THE GEOCHEMISTRY OF URANIUM AND THORIUM ISOTOPES IN THE WESTERN DESERT OF EGYPT

被引:16
作者
DABOUS, AA
机构
[1] Geology Department, Ain Shams University, Cairo
关键词
D O I
10.1016/0016-7037(94)90193-7
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The concentration of U-238, U-234, Th-232, and Th-228 have been measured in the groundwaters of the Bahariya and Farafra oases of the Western Desert of Egypt. These waters are characterized by normal amounts of U, but unusually high concentrations of Th. The pattern of variation of the parent isotopes, U-238 and Th-232, as well as the daughter isotopes, U-234, Th-230, and Th-228, is systemic within and between the two oases. From the unusually consistent distribution of the U-234/U-238 activity ratios one can conclude that the samples from both oases are representative of a two-component mixing system. One component, characterized by low U content and a high U-234/U-238 activity ratio, is typical of deep artesian systems and probably represents flowthrough water derived from the Nubian highlands to the south. The second component is characterized by a greater U concentration and a low activity ratio. This signature is hypothesized as being derived by leaching of downward infiltrating water during pluvial times. The source of the U may be the uraniferous phosphate strata that overly the sandstone aquifer in both oasis areas. Higher Th values are associated with the artesian flow component of the mixing system and suggests that Th-bearing minerals may be abundant in the Nubisan sandstone aquifer. The distribution of Th-230 and Th-228 in the water samples supports this interpretation.
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页码:4591 / 4600
页数:10
相关论文
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