Epigenetic Alteration and Its Constraints on Uranium Mineralization from the Qianjiadian Uranium Deposit, Southern Songliao Basin

There are many controversies about the metallogenic mechanism for the Qianjiadian uranium deposit in the southern Songliao basin. Using a series of tests including micropolariscope, SEM and XRD, the epigenetic alteration of the Qianjiadian uranium deposit have been described. It has been shown that this deposit contains six types of alteration: Haematization, ferritization, pyritization (gelatinous pyrite, framboidal pyrite and granular pyrite), argillation (hydromicazation, kaolinization and illitization), carbonatation (calcilization, ankeritization and sideritization) and uranium mineralization. Haematization, ferritization, hydromicazation, kaolinization, illitization and calcilization frequently occur in the red sandstones and yellow sandstones, and the extent of haematization, ferritization and hydromicazation is lower in the yellow sandstones than that in the red sandstones. Weak haematization, pyritization, kaolinization, illitization, ankeritization and sideritization can often be seen in the non-mineralized grey sandstones. Pyritization, kaolinization, illitization, ankeritization, uranium metallization and sideritization are primarily formed in the mineralized grey sandstones. Pyritization and sideritization often occur in the primary grey sandstones. The Qianjiadian uranium deposit has undergone neutral-alkalescent environment during the diagenetic period, acidic environment during the early metallogenic period, alkalescent-alkalic environment during the late metallogenic period, and alkali environment during the postmineralization. The neutral-alkalescent environment during the diagenetic period is characterized by formation of siderite. The acidic environment during the early metallogenic period is characterized by formation of hematite, allcharite, pyrite, gyulekhite and kaolinite. The alkalescent-alkalic environment during the late metallogenic period is characterized by formation of ankerite. The alkali environment during the postmineralization is characterized by formation of calcite.