Northern Eastern Desert Research Articles

Radioactive potentiality and uranium migration as assessed from airborne gamma-ray spectrometric data, north Wadi Qena area, Northern Eastern Desert, Egypt

Radioactive potentiality and uranium migration as assessed from airborne gamma-ray spectrometric data, north Wadi Qena area, Northern Eastern Desert, Egypt

Processing of mineralized microgranite dike for the recovery of niobium, tantalum, and rare earth elements using 1, 2-propyleneglycol extractant

ABSTRACT A number of strategic and economic rare-metal and Rare Earth Elements (REEs)-bearing minerals were recorded in mineralized microgranite dike (MMGD) from Ras Abdah area located in the Northern Eastern Desert of Egypt. Firstly, by sulphuric acid digestion at 300 °C, 3 h, 1/3 ore/Acid ratio, the RE, Nb, and Ta present in the MMGD can be efficiently extracted into the leach solution while Zr, Fe, and Th remained in the unattacked residue. The experimental digestion proved the dissolution of 98.9, 99.2, and 96 % for Nb, Ta, and REEs, respectively. In this study, a novel method was used to selectively recover Nb and Ta content from REEs in the digested concentrate sulphate solution. Solvent extraction using 1, 2-propyleneglycol was applied for the first time to achieve this secondary recovery process. From infrared and 1H-NMR data, the extraction was achieved, and the extractant bonded to Nb and Ta through glycol and alcoholic oxygen atoms. Niobium and Tantalum ions were stripped with water for Ta and 1M HF for Nb, achieving 98.6 and 98.8 % stripping efficiency, respectively. By employing an oxalic acid precipitation technique, a precipitate of extremely pure REEs was extracted from the raffinate solutions.

Mineralogy and Geochemistry of Titaniferous Iron Ores in El-Baroud Layered Gabbros: Fe-Ti Ore Genesis and Tectono-Metallogenetic Setting

The Neoproterozoic pyroxene gabbros and gabbronorites in the El-Baroud mafic intrusion in the Northern Eastern Desert (NED) of Egypt host Fe-Ti oxide ore deposits. This study discusses the major and trace elements of both titaniferous iron ores and their host rocks, along with the mineral chemistry (major and in situ trace elements) of interstitial clinopyroxene (Cpx), to gain a deeper understanding of the Fe-Ti oxide genesis. These ores occur as disseminated (55–60 vol.% of Fe-Ti oxides) and massive types (85–95 vol.%) in the form of the dyke, layer, and lens. They are composed of titanomagnetite (80–87 vol.%) with subordinate ilmenite (10–15 vol.%) and magnetite (3–5 vol.%), in accordance with their high Fe2O3 (75.66 wt.% on average) and TiO2 contents (16.30–17.60 wt.%). The Cpx in the investigated ores is diopside composition (Mg#; 0.72–0.83) and exhibits a nearly convex upward REE pattern, similar to Cpxs in the ferropicrite that originated from the primitive mantle. Melts in equilibrium with this Cpx resemble Greenstone ferropicrite melts; the parent melt of El-Baroud gabbros is possibly a ferropicritic melt that was derived from the lithospheric mantle during plume interaction. The El-Baroud gabbroic rocks were generated during the arc rifting and crystallized under a high oxygen fugacity at a temperature of 800–1000 °C and a pressure of 3 kbar with a depth of 12 km. The Fe-Ti oxide ores have been formed from ferropicritic parent melts by two processes, including in situ crystallization that leads to the formation of disseminated Fe-Ti oxides in the iron-rich gabbros at the bottom and liquid immiscibility that is responsible for the formation of thick Fe-Ti ore lenses and layers at the top of the gabbroic intrusion. Initially, titanomagnetite crystallized from the primary Ti-rich oxide melt. As cooling progressed, some of the excess titanium in this melt was exsolved in the form of the exsolution ilmenite lamellae within the titanomagnetite. The Fe-Ti oxide layers in the NED follow the trend of NW-SE (Najd trend), where their distribution is possibly controlled by the composition of parent melts (rich in Ti and Fe), high oxygen fugacity, and the structure related to the Najd fault system. The distribution of Fe-Ti oxide ores increases from the NED to the Southern Eastern Desert (SED), suggesting the dominant mantle plumes and/or shear zones in the SED relative to the NED.

Evaluation of the environmental and structural impacts on urban expansion using airborne geophysical data at Hurghada city, Northern Eastern Desert, Egypt.

