Role of Organic Matter in Uranium Mineralisation in Vempalle Dolostone; Cuddapah Basin, India

Abstract

Dolostone of Vempalle Formation near Tummalapalle hosts large uranium deposit (>100,000 tonnes with an average grade of 0.045%U3O8). It is a unique type of uranium deposit because carbonate formations have been considered to be among the least uraniferous of all the rocks of the Earth’s crust due to mobility of uranium in aqueous fluid in the presence of carbonate and bicarbonate ions. Vempalle dolostone hosts syn-sedimentary uranium mineralization in the form of discrete uranium phases (pitchblende and coffinite) associated with collophane, and adsorbed uranium in organic matter. The organic matter has played dual role of concentrating uranium from solution and also chemically reducing it to pitchhblende and coffinite.

Gypsum–anhydrites in 1.9 Ga Vempalle Formation, Cuddapah basin, India: A note on the Palaeoproterozoic environment and diagenetic condition

“…The cycles of transgression and regression are not dealt in detail in this context. The presence of stromatolites in this sequence possibly is related to sulphate reducing bacteria of that time, which have supported the dolomite precipitation by removing sulphate from water (Goswami et al 2015(Goswami et al , 2017a. The alteration during the burial and diagenesis by groundwater is already mentioned to be a phenomenon related to the uranium mineralisation (Rai 2012;Bhagat et al 2014).…”

“…These are interpreted to have been deposited in intertidal to supratidal environments and the red shale facies that is sandwiched between lower phosphatic dolostone and upper cherty dolostone-shale facies with the presence of evaporite gypsum in the upper as well as lower part of the shale indicates sub-aerial exposure of tidal flat (Bhattacharjee et al 2012). Based on the sedimentological attributes Goswami et al (2015Goswami et al ( , 2017a described the Papaghani sub-basin as a shallow small basin lying close to the shore in arid condition. The presence of sedimentary features, such as mud cracks and ripple marks, indicates its shallow water condition.…”

“…Acidicity lowered the pH along pore spaces to dissolve carbonates and is replaced by the silica precipitation. The role of organic matter as a reductant for uranium precipitation is well documented (Goswami et al 2017a). The stable isotopic data interpretation of Rai (2012) suggests that the uranium-bearing meteoric water influx during the diagenesis is related to the uranium mineralisation.…”

Uranium Traps in Phreatic Sandstone-type Prospect, Taunsa Area, Dera Ghazi Khan, Eastern Sulaiman Range, Pakistan: Evidences from Autoradiography and Optical Microscopy

“…In addition, some greyish brown micritic (microcrystalline calcite) fragments show alpha tracks. Carbonate rocks are generally considered to lack uranium resources due to mobility of uranium in water containing carbonate and bicarbonate complexes (Goswami et al, 2017). However, some carbonate rocks are uranium resources, e.g., Todilto limestone in USA (Berglof and Mclemore, 2003) and dolostone of the Vempalle Formation in India (Goswami et al, 2017).…”

“…Carbonate rocks are generally considered to lack uranium resources due to mobility of uranium in water containing carbonate and bicarbonate complexes (Goswami et al, 2017). However, some carbonate rocks are uranium resources, e.g., Todilto limestone in USA (Berglof and Mclemore, 2003) and dolostone of the Vempalle Formation in India (Goswami et al, 2017). Todilto limestone is associated with evaporites, and is considered to have deposited in lacustrine environment (Berglof and Mclemore, 2003).…”