The Saqisan, Sanqilinyi and Sanbaqi deposits are hosted by Devonian to Carboniferous carbonate rocks rich in organic matter and clays. The organic matter is chiefly of marine origin and in unmineralised samples is immature, indicating a history of generally low temperatures and shallow maximum burial. The deposits formed as a result of repeated karstification during the Hercynian and Yanshanian regional tectonic periods, accumulation of organic matter and clays in the caverns and breccias, fixation and adsorption of uranium leached from the host carbonates, reduction by organic matter, and reworking of the protores to form uraninite and coffinite., The Saqisan, Sanqilinyi and Sanbaqi deposits are hosted by Devonian to Carboniferous carbonate rocks rich in organic matter and clays. The organic matter is chiefly of marine origin and in unmineralised samples is immature, indicating a history of generally low temperatures and shallow maximum burial. The deposits formed as a result of repeated karstification during the Hercynian and Yanshanian regional tectonic periods, accumulation of organic matter and clays in the caverns and breccias, fixation and adsorption of uranium leached from the host carbonates, reduction by organic matter, and reworking of the protores to form uraninite and coffinite.