface. This peculiar structure is linked to the geodynamic history of the Indian Peninsula that underwent alternate Weathering and erosion-dominated phases. The Profile is thus composed, from top to bottom, up to a total depth of 35 m, of sandy regolith saprolite (1–3 m), 10–15 m of laminated saprolite containing unusual preserved fissures and a 15–20 m thick fissured layer. By comparing various case studies in similar terrain, a generalized 3-D geological and hydrogeological conceptual model of granite-type aquifers (granites, gneisses, etc.) is proposed. In granite-type rocks, single Weathering or multiphase Weathering and erosion processes induce similar geological structures. A few main geological differences arise from the comparison of single phase and multiphase Weathering Profiles: (i) in the later, the respective thicknesses of the various layers can be deeply modified, (ii) the ancient fissured layer can be re-weathered, and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures, and (iii) the upper part of the fissured layer is more densely fissured. As a result of the same Weathering processes, the fissures from the fissured layer of single phase or multi-phase Profiles exhibit very similar hydraulic conductivities, and show both a higher density of conductive fissures at the top of the layer. The preserved ancient fissures within the laminated layer of a multiphase Profile are partly obliterated by the recent Weathering; their hydraulic conductivity is thus significantly reduced. Nevertheless, they do significantly contribute to borewell yield. These Weathering-induced fissures provide most of the aquifer permeability. The use of such a conceptual model for the precise geological mapping of the Weathering structure appears to be a prerequisite for groundwater development and management in hard-rock areas as it answers to several key issues.
Oliver A Chadwick - One of the best experts on this subject based on the ideXlab platform.
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pedogenic origin of dolomite in a basaltic Weathering Profile kohala peninsula hawaii
Geology, 2000Co-Authors: Rosemary C Capo, Charles E Whipkey, J R Blachere, Oliver A ChadwickAbstract:We document stoichiometric dolomite occurring in a nonsaline Quaternary soil on the Kohala peninsula, northwestern Hawaii. Geologic constraints and geochemical and isotopic data confirm that this dolomite is not the result of marine influence or wind-blown dust. The strontium isotopic composition of the dolomite (87Sr/87Sr = 0.7045–0.7048) is indicative of its derivation primarily from the Weathering of basaltic parent material rather than from meteoric water or seawater. Infiltration of soil waters with elevated Mg/Ca (>1) derived from alteration of ferromagnesian minerals such as olivine likely led to dolomitization of early-precipitated soil calcite and/or to direct dolomite precipitation in the Profile. This demonstrates that well-ordered dolomite can form in a nonmarine environment at temperatures <100 °C without undergoing burial diagenesis.
Jeanchristophe Marechal - One of the best experts on this subject based on the ideXlab platform.
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respective roles of the Weathering Profile and the tectonic fractures in the structure and functioning of crystalline thermo mineral carbo gaseous aquifers
Journal of Hydrology, 2017Co-Authors: Benoit Dewandel, M Alazard, Patrick Lachassagne, Vincent Baillycomte, Renaud Coueffe, Sandrine Grataloup, Bernard Ladouche, Sandra Lanini, Jeanchristophe Marechal, Robert WynsAbstract:Crystalline thermo-mineral and carbo-gaseous (CTMCG) hydrosystems are well known for their economic importance in fields such as thermal, spa activities and natural mineral water (NMW) bottling. Such systems are usually associated with strong structural complexity, which is rarely characterised in detail or robustly. This research focuses on a CTMCG hydrosystem associated with a peri-alpine graben. A multidisciplinary approach with a very large set of data and methods – geological modelling with geophysics and geological data from outcrops and several boreholes, hydrodynamic data, hydrochemistry, hydrogeological and geochemical modelling – reveals very novel results and allows a robust conceptual model to be constructed. The aquifer at the origin of the carbo-gaseous natural mineral water is the 100–125 m-thick fractured stratiform layer of the Weathering Profile of the crystalline rock (granite). It forms a rather large and thick inertial aquifer that can be numerically modelled, in a similar fashion to a porous medium. The majority of tectonic faults length act as impervious boundaries that divide this aquifer into around ten elongated compartments that were precisely delineated. These tectonic faults are permeable only along two small areas that were also precisely located. These permeable zones feed some aquifer compartments with deep, highly mineralised carbo-gaseous water, which mixes with “fresher” water and forms the exploited NMW. These results can be generalised and in particular show a strong opposition between low-inertia CTMCG hydrosystems without a subsurface reservoir, as the Weathering Profile was eroded, and high-inertia hydrosystems such as the one studied.
