Soil gas radon emanometry: A tool for delineation of fractures for groundwater in granitic terrains

Reddy, D. V.; Sukhija, B. S.; Nagabhushanam, P.; Reddy, G. K.; Kumar, Devender; Lachassagne, Patrick

doi:10.1016/j.jhydrol.2006.02.033

Cited by 22 publications

(5 citation statements)

References 11 publications

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“…In the second case (no or unsaturated SFL), techniques for well siting such as lineament analysis, geophysics and radon surveys (Lachassagne et al 2001b;Reddy et al 2006), can be used. As weathering is also the main driver of aquifer development in this context, linking open discontinuities to past or recent tectonic events and to recent or paleo stress-field data is not of interest, as indirectly shown by Holland and Witthüser (2011).…”

Section: Strategy For Water-well Siting In Hard-rock Aquifersmentioning

confidence: 99%

Review: Hydrogeology of weathered crystalline/hard-rock aquifers—guidelines for the operational survey and management of their groundwater resources

2021

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Hard rocks or crystalline rocks (i.e., plutonic and metamorphic rocks) constitute the basement of all continents, and are particularly exposed at the surface in the large shields of Africa, India, North and South America, Australia and Europe. They were, and are still in some cases, exposed to deep weathering processes. The storativity and hydraulic conductivity of hard rocks, and thus their groundwater resources, are controlled by these weathering processes, which created weathering profiles. Hard-rock aquifers then develop mainly within the first 100 m below ground surface, within these weathering profiles. Where partially or noneroded, these weathering profiles comprise: (1) a capacitive but generally low-permeability unconsolidated layer (the saprolite), located immediately above (2) the permeable stratiform fractured layer (SFL). The development of the SFL’s fracture network is the consequence of the stress induced by the swelling of some minerals, notably biotite. To a much lesser extent, further weathering, and thus hydraulic conductivity, also develops deeper below the SFL, at the periphery of or within preexisting geological discontinuities (joints, dykes, veins, lithological contacts, etc.). The demonstration and recognition of this conceptual model have enabled understanding of the functioning of such aquifers. Moreover, this conceptual model has facilitated a comprehensive corpus of applied methodologies in hydrogeology and geology, which are described in this review paper such as water-well siting, mapping hydrogeological potentialities from local to country scale, quantitative management, hydrodynamical modeling, protection of hard-rock groundwater resources (even in thermal and mineral aquifers), computing the drainage discharge of tunnels, quarrying, etc.

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Section: Strategy For Water-well Siting In Hard-rock Aquifersmentioning

confidence: 99%

Review: Hydrogeology of weathered crystalline/hard-rock aquifers—guidelines for the operational survey and management of their groundwater resources

2021

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“…) from geological, radon (e.g. Lachassagne et al ., ; Reddy et al ., ) and geophysical surveys and the drilling of 39 boreholes (47–124 m deep) as part of a 1999–2008 groundwater exploration programme (Frissant et al ., ). Mayotte, the southernmost island in the Comoros archipelago, with a surface area of 374 km 2 , is a French Overseas Department with about 200 000 inhabitants.…”

Section: Introductionmentioning

confidence: 99%

High‐resolution conceptual hydrogeological model of complex basaltic volcanic islands: a Mayotte, Comoros, case study

et al. 2014

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International audienceWe present a high-resolution conceptual hydrogeological model for complex basaltic volcanic islands based on Mayotte Island in the Comoros. Its geological structure and hydrogeological functioning are deduced from a large dataset: geological mapping, geophysics, some forty new boreholes, piezometric data, hydraulic conductivity, hydrochemical data, etc. We describe previously unknown deep cut-and-fill palaeovalleys. The resulting conceptual geological and hydrogeological model of the island is very different from the Hawaiian model, in that it lacks a low-elevation basal aquifer and dyke-impounded high-level aquifers. It is closer to the Canary Islands model, which has, however, not yet been described at a high-resolution scale. It does not have a continuous aquifer, but rather a discontinuous succession of perched aquifers separated by aquicludes and aquitards. This results more from the complex geological structure of the island, which has experienced several phases of volcanism, erosion and weathering, than from its age, but is also a result of the high-resolution scale of the model. High-resolution conceptual modelling is now necessary to solve problems of applied geology and hydrogeology

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“…The EM anomalies on fractured zones are associated with radon maxima. However, further studies by Reddy et al (2006) support the view of Pointet and Wright and Carruthers. In this regard Lachassagne et al (2001) clarify that higher radon concentration can be observed only where hydraulically active fractures are present.…”

Section: Radon Gas Measurementmentioning

confidence: 56%

Integrated geophysical survey

2015

Groundwater Geophysics in Hard Rock

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Soil gas radon emanometry: A tool for delineation of fractures for groundwater in granitic terrains

Cited by 22 publications

References 11 publications

Review: Hydrogeology of weathered crystalline/hard-rock aquifers—guidelines for the operational survey and management of their groundwater resources

Review: Hydrogeology of weathered crystalline/hard-rock aquifers—guidelines for the operational survey and management of their groundwater resources

High‐resolution conceptual hydrogeological model of complex basaltic volcanic islands: a Mayotte, Comoros, case study

Integrated geophysical survey

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