Compositional Trends in Euxenite-Group Minerals Investigated from Preliminary XRF Data

A tentative investigation into the chemical compositions of euxenite-group minerals was conducted independently by the author. Based on theory, euxenite-(Y) can be defined as the Y-dominant endmember of the euxenite group, with an idealised chemical formula of YTiNbO₆. Via two cation coupled substitution patterns: (a) fersmite-vector and (b) uranopolycrase-vector, positive correlations between Ca²⁺ and (Nb,Ta)⁵⁺ concentrations, as well as between (U,Th)⁴⁺ and Ti⁴⁺, were expected. This hypothesis was tentatively tested via semi-quantitative commercial XRF data of 12 euxenite group mineral specimens from 5 different localities worldwide. As a result, a non-negligible to moderate correlation was found between Ca²⁺ and (Nb,Ta)⁵⁺, as well as a moderate correlation between (U,Th)⁴⁺ and Ti⁴⁺, as expected. In contrast, no correlation was observed between REE³⁺ and Ti⁴⁺, where none was expected. These findings, while not robust due to the small sample size and the limitations of XRF analyses, point towards the presence of both (a) fersmite-vector and (b) uranopolycrase-vector, suggesting that the theory is likely partly accurate in describing the chemical behaviour of euxenite-group minerals. This document has not undergone peer-review.