Al-Hilal and Al-Ali reported in 2016 that a detailed radiometric survey including soil gas radon measurements and field gamma ray survey, in accordance with geochemical and geological investigations were carried out in Al Nassrieh basin (central Syria), for the purpose of uranium exploration. Thirty six samples were collected from various lithofacies of the survey area and analyzed by γ-ray spectrometric technique for determining the concentration values of major radioelements. The relationships between the concentrations of equivalent eU, eTh, and their ratios were examined in order to define their trend of variations and evaluate the degree of uranium remobilization and redistribution.
Although the initial results indicated that uranium enrichment is mostly restricted to the upper Cretaceous phosphate rocks, a considerable portion of uranium appeared to be leached out of the primary phosphatic source and dispersed in the adjacent recent sediments. Further, notable increases of radon level associated with relatively high values of uranium concentration and gamma count rates were found to be spatially correlated with the transition zone between the marine Paleogene and continental Neogene formations throughout the study basin. This observation demonstrates the importance of the concerned zone as a suitable geological environment for hosting probable uranium mineralization along a chemically reducing interface where surface water of terrestrial and marine origin mingled at depth and away from surficial conditions.
Radiometric survey integrated with geochemical and geological investigations have successfully defined the locations of the uranium-bearing phosphate rocks in AlNassrieh basin, and outlined the general pattern of uranium dispersion in the surrounding environment. The obtained radiometric data is regarded as a vital source of information for exploring and identifying the economically important phosphate deposits in the region. On the other hand, the
correlation between eU, eTh and their ratios, besides the tendency of radon variations and γ-ray activity along the measuring profiles, indicated that a considerable portion of the original uranium was presumably remobilized out of the
Cretaceous phosphate rocks and consequently dispersed through the adjacent recent sediments. Remarkable increases of radioactivity levels were noticed across the transitional zone between the marine Paleogene and continental Neogene formations throughout the study basin. This could be an important evidence of probable downward migration of the leached uraniferous solutions to some depth below the erosion surface where uranium might have precipitated along a promising geological environment that is suitable for hosting uranium mineralization.
Accordingly, a new model has been proposed to explain the likely fate of the dissolved uranium towards appropriate structures that would provide the necessary conditions for preserving potential uranium deposits along a chemically reducing zone where surface water of terrestrial and marine origin combined at depth and away from surficial weathering. Such depositional structures merit further detailed studies throughout the Palmyrides region in order to evaluate their radioactive characteristics and delineate their subsurface extensions.
Finally, a fairly good correlation has been found between the results of field and laboratory γ-ray spectrometric data, which may demonstrate the accuracy of measurements and certify the sensitivity of the detection limits for both methods.
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