Northeastern Desert Of Egypt Research Articles

Resolution enhancement of foraminiferal biostratigraphy of the Campanian-Maastrichtian interval: A case study from the Eastern Desert, Egypt

The Campanian-Maastrichtian (C-M) rocks exposed at the Southern Galala Plateau, North Eastern Desert of Egypt are represented by Sudr Formation, which consists of snow white chalky limestone, rich in planktonic and benthonic foraminifera. The major C-M transgression resulted in a deposition of Sudr Formation in outer neritic environment with high diversity and abundance of species, which led to defining nine planktonic foraminiferal zones and establishing the stage boundaries. In comparison with the foraminiferal zones of the GSSP of the C/M boundary, the lowest occurrence of Rugoglobigerina scotti is here considered to be the only marker for this boundary. In contrast, the other species (e.g. Contusotruncana contusa) that used to define this boundary at the GSSP is a diachronous and not save to depend on it in definition of the C/M boundary. Therefore, the present study helps in refinement of the C/M boundary definition not only in the study area, but also elsewhere.

Hydrothermal alteration and evolution of Zr-Th-U-REE mineralization in the microgranite of Wadi Ras Abda, North Eastern Desert, Egypt

Ras Abda plutonic suite, North Eastern Desert of Egypt, consists predominantly of Neoproterozoic calc-alkaline older granites. Minor exposures of pink microgranite are occurring along Wadi Ras Abda within the older granites. Previous studies on this area demonstrated that the microgranite is altered in some parts and contains anomalous concentrations of rare metal elements (Zr, Th, and U). These altered and mineralized zones are re-assessed using field observations, chemical analysis, and by the application of various transmitted light and electron microscopic techniques. The rare metals exist as mineral segregation grew freely into open cavities of the microgranite and concordant with the NNE strike-slip fault movement. The mineralized zones contain an assemblage of secondary magnetite, zircon, uranothorite, columbite-(Mn), fergusonite-(Y), and allanite-(Ce). The extreme abundance of zircon in the mineralized zone, along with other evidence, indicates a hydrothermal origin of this zircon together with associated rare metals. The geochemical investigation and mass balance calculations revealed extreme enrichment of Zr, Th, U, Y, Nb, Ta, and REE. Post-magmatic hydrothermal alterations resulted in such pronounced chemical and mineralogical heterogeneity. The hydrothermal fluids are thought to be oxidizing, alkaline and of medium temperature (> 250 °C). The average contents of the elements Zr (1606 ppm), Th (1639 ppm), U (306 ppm), Nb (955 ppm), and REE (1710 ppm) in the mineralized microgranite reach sub-economic levels and could be a potential source of these elements.

Fluid evolution of Au-Cu zones in Um Balad area, North Eastern Desert of Egypt: Implications from mineral chemistry and fluid inclusions

Scanning electron microscope (SEM), Electron microprobe (EMPA) and fluid inclusion studies of the ore body, as well as geochemical analyses of country rocks were performed to determine the nature and characteristics of the mineralizing fluid responsible for Au-Cu deposits in Um Balad area, Northern Eastern Desert of Egypt. The Um Balad Au-Cu deposits are confined to well developed-quartz veins and veinlets cutting through the hosting country rocks. Petrographic and geochemical investigations of the hosting rocks distinguished between two main rock units; 1) metagabbro-diorite rocks with tholeiitic nature derived in island arc/continental margin tectonic regime, and 2) granodiorite rocks formed from calc-alkaline magma in continental margin regime. Wallrock alterations are represented by propylitic and argillic types. The mineralized quartz veins are striking in NE-SW direction and dipping between (35°–45°) in SE direction, other mineralized mafic dykes enriched with auriferous quartz veinlets are trending NE-SW and dipping 70°/SE. The main ore minerals are represented by gold, chalcopyrite, pyrite, sphalerite, malachite, covellite and goethite. While, geffroyite, cuprite, chrysocolla, pseudomalachite, britholite, wolframite, scheelite, hematite and rutile are detected as minor constituents. Fluid inclusions microthermometry and isochore calculations combined with chlorite geothermometry revealed that the Um Balad deposits were formed at temperature ranging from 305 °C to 325 °C and pressure between (100–500 bar). The mineralization had been developed in the shallow levels, beneath the water table at depth of 350–1760 m, rather than common mesothermal vein-type deposits in Egypt. Magmatic water have been suggested as the main source for the mineralized fluid. The transportation of the gold metal seems to be happen as bisulfide complexes in moderately acidic environment. The deposition was resulted from combination of changes in physico-chemical parameters, temperature and pressure plus the instability of the reduced sulfur complexes. A contamination with metamorphic and/or meteoric water was also proposed that has strong influence during the depositional process.

