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| Titel |
Noble gas isotopic signatures in thermal waters of the Dead Sea Transform |
| VerfasserIn |
Neta Tsur, Tillmann Kaudse, Werner Aeschbach-Hertig |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096855
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| Publikation (Nr.) |
 EGU/EGU2014-12383.pdf |
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| Zusammenfassung |
| Noble gas isotope composition in thermal groundwater provides information about
crust-mantle interactions, in form of geotectonic activity, volcanism and advective heat
transfer. The knowledge of the geothermal state of the crust is useful for the indication of
thermal energy resources, which are of significant environmental and economic importance.
In this study, groundwater samples were collected in Israel and Jordan in 2012, along the east
and west sides of the central Dead Sea Transform.
The helium isotope ratio, 3He/4He, is a well-established marker to discriminate three
different geochemical reservoirs: Atmosphere, crust and mantle. The distinct isotope ratios in
each reservoir make it possible to separate the total helium concentration in groundwater into
mantle, crustal (radiogenic) and atmospheric components. The 3He/4He ratios of all sampled
waters exceed the typical crustal ratio, indicating contributions of mantle-derived helium to
the total helium concentration. Most of the samples contain less than 3% atmospheric helium,
whereas the mantle-derived helium component ranges from 1% to 61%. In Israel, a
clear trend is observed. Samples from the northern parts of the sampling area show
higher 3He/4He ratios than samples from southern parts. These findings confirm
Torfstein et al. [1], who analyzed thermal groundwaters from Israel. In our data from
Jordan, however, no north-south trend is seen, but a local anomaly is observed in the
area between the Dead Sea and the Sea of Galilee, with a 3He/4He ratio that is 5
times higher than the atmospheric 3He/4He ratio. Moreover, some samples from
North Jordan exhibit only minor mantle contributions, compared to the samples
from the north of Israel. Our results emphasize the importance of local faulting
patterns, which enable a better transfer of mantle derived helium into the shallow
crust.
In addition to helium, the origin of CO2 in the water was examined. Measurements of
δ13C suggest that CO2 originates from metamorphic processes rather than from the mantle.
Furthermore, δ18O and δ2H data indicate a water reservoir temperature above 100°C only at
one location.
References:
[1] Torfstein, A. et al. 2013: Helium isotopes in Dead Sea Transform waters. Chemical
Geology, 352, 188-201 |
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