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

Abstract

Taunsa uranium occurrence like other uranium resources in Pakistan is hosted by the Late Miocene-Pliocene age Litra Formation of the Siwalik Group molasse sediments. Taunsa uranium prospect is a unique phreatic-type uranium resource in terms of its disturbed geological setting of the eastern limb of the Zindapir anticline in the eastern Sulaiman range. Autoradiography technique was used to locate the spots of anomalous uranium concentration in thin sections from ore of Taunsa prospect. Twenty polished thin sections from uranium ore ranging from 200 ppm-600 ppm were attached to detectors for a month which produced prominent alpha track which were used to find the traps of uranium. Subsequently, these spots were studied under SEM and EPMA for further investigations of uranium phases. Autoradiography revealed that Taunsa uranium ore is mostly associated with organic matter (probably petroleum), black shale clasts, biotite, fougerite (a green colour rusty mineral) and with micritic clasts. This study suggests that prospective facies of the host sandstone containing relatively abundant black shale clasts, organic matter and biotite may be targeted during exploratory drilling in Taunsa uranium deposit and its extensions in the eastern limb of Zindapir anticline