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The fracture permeability of Hard Rock Aquifers is due neither to tectonics, nor to unloading, but to weathering processes

Abstract : The hydrogeology of superficial (∼0-100 m b.g.l.) Hard Rock Aquifers (HRA; i.e. plutonic and metamorphic rocks) has so far been dominated by a few concepts considered to be relevant by a large majority of the HRA community. One of the most fundamental of these concepts is that their (secondary, fissure/fracture) permeability is either of tectonic origin or related to unloading processes. We will show that these genetic concepts are erroneous. We will demonstrate how the hydraulic conductivity of HRAs is a consequence of the (palaeo) weathering processes, with a stratiform fissured layer located immediately below the unconsolidated saprolite and, to a lesser extent, a verticalized fissured layer at the periphery of (or within) pre-existing discontinuities (veins, joints, ancient faults, lithological contacts, etc.). This result opens up large perspectives in terms of applied hydrogeology and applied geology. A specifically dedicated methodological toolkit well adapted to the operational survey, management and protection of HRAs is briefly presented.
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https://hal-brgm.archives-ouvertes.fr/hal-00677122
Contributor : Anne-Marie Pouget <>
Submitted on : Wednesday, March 7, 2012 - 12:14:24 PM
Last modification on : Friday, April 2, 2021 - 11:06:02 AM

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Patrick Lachassagne, Robert Wyns, Benoît Dewandel. The fracture permeability of Hard Rock Aquifers is due neither to tectonics, nor to unloading, but to weathering processes. Terra Nova, Wiley-Blackwell, 2011, 23 (3), pp.145-161. ⟨10.1111/j.1365-3121.2011.00998.x⟩. ⟨hal-00677122⟩

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