Evidence of heterovalent europium in zoned Llallagua apatite using wavelength dispersive XANES

Eu L, X-ray absorption near edge structure (XANES) spectroscopy was conduct ed with a wavelength dispersive (WDS) spectrometer to determine the valence state of europium in a natural, Mn-and REE-rich apatite from Llallagua, Bo livia. Europium exists in both the divalent and trivalent states in the Lla llagua apatitie with a Eu2+/Eu3+ ratio between 0.12 and 0.22. With the enha nced energy resolution of WDS the EuL alpha (1) fluorescence line can be re solved from the MnK alpha line, allowing for significant reduction of backg round in the EuL3 absorption edge region and resolution of the Eu XAS, whic h is difficult by conventional methods because of fluorescence peak interfe rence. The anomalous partitioning behavior of Eu in these samples (Rakovan and Reeder 1996) can be explained by the observed presence of Eu2+ and Eu3 and is consistent with the suggested size effect on intrasectoral zoning o f REEs in apatite.