Genetic link between uranium mineralization and the emplacement of limited intrusion adjacent to alkaline granites, Abu Hamr area, north Eastern Desert, Egypt

The recorded uranium mineralization is genetically related to the U content and structural setting of syenogranitic dyke that occurs near alkaline granites, Abu Hamr area, north Eastern Desert of Egypt. The associated abnormal level of radioactivity exhibits maximum equivalent uranium (eU) of 155.6 parts per million (ppm) with an average of 54 ppm while the maximum of eTh reaches up to 235 ppm with average content of 120 ppm. The nearby alkaline granites of Gabal Abu Hamr show a normal distribution of eU and eTh resembling that of normal granites (4 ppm eU and 8 ppm eTh). Radioactive anomalies can be interpreted as successive concentrations of U-Th, which are related to magmatic processes of syn-shearing syenogranite dyke formation followed by hydrothermal redistribution during the emplacement, and then supergene enrichment. Testing of uranium equilibrium has revealed major chemical U addition to both the syenogranitic dyke and, to less extent, the alkaline granites. The rare-earth element (REE) patterns display pronounced enrichment of light REEs and heavy REEs of the syenogranitic dyke in contrast to the alkaline granites, which might have attributed to the subsequent hydrothermal circulation. The studied dyke is also characterized by well-developed U, Th, and Pb enrichments. Post-magmatic hydrothermal activity is evident from the presence of dark violet fluorite with inclusion of U and Th minerals, in addition to the presence of zircon crystals with overgrowth, xenocrystic cores, REE replacements, and spatially inclusions of allanite-(Ce) with irregularly distributed patchy overgrowths of U and Th.

Ra’s Abdah of the north Eastern Desert of Egypt: the role of granitic dykes in the formation of radioactive mineralization, evidenced by zircon morphology and chemistry

Syenogranitic dykes in the north of Egypt’s Eastern Desert are of geological and economic interest because of the presence of magmatic and supergene enrichment of radioactive mineralization. Zircon crystal morphology within the syenogranitic dykes allows precise definition of sub-alkaline series granites and crystallized at mean temperature of about 637 °C. The growth pattern of the zircons suggest magmatic and hydrothermal origins of radioactive mineralization. Hydrothermal processes are responsible for the formation of significant zircon overgrowth; high U-zircon margins might have occurred contemporaneously with the emplacement of syenogranitic dykes which show anomalous uranium (eU) and thorium (eTh) contents of up to 1386 and 7330 ppm, respectively. Zircon chemistry revealed a relative increase of Hf consistent with decreasing Zr content, suggesting the replacement of Zr by Hf during hydrothermal activity. Visible uranium mineralization is present and recognized by the presence of uranophane and autunite.

Structural evolution and Cenozoic tectonostratigraphy of the Cairo-Suez district, north Eastern Desert of Egypt: Field-structural data from Gebel Qattamiya-Gebel Um Reheiat area

