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| Titel |
New online method for water isotope analysis of fluid inclusions in speleothems |
| VerfasserIn |
Stéphane Affolter, Markus Leuenberger, Dominik Fleitmann |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250079955
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| Zusammenfassung |
| Speleothems are increasingly becoming key archives for paleoclimate reconstruction. The
fluid inclusions contained in these speleothems represent natural repositories of cave drip
waters. The hydrogen (δD) and oxygen (δ18O) isotopic composition of fluid inclusions can
yield direct information on the isotopic composition of paleoprecipitation, which can then be
combined with isotopic analyses of speleothem calcite to either directly calculate
paleotemperatures or to reveal changes in the source of moisture. To liberate speleothem
fluid inclusion water and to measure its isotopic composition, a new method was
developed. It consists of a simple hydraulic crushing device similar to the one used
to extract noble gases from fluid inclusions. Prior to crushing, the sample tube is
conditioned by heating and flushing with nitrogen in order to release adsorbed water.
Thereafter, the speleothem sample (approximately 1g of calcite) is crushed and the
released water from fluid inclusions is transferred by a nitrogen gas stream to a laser
spectrometer using a wavelength-scanned cavity ring-down spectroscopy (WS-CRDS)
technology that allows us to simultaneously monitor hydrogen and oxygen isotopes. The
main task we would like to address with this method is a comparison between the
isotope signals of the fluid inclusion and calcite to reduce uncertainties associated
with the interpretation of calcite δ18O values in speleothems in Switzerland and
Turkey.
Currently, we are mainly focussing on a stalagmite (M6) from Milandre cave, Jura,
Switzerland. We installed a high precision drip logger, which continuously counts the number
of water drops per time unit using an acoustic technique. This way we can monitor the drip
water rate at the sampling site and collect drip water, which was originally dripping and
precipitating on the M6 stalagmite. In parallel, we collected rainfall water at the MeteoSwiss
station “Le Mormont” located close to the cave. Thus we are able to compare δD and δ18O
isotopic composition of drip and rainfall water. This will help us to characterize the water
transfer through the soil zone and bedrock into the cave and to understand the fractionation
process that can precede the calcite production and the formation of fluid inclusions. |
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