Abstract
Helium and carbon isotope analyses are reported for groundwater samples from the Rhenish Massif, the Rhine Graben and Black Forest. Most of the samples contain a resolvable component of mantle-derived 3He, which varies from < 1\% up to ∼ 70\% of the total He present. The presence of mantle-derived 3He in deep groundwaters is discussed in relation to the distribution of surface volcanics, tectonic activity, regional seismicity and heat flow. Although there is a crude relationship between the presence of mantle-derived 3He and surface volcanics, 3He occurs over a larger geographic area than do surface volcanics. A correlation between the distribution pattern of mantle-derived 3He and tectonic activity, local seismicity or heat flow is not apparent from the present data set. δ13CCO2-values for CO2-rich mineral waters vary from - 25 to - 5‰ (PDB) and indicate a contribution of organicderived carbon to the CO2-bearing groundwater. In geographically restricted areas simple mixing relationships exist between the isotope composition of carbon and that of helium. This can be approximated by a two-component model, where a \"magmatic\" end-member with ( R R1)c6 and -8‰<δ13CCO2<- 5‰ is diluted by a \"crustal\" end-member with ( R Ra)c<0.1 and δ13CCO2<-15‰. The observed relationship between He and C strongly points to the presence of mantlederived CO2 in some groundwaters, particularly in waters from the East and West Eifel districts, and the Vogelsberg and Kaiserstuhl volcanic sites.
| Item Type: | Journal article |
|---|---|
| Faculties: | Geosciences > Department of Earth and Environmental Sciences > Crystallography and Materials Science |
| Subjects: | 500 Science > 550 Earth sciences and geology |
| Language: | English |
| Item ID: | 18601 |
| Date Deposited: | 10. Mar 2014, 14:11 |
| Last Modified: | 29. Apr 2016, 09:15 |
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