Detailed field mapping reveals that continental rifting is strongly deforming the Gebel Qattamiya-Gebel Um Reheiat area and the entire Cairo-Suez district, in north Eastern Desert of Egypt. Rift-related structures are predominantly represented by E to WNW, NNW and NW oriented faults. The E to WNW oriented faults are small and build up the Gebel Qattamiya en echelon fault belt, whereas the faults trending NNW and NW establish a pervasive horst and graben structural style involving some rhomb-shape horsts as Gebel Qattamiya (GQRH), Gebel Um Reheiat (GURRH) and south Gebel Um Reheiat (SGURRH). Rock units of the Eocene succession and Oligocene sediments are well exposed and highly controlled by rift-related structures. Rifting was developed through two rift-phases; initial and major ones. The initial phase (a newly recognized phase in this contribution) has been occurred in Late Eocene (Priabonian), while the main phase was prevailing during Late Oligocene-Early Miocene time and is characterized by hydrothermal veins and basaltic eruptions. Continental transtension in the Cairo-Suez district, including the study area, was probably synchronous with a major tectonic stage (Pyrenean-Atlasic movement) of continental collision between African–Arabian and Eurasian plates in Late Eocene–Oligocene time.Field investigation suggests that the transfer of displacement (slip) from the Gulf of Suez proto-rift into the E–W oriented faults ‘‘relays’’ is an important mechanism, which helps to explain the current structural framework and tectonic evolution of the Cairo-Suez district. Reactivation of such faults with right-lateral divergent wrenching with NE–SW oriented extension deformed the Cairo-Suez district with several E–W oriented en echelon fault belts (e.g. Gebel Qattamiya fault belt in the study area). Thus the Cairo-Suez district represents an accommodation or transfer zone in northeastern Egypt, intercepting the ‘‘far-field stresses’’ from the Arabian–Nubian Shield, the Red Sea-Gulf of Suez rift and the Maghrebian Shield.

Sequence stratigraphy and depositional environments of Late Cretaceous–Early Palaeogene succession, North Eastern Desert, Egypt

The foraminiferal contents and geochemistry of 199 samples collected from three surface sections in the southern Galala Sub-basin, North Eastern Desert of Egypt, have been studied in detail. From south to north these sections are situated at Gebel Tarboul, Wadi Tarfa, and Bir Dakhl. The results allow reconstructing of the depositional environments and high resolution sequence stratigraphy of the Upper Cretaceous–Palaeogene succession. The quantitative and qualitative distribution patterns of benthic foraminifera of the Upper Cretaceous–Lower Palaeogene succession suggests a depositional environment from outer neritic to bathyal, at 200 to ~700 m water-depth. Based on sequence stratigraphic analyses, ten complete third order depositional sequences have been recognized. These depositional sequences from base to top are as follows: CaSGB-1 sequence, CaSGB-2 sequence, MaSGB-1 sequence, MaSGB-2 sequence, DaSGB sequence, Da/SeSGB sequence, SeSGB sequence, ThSGB sequence, Sp/YpSGB, and YpSGB sequence. These sequences are controlled by both eustatic sea-level changes and tectonic movements that prevailed during deposition.

Petrogenesis of U- and Mo-bearing A2-type granite of the Gattar batholith in the Arabian Nubian Shield, Northeastern Desert, Egypt: Evidence for the favorability of host rocks for the origin of associated ore deposits

Hydrothermal ore deposits associated with granitic rocks are the result of combinations and series of successive processes, events and conditions in a magma system and at post-magmatic stage. The metal content of a granitic magma as well as fractional crystallization, metal–ligand complexation, emplacement mechanisms and tectonic processes influence the metal precipitation and content of a hydrothermal ore deposit. The present study of the Gattar batholith evaluates how these processes contribute to the generation of an ore deposit. Gattar batholith in the north Eastern Desert of Egypt as part of the northern region of the Arabian–Nubian Shield (ANS) is geographically, mineralogically and geochemically divided into two distinctive areas. The southern part mainly consists of syenogranite while the northern part is dominated by highly evolved alkali-feldspar granite. Uranium and Mo mineralization occurring here is mostly limited to the margin of the highly evolved alkali-feldspar granites. New U–Pb zircon geochronology within this study indicates an age of ~620–600Ma, although high common Pb and discordant age data of many zircon grains reflect alteration by F-rich fluids. Some zircons with distinct older U/Pb ages were considered to be inherited from the wall rocks representing juvenile crust of the ANS. The two different granitic rocks are comagmatic in origin and have A-type characteristics generated by partial melting of lower juvenile crust of the ANS. Geochemical data are in good agreement with a magmatic origin of the alkali-feldspar granites, suggesting fractional crystallization of a syenogranitic source as the most favorable process of their formation. Petrography, geochemistry, and geochronology studies of the Gattar granites along with field observations provide evidence for multiple intrusions as a result of successive magma pulses with different chemical composition. This led to the formation of reverse zoning within the intrusive complex. This kind of magma emplacement promotes the escape of exsolved metal-bearing volatile-rich fluids into the boundary of the Hammamat Sedimentary Rocks (HSR) and Gattar granite at the northern part of the batholith. Build-up of volatiles is a common phenomenon in granitic rocks and typically results in enhanced contents of F, alkalis and ore metals released at subsolidus stage.