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a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase Weathering
Journal of Hydrology, 2006Co-Authors: Benoit Dewandel, Patrick Lachassagne, Jeanchristophe Marechal, Robert Wyns, N S KrishnamurthyAbstract:Summary The weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas. These Weathering Profiles generally develop under both stable geodynamic conditions (Weathering rate ≫ erosion rate) and a hydrolysing climate. They are composed of thick stratiform layers that follow the paleo-landscape (paleotopography) and thus present a gently dipping sequence at a regional scale. The structure and the hydrodynamic properties of the Weathering Profile of a granitic area (53 km 2 Maheshwaram catchment, state of Andhra Pradesh, India) were characterized in detail and mapped from observations on outcrops, 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones. The structure of the Weathering Profile results from a multiphase process: an ancient Weathering Profile was partly eroded, down to its fissured layer. It was later re-weathered more or less parallel to the current topographic surface. This peculiar structure is linked to the geodynamic history of the Indian Peninsula that underwent alternate Weathering and erosion-dominated phases. The Profile is thus composed, from top to bottom, up to a total depth of 35 m, of sandy regolith saprolite (1–3 m), 10–15 m of laminated saprolite containing unusual preserved fissures and a 15–20 m thick fissured layer. By comparing various case studies in similar terrain, a generalized 3-D geological and hydrogeological conceptual model of granite-type aquifers (granites, gneisses, etc.) is proposed. In granite-type rocks, single Weathering or multiphase Weathering and erosion processes induce similar geological structures. A few main geological differences arise from the comparison of single phase and multiphase Weathering Profiles: (i) in the later, the respective thicknesses of the various layers can be deeply modified, (ii) the ancient fissured layer can be re-weathered, and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures, and (iii) the upper part of the fissured layer is more densely fissured. As a result of the same Weathering processes, the fissures from the fissured layer of single phase or multi-phase Profiles exhibit very similar hydraulic conductivities, and show both a higher density of conductive fissures at the top of the layer. The preserved ancient fissures within the laminated layer of a multiphase Profile are partly obliterated by the recent Weathering; their hydraulic conductivity is thus significantly reduced. Nevertheless, they do significantly contribute to borewell yield. These Weathering-induced fissures provide most of the aquifer permeability. The use of such a conceptual model for the precise geological mapping of the Weathering structure appears to be a prerequisite for groundwater development and management in hard-rock areas as it answers to several key issues.
Patrick Lachassagne - One of the best experts on this subject based on the ideXlab platform.
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respective roles of the Weathering Profile and the tectonic fractures in the structure and functioning of crystalline thermo mineral carbo gaseous aquifers
Journal of Hydrology, 2017Co-Authors: Benoit Dewandel, M Alazard, Patrick Lachassagne, Vincent Baillycomte, Renaud Coueffe, Sandrine Grataloup, Bernard Ladouche, Sandra Lanini, Jeanchristophe Marechal, Robert WynsAbstract:Crystalline thermo-mineral and carbo-gaseous (CTMCG) hydrosystems are well known for their economic importance in fields such as thermal, spa activities and natural mineral water (NMW) bottling. Such systems are usually associated with strong structural complexity, which is rarely characterised in detail or robustly. This research focuses on a CTMCG hydrosystem associated with a peri-alpine graben. A multidisciplinary approach with a very large set of data and methods – geological modelling with geophysics and geological data from outcrops and several boreholes, hydrodynamic data, hydrochemistry, hydrogeological and geochemical modelling – reveals very novel results and allows a robust conceptual model to be constructed. The aquifer at the origin of the carbo-gaseous natural mineral water is the 100–125 m-thick fractured stratiform layer of the Weathering Profile of the crystalline rock (granite). It forms a rather large and thick inertial aquifer that can be numerically modelled, in a similar fashion to a porous medium. The majority of tectonic faults length act as impervious boundaries that divide this aquifer into around ten elongated compartments that were precisely delineated. These tectonic faults are permeable only along two small areas that were also precisely located. These permeable zones feed some aquifer compartments with deep, highly mineralised carbo-gaseous water, which mixes with “fresher” water and forms the exploited NMW. These results can be generalised and in particular show a strong opposition between low-inertia CTMCG hydrosystems without a subsurface reservoir, as the Weathering Profile was eroded, and high-inertia hydrosystems such as the one studied.
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a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase Weathering
Journal of Hydrology, 2006Co-Authors: Benoit Dewandel, Patrick Lachassagne, Jeanchristophe Marechal, Robert Wyns, N S KrishnamurthyAbstract:Summary The weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas. These Weathering Profiles generally develop under both stable geodynamic conditions (Weathering rate ≫ erosion rate) and a hydrolysing climate. They are composed of thick stratiform layers that follow the paleo-landscape (paleotopography) and thus present a gently dipping sequence at a regional scale. The structure and the hydrodynamic properties of the Weathering Profile of a granitic area (53 km 2 Maheshwaram catchment, state of Andhra Pradesh, India) were characterized in detail and mapped from observations on outcrops, 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones. The structure of the Weathering Profile results from a multiphase process: an ancient Weathering Profile was partly eroded, down to its fissured layer. It was later re-weathered more or less parallel to the current topographic surface. This peculiar structure is linked to the geodynamic history of the Indian Peninsula that underwent alternate Weathering and erosion-dominated phases. The Profile is thus composed, from top to bottom, up to a total depth of 35 m, of sandy regolith saprolite (1–3 m), 10–15 m of laminated saprolite containing unusual preserved fissures and a 15–20 m thick fissured layer. By comparing various case studies in similar terrain, a generalized 3-D geological and hydrogeological conceptual model of granite-type aquifers (granites, gneisses, etc.) is proposed. In granite-type rocks, single Weathering or multiphase Weathering and erosion processes induce similar geological structures. A few main geological differences arise from the comparison of single phase and multiphase Weathering Profiles: (i) in the later, the respective thicknesses of the various layers can be deeply modified, (ii) the ancient fissured layer can be re-weathered, and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures, and (iii) the upper part of the fissured layer is more densely fissured. As a result of the same Weathering processes, the fissures from the fissured layer of single phase or multi-phase Profiles exhibit very similar hydraulic conductivities, and show both a higher density of conductive fissures at the top of the layer. The preserved ancient fissures within the laminated layer of a multiphase Profile are partly obliterated by the recent Weathering; their hydraulic conductivity is thus significantly reduced. Nevertheless, they do significantly contribute to borewell yield. These Weathering-induced fissures provide most of the aquifer permeability. The use of such a conceptual model for the precise geological mapping of the Weathering structure appears to be a prerequisite for groundwater development and management in hard-rock areas as it answers to several key issues.
