MINERALOGICAL AND SEDIMENTOLOGICAL
CHARACTERS OF GARNETS FROM WEST ROSETTA,
EGYPT
SALAH S. EL BALAKSSY, FATHY A.
AMMAR, HAMED I. MIRA
and NAGDY M. ABDOU
Nuclear Materials Authority, Cairo, Egypt |
Rosetta garnet exhibits diverse magnificence characters. Its average percentage in the studied area is about 0.57%. It is more concentrated in light Clerici´s fraction than the heavy
part. The heavy garnets are more abundant in magnetic fraction 45x10-6 cgs than 7.2x
10-6cgs, while the light garnet are more concentrated at magnetic faction
7.2x10-6cgs than 45x10-6cgs. Rosetta garnet has a unimodal grain size distribution with the modal class lies in the fine sand size class. It displays general sedimentological characters, where it is described as fine sand, moderately well sorted, nearly symmetrical and mesokurtic. On the other hand, three modes of transportion were proposed which are the saltation ,suspension and rolling.
Rosetta garnet exhibits different colours. These colours vary from rose, deep red, reddish brown, orange, green and dark brown. Several crystal habits were recorded. The subrounded grains are more frequent and constitute about 41.20% . The euhedral particles are less common and constitute about 8.10%. The euhedral crystal include Rhombic Dodecahedron, and Trapezohedron beside combination
forms. Rosetta garnet displays higher unit cell dimensions than the ASTM card. Therefore, the deformation features in the garnet crystal lattice take place. In addition, some characteristic surface features were shown and represented by the well developed etch rectangular patterns, disintegration, faceted, mammillated and pitted. Almandine is the most common garnet mineral . Andradite garnet is very rare. The grape garnet, calderite garnet, rhodolite garnet and the kimzeyite garnet represent the less common garnet varieties. The schist rocks from the metamorphic terrain of the Ethiopian highlands, the metamorphic rocks draining the Eastern Desert of the Southern Egypt. Futhermore, the wadies drained frorn the Red Sea Hills as Wadi El Allaqi and the granitic terrain of the Central African Plateau represent the dominant provenances of the studied garnet. Geochemically, the studied garnet is characterized by enrichment in HREF than LREE with pronounced negative Eu anomaly, which suggested the schist source.
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