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| Titel |
A new technique for trace elemental analysis of speleothems using microbeam xrf |
| VerfasserIn |
J. Buckles, H. Rowe, Y. Gao, H. Cheng, R. L. Edwards, G. Springer, B. Hardt |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063763
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| Zusammenfassung |
| Trace element ratios in speleothems (Sr/Ca, Mg/Ca, Ba/Ca) have been used to interpret the hydrogeochemical processes in the epikarst zone as well as the partitioning that occurs at the calcite-water interface. During periods of low rainfall, trace element ratios generally increase as a result of the longer residence time of water in the soil and epikarst zones. High-resolution time series analyses of these elements in speleothems provide evidence for changing paleohydrological and geochemical conditions over time.
The conventional methods of trace metal analysis of speleothems- Laser Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICPMS) and Inductively-Coupled Plasma Optical Emission Spectroscopy (ICP-OES) have yielded many high-quality data sets. However, these methods can be expensive, time-consuming, and require the destruction – either by ablation, micro-milling, or powdering of speleothem samples. The many caveats of these conventional methods have led to the search for a viable alternative – one that will provide the same high-resolution result, but that is affordable, rapid, and non-destructive.
Presented here are trace element analysis results using microbeam X-ray Fluorescence Spectrometry. The Brüker-AXS ARTAX microbeam XRF spectrometer permits a multi-element analysis from Na to U with a spatial resolution of 70 µm. The method is non-contact and non-destructive, therefore preserving the sample for additional analyses (e.g. stable isotopes). A simple calibration method for Sr/Ca using pressed mixed powders will be described.
It will be demonstrated that microbeam XRF is an important tool in trace element analysis of speleothems and a viable alternative to conventional methods. Sr/Ca ratios were obtained for multiple speleothems and serve as a preliminary test of microbeam XRF suitability. Analyses of variable count times, temporal and spatial reproducibility along transects, and a comparison between microbeam XRF spectra and ICP-OES spectra for the same transect of a speleothem growth axis will be presented. In addition, ARTAX multi-transect area-mapping will demonstrate trace element abundances along both calcite bands and the growth axis. |
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