Airborne gamma-ray spectrometry to quantify chemical erosion processes |
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| Authors: | F Carrier B Bourdon Pili C Truffert R Wyns |
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| Institution: | aBRGM-CDG / Modélisation et Applications-45060 Orléans La Source, France;bIPGP-Laboratoire de Géochimie et Cosmochimie-75252 Paris cedex 05, France;cCEA-Département Analyse, Surveillance, Environnement-91680 Bruyères-le-Châtel, France |
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| Abstract: | Airborne gamma-ray spectrometry data (uranium, potassium and thorium contents) reveal geochemical heterogeneities within the monolithological Hyrôme watershed (ca. 150 km2) in the Armorican massif (western France). Our observations and computations provide important constraints on the spatial distribution and the associated magnitudes of chemical erosion processes at the scale of a small watershed. Two distinct, partially preserved, weathering profiles exhibit a strong correlation between regolith evolution and airborne-derived K/Th ratios, suggesting that the variability is linked to supergene processes. Using both airborne data and laboratory measurements on rock samples, the total net export of potassium has been estimated at 422 ± 50 kg/m2 and the chemical weathering rate of potassium at 17 ± 2 kg/km2/a. |
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| Keywords: | Airborne gamma-ray spectrometry Weathering profile Chemical erosion rates Watershed |
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