Mobility, geochemical uranium

Moulin V, Ouzounian G (1992) Role of colloids and humic substances in the transport of radio-elements through the geosphere. Appl Geochem (Suppl. Issue 1 179-186 Murakami T, Ohnuki T, Isobe H, Sato T (1997) Mobility of uranium during weathering. Am Mineral 82 888-899... 

Alteration assemblages may include primary chlorite, illite, smectites, and/or kaolinite, and various primary and secondary iron oxides, carbonates, and sulfides (Fig.1), any one of which may serve as indicators of fluid composition. Lithologic geochemical surveys rely on an understanding of these patterns to vector towards uranium deposits. The interpretation of hydromorphic geochemical surveys, including lake and stream sediment, and soil, depends on the mobility of uranium and associated elements in the surface and near surface environment. 

With -V, y in the range of a few ppm U and X and Y some 150kg/cm, m = 0.001 mg/kg, A/= 280kg/cm and, in terms of flow, fT=0.02kg/year cm with w = 0.0005 mg/kg. The geochemical mobility of uranium can be expressed by assuming that about one-thousandth of its total mass in sediments, or of its total removed mass from crystalline lithosphere, is dissolved in ocean water and, hence, is available for transport and precipitation anywhere on earth. 

FIolk, G.J., Kyser, T.K. Don Chipley, FIiatt, E.E., Marlatt, J. 2003. Mobile Pb-isotopes in Proterozoic sedimentary basins as guides for exploration of uranium deposits. Journal of Geochemical Exploration, 80, 297-320. 

Reimer, G.M., Denton, E.H., Friedman, I. and Otton, J.K., 1979b. Recent developments in uranium exploration using the US Geological Survey s mobile helium detector. J. Geochem. Explor., 11 1-12. 

Invariably, the few factors that explain most of the data can be related to geochemical processes. In Table 5 five factors explain 82% of a total matrix of 121 groundwater samples and 12 determinations. Elements of low significance in each factor occur between the horizontal bars. The remaining parameters suggest the geochemical process represented by each factor (1) the maturity of the water, (2) the tendency for elements to become mobilized, (3) the tendency for the water to become alkaline, (4) the tendency for selenium to go into solution if available and (5) the large-scale occurrence of pathfinder elements for uranium. 

A consideration of other elements associated with roll-front deposits improves the accuracy and confidence in locating favourable trends (Fig. 9). Sulphate concentration and conductivity increase toward the redox front and then decrease abruptly owing to precipitation of iron sulphide, followed by calcium carbonate. High values of bicarbonate and selenium also contribute to identification of the zone of uranium mobilization on the oxidized side of the front. Molybdenum concentrations are normally associated with sandstone deposits, but haloes in the groundwater may be to the side of or farther down-dip than the centre of the geochemical cell. Arsenic is most valuable for its regional halo around areas of mineralization. 

Use of radium in detailed soil geochemical exploration Because of its weak mobility in relation to uranium, it is particularly useful to determine the radium content in the soil during detailed prospecting. The contrary geochemical behaviour of radium and uranium (mobility in reducing conditions, immobility in oxidizing conditions) may be used to interpret specific anomalies (swamps, stream beds, etc.). 

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