Specific activity and activity ratios of different radionuclides in uranium series were measured by HPGe-detector for 14 metamorphosed sandstone samples. The 232Th/238U concentration ratios are ranging between 0.12 and 3.14 which indicate U migration-in. The ratios between nuclides of U- series showed obvious deviations from secular equilibrium, indicating the deposition of uranium during the last 1 Ma and of radium during the last 8×103 yr. The shear zones represent channels for ground- and surface water flow, where the migration of uranium-series radionuclides along the fracture zones may be due to adsorption onto the alteration products (clays, iron oxides) of the surrounding rocks or by later mobility by ground and surface water. The calculated ages of metamorphosed sandstone samples indicate major U accumulation in age ranges between 109.6 and 460.1 ky ago for Sikait-1 and between 57.97 and 211.8 ky ago for Sikait-2. The 230Th/232Th activity ratios range between 0.65 and 22.15 for Sikait-1 samples and between 0.79 and 2.49 for Sikait-2 samples which are smaller than 20 except one sample (S8), indicating a contamination of the samples by detrital 230Th. So, after subtraction the detrital 230Th, the corrected age for Sikait-1 samples vary from 97.17 to 441.9 kyr while for Sikait-2 samples vary from 53.71 to 201.1 kyr. These ages are conformable with U-series ages reported for secondary uranium minerals in the eastern and western deserts and indicate that there is more than one phase of uranium mineralization in the studied area.
