Abstract:Blockage tended to occur in high-TDS groundwater area in Xinjiang, China when sandstone-type uranium deposit was acid or alkaline in-situ leached of uranium. The blockage mechanism was discussed based on geochemical simulation PHREEQCI and a series of in-lab experiments. The results show that the main factors to cause blockage are high concentration of TDS, Ca2 , Mg2 , SO42-, and HCO3- in groundwater, which are 8~12 g/L, 386.17~775.95 mg/L, 250.83~377.21 mg/L, 2 036.47~2 436.08 mg/L and 108.66~527.55 mg/L, respectively. Calcite and gypsum are close to saturation state. chemical jamming occurs with the formation of calcite and gypsum deposit respectively produced by acid or alkaline in-situ leaching of uranium. The dilution or treatment-weak alkaline technologies are feasible to treat sandstone uranium ores.