A CONTRIBUTION TO THE GEOCHEMISTRY OF EL-SIBAIYA PHOSPHORITES, NILE VALLEY, EGYPT

Document Type : Original Article

Authors

1 Department of Geology, Faculty of Science, Minufiya University, Minufiya, Egypt

2 Nuclear Materials Authority, Cairo, Egypt

Abstract

El-Sibaiya phosphorites represent a part of the Middle East to North Africa phosphogenic province.
They encountered in the Gabal (G.) Duwi Formation of Late Cretaceous to Paleogene age. The studied
samples have been collected from the eastern and western sides of the Nile River.
Major elemental analysis of the collected samples declared positive correlations between P2O5 and
CaO and F. These correlations indicate that these elements are contained in the apatite phase. On the other
hand, P2O5 shows negative correlations with other major elements such as Al2O3, SiO2, Fe2O3 and MgO.
Some trace elements such Cr, Sr and V show positive correlation with P2O5.
The average of the total rare earth elements (!REEs) in the studied phosphorites is 262ppm.
Chondrite-normalized patterns of !REEs of the studied phosphorites show a good coherence with the world
average of shale suggesting that !REEs in the studied phosphorites were derived from the associated
clastic debris through the diagenetic remobilization. The week negative Ce and Eu anomaly of the studied
samples and the marked enrichment in LREEs emphasize that the studied phosphorites subjected to a later
post-depositional modification.
Laser ablation analysis showed that apatite mineral of the studied phosphorites is enriched in some
elements such as Ca, F, Cr, Sr, V, Zn, Ba and REEs. This explains the major role of substitution processes
of these elements within apatite lattice.
The uranium average in El-Sibaiya East phosphorites is 81.6 ppm, while in El-Sibaiya West
is 51.1ppm. Apatite minerals play an important role in the accumulation of U within the studied
phosphorites.

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