Accumulation Of Cesium By Microorganisms And Role Of Microorganisms In The Formation Of Cesium-Bearing Geyserite In Geothermal Areas, Tibet

A new type of hydrothermal cesium ore—cesium-bearing geyserite was found in Tibet in the late 1980s and the early 1990s. Large-scale mineralization is now still ongoing, and cesium-bearing geyserite is being formed continuously in cesium-bearing geyserite area. Microorganisms grow in large quantities in these areas. We studied the adsorption and absorption of cesium, and influence on the Si-Fe system by microorganisms. In addition, we collected water and geyserite samples from these areas, performed related geochemical analysis and detailed microexamination.Study shows that bacteria and algae dominate in the areas with Calothrix sp., Oscillatoria sp. and Denticula elegans as the dominant species of the algae. These species of microorganisms have a regular population distribution pattern in the area: bacteria and diatoms are the dominant species in spring water; microbial mats dominate at the bottom of a spring, with Calothrix sp. and Oscillatoria sp. as the dominant species; bacteria dominate in bed mud and geyserite, but archean and algae are also developed.Abundant fossil organisms are found in geyserite, high affinity to jelly opal grains in spatial distribution. The fossil organisms were verified to be culturable, and the cultured living bodies resemble the dominant species in the area, indicating that they are the same or similar species.The geyserite shows distinct algal laminated structure. Geochemical and electron microprobe analysis indicats that the cesium content in algae lamination is higher than that in opal lamination.All the dominant species, i.e. Thermus sp. TibetanG6, Calothrix sp., Oscillatoria sp. and Denticula elegans, in the area, show the ability to accumulate cesium from solution. The microbial mats beneath water contain cesium. The solution containing the strain TibetanG6 can efficiently enhance the effect of leaching of cesium from cesium-bearing geyserite. In addition, these dominant species can promote silica precipitation in water. All the above evidences show the biological origin of the cesium-bearing geyserite. At last we present a composite mineralization model of cesium-bearing geyserite from a biological view.