Wassenburg, J.A. and Scholz, D. and Jochumb, K.P. and Cheng, H. and Ostere, J. and Immenhauser, A. and Richter, D.K. and Häger, T. and Jamieson, R.A. and Baldini, J.U.L. and Hoffmann, D. and Breitenbach, S.F.M. (2016) 'Determination of aragonite trace element distribution coefficients from speleothem calcite–aragonite transitions.', Geochimica et cosmochimica acta., 190 . pp. 347-367.
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 (1σ SD). For one speleothem from western Germany, 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.
|Full text:||(AM) Accepted Manuscript|
Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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|Publisher Web site:||http://dx.doi.org/10.1016/j.gca.2016.06.036|
|Publisher statement:||© 2016 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/|
|Date accepted:||29 June 2016|
|Date deposited:||14 October 2016|
|Date of first online publication:||07 July 2016|
|Date first made open access:||07 July 2017|
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