Robert Wyns

Retired from French Geological Survey · Georessources

Hard rocks (HR) 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. Since about 15 years, i...

We developed a high-resolution MIKE SHE/MIKE 11 model of a 231.3 ha headwater catchment in the granitic uplands of the French Massif Central to estimate the contribution of groundwater upwelling to the water balance of the Dauges mire, an acidic valley mire of international importance for nature conservation. We estimated that groundwater upwelling...

Une campagne de terrain réalisée de 2017 à 2019 dans le massif cristallin des Vosges dans le cadre d’une étude sur les ressources en eau souterraine a permis de faire l’inventaire des anciens profils d’altération latéritique de ce massif. On observe ainsi un profil intra-Carbonifère, un profil infrapermien, un profil infratriasique, et un profil pr...

L'altération météorique a été depuis longtemps reliée aux ceintures climatiques telles que nous les connaissons et considérée comme contrôlée essentiellement par le climat. La multiplication récente des datations de profils latéritiques et le développement du pa-léomagnétisme, permettant de connaitre la paléolatitude d'un continent à une époque don...

Abstract. The contribution of groundwater to the hydrology of hard rock regions has long been assumed to be small. This is being progressively challenged and conceptual hydrological models of headwater wetlands in these regions may need to be revised. We developed a high-resolution MIKE SHE/MIKE 11 model of a 231.3 ha headwater catchment in the gra...

The post-orogenic evolution of the European Variscan basement remains difficult to constrain due to the absence of postorogenic sedimentary records. One of the current ways to access this history is to constrain the thermal evolution of these basement areas through indirect methods such as low-temperature thermochronology (LTT) thermal modelling. I...

Le début du Crétacé a été marqué en Europe occidentale par le développement de paléoaltérations de type latéritique. Les argiles rouges à cuirasse ferrugineuse pisolitique du graben de Saint-Maixent-l’École (seuil du Poitou) peuvent constituer un exemple-témoin de ce type d’altération. Toutefois, leur âge reste inconnu et leur position stratigraphi...

70 % du territoire métropolitain est couvert par les formations superficielles ou formations du " Régolithe " mais seulement 40 % sont cartographiées et 10 % possèdent une information décrivant leur épaisseur (données obtenues par modélisation) ou leurs propriétés physico-chimiques (BRGM, Rapport d’activité 2017). Pourtant, elles font l’objet d’un...

Les roches cristallines ou roches « de socle » sont des roches en général anciennes, de deux types principaux : les roches plutoniques, telles que les granites, et les roches métamorphiques, comme les gneiss, schistes, micaschistes... Elles constituent le soubassement de l'ensemble des continents et y sont donc très communes. Leurs propriétés hydro...

The Penmarc’h granitic coastal domain, SW Brittany (Western France), offers the opportunity to address the little investigated issue of erosional processes in a granitic coastal context. From land to sea, the granitic coast is composed of 1) an aerial marine terrace ( <4 km), 2) a large shore platform ( <800 m), 3) an extensive submarine rocky plat...

The discovery, during the last 1990s, of a thick fractured layer below the saprolite in lateritic profiles developed on crystalline rocks has resulted in a redefinition of hardrock aquifers. During the first 2000s, numerous researches were conducted in different continents in order to validate the new concept of stratiform hardrock aquifer linked t...

Hard Rocks (HR) 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, large parts of Eurasia, etc.. Well yields from hard rock aquifers are modest compared to those from other types o...

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 a strong structural complexity, which is rarely characterized in detail or robustly. This research focused on a CT...

From the study of the Strengbach and Ringelbach watersheds we propose to illustrate the interest of combining the geochemical tracing and geochemical modeling approaches on surface and deep borehole waters, to decipher the diversity of the water flow and the associated water–rock interactions in such elementary mountainous catchments. The results p...

Crystalline thermo-mineral and carbo-gaseous (CTMCG) systems are associated to specific geological structures, such as faulted bedrock, allowing the upward flow of deep hot/mineral fluids and/or gases. Although conceptual models based on groundwater flow through faults can be relevant, the 3-D extension and hydraulic properties of such aquifers exp...

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 CTMC...

The morphology of the Pyrenees is characterized by the presence of high-elevation, low-relief surfaces. The origin of these Lower-Miocene surfaces is still debated. Two major interpretations have been proposed, both assuming that these surfaces are remnants of a single composite planation surface. The first interpretation proposes that this surface...

Borehole CDB1 (675.05m) crosses the deepest Cenozoic sedimentary basin of the Armorican Massif, the Rennes Basin, to reach the underlying basement at a depth of 404.92m, made up of the Late Neoproterozoic to Early Cambrian Brioverian Group, weathered down to 520m depth. The basin's Cenozoic deposits are divided into seven formations, ranging from E...

Hard Rocks (HR; plutonic and metamorphic rocks) constitute most of the emerged continents, as in shields areas of Africa, India, North and South America, Australia, Europe, etc. They are or were exposed to deep weathering processes. The result is weathering profiles which, when not later partly or totally eroded, can reach a thickness of several te...

