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Uranium distribution in the Upper Cretaceous-Tertiary Belqa Group, Yarmouk Valley, Northwest Jordan

By Basem K. Moh'd and John H. Powell


Uranium distribution has been studied in the outcropping Upper Cretaceous-Tertiary rocks (Belqa Group) in northwest Jordan. Representative samples of phosphorite, chert, silicified limestone, chalk, marl, fossiliferous limestone and glauconitic limestone were collected and chemically analyzed using XRF techniques. Uranium values range between less than 1 ppm and 70 ppm. The highest U concentration (52-70 ppm) was encountered in the phosphatic rocks. Uranium values in other lithologies are up to 19 ppm. The lowest values were encountered in fossiliferous limestone (<1 ppm), chert (2 ppm), silicified limestone, almost pure chalk and silicified chalk (4 ppm). Uranium concentrations in northwest Jordanian chalks are higher than Cretaceous chalks of the USA and Europe (North Sea). Uranium is positively related with P2O5 (francolite in phosphorite). Organic matter could be related to elevated levels of uranium in highly bituminous marl (average of 25 ppm). Uranium is positively associated with Cr, Zn, Mo, As, Sc and V (correlation coefficients r> 0.80). When U is cross-plotted against other variables, aggregation based on lithology became clear and the importance of other factors (with r>0.80) such as alumina, total iron oxides, P2O5, LOI (loss on ignition) Ni, Cl, As, Mo, Cd, La became evident. Factor analysis showed that uranium is distributed in clay and carbonates, depositional groundwater and organic matter, and phosphorite. Weak loadings are observed with factor 2 in comparison to factors 1 and 3.\ud Uranium concentrations in Jordanian and similar chalks can be predicted from the knowledge of alumina, total iron oxides, P2O5, and LOI

Year: 2010
OAI identifier: oai:nora.nerc.ac.uk:12865

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