Titre :

(Ra-228/Ra-226) ratios in hydrothermal carbonates and the origin of radium in CO2-rich waters of the Lodeve Basin (South of France)

Auteur(s) :

Condomines, Michel [Auteur correspondant]
Géosciences Montpellier
Lloret, Emily [Auteur]
Laboratoire Génie Civil et Géo-Environnement [Béthune] [LGCgE]
Seidel, Jean-Luc [Auteur]
Hydrosciences Montpellier [HSM]
Lopez, Michel [Auteur]
Bassins

Titre de la revue :

Chemical Geology

Pagination :

46-53

Éditeur :

Elsevier

Date de publication :

2014-04-24

ISSN :

0009-2541

Mot(s)-clé(s) en anglais :

Radium isotopes
Hydrothermal carbonates
CO2-rich waters
Ra-226-Pb-210 dating
Ra-228-Th-228 dating
U-series

Discipline(s) HAL :

Planète et Univers [physics]/Sciences de la Terre/Géochimie
Sciences de l'environnement/Milieux et Changements globaux

Résumé en anglais : [en]

The present study reports data on CO2-rich geothermal waters and their associated carbonate deposits from the SW part of the Permian Lodève Basin (South of France). Both waters and carbonates are enriched in 226Ra, with ...
Lire la suite >The present study reports data on CO2-rich geothermal waters and their associated carbonate deposits from the SW part of the Permian Lodève Basin (South of France). Both waters and carbonates are enriched in 226Ra, with activities up to 2.2 Bq/L and 3.5 Bq/g respectively. A series of carbonate samples precipitated around the studied wells since 1990 were dated through the 226Ra-210Pb and 228Ra-228Th methods, and the results are discussed in a new Concordia diagram. While both methods give comparable dates for many samples, Ra-Pb ages are sometimes much older than Ra-Th ages. We propose that these discrepancies result from the adsorption of 222Rn daughter nuclides in such a Rn-rich environment. The (228Ra/226Ra)0 activity ratios calculated at the time of deposition are remarkably constant for about 12 years, suggesting the presence of a steady-state aquifer. The low (228Ra/226Ra)0 ratios (0.348 ± 0.008) are best explained if most of the Ra derives from the Cambrian carbonate series (mainly dolostone) underlying the Permian Basin, which have low Th/U and similar (228Ra/226Ra) ratios. This study suggests that Ra and other alkaline-earth elements do not necessarily originate from the rocks surrounding the deep geothermal reservoir, but rather may be introduced into the CO2-rich water during its transfer towards the surface and interaction with carbonate rocks.Lire moins >

Langue :

Anglais

Comité de lecture :

Oui

Audience :

Internationale

Vulgarisation :

Non

Collections :

• Laboratoire Génie Civil et géo-Environnement (LGCgE) - ULR 4515

Source :

Harvested from HAL

Date de dépôt :

2025-02-26T13:29:23Z