REE Concentrations in Secondary Uranium Minerals from the Izera Metamorphic Complex (SW Poland)

Abstract

The subject of this work was supergene uranium mineralization and the YREE concentrations within. YREE differentiation patterns were used to recreate the prevailing crystallization conditions of abandoned mine dumps in Kromnów, Kopaniec, and Radoniów, located in the Izera Metamorphic Complex, Sudetes Mts. The collected samples were investigated using PXRD, SEM-EDS, and EPMA. YREE concentrations were measured using LA-ICP-MS. The secondary uranium mineralization from these locations consists of phosphates (meta-autunite, meta-torbernite, metauranocircite-I, saleéite, bassetite, phosphuranylite), arsenates (zeunerite), silicates (uranophane, sklodowskite), and uranyl hydroxides (likely becquerelite). Moreover, in Radoniów, phosphuranylite was found; it had not been found in Poland previously. Uranyl mineral assemblages indicate the diversity of chemistry of their mother solutions and suggest their weakly acidic character. The YREE content in secondary uranium minerals also reflects the pore solutions’ chemistry variation. The negative Y anomaly is observed in all uranyl phases. Similar behavior of Sm is also noted, excluding metatorbernite and torbernite. Among the uranyl minerals studied, only metatorbernite from Kromnów showed a positive Nb anomaly, which was probably related to proximity to weathering in YREE-breeding phases. Nevertheless, the YREE and chemical results suggest that this mineralization originated from the oxidizing solutions generated during the weathering of primary hydrothermal mineralization. In order to better understand the weathering zones in these locations, more detailed studies on pore solution chemistry are needed.