Uranium, mobility

Another area for research is how groundwater fluxes of vanadium (critical for carnotite precipitation) and phosphate (enhances uranium mobility) are controlled by geology and geomorphology. This may assist in targeting economic from sub-economic targets. 

Parsons, A. 2007. Potential for Uranium mobilization from weathered outcrops of uranium-bearing sedimentary strata, southern Nova Scotia. BSc Honours Thesis, Earth Sciences, Dalhousie University. 

Reduction-oxidation processes, which are the dominant control for uranium mobility and deposit formation, are also responsible for elevated molybdenum and vanadium contents observed associated with mineralization. 

Arthur, J.D., Cowart, J.B. and Dabous, A.A. (2000) Arsenic and uranium mobilization during aquifer storage and recovery in the Floridan aquifer system. Abstracts with Programs. The Geological Society of America, 32(7), 356. 

DEUTSCH AND SERNE Uranium Mobility and Roll-Front Deposits... 

Information concerning the effect of in situ mining on the potential concentration of uranium in solution and concerning the experimentally determined effect of solution/sediment interactions on uranium mobility in the aquifer environment can be used to estimate the response of a geologic nuclear waste repository to the ingress of oxidizing water. 

Other factors also affect the mobility of uranium in soil. A field study performed near an active carbonate leach uranium mill showed that uranium in an alkali matrix can migrate to the groundwater (Dreesen et al. 1982). Uranium mobility may also be increased due to the formation of soluble complexes with chelating agents produced by microorganisms in the soil (Premuzie et al. 1995). 

The relative ratio between flows in processes 1 and 2 (Fig. 1) varies according to the distribution of uranium atoms in the different molecular sites in the source rock—indeed, such distribution determines the way in which uranium mobilization occurs. Uranium contained in insoluble accessories is leached to a very limited extent, so it is presumed to be transported to and concentrated in resistate sediments as clastic material. Adams and co-workers estimated that 60-85% of the uranium in igneous rocks is present in mineral phases that are resistant to chemical alteration approximately 15-40% is transported in the dissolved form by liquid water. The above fraction of uranium takes part in the processes of erosion and sedimentation (represented by the arrow in the upper part of Fig. 1 that connects the source rock box directly with the sediment box). 

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. 

Fyfe W. S. et al. Uranium mobilization into overthrust Archaean basement, Bahia, Brazil. In GAC-MAC joint annual meeting, programme with abstracts (Waterloo, Ont. Geological Association of Canada, 1982), 51. 

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.). 

Oliver, I.W., Graham, M.C., MacKenzie, A.B., et al, 2008a. Depleted uranium mobility across a weapons testing site isotopic investigation of porewater, earthworms, and soils. Environ. Sci. Technol 42, 9158-9164. 

---