Publication details

Trace element signatures of uraninite controlled by fluid-rock interactions: A case study from the Eastern Moldanubicum (Bohemian Massif)

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Year of publication 2022
Type Article in Periodical
Magazine / Source Journal of Geochemical Exploration
MU Faculty or unit

Faculty of Science

Keywords Uraninite; Trace elements; Geochemistry signatures; Fluid-rock interaction; REE; HFSE
Description The eastern part of the Moldanubian Zone (Bohemian Massif, Czech Republic) hosts the Western Moravian uranium (U) province where U exploitation was active from 1957 to 2017 with total production about 24,000 t of U. A set of 369 laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses were performed to simultaneously assay 50 chemical elements in samples of unaltered uraninite from this U province, alongside 246 electron microprobe analyses (EMPA) to determine the major and minor element compositions of the latter. Such large sets of analyses allowed comparisons to be made and a possible classification of individual deposits and/or ore fields based on the major, minor, and trace elements compositions of uraninite. According to the results, uraninite samples from individual U ore fields or even deposits exhibited contrasting trace element signatures. For example, minor elements such as Ca differed significantly (median of CaO 3.1–9.0 wt%), while ?REE and Y, which are common substituents in uraninite, reached median values on 4.3–6495 and 6.5–1552 ppm, respectively. The REE chondrite normalized patterns along with Eu anomalies (EuN/EuN* 0.06–1.50) of uraninite varied significantly among the studied deposits. The Zr contents commonly ranged over only a few ppm. However, the uraninite samples from two deposits of the ore province (Rozsochy and Roˇzn ´a-Jasan) yielded anomalously high Zr contents (medians of thousands of ppm and maximum contents of up to 2 wt%) which are not common for hydrothermal uraninite. Furthermore, significant variations were also observed in the concentrations of Nb, Ti, and V, for example. All deposits in the province have very similar mineralogical, ore textural, or structural features (low temperature shear zone hosted U veins) as well as timing of mineralization events (Permian age). Such significant trace element variations in uraninite within one U ore province are uncommon and may underline the limitations of using the trace element compositions of uraninite as a tool for provenance studies or determining the function of a type of U deposit. We suggest that factors such as the physico-chemical conditions, lithological controls, and fluid-rock interaction processes on a deposit/ore field scale can significantly control the minor and trace element compositions of uraninite.
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