The isotopic and chemical composition of CO2-rich thermal waters in the Mont-Dore region (Massif-Central, France)

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doi: 10.1016/S0883-2927(97)00010-3
Authors:Pauwels, H.; Fouillac, C.; Goff, F.; Vuataz, F. D.
Author Affiliations:Primary:
BRGM, Research Division, Orleans, France
Other:
Los Alamos National Laboratory, United States
University of Neuchatel, Switzerland
Volume Title:Applied Geochemistry
Source:Applied Geochemistry, 12(4), p.411-427. Publisher: Pergamon, Oxford-New York-Beijing, International. ISSN: 0883-2927
Publication Date:1997
Note:In English. 60 refs.; illus., incl. 7 tables, sketch map
Summary:Samples collected between 1974 and 1986 were examined. The fluids emerge from Quaternary volcanics or Palaeozoic granite at 4-62°C; they are of meteoric origin and can be classified as bicarbonate, mixed bicarbonate-chloride and acid-sulphate; only two contain enough Cl- to be considered 'mature'. It was previously shown that all contain partly mantle-derived CO2 gas, and that the gas phase and bicarbonate-chloride waters are separated at depth. Mineralized fluids circulate at depth and undergo several processes during their ascent so the CO2-rich gas phase can be partly dissolved in freshwater, or in deep fluids after dilution. This leads to dissolution of surrounding rocks, a process which is discussed. Dissolution of S-bearing minerals has also been demonstrated. The presence of the CO2-rich gas phase also leads to isotope exchange between CO2 and H2O. Some mineralized fluids are less affected by these processes than others, in which case they display the chemical and isotopic characteristics of the original deep fluids. Although the applicability of geothermometry to these waters is limited, some geothermometers can be used to estimate the T of the deep fluids from the chemical composition of the less modified fluids. It seems that fluids emerging from volcanics in the Dordogne valley are ∼ 100-130°C at depth, while those issuing from the granite at Saint-Nectaire are 160-175°C at depth. [R.E.S.]
Subjects:Alkali metals; Alkaline earth metals; Bicarbonate ion; Boron; Bromine; Calcium; Carbon dioxide; Chemical composition; Chloride ion; Chlorine; Cooling; D/H; Deuterium; Discharge; Fresh water; Geochemistry; Geologic thermometry; Halogens; Hydrochemistry; Hydrogen; Isotope ratios; Isotopes; Lithium; Magnesium; Major elements; Metals; Meteoric water; Mineralization; Minor elements; Mixing; O-18; O-18/O-16; Oxygen; PH; Potassium; Radioactive isotopes; S-34; S-34/S-32; Sampling; Sodium; Solutes; Solution; Springs; Sr-87/Sr-86; Stable isotopes; Strontium; Sulfate ion; Sulfur; Temperature; Thermal waters; Tritium; Water; Water wells; Central Massif; Europe; France; Mont-Dore France; Puy-de-Dome France; Western Europe; Chaudefour Valley; Dordogne Valley; Silicon dioxide; Wells
Abstract Numbers:98M/2894
Record ID:1997062995
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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