Lu–Hf and O isotopic compositions on single zircons from the North Eastern Desert of Egypt, Arabian–Nubian Shield: Implications for crustal evolution

Neoproterozoic juvenile crust is exposed in the Eastern Desert of Egypt, between the Nile and the Red Sea, forming the basement to Cambrian and younger sedimentary strata in the northernmost part of the Arabian–Nubian Shield (ANS). In order to reveal how the crust of this vast region was formed, four examples of widespread Neoproterozoic (653–595Ma) calc-alkaline and alkaline intrusive rocks in the northwestern most exposures, in the NE Desert of Egypt (NED) were studied. Single zircon Hf–O isotopic compositions of these intrusives were used to characterize the Neoproterozoic syn- and post-collisional granitoids in the NED. The ~653Ma Um Taghir syn-tectonic granodiorite (I-type) displays isotopic characteristics of a depleted mantle source, such as high εHf(t) (+9.1 to +11.2) and mantle δ18O (mean=+5.12‰). In contrast, the ca. ~600Ma post-collision A-type granites (Al-Missikat, Abu Harba, and Gattar) show slightly higher δ18O values (+5.15 to 6.70) and slightly lower εHf(t) values (+6.3 to +10.6, mean=+8.6). We interpret these isotopic data to reflect melting of a juvenile Neoproterozoic mantle source that assimilated slightly older Neoproterozoic crustal material during magma mixing. The involvement of crustal component is also supported by Hf-crustal model ages (0.67–0.96Ga) and by the occurrence of xenocrystic zircons with U–Pb ages older than the crystallization ages, indicating melting of predominantly Late Neoproterozoic crustal protoliths.

Pan-African adakitic rocks of the north Arabian–Nubian Shield: petrological and geochemical constraints on the evolution of the Dokhan volcanics in the north Eastern Desert of Egypt

The Precambrian basement of Egypt is part of the Red Sea Mountains and represents the north-western part of the Arabian–Nubian Shield (ANS). Five volcanic sections are exposed in the Egyptian basement complex, namely El Kharaza, Monqul, Abu Had, Mellaha and Abu Marwa. They are located in the north Eastern Desert (ED) of Egypt and were selected for petrological and geochemical studies as they represent the Dokhan volcanics. The volcanics divide into two main pulses, and each pulse was frequently accompanied by deposition of immature molasse type sediments, which represent a thick sequence of the Hammamat group in the north ED. Compositionally, the rocks form a continuum from basaltic andesite, andesite, dacite (lower succession) to rhyodacite and rhyolite (upper succession), with no apparent compositional gaps. These high-K calc-alkaline rocks have strong affinities to subduction-related rocks with enriched LILEs (Rb, Ba, K, Th, Ce) relative to high field strength elements (Nb, Zr, P, Ti) and negative Nb anomalies relative to NMORB. The lower succession displays geochemical characteristics of adakitic rocks with SiO2 >53 wt%, Al2O3 >15 wt%, MgO >2.5 wt%, Mg# >49, Sr >650 ppm, Y 25 ppm, Cr >50 ppm and Sr/Y >42.4. They also have low Nb, Rb and Zr compared to the coexisting calc-alkaline rhyodacites and rhyolites. The highly fractionated rhyolitic rocks have strong negative Eu anomalies and possess the geochemical characteristics of A-type suites. Trace element geochemical signatures indicate a magma source consistent with post-collisional suites that retain destructive plate signatures associated with subduction zones. The adakitic rocks in the northern ANS are generated through partial melting of delaminated mafic lower crust interacting with overlying mantle-derived magma. The Dokhan volcanics were likely generated by a combination of processes, including partial melting, crystal fractionation and assimilation.

