الفهرس 
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Abstract
The aim of this study is to determine the uranium fingerprint of studied samples collected from of Gabal Allouga, southwestern Sinai, Egypt through the calculation of different activity ratios, uranium age dating, lead concentration and REEs concentration. High purity germanium detector was used to estimate the specific activities and activity ratios of different radionuclides in the studied samples and ICP-OES was used to evaluate lead and REEs concentration.
The activity concentrations for Quarry face and north Quarry face of Gabal Allouga for 238U are 4957.82±77.42 and 6480.03±95.77 Bq/kg, respectively while for 226Ra are 12088.26±40.28333 and 11668.66±24.05 Bq/kg, respectively. It is clear that, all samples have higher activity concentrations of 238U and 226Ra than the permissible level (32 Bq/kg) and (33 Bq/kg), respectively.
232Th activity concentrations are 17.79±1.87 (Quarry face) and 67.89±2.1 Bq/kg (north Quarry face). All samples which are black shale and dolostone have activity concentrations of 232Th less than the permissible level (45 Bq/kg) but variegated shale samples have high values.
The activity concentrations for 40K are 113.48±3.9 (Quarry face) and 445.64±7.12 Bq/kg (north Quarry face). The all studied samples have activity concentrations of 40K less than the permissible level (412 Bq/kg) except B.1, B.3 and B.4 (variegated shale).
The activity ratios of various radionuclides in different rock types show what occurred in these rocks. The 234U/238U, 230Th/238U, 230Th/234U and 226Ra/238U activity ratios for the examined samples show fractionation of uranium and thorium isotopes during chemical weathering.
It is noticed that the uranium was migrated- out from the variegated shale of the north Quarry face (sample B.1) to the black shale in the Quarry face (sample MR.2). The other samples and rock types have equilibrium between the two isotopes.
234U/238U ≤ 1 and 230Th/234U > 1 are common characteristics of uranium removal from rocks which are similar to the studied samples (MR.3, MR.4, B.1, B.2 and B.3). Reason for these ratios is that groundwater leaches 234U preferentially to 238U and removes both uranium isotopes in comparison to 230Th; nevertheless, the activity ratios later changed to 234U/238U < 1 and 230Th/234U < 1 like the samples (MR.1, MR.6 and B.4). This is due to the late adsorption of uranium from water with 234U/238U < 1 by the rock. 226Ra/230Th A.R >1 for all samples from Quarry face and north Quarry face which indicate all samples show 226Ra migration- in; so the Allouga area show 226Ra migration-in.
The ages of uranium depositions for black shale and dolostone samples are 38.08, 36.63, 37.01 and 37.76 ky, respectively, while for variegated shale sample is 84.06 ky. So, after subtraction the detrital 230Th, the corrected ages for Quarry Face samples vary from 32.82 to 37.77 ky while for upper part (variegated shale) sample is 82.81 ky.
The results of the chemical analysis for the Pb in the studied rock samples are measured by ICP-OES. It is observed that the total lead concentrations in variegated shale vary from 63.17 to 117.13 ppm with average 80.91 ppm which was higher than that for black shale and dolostone samples.
ΣREEs contents are varied between 99.55 and 214.91 ppm with average 175.13 ppm in black sahle, 116.41 to 149.57 ppm with average 129.97 ppm in dolostone and for variegated shale varied between 463.04 and 619.9 6 ppm with average 549.76 ppm. It is clear that variegated shale samples have higher REEs content and dolostone samples have lowest REEs content.
All different types of studied sedimentary rocks have higher average values of Nd, Ce and Y; where Nd was higher than abundance in the earth’s crust (41.5 µg/g) in all types of rocks but average abundants of Ce and Y are higher than abundance in the earth’s crust (66.5, 33) µg/g in variegated shale.