Determination of aragonite trace element distribution coefficients from speleothem calcite–aragonite transitions
Determination of aragonite trace element distribution coefficients from speleothem calcite–aragonite transitions
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从洞穴沉积物方解石-文石转变确定文石微量元素分配系数
DOI：
10.1016/j.gca.2016.06.036
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发表时间：
2016-10
影响因子：
5
通讯作者：
J. Wassenburg;D. Scholz;K. Jochum;Hai Cheng;J. Oster;A. Immenhauser;D. Richter;T. Häger;R. A. Jamieson;J. Baldini;D. Hoffmann;S. Breitenbach
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文献类型：
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作者：
J. Wassenburg;D. Scholz;K. Jochum;Hai Cheng;J. Oster;A. Immenhauser;D. Richter;T. Häger;R. A. Jamieson;J. Baldini;D. Hoffmann;S. Breitenbach
控制（微量）元素进入洞穴沉积物的过程往往与环境变化有关。虽然元素纳入到speleothemcalciteis现在合理地很好地理解，目前的知识，关于微量元素的变化speleothemagoniteis非常有限。特别感兴趣的是微量元素的分配系数是否高于或低于一个，以评估在何种程度上以前的文石沉淀影响了speleothem文石微量元素records.This研究使用9方解石到文石的转变，在7个speleothem从不同的环境设置，以获得第一个定量估计的分配系数为几个元素在speleothemagonite：DMg（Ar）= 9.7E−5 ± 9.01E−5，DBa（Ar）= 0.91 ± 0.88，DSr（Ar）= 1.38 ± 0.53，DU（Ar）= 6.26 ± 4.54（1σSD）。对于来自德国西部的一个洞穴沉积物，分配系数通常较高，这可能与该样品非常低的生长率（<11 μm/年）有关。特别是当生长速率小于20 μm/年时，DSr（Ar）与生长速率呈负相关，表明洞穴沉积文石DMg（Ar）小于1，DU（Ar）大于1，DSr（Ar）大于1或接近1。对于DBa（Ar），由于相对较高的不确定性，很难得出类似的结论。因此，增强之前的文石沉淀将导致洞穴沉积物文石中较低的U和较高的Mg浓度，尽管在许多情况下，洞穴沉积物文石中的Mg很可能由其他过程主导。这一结果表明，U浓度文石石笋可以作为一个非常有效的代理古降雨。
The processes that govern the incorporation of (trace) elements into speleothems can often be linked to environmental changes. Although element incorporation into speleothemcalciteis now reasonably well understood, current knowledge regarding trace element variability in speleothemaragoniteis 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 speleothemaragonite: DMg(Ar)= 9.7E−5 ± 9.01E−5,DBa(Ar)= 0.91 ± 0.88,DSr(Ar)= 1.38 ± 0.53, andDU(Ar)= 6.26 ± 4.54 (1σSD). 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 aragoniteDMg(Ar)is below one,DU(Ar)is considerably above one, andDSr(Ar)is above one or close to unity. ForDBa(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.