SHRIMP U–Pb zircon geochronology: evidence for emplacement time of some granitoids north Eastern Desert, Egypt

In an effort to better constrain the crystallization ages of some Neopreterozoic granitic plutons, the precise SHRIMP U–Pb zircon geochronology was used. The studied granites comprise G. Abu Marwa, G. El-Glouf, G. Faliqu El-Sahl and Faliqu El-Waar, and G. Gattar in the north Eastern Desert of Egypt. The crystallization ages for the studied monzogranites and syenogranites range between 595 to 605 Ma (Abu Marwa, 595 ± 8.5 Ma, El-Glouf 596.4 ± 11.2 Ma, Faliqu El Sahl and El Waar 605.1 ± 10 Ma), whereas Gattar granites recorded 580 ± 22.2 Ma. The obtained data revealed the ages of magmatic crystallization as well as the presence of slightly older presumably inherited zircon grains. Xenocrystic zircons are found in most of the younger granitoid samples; the xenocrystic grains are all of Neoproterozoic ages. They fall into three age ranges that correspond to the ages of other Eastern Desert igneous rocks. Discordant ages are related to the presence of slightly older inherited zircon grains and to the effect of radiation damage which acts as open system in which gain and loss of U and Pb and intermediate radiogenic daughter are common. These older zircons may be entrained from wall rock during late contamination inherited from contributing source materials. These older zircon are corresponding to Neoproterozoic igneous rocks.

CONTRIBUTION TO THE MIERALOGY AND RADIOACTIVITY OF STREAM SEDIMENTS OF WADI RAS BAROUD AREA, NORTH EASTERN DESERT, EGYPT

Wadi Ras Baroud area is located in the North Eastern Desert of Egypt, covering an area of about 170km2. It is covered bybasement rocks and dissected by several wadies. The rock assemblages cropping out at Wadi Ras Baroud area comprise, quartzdiorites, granodiorites, syenogranites, dykes and Quaternary sediments filling the streams of the studied area.The grain size analysis and their distribution is a fundamental descriptive measure for clastic sediments. The results of thestatistical parameters are a graphic mean (Mz) ranging from 0.4 to2, inclusive graphic standard deviation (I) ranging from1.2 to 1.9, inclusive graphic skewness (SkI) ranging from -0.3 to 0.22, and inclusive graphic kurtosis (Kg) ranging from 0.7 to1.1. These parameters clear that they are coarse to medium sand, poorly sorted, near to coarse skewed samples, and platykurticand mesokurtic, so these sediments are represented by the turbidity currents environments.The identified minerals in the heavy fractures are represented by magnetite, ilmenite, hematite, garnet, rutile, titanite, zircon,thorite, ferogusnite, and columbite. The radiometric study of the stream sediments of Wadi Ras Baroud indicates that theaverage concentrations of U and Th are 10.38ppm and 25.5ppm respectively

Appliance of Geophysical Methods to Detect the Ancient Remains at “Tell Defenneh” Area, Ismailia, Egypt

The main target of this study is to detect the ancient archaeological remains by using Helicopter Electromagnetic Method (HEM) and Ground Penetrating Radar (GPR) survey at “Tell Defenneh” Area, which is located in the west bank of Suez Canal at the northeastern Desert of Egypt. It is far about 15 Km to the northeast of “Qantara Gharb” town which is a part of “Ismailia” governorate. This area is full of different archaeological features, because it is located in the ancient international trade-military road (Horus Road). This road connected ancient Egypt with its neighboring eastern countries. In additional to that, this area used to protect ancient Egypt from invaders, who came from the East. HEM has been used to detect the conductivity anomalies over the study area. These anomalies are useful to show the different and distinctive places which can be focused, on small scalar, by GPR to identify it more clearly in the study area. According to the HEM data, it was noticed that there are distinctive geometric shape with very low resistivity or very high conductivity values in the northeastern part of the study area. These data have been supported by GPR survey focused on this part. It was suggested that these anomalies may be due to old man-made mud bricks that was customary used in the building in ancient times. The subsequently archaeological excavations, which are based on these interpreted data as a guide and proof, revealed that the remains belong to the citadel of pharaoh “Psamtik I” (664-610 BC). This result confirms that the incorporated geophysical methods can be efficiently supplied in the archaeological prospection in Egypt.

