Preliminary Study On Microbe Groups In The Shihongtan Uranium Deposit In Xinjiang And Their Mineralization

By using biological method, microorganisms in the uranium deposit were isolated and identified for the first time at home. The reduction of U(VI) caused by sulfate-reducing bacteria isolated from the uranium deposit and their effecting on the formation of uranium deposit were studied, the mechanism of the mineralization of uranium deposit caused by microorganisms was analyzed at a biological angle.Objectives: Investigate the main microbe groups in the Shihongtan uranium deposit in Xinjiang. Research the role of microorganisms in the mineralization. Methods: By using biological method, microorganisms in the Shihongtan uranium deposit in Xinjiang were isolated and identified. The reductive experiment of uranium caused by sulfate-reducing bacteria was done. The simulation experiment of the function of microorganisms during the formation of uranium deposit was investigated by the water-rock-bacteria three-phase experiment system. Results: 1. The distribution of the main microbe groups in the subzones was different and the geochemical characteristics were obvious. From the oxidation zone, the intermediate zone of oxidation and reduction to the reduction zone, the quantity of aerobic bacteria was gradually decreased, on the contrary, the quantity of anaerobic bacteria was gradually increased, the distribution of microorganisms in different zones was controlled by the organic carbon content and the existing state and content of ferrum in the mineral deposits, and also controlled by the content of soluble oxygen and sulfate in the groundwater. 2. Sulfate-reducing bacteria could reduce SO₄^2- in the experiment system into H₂S and then U(VI) was changed into U(IV) by H₂S. 3. The result of the simulation experiment done by the water-rock-bacteria three-phaseexperiment system indicated that sulfate-reducing bacteria could absorb organic carbon as nutrition materials to grow, at the same time, could reduce SO42 in the groundwater to generate H2S, which could give rise to the rising of pH and the dropping of Eh and form the reduction environment beneficial to gather and precipitate U(VI), at last, uranium was reduced and precipitated. Conclusions: The geochemical characteristics of the distribution of the main microbe groups in the subzones of the Shihongtan uranium deposit were distinct, sulfate-reducing bacteria and Iron bacteria were the dominant microbe groups in the whole deposit. Sulfate-reducing bacteria, as the key group during the formation of uranium deposit, on the one hand, oxidized and consumed organic carbon in the surrounding rocks, on the other hand, reduced sulfate in groundwater to produce H2S and provid the strong reduction geochemical environment for the reduction and precipitation of U(VI).