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This work reports, for the first time, the Pb, Sr and Nd isotopes of the clay fractions (<2 mu m) from sedimentary kaolin deposits in Egypt of different ages (Carboniferous and lower Cretaceous), localities (Sinai, Red Sea and Aswan), lithologies (flint and plastic) and clay minerals composition (pure kaolinite and mixture of kaolinite, illite and chlorite) to determine their source area compositions and examine the effect of provenance on their isotopic compositions.

Measured (present day) and age-corrected Pb isotopes data (100 and 300 My for the Cretaceous and Carboniferous deposits, respectively) are more or less homogeneous in all deposits regardless of their ages, localities, and compositions. This, therefore, suggests that the Pb isotopes cannot be used as a tracer for source area compositions of these kaolin deposits. On the other hand, the studied kaolin deposits show variations in their measured and age-corrected Sr and Nd isotopes regarding to their ages and compositions. The Carboniferous illite-rich kaolin deposits in the Khaboba and Hasbar areas, Sinai have higher measured and age-corrected Sr-87/Sr-86 ratios (average of 0.715742 and 0.711156 for measured and agecorrected, respectively) compared to the non-illitic Carboniferous deposit at Abu Natash area (average of 0.70772 and 0.70769 for measured and age-corrected, respectively) and the lower Cretaceous deposits in all areas (average of 0.70827 and 0.70821 for measured and age-corrected, respectively). The Carboniferous kaolin deposits in the Khaboba and Hasbar areas also have lower Nd-143/Nd-144 ratios (average of 0.51206 and 0.51180 for measured and age-corrected, respectively) compared to the Carboniferous Abu Natash deposit (average of 0.51253 and 0.51231 for measured and age-corrected, respectively) as well as the lower Cretaceous deposits in all areas (average of 0.51248 and 0.51239 for measured and age-corrected, respectively). Initial epsilon Nd values are negative in the Carboniferous kaolin deposits in the Khaboba and Hasbar areas (average of -8.8) and lower Cretaceous deposits (average of -2.3), while the initial shld values are positive in the Carboniferous Abu Natash deposit (average of 0.95).

The comparison of radiogenic isotopic compositions of the studied sedimentary kaolin with those of the Arabian Nubian Shield (ANS) and East Sahara Craton (ESC) basement rocks indicates that the source of these kaolin deposits is not a simple source but rather a mixture of different rock types represent the composition of the ANS and ESC basement rocks. The (87S)r/Sr-88 ratios and eNd values suggest an old crustal source (ESC) for the Carboniferous kaolin deposits in the Khaboba and Hasbar areas but younger and more juvenile crustal sources (ANS) for the Carboniferous kaolin deposit in the Abu Natash area as well as the lower Cretaceous deposits in all areas.

The homogeneity of the Pb isotopes in the studied kaolin deposits indicates that the Pb isotopes cannot be used as tracer for source area composition of kaolin deposits, while the systematic variations of both Sr and Nd isotopes among the studied deposits suggest their possible use to differentiate between sedimentary kaolin deposits based on their source rock compositions. (C) 2014 Elsevier Ltd. All rights reserved.