Conditions for uranium biomineralization during the formation of the Zoovch Ovoo roll-front-type uranium deposit in East Gobi Basin, Mongolia

The Zoovch Ovoo uranium roll-front-type deposit is hosted in the Sainshand Formation, a Late Cretaceous siliciclastic reservoir, which constitutes upper part of post-rift infilling Mesozoic East Gobi Basin SE Mongolia. Formation consists unconsolidated medium-grained sand, silt and clay intervals deposited fluvial-lacustrine settings. confined within 60–80 m thick sequence inside aquifer-driven systems. overall system experienced shallow burial was never subjected to temperatures higher than 40 °C. This study proposes comprehensive metallogenic model for this deposit. Sedimentological mineralogical observations from drill core samples microscopic scale (optical Scanning Electron Microscopy) together with situ geochemistry late-formed phases (Laser Ablation–Inductively Coupled Plasma Mass Spectrometry, Probe Microanalysis, Fourier Transform–Infrared Spectroscopy) were considered reconstruction main stages U trapping. In mineralized zone, ore expressed as Ca–enriched uraninite (UO2) less commonly phospho-coffinite (U, P)SiO4. Trapping mechanisms include i) complexation (i.e. uranyl-carboxyl complexes), ii) adsorption on organic or particles) iii) reduction by pyrite bacterial activity amorphous uraninite. all cases, matter plays either role trap nutrient bacteria that can through their metabolism. diagenesis conditions do not allow direct U(VI) carbon. δ34S values iron disulfide are very diverse, fluctuating extreme cases between −50 + 50‰, an average value framboidal at 2‰, −20‰ euhedral pyrite. positive negative reflect close versus open fractionation systems, while sulphate (BSR) active during whole diagenetic history essential source reduced sulfur. Therefore, using detrital carbon source, microorganisms play significant trapping, reducing agent formation, will redox driven epigenetic processes.