Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Michal Roll, Viktor Goliáš, Jiří Zachariáš, Jakub Plášil, Lukáš Falteisek

Newly described uranium mineralization with ruthefordine from former arsenic mine Giftkies, Jáchymov ore district, Czech Republic

Journal of Geosciences, volume 69 (2024), issue 2, 77 - 86

DOI: http://doi.org/10.3190/jgeosci.382

The Giftkies mine is the only known locality of rutherfordine within the Jáchymov ore district s. l., which is famous for the occurrence of many uranyl carbonates. Uranyl monocarbonate rutherfordine, UO₂(CO₃), investigated in this study, has been found in significant amounts in the abandoned arsenic mine at Giftkies site (Jáchymov, Czech Republic), together with other uranyl carbonates, common liebigite and scarce agricolaite. The possible specific conditions of rutherfordine formation prompted the detailed study with the following analytical methods. XRD methods helped identify above mentioned minerals as well as other secondary minerals reported from this site, 31 minerals in total. The mineralization sequence was investigated and determined by both optical and scanning electron microscopy to be: quartz → early siderite → late siderite → pyrite → iron oxyhydroxides → rutherfordine. This microscale investigation of textural features and element admixtures helped to create above mentioned paragenetic scheme. Further on alpha spectrometry and radiometric dating of rutherfordine helped to build a timeframe. A daughter deficiency method using ²³⁰Th/²³⁴U isotopic pair provides late Holocene ages and suggests at least two rutherfordine formation episodes (4600-2600 years BP and 1350-300 years BP respectively). According to data, we claim that supergene processes that lead to rutherfordine crystallization at the site started at the beginning of the Subboreal period and lasted until nowadays.