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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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Drill cores obtained during the drilling of the Bendix/Department of Energy radon emanometry grid, Red Desert, Sweetwater County, Wyoming, have been analyzed for Polonium-210 and studied using alpha sensitive, nuclear emulsions. These nuclear track plates provide descriptive information on the physical distribution of U-238 and its alpha emitting daughter products. Microscopic examination of exposed and developed plates on which non-ore zone core samples were dispersed suggests that U-238 and its long-lived daughters U-234, Th-230, and Ra-226 deposit on grain surfaces in very low concentrations (U-238 in sub-picogram amounts). Many of these atoms are bound to the surfaces so lightly that they, as well as Rn-222, are free to enter the underlying emulsion where their decays are recorded. Concentrations of alpha activity usually associated with discrete uranium minerals were not observed. Ra-226 appears to be more mobile than Rn-222. Measurements of Po-210 in the sequential decay, Rn-222 (3.8 days) ^rarr Pb-210 (22 years) ^rarr Po-210 (138 days), provide an indirect means of estimating the number of Rn-222 atoms that have decayed in a sample over the last 80 to 100 years. Many Po-210 highs have been observed in the Red Desert cores, some directly associated with uranium mineralization. To date, evidence for the predicted Po-210 concentration gradient produced by the decay of mobile, unsupported Rn-222 either in transit to the surface or over short distances, has not been found. These Po-210 analyses and microscopic studies suggest that observed Rn-222 and Po 210 surface anomalies may be associated with widely dispersed very low concentration halos of Ra-226 or its longer lived parents which surround the ore.
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