Sandstone uranium deposits

 Sandstone uranium deposits

Uranium deposits hosted in Sandstone, occur in medium to coarse-grained sandstones deposited in a continental fluvial or marginal marine sedimentary environment. Impermeable shale/mudstone units are interbedded in the sedimentary sequence and often occur immediately above and below the mineralized sandstone. Uranium precipitated under reducing conditions caused by a variety of reducing agents within the sandstone including: carbonaceous material (detrital plant debris, amorphous humate, marine algae), sulphides (pyrite, H2S), hydrocarbons (petroleum), and interbedded basic volcanics with abundant ferro-magnesian minerals (eg chlorite).
There are five main sub-types of sandstone deposits, often mixed:
  1. Basal channel deposits – wide channels filled with permeable sediments. Examples are Dalur and Khiagda (Russia), and Beverley and Honeymoon (South Australia).
  2. Tabular deposits – irregular, elongate lenticular bodies parallel to the depositional trend, deposits commonly occur in palaeochannels incised into underlying basement rocks. Examples are Akouta, Arlit, and Imouraren (Niger), Hamr-Stráž pod Ralskem (Czech Republic) and those of the Colorado Plateau (USA).
  3. Roll-front deposits – arcuate bodies of mineralisation that crosscut sandstone bedding, often in palaeochannels. Examples are Budenovskoye, Tortkuduk, Moynkum, Inkai and Mynkuduk (Kazakhstan) and Crow Butte and Smith Ranch (USA).
  4. Tectonic/lithologic deposits – occur in sandstones adjacent to a permeable fault zone. Examples are in the Lodève District (France) and the Franceville Basin (Gabon).
  5. Mafic dykes or sills in Proterozoic sandstones – examples at Matoush (Canada) and Westmoreland (Australia).
The three main types of sandstone deposits (in black): Roll Front, Tabular and Tectonological.

Idealized cross section of a sandstone hosted uranium roll front deposit.  (Cyclone Uranium Corporation, 2012)

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