Development of High-Energy -X-ray Fluorescence and X-ray Absorption Fine Structure for the Distribution and Speciation of Rare Earth Elements in Natural Samples

yyMicro-X-ray fluorescence and X-ray absorption fine structure (mu-XRF-XAFS) is one of the most powerful tools to identify the distribution and speciation of trace elements in natural samples with mu m spatial resolution. However, conventional mu-XRF-XAFS studies applied to rare earth elements (REEs: lanthanide elements + Y in this study) are mainly limited to their L-edges and L lines (except for Y) that are subject to strong interferences from other elements (mainly transition metals). In this study, we extend mu-XRF-XAFS to the higher energy region (HE-mu-XRF-XAFS) by using an incident X-ray microbeam (size: ca. 1 x 1 mu m(2)) between 38 and 54 keV to realize K-edge excitation lanthanide analysis without interferences from other elements at the BL37XU beamline, SPring-8 (Japan). This method enables us to simultaneously analyze (i) REE patterns (from La to Dy), (ii) XAFS spectra, and (iii) mu m-scale distribution of each REE in the natural sample. The proposed method also realizes the simultaneous application of mu-XAFS at low (e.g., Fe K-edge) and high (lanthanide K-edges) energy at the same spot without changing the setup of the mu-XRF-XAFS system using the detuning technique.