Determination of aragonite trace element distribution coefficients from speleothem calcite–aragonite transitions

Wassenburg, J.A., Scholz, D., Jochum, K.P., Cheng, H., Oster, J., Immenhauser, A., Richter, D.K., Häger, T., Jamieson, R.A., Baldini, J.U.L., Hoffmann, D. and Breitenbach, Sebastian (2016) Determination of aragonite trace element distribution coefficients from speleothem calcite–aragonite transitions. Geochimica et Cosmochimica Acta, 190. pp. 347-367. ISSN 0016-7037

[img]
Preview
Text
Wassenburg_Ar_partitioning_revised.pdf - Accepted Version
Available under License Creative Commons Attribution Non-commercial No Derivatives 4.0.

Download (334kB) | Preview
Official URL: https://doi.org/10.1016/j.gca.2016.06.036

Abstract

The processes that govern the incorporation of (trace) elements into speleothems can often be linked to environmental changes. Although element incorporation into speleothem calcite is now reasonably well understood, current knowledge regarding trace element variability in speleothem aragonite is very limited. Of particular interest is whether trace element distribution coefficients are above or below one in order to assess the extent to which prior aragonite precipitation has affected speleothem aragonite trace element records. This study uses nine calcite-to-aragonite transitions in seven speleothems from diverse environmental settings to derive the first quantitative estimates of the distribution coefficients for several elements in speleothem aragonite: DMg(Ar) = 9.7E-5 ± 9.01E-5, DBa(Ar) = 0.91 ± 0.88, DSr(Ar) = 1.38 ± 0.53, and DU(Ar) = 6.26 ± 4.54 (1s SD). For one speleothem from westernGermany, the distribution coefficients are generally higher, which is potentially related to the very low growth rates (<11 µm/year) of this sample. In particular, DSr(Ar) appears to show a negative correlation with growth rate when growth rate is below 20 µm/year. In summary, our results demonstrate that speleothem aragonite DMg(Ar) is below one, DU(Ar) is considerably above one, and DSr(Ar) is above one or close to unity. For DBa(Ar), reaching a similar conclusion is difficult due to the relatively high uncertainty. Enhanced prior aragonite precipitation will thus result in lower U and higher Mg concentrations in speleothem aragonite, although in many cases Mg in speleothem aragonite is most likely dominated by other processes. This result suggests that U concentrations in aragonitic stalagmites could serve as a very effective proxy for palaeo-rainfall.

Item Type: Article
Uncontrolled Keywords: Speleothem, Aragonite, Trace element, Distribution coefficient, Cave
Subjects: F600 Geology
F700 Ocean Sciences
F800 Physical and Terrestrial Geographical and Environmental Sciences
F900 Others in Physical Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Rachel Branson
Date Deposited: 19 Feb 2020 12:28
Last Modified: 19 Feb 2020 12:31
URI: http://nrl.northumbria.ac.uk/id/eprint/42141

Actions (login required)

View Item View Item

Downloads

Downloads per month over past year

View more statistics