The Saint-Galmier (Massif central, France) CO2 rich natural mineral waters are known and drunk at least since the Roman times and are bottled since more than two centuries under the "Badoit" sparkling mineral water brand (Danone Group). A synthesis, processing, and interpretation of a large data set from this hydrogeological area has been performed...

Mineralization processes in ultramafic laterites are partly controlled by fluid flow regimes in these porous and permeable systems. During weathering of ultramafic rocks, exothermic chemical reactions, such as hydration of olivine, may generate shallow subsurface (< 200 m) temperatures of several tens of °C. The reaction-induced fracturing leads to...

During shallow subsurface (< 200 m depth) weathering processes, temperatures may reach several tens of deg C as a result of exothermic chemical reactions, such as hydration of olivine in ultramafic rocks or chloritization of biotite in granitic rocks. These mineralogical transformations enhance mineral fracturing, and the growth of fracture network...

L’altération soustractive des roches cristallines met en jeu des réactions d’oxydation et d’hydratation fortement exothermiques au sein des profils latéritiques : l’altération complète d’un mètre cube de granite libère théoriquement plusieurs centaines de mégajoules d’énergie sous forme de chaleur. Lorsque la perméabilité du milieu (arène ou horizo...

During shallow subsurface (< 200 m depth) weathering processes, temperatures may reach several tens of °C as a result of exothermic chemical reactions, such as hydration of olivine in ultramafic rocks or chloritization of biotite in granitic rocks. These mineralogical transformations enhance mineral fracturing, and the growth of fracture networks l...

L'altération soustractive des roches cristallines met en jeu des réactions d'oxydation et d'hydratation fortement exothermiques au sein des profils latéritiques : l'altération complète d'un mètre cube de granite libère théoriquement plusieurs centaines de mégajoules d'énergie sous forme de chaleur. Lorsque la perméabilité du milieu (arène ou horizo...

Keywords: Géologie , Altération, Formations superficielles, Propriétés physiques, Hydrogéologie, Géophysique, Sismique, SASW, Résonance Magnétique protonique, Géotechnique, Pénétromètre dynamique, Limites d’Atterberg, Valeur au bleu

Flat high-elevation surfaces in the Pyrenees are defined by thick weathered horizons that were developed from granitic lithology. We analysed such horizons in detail within two areas: the Bordères-Louron granite and the Aston massif. They are characterized by a lower fissured zone overlain by unconsolidated saprolite. Mapping these horizons allows...

Weathering profiles are mostly studied on their upper part (crust, saprolite) where leaching and concentration/precipitation of valuable element occur. For water resource and hydrocarbon purpose, the transition between saprolite and fresh basement is of utmost importance. Here is found the fissured layer, a highly fissured bedrock that it favorable...

Most Hard Rocks are or were exposed to deep weathering processes, as in large shields of Africa, India, North and South America, Australia and Europe. It turns out that the hydraulic conductivity of hard rocks is inherited from these weathering processes, within their Stratiform Fissured Layer located immediately below the unconsolidated weathered...

GÉLY J.-P., HANOT F. (dir.), AMÉDRO F., BERGERAT F., DEBEGLIA N., DELMAS J., DEROIN J.-P., DOLIGEZ B., DUGUÉ O., DURAND M., EDEL J.-B., GAUDANT J., HANZO M., HOUEL P., LORENZ J., ROBASZYNSKI F., ROBELIN C., THIERRY J., VICELLI J., VIOLETTE S., VRIELINCK B., WYNS R. et coll. (2014). Le Bassin parisien, un nouveau regard sur la géologie. Bull. Inf. G...

Le sélénium est un élément essentiel au bon fonctionnement du métabolisme humain, néanmoins son déficit ou son excès provoque des perturbations de l'état sanitaire. Afin de connaitre l'origine de cet élément dans les eaux souterraines, diverses études ont été réalisées qui ont montré une origine naturelle pour cet élément. Une étude a été menée de...

Terra Nova, 23, 145–161, 2011AbstractThe 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)...

http://home.agh.edu.pl/~iah2010/extab/ext-abstract/460-iah2010_wyns.pdf

A country-scale (1:1,000,000) methodology has been developed for hydrogeologic mapping of hard-rock aquifers (granitic and metamorphic rocks) of the type that underlie a large part of the African continent. The method is based on quantifying the "useful thickness" and hydrodynamic properties of such aquifers and uses a recent conceptual model devel...

Hard rocks (granites, metamorphic rocks) occupy large areas of Africa and India. Well yields from hard rock aquifers are modest, commonly 2–3 m 3 ·h -1 compared to those from other types of aquifers. However, these resources are geographically widespread and well suited to scattered settlement and small-to medium-size cities. They contribute greatl...

A palaeomagnetic study was carried out on the Borne de Fer ferricrete in north-eastern France, close to the Luxembourg border. This ferricrete is overlain by kaolinitic red clay and caps a silto-argilaceous saprolite 15 to 40 m thick showing weathering features, evolution of the clay minerals from the base to the top and karstic solution pipes bene...

When a mantle plume rises and impinges on the base of the lithosphere, it expectably produces variations in surface topography. Taking into consideration a realistic mantle rheology, plume ascent rates can reach tens to hundreds of metres per year, whereupon the impingement of the plume head at the base of the lithosphere can be considered as an "i...