SEDIMENTATION OF SOME EGYPTIAN CENOMANIAN
GLAUCONY DEPOSITS: MINERALOGICAL AND
GEOCHEMICAL EVIDENCES
KADRY N. SEDIEK
Geology Department,Faculty of
Sciences, Alexandria University |
Cenomanian Glaucony sediments of the Eastern Desert and west-central Sinai were studied to determine their distinctive characteristics. Petrographic study revealed three main glaucony facies namely:glaucony sandstone, sandy glaucony mudstone and calcareous glaucony sandstone.
The mineralogical composition of the glaucony clayey samples was investigated by XRD, which revealed illitic composition with randomly interstratified illite, smectite and traces of kaolinite. Scanning Electron Microscopy investigation shown that the studied glauconv clay have various micro-textures and micro-structures expressed by micrograins and microcrystals, which form box-work, rosette-like structures and lamellar or platelets structures. The chemical analysis of hand picked glaucony grains pointed that the studied glaucony have high contents of silicon, ferric iron, potassium, and low content of magnesium, copper , zinc and traces of calcium, sodium, vanadium and titanium.
The difference in petrographical, mineralogical and chemical compositions of the glaucony grains shows that every grain is considered as a separete chemical system, which expresses its local conditions within the environment of deposition and consequently the degree of glauconitization.
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