Slip distribution model of two small-sized inland earthquakes and its tectonic implication in north-eastern desert of Egypt

Two slip distribution models of the 1999 and 2006 Beni-Suef earthquakes ( M w 4.5 and M w 4.2, respectively) were revealed using waveform inversion with an empirical Green’s function method. Waveform data used were recorded by the Egyptian Seismic Network’s short-period stations. To identify the active fault plane associated with each event and to estimate the best fitting rupture velocity, a set of slip distribution models was recovered on both nodal planes of the focal mechanism with a range of fixed rupture velocities. The result for the 1999 event shows that the northwest trending plane consistently provided better fitting solutions than the southwest trending plane. This implies that the slip was left-lateral on a northwest trending plane dipping toward the southwest. The 2006 event caused a slip movement on a dip-slip fault dipping towards the north. The rupture velocities were founded to be 3.5 km/s and 3.0 km/s which gave a comparatively small residual for the 1999 and 2006 earthquakes, respectively. The corresponding slip distribution models for the 1999 and 2006 events provide their seismic moments of 7.6E + 15 N m and 2.5E + 15 N m and moment magnitudes of 4.5 and 4.2, respectively. From the viewpoint of tectonics in the region, the present results imply an extensional tectonic process along the pre-existing WNW–ESE/NW–SE faults that may be transferred from the Gulf of Suez–Red Sea rift towards the northeastern desert in Egypt. This finding implies the diving of the northeastern of African plate beneath the Eurasian plate.

Origin and evolution of post-collisional volcanism: an example from Neoproterozoic Dokhan volcanics at Gabal Nugara area, Northeastern Desert, Egypt

Nugara volcanics are one of the northernmost outcrops of the Arabian–Nubian Shield. Two distinct volcanic successions are found in the Nugara basin: (1) old volcanic sequence composed of voluminous medium- to high-K calc-alkaline lavas and minor alkali basalt and (2) young volcanic sequence composed of subordinate tholeiitic mafic lavas. Their eruptions were punctuated by occasional volcaniclastic deposits that generated fall, flow, or reworked suites compositionally identical to the lava flows. These volcanics are a part of a post-subduction and extensional-related magmatic event in Northeastern Desert of Egypt. The volcanic rocks of the Nugara basin are characterized by strong enrichment in LILE relative to HESF, high LILE/HFSE ratios, and depletions of Nb on MORB-normalized multi-element diagrams. The geochemical features of the volcanic rocks suggest that they experienced fractional crystallization, along with mixing processes. Crustal contributions to the magma sources may also have occurred during magmatic evolution. These processes have resulted in scattered major and trace element variations with respect to increasing silica contents. The model proposed for their origin involves contrasting ascent paths and differentiation histories through crustal columns with different thermal and density gradients. The geochemical features of the most mafic samples suggest that the volcanic rocks in the region were derived from a mainly lithospheric mantle source that had been heterogeneously metasomatized by previous subduction events during convergence between the East and West Gondwanaland. The volcanic activity in the region is best explained by the delamination of lithospheric mantle slices that were heterogeneously enriched by previous subduction-related processes.

