µ-XRF SPECTROMETRY OPTIMIZATION IN TRACE ELEMENT ANALYSIS IN SPELEOTHEMS

Trace element ratios in speleothems (Sr/Ca, Mg/Ca, Ba/Ca) have been utilized in paleoclimate reconstructions as indicators of the hydrogeochemical processes which occur in the vadose zone. Trace element concentrations in speleothem calcite serve as indicators of the residence time of waters in the epikarst, as the longer the contact time between the waters and the host rock, the greater the impact of weathering reactions. The residence time of the water in karst systems is a direct result of the amount of effective precipitation and infiltration.

The Bruker Artax µ-XRF spectrometer is a viable alternative to traditional methods of trace element analysis for Sr/Ca measurements, as it is non-contact and non-destructive, thereby preserving the sample for additional or future analyses. The system will be demonstrated to produce the same high-quality results as the conventional methods.

µ-XRF scans were performed with two different tube and filter configurations: 1) Rh tube and Al-Ti-Cu filter and 2) W tube and Al 315.00 µm filter, in order to establish the optimal machine configuration. With the Rh tube, the beam size is approximately 70 microns, while with the W tube beam it is larger, at 650 microns, but allows for a higher detection rate of Sr. The results from the scans will be compared, in order to determine whether the higher spatial sensitivity afforded by the Rh tube or the higher detection rate through the W tube produces more valuable results. The optimization of machine parameters through statistical analysis will ultimately allow for the reduction of analysis time and the maximization of precision.