Report of subproject TP3 – Fluid inclusions

W. Aeschbach-Hertig, A. Mangini, T. Kluge

Project summary

The primary goals of this sup-project were to develop methods for the extraction and analysis of noble gases from fluid inclusions in carbonate precipitates and to clarify whether noble gas temperatures can be derived from such measurements. If such a new method for paleoclimate reconstruction could be established, this would allow us to derive absolute temperature records that would ideally complement the interpretation of stable isotope profiles from speleothems. It would combine the advantages of the speleothem archive (precise, high-resolution dating) and the noble gas thermometer (reliable absolute temperatures).

In view of the high risk involved in this innovative project, it is remarkable that it can be said that the main objectives have successfully been achieved after little more than two years. First, methods for noble gas extraction and analysis from speleothems were developed. As expected, samples of about 1 g of stalagmite were found to contain sufficient noble gases for a precise measurement. The problem of the water determination in order to obtain precise noble gas concentrations could also be solved by a manometric measurement. The principal difficulty that was initially encountered was the presence of unexpectedly high fractions of air-derived noble gases in the samples. At first, this seemed to render the determination of reasonably precise noble gas temperatures impossible.

However, screening a variety of speleothem samples available in the framework of the "daphne" research unit enabled us to find particular speleothems that contain comparatively little air. Especially several stalagmites from Bunker Cave, one of the main "daphne" sites, proved well-suited for the noble gas method. These samples enabled us to derive for the first time precise (better than ± 1 °C) and reproducible noble gas temperatures from speleothems (Kluge et al., in press). The principal feasibility of the new method was thus established. In particular, it could be shown that a simple model of an air-equilibrated water component plus atmospheric air could describe the noble gases in these stalagmites.

In addition to deriving noble gas temperatures from selected samples, methods for a separation of the water- and air-derived components by stepwise crushing and heating are currently being developed. Preliminary results seem to indicate that a reduction of the air/water volume ratio by about an order of magnitude may be feasible, which would considerably expand the range of suitable samples. Clearly, the method is still a long way from being established as a tool that could routinely be applied to speleothems, but first promising steps have been taken. The results encourage us to proceed with the development of this new method, which we hope may eventually have far-reaching impact on speleothem studies and on paleoclimate research in general.

Link to the "dated speleothems - archives of the paleoenvironment" homepage

Publications related to this project

Papers

Kluge, T., Marx, T., Scholz, D., Niggemann, S., Mangini, A., Aeschbach-Hertig, W., in press. A new tool for paleoclimate reconstruction: noble gas temperatures from fluid inclusions in speleothems. Earth Planet. Sci. Lett.

Conference Presentations

Aeschbach-Hertig, W., Kluge, T., 2006. On the feasibility of applying the noble gas thermometer to fluid inclusions in speleothems. Workshop Daphne 2006, Innsbruck.

Aeschbach-Hertig, W., Friedrich, R., Kluge, T., Kreuzer, A., 2008. Noble gases in paleoclimate archives, EGU 2008, Vienna.

Kluge, T., Aeschbach-Hertig, W., 2006. Mass spectrometric determination of noble gas concentrations in stalagmites- first results. Workshop Daphne 2006, Innsbruck.

Kluge, T., Aeschbach-Hertig, W., 2007. The way to noble gas paleotemperatures derived from fluid inclusions in stalagmites. EGU 2007, Vienna.

Kluge, T., Aeschbach-Hertig, W., 2007. Noble gas measurements on fluid inclusions in stalagmites. Minoga 2007, Potsdam.

Kluge, T., Marx, T., Aeschbach-Hertig, W., 2008. Pilot studies on noble gas temperature (NGT) determination using fluid inclusions in speleothems. Workshop Daphne 2008, Heidelberg.

Kluge, T., Marx, T., Aeschbach-Hertig, W., 2008. Paleotemperatures derived from fluid inclusion in stalagmites using noble gas mass spectrometry. EGU 2008, Vienna.

Kluge, T., Marx, T., Aeschbach-Hertig, W., 2008. Noble gas measurements on fluid inclusions in speleothems. DPG 2008, Darmstadt. Marx, T., Kluge, T., Aeschbach-Hertig, W., 2008. Methods for the determination of noble gas temperatures from fluid inclusions in speleothems. Workshop Daphne 2008, Heidelberg.