Neoproterozoic SHRIMP U–Pb zircon ages of silica-rich Dokhan Volcanics in the North Eastern Desert, Egypt

Chronology of Neoproterozoic volcanosedimentary successions remains controversial for many regions of the Arabian–Nubian Shield, including the Dokhan Volcanics of NE Egypt. New U–Pb zircon SHRIMP ages have been obtained for 10 silica-rich ignimbrites and two subvolcanic dacitic bodies, mapped as Dokhan Volcanics, from the North Eastern Desert of Egypt. Crystallization ages range between 592 ± 5 and 630 ± 6 Ma (Early Ediacaran). Apparently, the late consolidation of the Arabian–Nubian Shield was accompanied by the evolution of isolated volcanic centres and basin systems which developed during a period of approx. 40 Ma, independently in space and time and probably under changing tectonic regimes. The obtained age data together with other previously published reliable ages for Dokhan Volcanics suggest two main pulses of volcanic activity: 630–623 Ma and 618–592 Ma. Five samples contain inherited zircons, with ages of 669, 715–746, 847 and 1530 Ma, supporting models that North Eastern Desert crust is mainly juvenile Neoproterozoic crust.

Integration of space images and airborne radiometric data for discrimination of radioactive mineralizations at Wadi Araba area, North Eastern Desert, Egypt

This research aims at integrating airborne gamma-ray spectrometric and remote sensing satellite data to appointment radioactivity of the rocks at Wadi Araba, which is located in the North Eastern Desert of Egypt. Airborne gamma-ray spectrometric data of the ore as well as construction of lithological and structural maps from Landsat ETM + image are used to achieve the present study. The processing of airborne gamma-ray spectrometric data covering the area produced maps that showed the distribution and intensities of (eU), (eTh) and ( 40K%). These maps were correlated with lithologic and structural maps, which were interpreted from Landsat ETM + image, to show the probably hosting zones of radioactive materials. This study is based on the differences of radiometric data, brightness Digital Number (DNs) values of the rocks, predominant trends and densities of the structural lineaments, shape and type of weathering products. The study area is divided into nine lithologic units according to the physical characteristic differences as well as gamma-ray spectrometer measurements to reveal the mineralized units and zones as well as the best conditions for exploration of radioactive materials. These studies recorded some uranium anomalies distributed along NE-SW trending fault zones. These occurrences are hosted in Rod El-Hamal, El Galala and Duwi Formations. The gamma-ray spectrometer measurements for some representative zones indicate the presence of eU up to 20 ppm in the northeast direction and exceeding more than 35 ppm along zones fault cutting G. El Galala El Bahariya and G. El Galala El Qibliya. The characteristic features responsible for the uranium mineralization are the high fracture density of the Rod El-Hamal, Sudr and Duwi Formations. These fractures acted as good channels for hydrothermal ascending fluids and/or the percolating meteoric water. The hematitization accompanied these zones leached uranium which is redeposited and adsorbed onto hematite especially at the sites of intersection of the main fractures. The study shows that integrated application of satellite remote sensing techniques and airborne processed data is a powerful tool in the exploration of radioactive materials.

Late Proterozoic older granitoids from the North Eastern desert of Egypt: petrogenesis and geodynamic implications

Major, trace, and REE data for three localities of calc–alkaline older granitoid rocks exposed in the north Eastern Desert of Egypt are presented. These rocks were selected to cover wide compositional spectrum of the Egyptian older granitoid varieties. They are petrographically represented by granodiorite, tonalite, quartz–diorite, and quartz–monzodiorite. The rocks are comparable with the peraluminous, unfractionated calc–alkaline suites and fall within the volcanic arc and I-type granite fields. So, they can be regarded as belonging to the volcanic arc collision stage (665–614 Ma). The granitoids are geochemically similar to other rocks recorded from continental margin arc-systems being exhibit light-REE enriched patterns with variable but chiefly positive Eu anomaly. The latter has reverse relationship with the ΣREE, which was attributed to the fractionation of hornblende during partial melting. These patterns are comparable with models involving partial melting of amphibolitic source. This source must represent basalts, gabbros, or volcanics of an island arc system that were transformed to the level of the island arc crust during continental growth where the P–T conditions are suitable for partial melting. Thus, it is plausible that the studied rocks were derived by partial melting of LREE-enriched, garnet-free, and amphibole-bearing (i.e., hydrated) mafic source. Wadi Milaha granitoids are consistent with the derivation by a high degree of partial melting (30–40%) of amphibolite protolith in the deep crust. However, the two other localities (Wadi Umm Anab and West Gharib) are matching with 20–30% partial melting. Within each locality, variation in rock types from granodiorite to tonalite is said to be dominated by variable degree of restite separation during magma ascent. The high water and volatile contents in Wadi Milaha granitoids allowed higher degree of partial melting (30–40%). Moreover, the lower volatile contents in the other two localities (Wadi Umm Anab and West Gharib) gave lower degrees of partial melting (20–30%). These processes may resemble important geodynamic features of the Arabo-Nubian Shield evolution in the north Eastern Desert of Egypt.

