Geochemistry and origin of the Cretaceous sedimentary kaolin deposits, Red Sea, Egypt

• Published in: Chemie der Erde 2014-06, Vol.74 (2), p.195-203
• Main Author: Baioumy, Hassan M.
• Format: Article
• Language: English
• Subjects: Geochemistry; Mineralogy; Red Sea; Sedimentary kaolin deposits; Source
• ISSN: 0009-2819; 1611-5864
• DOI: 10.1016/j.chemer.2013.06.008

This work reports, for the first time, the mineralogical and geochemical characteristics of the Cretaceous sedimentary kaolin deposits in the Red Sea area, Egypt and sheds the light on their source. Mineralogical and geochemical analyses of both bulk deposits and the sand and clay fractions of these deposits indicated that they are composed of kaolinite (average of 75wt.%) and quartz (average of 22wt.%). Traces of anatase (average of 1wt.%) were identified in all kaolin samples, while traces of halite (average of 2wt.%) and hematite (average of 1wt.%) were reported in the majority of the analyzed samples. The clay fractions show relatively high contents of TiO2 (average of 2.1%), Ni (average of 103ppm), Nb (average of 98ppm), Y (average of 67ppm), and Zr (average of 630ppm). Sum of the rare earth elements (ΣREE) in the clay fractions varies between 193 and 352ppm. Chondrite-normalized REE patterns show enrichment of the light REE relative to the heavy REE ((La/Yb)N=9) and negative Eu anomaly (Eu*/Eu=0.67). Major, trace, and rare earth elements geochemistry of the clay fractions from the studied kaolin deposits suggested that these deposits were derived from a mixture of more than source rocks probably a mixture of mafic, granitic, and alkaline rocks. The contribution of granitic rocks was proposed based on the REE pattern and negative Eu anomaly as well as the high Zr and Y contents, while the contribution of mafic rocks to the source was suggested based on the relatively high TiO2 and Ni contents. The abnormally high Nb contents in the clay fractions of the Red Sea kaolin deposits indicated a contribution of alkaline rocks to the source of these deposits. Igneous and metamorphic rocks of different composition belonging to the Arabian-Nubian Shield are located very close to the studied deposits. The monomineralic nature of the Red Sea kaolin deposits as kaolinite, abundance of organic matter, and absence of any marine fossils suggested a non-marine depositional environment of these deposits. Occurrence of halite in the studied deposit is probably due to sea breezes since the studied deposits are located close to the Gulf of Suez.