Airborne gamma-ray spectrometric and magnetic data were processed and interpreted aiming to evaluate the environmental and structural impacts on urban expansion, Hurghada City, Northern Eastern Desert, Egypt. The eastern (coastal area), northern, and southeastern parts of the study area possess the lowest level of absorbed dose rate (ADR) and annual effective dose equivalent (AEDE), which were estimated from the airborne gamma-ray spectral data of this area. Consequently, these parts are considered as suitable sites for urban expansion from the radioactivity point of view. The relatively high level of ADR and AEDE is associated with granitic rocks, some parts of Gabir formation and recent Wadi sediments, situated at southwestern, central, and eastern parts of the study area. The ADR and AEDE of these parts are considered harmful to individuals. Airborne magnetic data were also used to detect major structures that may affect various construction projects in the study area in the future. The NNW-SSE, NW-SE, N-S, and NE-SW trends represent the common structures in the study area. The obtained results of airborne gamma-ray spectrometric and magnetic data illustrated that the urban expansion should not be constructed to the west of the ring road. However, site investigations must be carried out on this part of the study area before starting any construction projects there. The present study proved the important role of airborne gamma-ray spectrometric and magnetic surveys as useful tools to delineate the environmental and structural impacts on urban expansion.

A remnant root of a Neoproterozoic island arc in the Northern Eastern Desert of Egypt: Evidence from the whole-rock and amphibole chemistry of the Gattar gabbro

The tectonic settings and petrogenesis of Neoproterozoic gabbroic rocks are critical to understand the formation and evolution of the Arabian-Nubian accretionary orogen. We present the whole-rock chemistry and amphibole chemistry of the Gattar gabbro in the northern Eastern Desert of Egypt to better understand the formation of this part of the orogen. The Gattar gabbro is composed of variable proportions of amphibole and plagioclase, which imply the hydrous nature of its parent magma. Trace element patterns of the gabbro and the calculated liquids in equilibrium with its amphibole show enrichment in large ion lithophile elements relative to high field strength elements, which indicate that the Gattar magma formed above a subduction zone. The low abundances of high field strength element in the gabbro are consistent with a depleted mantle source similar to intra-oceanic island arc rocks. However, the high Nb/La ratio of the Gattar gabbro (0.46–10.71) is reminiscent to Nb-enriched mafic rocks from subduction settings. The amphibole chemistry suggests that the hydrous magma of the gabbro crystallized at temperature and pressure estimates of 930 °C and 8 kbar and under oxidizing conditions. The Gattar gabbro is affiliated with the Tonian-Cryogenian arc-related mafic gabbro, which is rarely recorded in this northernmost segment of the Arabian-Nubian orogen. In terms of comparison with the Ediacaran post-orogenic gabbros from the northern Eastern Desert, the Gattar gabbro shows lower concentrations of incompatible elements and Ti/V ratio.

Mineralogical, fluid inclusion and radiometric studies on Wadi El-Dob pegmatites, northern Eastern Desert, Egypt.

Mineralogical, fluid inclusion and radiometric studies on Wadi El-Dob pegmatites, northern Eastern Desert, Egypt.

Using edge detection techniques and machine learning classifications for accurate lithological discrimination and structure lineaments extraction: a comparative case study from Gattar area, Northern Eastern Desert of Egypt

Using edge detection techniques and machine learning classifications for accurate lithological discrimination and structure lineaments extraction: a comparative case study from Gattar area, Northern Eastern Desert of Egypt

The evolution of Pan-African mafic-felsic suite of the Dara area, Northern Eastern Desert, Egypt: Implication for the genesis of Iron Oxide-Copper–Gold (IOCG) mineralization

The evolution of Pan-African mafic-felsic suite of the Dara area, Northern Eastern Desert, Egypt: Implication for the genesis of Iron Oxide-Copper–Gold (IOCG) mineralization

Large-scale geological structures of the Egyptian Nubian Shield

Integration of potential field- and structural data make it possible to trace surface and subsurface large-scale geological structures of the Egyptian Nubian Shield (ENS). Obtained results indicate that the Northern Eastern Desert (NED) of the ENS is dominated by relatively younger (c. 580 Ma) E–W and NE–SW trending extensional structures that were controlled by the evolution and retreat of the Cadomian Arc. Density of such extensional structures increases with depth as displayed by the potential data. The prevailing structural trends in the Central Eastern Desert (CED) are NW–SE and WNW–ESE. Both trends are highly prompted by the timing of deformation upon the Najd Fault System, and are themselves dissected by a relatively younger NE–SW shearing trend. Lineament density in the CED is subordinate for both subsurface and near surface structures. The South Eastern Desert exhibits compressional and extrusion-related structures of two main prominent trends; WNW-to-NW (to the western part) and the N-, NNE- to NE (to the eastern part). The previously mentioned Neoproterozoic trends are remarkably influenced by the Oligocene–Miocene Red Sea-Gulf of Suez rift related fractures in the vicinity of the rift shoulder. The remarkable change in trends and densities of structural trends, especially in the NED, is interpreted in terms of concealing of the older structures by the younger extensional structures which in turns reflect an N-ward progressive deformation in the entire ENS. Gravity data are more appropriate in delineating the structural trends compared to the magnetic data which are largely affected by lithological variations and/or alteration zones and magnetic mineralogy.