Aeromagnetic Data Interpretation of Wadi Hawashiya Area for Identifying Surface and Subsurface Structures, North Eastern Desert, Egypt

The studied area is located within the North Eastern Desert of Egypt. The lithology of this area comprises rocks related to Precambrian, Cambrian, Carboniferous, Albian to Cenomanian, Late Cenomanian to Early Turonian and Quaternary. Aeromagnetic data are fully analyzed and interpreted where the analysis and interpretation are mainly devoted towards outlining significant surface and subsurface tectonic trends and their relationship with T.C. radiometric anomalous zones. According to the qualitative interpretation of the geological and aeromagnetic, and its shaded relief maps, the lineament structural map is constructed through the signatures of the contours and shaded relief of the total aeromagnetic data. Werner de-convolution (dyke model) was applied to the aeromagnetic anomaly map. The depth estimates calculated for these major magnetic anomalies range between 0.5 and 3.9 km. lineament structural map and magnetic depth map values have been utilized to construct the interpretation of the main subsurface structures affecting the studied area, which correlate with the previous studies of aeroradiomtric anomalous zones allover the study area. The obtained results showed the most significant structural trends affecting the distribution of these radiometric anomalies in the present study area. Four main tectonic trends are outlined from the total aeromagnetic and shading relief maps. These trends were defined as N60E, N45W and E-W.

Petrological and geochemical constraints on the tectonomagmatic evolution of the late Neoproterozoic granitoid suites in the Gattar area, North Eastern Desert, Egypt

Late Neoproterozoic granitoid rocks from the Gattar area, north Eastern Desert of Egypt, belong to three distinctive magmatic suites, namely: (1) calc-alkaline older granitoids, (2) mildly alkaline subsolvus younger granitoids, and (3) alkaline hypersolvus younger granitoids. These suites are genetically unrelated. The older granitoids consist of three main varieties: quartz-monzodiorite, quartz-monzonite and granodiorite. They show enrichment of LIL elements, high LREE/HREE ratio, with little or no Eu anomalies, and HFS elements are generally low, and further, exhibit metaluminous (ASI < 1) affinity with I-type features. The parental magma for this suite is most probably of mantle derivation. The most mafic quartz monzodiorite represents 25 % batch melting of garnet lherzolite lower crustal source followed by fractional crystallization producing quartz-monzonite and granodiorite emplaced in a volcanic arc environment. The Gattar younger granitoids have metaluminous to slightly peraluminous and alkaline affinities. They can be classified as mildly alkaline subsolvus and alkaline hypersolvus granites. The younger granitoids cannot be related to the older granitoids by simple fractionation from one parental magma. Hypersolvus granites have higher contents of Rb, Y, and Nb and lower contents of TiO 2 , Sr, Ba and REE and have more pronounced negative Eu anomalies than the subsolvus granites. Subsolvus granites have post-orogenic (A2-subtype) features, while hypersolvus granites have anorogenic (Al-subtype) characters. Mildly alkaline subsolvus granites have been generated by fractional crystallization of mainly K-feldspar, plagioclase, biotite, hornblende and accessory phases such as allanite, titanite and zircon from a mafic magma in order to generate their chemical variations. The alkaline hypersolvus granites, on the other hand, could be generated by about 10 % batch melting of amphibolite in the lower crust. The presence of leached biotite-hematite-fluoride clots in the hypersolvus granites suggests that fluid fractionation and fluorine complexing have played some role during the evolution of the hypersolvus granites.