Integrating of Remote Sensing and Airborne Magnetic Data to Outline the Geologic Structural Lineaments That Controlled Mineralization Deposits for the Area around Gabal El-Niteishat, Central Eastern Desert, Egypt

The Gabal (G.) El-Niteishat area lies in the Central Eastern Desert of Egypt which is known for various mineral resources and geological structures. Umm Gheig, Umm Naggat, Umm Shaddad, Wadi (W.) Zeidun and Sigdit represent some important regions that contain mineral deposits in the study area. Various filters such as first vertical derivative (FVD), horizontal gradient magnitude (HGM), tilt derivative (TDR) and near-surface were applied to the airborne magnetic data for the study area to deduce the structural lineaments and magnetic source edges which were controlled by the presence of mineral deposits. Processed Landsat ETM+ images are used for delineating the rock unit boundaries that are exposed in the study area such as serpentinite, metagabbro, metavolcanics and metasediments. Also, band ratios, principal component analysis (PCA) and false-color composite image (Crosta alteration image) were applied to get specific results about the alteration zones. The structural lineaments analysis illustrated that the common trends that affected the study area were NW-SE, NE-SW, E-W and N-S. Integration of remote sensing and airborne magnetic data exhibited the relation between mineralization and structural lineaments.

Anisotropy of Magnetic Susceptibility (AMS) of Bostonite Rocks, Um-Gir and El-Atshan-II Uranium Prospect Areas, Central Eastern Desert, Egypt

Um-Gir and El-Atshan-II areas represent important structurally-controlled radioactive anomalies and have become promising areas for U exploration. The bostonite rocks represent the most promising rock unit in the two studied areas. They form the most promising rocks due to their high radioactivity and, hence uranium mineralization. Anisotropy of magnetic susceptibility (AMS) measurements was carried out for Um-Gir and El-Atshan-II bostonite rocks. The AMS results show that the mean magnitude of magnetic susceptibilities is low, of the order of 10-5 S.I. units. Consequently, the bostonite rocks of the two areas are considered as non-magnetic, reflecting the presence of hematite as the main ferromagnetic mineral. These results are in agreement with the measurements of initial remnant magnetization (NRM) and the results of isothermal remnant magnetization (IRM) for the two areas. Besides, the results of magnetic anisotropy degree (PJ), refer to and concluded that the magnetic fabric of bostonite of two the areas has secondary fabric. AMS results clearly show the differences between the bostonite dyke of Um-Gir and Bostonite sill of El Atshan-II. The lineation (P1) > foliation (P3), and the negative values of the ellipsoid shape (T) of Um-Gir bostonite reflect clearly magnetic lineation (prolate ellipsoid). However, in El Atshan-II, (P3 > P1), the values of T are positive, which indicate the predominance of magnetic foliation (oblate ellipsoid) over lineation. Furthermore, the foliation planes of the bostonite dyke of Um-Gir possess a shallow to moderate inclination and a nearly N-S direction, while, the foliation planes of the bostonite sill of El-Atshan-II show a shallow to moderate inclination and a NNE direction. Finally, the AMS method is a powerful tool for detecting the structures that affect the bostonite rocks of the two studied areas.

Mineralogy,M-type tetrad effect and radioactivity of altered granites at the G.Abu Garadi shear zone,central Eastern Desert,Egypt

The G. Abu Garadi area is covered mainly by metasediments, alkali feldspar granites and stream sediments. The alkali feldspar granite is traversed by a major strike-slip fault trending in an N-S direction as well as two subordinate sets of faults trending NW to WNW for the first one and NE for the second one. These faults represent the shear zones affected by magmatic (syngenetic) as well as hydrothermal (epigenetic) activities causing alteration of the granitic rocks. The most common alteration features are albitization, greisenization and koalinitization. The mass balance calculations of the studied altered samples show enrichments in Zr, Y, Ni, U, Th and Ga and depletions in Zn, Sr, Nb, Ba, Pb, Cu and V. Only the greisenized samples exhibit a significant enrichment in Nb, ∑REE budget and pronounced lanthanide tetrad effect (M-type), especially TE1,4, while weakly expressed tetrad effects are for the other albitized and koalinitized samples. Mineralogically, the common accessory minerals in the altered samples include samarskite-(Y), betafite, uranothorite, zircon, fluorite and cassiterite. The greisenized granites contain high eU and eTh than the other altered types, where they are characterized by an assemblage of the radioactive minerals; samarskite-(Y), betafite, uranothorite in addition to zircon. The inter-element relationships between U and Th and also their ratios illustrate that the radioelement distribution in these granites is mainly governed by magmatic processes, in addition to post-magmatic ones. The distribution of chemical elements and the fractionation of some isovalents within the shear zone are largely controlled by the newly formed mineral phases. With respect to uranium mobilization, uranium migrated from the host alkali feldspar granites of G. Abu Garadi, while the shear zones acted as traps for the migrated uranium. Moreover, U migrated in the shear zone during greisenization and albitization, and migrated out during koalinitization.

Characterization of a Post Orogenic A-Type Granite, Gabal El Atawi, Central Eastern Desert, Egypt: Geochemical and Radioactive Perspectives

The alkali feldspar granite of Gabal El Atawi is post orogenic granite originated from subalkaline magma in extensional suite. It is developed within plate tectonic setting and has A2-type character which generated from apparent crustal source. The petrographic, geochemical and radioactive characteristics of El Atawi granite meet and fulfill the requirements of being fertile granite and it can be considered as promising uraniferous granite. Fluid inclusion studies of the altered granite elucidated two different solutions acting on the host granitic pluton. The first is NaCl-CaCl low temperature fluid with a wide range of salinity. The second is high temperature and salinity Fe-Mg-Na chloride solution. Different fractures in the granite acted as good channels for the hydrothermal fluids that leached uranium from its bearing minerals disseminated all over the host granite and redeposited it in the alteration zones.