Transport and Deposition of Uranium in Hydrothermal Ore Fluids as Exemplified by Uranium Deposit 302

<正> Uranium Deposit 302 is a large hydrothermal uranium deposit occurring in fault zones within a granite.Pitchblende is the only primary uranium mineral found in the ore. The associated minerals include quartz,fluorite, hematite and pyrite. This paper focusses on the mechanism of transport and deposition of uranium in hydrothermal ore-forming solutions responsible for the deposit. It is concluded that uranium might be not only oxidized in arelatively reducing environment, but also reduced in a relatively oxidizing environment, depending on thespeciation of uranium in the solutions. The formation of pitchblende is closely related to uranium reduction atthe stage of uranium mineralization.