Enrichment characteristics and sources of the critical metal yttrium in Zhijin rare earth-containing phosphorites, Guizhou Province, China

Yttrium (Y) is a critical metallic element that is used widely in modern scientific, technological, and industrial applications. Phosphorites in the Zhijin area of Guizhou Province, China, are famous for Y enrichment, but the enrichment characteristics and sources remain unclear. Previous studies suggested that the sources of rare earth elements (REEs, La–Lu) and Y (REYs, La–Lu+Y) were related to hydrothermal deposition. However, this study presents evidence refuting that hypothesis, with major and trace elemental data collected with quadrupole–inductively coupled plasma–mass spectrometry (Q–ICP–MS) analysis. These data show that Y in Zhijin REYs-containing phosphorites has a normal distribution and is particularly enriched relative to other REYs. The Y enrichment degree is different at different ∑REY intervals. Specifically, the Y enrichment degree is higher at lower ∑REY values and lower at higher ∑REY values. The REYs-containing phosphorites show features of primary phosphorites. Both REEs and Y have good correlations with P2O5 in the phosphorites with low REYs contents (total REYs < 535 ppm), whereas at high REYs contents (total REYs ≥ 535 ppm), REEs have a good correlation with P2O5 but Y does not. Inconsistent enrichment processes of REYs are suggestive of complex sources of Y. Thus, seafloor hydrothermal fluids were not the direct source of Y. Normal seawater mixed with terrestrial sources might have contributed to the origin of Y here. This study could lead to improvements in Y mineral resource explorations and the situation involving the global REYs supply crisis.