Search publications of the members of the Royal Belgian institute of natural Sciences
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Naturally CO2-rich water springs in Belgium evidencing complex subsurface interactions
- Numerous naturally CO2-rich mineral water springs, locally called ‘pouhons’, occur in southeast Belgium. These are oversaturated in CO2 (up to 4g/L) and have attracted economic, touristic and scientific interest for centuries. Water sources occur within Palaeozoic rocks of the Rhenohercynian deformation zone, a fold-and-thrust belt at the north of the Variscan orogeny in central Europe. Many occurrences are concentrated in the Cambro-Ordivician Stavelot-Venn massif. A widely accepted model, supported by H-O isotopic signatures, is that sources are primarily fed by meteoric water, which infiltrates through Quaternary sediments, then reaching Lower Palaeozoic rocks to meet the mineral and CO2 source at unknown depth. Different ideas for the origin of CO2 are grouped in two main hypotheses: a) generation by dissolution of carbonate rocks and/or nodules, and b) volcanic degassing related to the neighbouring Eifel area in Germany. These well-known interpretations are mostly based on geochemical studies that are dispersed and poorly accessible. These have now been gathered in the light of new sampling campaigns, allowing to revisit and compare the views of earlier authors. We also for the first time include the geotectonic setting of the region. Carbonate rocks in the region are represented by Lower Carboniferous and Middle Devonian limestones. Depending on the assumed structural evolution for this foreland fold-an-thrust belt, these may occur at >2 km depth below the Stavelot-Venn massif. Carbonate nodules are present in other formations, but their limited volume is unlikely to originate high and long-lived quantities of CO2. Springs enriched in CO2 are also common in the volcanic Eifel area, with presence of mantle CO2 well established. The supposed extension of the Eifel plume would allow for a magmatic CO2 source below the Stavelot-Venn massif from degassing of the plume (>50 km deep), or of an unknown shallower magmatic reservoir. Available stable and noble isotopes point to a mixed carbonate-magmatic origin. If considering the presence of limestones at depth, meteoric water should infiltrate at least 2 km. Known deep-rooted faults are thought to act as preferential groundwater pathways. However, such deep circulation is incompatible with the low temperatures of springs (~10oC), unless the ascent is slow enough to fully dissipate heat prior to resurfacing. Another possibility is that meteoric water does not infiltrate as deep, with CO2 being transported upwards to meet groundwaters at shallower depths. The presence of CO2 surface leaks, locally called ‘mofettes’, could be evidence of such relatively shallow availability of CO2. The evaluation of existing hypotheses highlights complex subsurface processes that involve water infiltration, CO2 assimilation and water resurfacing in southeast Belgium (Figure 1). As such, this review is an important guide for the newly launched sampling campaigns. Acknowledgements This work is part of two research projects: GeoConnect³d-GeoERA that has received funding by the European Union’s Horizon 2020 research and innovation programme under grant agreement number 731166, and ROSEAU project, as part of the Walloon program «Doctorat en Entreprise», co-funded by the SPW Région Wallonne of Belgium and the company Bru-Chevron S.A. (Spadel group), under grant number 7984. References Barros, R., Defourny, A., Collignon, A., Jobé, P., Dassargues, A., Piessens, K. & Welkenhuysen, K., 2021. A review of the geology and origin of CO2 in mineral water springs in east Belgium. Geologica Belgica, 24 (1-2), p.17-31. https://doi.org/10.20341/gb.2020.023
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Towards a dynamic and interdisciplinary assessment for the sustainable management of geological resources
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Geophysical well log correlations in the Quaternary deposits of the Campine area, northern Belgium
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Areas Prone to Land Subsidence and their Evolutions in Belgium During the Last 30 Years
- PSInSAR analyses across Belgium using ERS 1-2, ENVISAT, TerraSAR-X and Sentinel 1 allowed to follow several ground movements areas during the last three decades. Several areas of regional importance are affected by land subsidence processes that have been observed during this period (i.e. the alluvial plain of the Schelde estuary in Antwerpen, a large area in the West Flanders province and one around Merchtem area). Other land subsidence areas associated to old coal mining both in Flanders (Campine basin) and Wallonia (Hainaut and Liège province) are affected by progressive uplifting conditions linked to the mining aquifer piezometric rebound. It is extremely important to follow the spatio-temporal behavior of these phenomena to forecast their influences and their effects on the urban developments.
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Land Subsidence Observed in the Merchtem Area (Flanders) – 30 Years of SAR Data Associated to Groundwater Withdrawal?
- A land subsidence affecting several towns at the joining limits of the Belgian Provinces of East Flanders, Antwerp and Flemish Brabant is followed during the last three decades. ERS 1–2, ENVISAT, TerraSAR-X and Sentinel-1A satellites SAR scenes were processed from 1992 till October 2020 to map the land subsidence evolution. The subsidence corresponds to a surface area of 220 km 2 during the ERS 1/2 time interval distributed over three distinct subsidence bowls. During the ENVISAT and TerraSAR-X time interval, only one residual subsidence bowl was mapped affecting a surface area of about 70 km 2 . Several towns (Londerzeel and Steenhuffel) remained in the center of the subsidence bowl. The annual average negative velocity values range between −5.99 and −0.5 mm/year. During the Sentinel-1A period, the subsidence bowl has lost half of its surface reaching 36 km 2 . The LOS velocity values have also decreased during the period 2016–2020.
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Archeo-antropologisch assessment van de menselijke resten aangetroffen tijdens de werfbegeleiding ‘Antwerpen Onze-Lieve-Vrouwekathedraal (2020I407)’ (2020-2021)
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Terreininterventie en archeo-antropologische detailstudie van menselijke resten uit WO I afkomstig van een toevalsvondst te Wijtschate – Voormezelestraat (2021) (TV ID 7365)
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A pathological ulna of Amurosaurus riabinini from the Upper Cretaceous of Far Eastern Russia
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Fouilles 1995-1996 à l'allée couverte de Lamsoul (Jemelle, Rochefort, Province de Namur)
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Rebecq/Rebecq-Rognon : un site mésolithique au lieu-dit "Le Spinoi"
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Namur/Malonne : sépulture collective du Mésolithique ancien au “Petit Ri”
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Sur les traces des premiers agriculteurs de nos régions : de la Hesbaye à la Moselle
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Op het spoor van de eerste landbouwers uit onze streken
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Les monuments mégalithiques de Lamsoul, "Wéris I" et "Wéris II". Un essai de comparaison.
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Recyclage ou charognage de matières premières dans le Groupe de Blicquy : une explication alternative à la présence de Blicquiens à Darion
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. Sur les traces de l'orge et du pavot : nouvelles données carpologiques sur l'agriculture danubienne de Hesbaye, dans un cadre européen
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Le mégalithisme de la Famenne à la lumière des recherches récentes et dans un contexte européen
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Beloeil/Aubechies : sauvetage de structures rubanées à "Coron Maton"
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Geer/Omal : relevé de fosses rubanées rue Stiernet
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Rochefort/Jemelle : fouilles 1995-1996 au monument mégalithique de Lamsoul
