Geochemistry characteristics of ion-absorbed rare earth deposits in low-grade metamorphic rock in the Ningdu area, southern Jiangxi Province and its prospecting significance

Ion-absorbed rare earth deposits in low-grade metamorphic rock are new-type rare earth deposits found recently in Jiangxi Province. This study mainly focused on Neoproterozoic low-grade metamorphic rocks of the Shenshan and Kuli Formations in southern Jiangxi Province. Based on field geological survey and experimental tests, the geochemical characteristics of the deposits of this kind were summarized. The low-grade metamorphic rocks in the study area are characterized by moderate SiO₂ and total alkalicontents, high K₂O/Na₂O ratios, low TFe₂O₃+MgO and CaO contents. They show high total ΣREE and ΣLREE, distinct LREE/HREE fractionation, as well as moderate Eu depletion. This study shows that parts of occurrences have been at the late stage of chemical weathering. Besides, the weathering crust in each rare earth ores display similar REE distribution patterns as their protoliths. The enrichment degree of REEs depends mainly on REE abundances and CIA values of protoliths. And weathering crust inherits the REE patterns of the protolith.