Mineralization Styles and Alteration Paragenesis of Metasomatic Zones in the Highly Fractionated Granite of Gabal Gattar, Northern Eastern Desert, Egypt

Mineralization Styles and Alteration Paragenesis of Metasomatic Zones in the Highly Fractionated Granite of Gabal Gattar, Northern Eastern Desert, Egypt

Petrogenesis of neoproterozoic Mo-bearing A-type granites in the Gattar area, northern Eastern Desert, Egypt: Implications for magmatic evolution and mineralization processes

Three Mo-bearing granitic intrusions, namely: Gattar, Abu Harba and Abu Marwa occur at the Gattar area in the North Eastern Desert of Egypt. These late tectonic granites intrude Neoproterozoic rocks of island arc metavolcanics and metagabbro-diorite complexes in addition to post-collision molasse-type sediments (Hammamat Group) and Dokhan-type volcanic rocks. U–Pb zircon geochronology yielded ages of 630 ± 27 Ma, 600.1 ± 8.5 Ma, and 601.1 ± 2.4 Ma for the Gattar, Abu Harba, and Abu Marwa granite intrusions, respectively.Whole-rock geochemical data showed the granites to be alkaline to peralkaline post-collision A-type granites. The three granite intrusions are considered co-magmatic as indicated by their similar ages and the continuous variation of major and trace elements on the variation diagrams. The inferred crystallization temperatures, as calculated from zircon geothermometry according to Watson et al. (2006), fall in the range of 616–690 °C, (average = 662 °C), 592–720 °C, (average = 653 °C), and 592–894 °C, (average = 706 °C) for the Gattar, Abu Harba, and Abu Marwa granite intrusions, respectively. This indicates that the Abu Marwa granite is the least evolved, followed by the Gattar and Abu Harba granites. The calculated logfO2 values for zircons from all the studied granites show highly oxidized magmatic features. The Abu Marwa granite (average logfO2 = −12.62) has the strongest oxidized state, whereas Gattar granite (average logfO2 is −15.46) and Abu Harba granite (average logfO2 = −15.99) have moderate logfO2 values implying moderate oxidized states. Guided by the tectonic evolution of the post-collision stage in the Arabian-Nubian Shield, it is suggested that the original magma of the granites in the Gattar area was formed by partial melting of an underplated crustal source, which had been fertilized by alkali-, HFSE-, and REE-rich fluids released and metasomatized by an underplating mantle-derived magma.Fractional crystallization and fluid differentiation/metasomatism were major processes in the petrogenetic evolution of these granite intrusions. Fluorine-complexing of HFSEs and REEs was involved in the early stages of fractional crystallization (i.e., crystallization of the Abu Marwa granite intrusion), resulting in a HFSE- and REE-rich residual melt that form the more evolved alkali feldspar granite of Gattar and Abu Harba intrusions. The late magmatic ore-forming fluids enhance the Gattar granite intrusion’s ability to become enriched in molybdenum relative to Abu Harba and Abu Marwa granites. The reason of the different degrees of molybdenite enrichment in the three intrusions depended on many factors (e.g., degree of fractionation and oxygen fugacity of the granitic magma).

Role of uranium redistribution in radioactive heat production of granitic rocks, Northern Eastern Desert, Egypt

Granitoid intrusions traditionally form a focus for geothermal heat exploration, as granite is a major host for Heat-Producing Elements (HPE; U, Th & K). Airborne spectral gamma-ray data for the study area highlight variations in HPE abundances in granitic rock units, indicating variation in the Radioactive Heat Production (RHP) values of these rocks. The computed arithmetic means of RHP for granitic rocks range from 0.96 µWm−3 for tonalite-quartz diorite to 1.10 µWm−3 for granodiorite, followed by a gradual increase to 1.52 µWm−3 for monzogranite and 2.51 µWm−3 for alkali-feldspar granite. The major control on the distribution of U and Th elements in the granitoid rocks appears to have been primarily of magmatic differentiation and is reflected in the linear correlation between these elements. Besides, subsequent post-magmatic hydrothermal fluids play their important roles in remobilization of profitable secondary U-mineralizations to be trapped and enrichment in the alkali-feldspar granitic rocks.

Geological, Mineralogical and Comparative Study of Biosorption for Uranium and Thorium Using Different Types of Algae at Wadi Dara Area, Northern Eastern Desert, Egypt.

Geological, Mineralogical and Comparative Study of Biosorption for Uranium and Thorium Using Different Types of Algae at Wadi Dara Area, Northern Eastern Desert, Egypt.

Geology and Radioactivity of the Pegmatitic Rocks of Gabal El Urf, Northern Eastern Desert, Egypt

Geology and Radioactivity of the Pegmatitic Rocks of Gabal El Urf, Northern Eastern Desert, Egypt

Rudists (Bivalvia) from a Cretaceous Platform in Northern Egypt: Taxonomy and Paleobiogeography

AbstractNew well‐preserved rudist materials come from the Barremian–Turonian marine formations in the Yelleg, Minsherah, Maaza, and Raghawi sections in North Sinai, northern Egypt. There, 17 discovered rudist species belonging to 13 genera and seven taxonomic families are described in detail as follows: Eoradiolites plicatus (Conrad), Eoradiolites liratus (Conrad), Praeradiolites ponsianus (d'Archiac), Archaeoradiolites sp., Bournonia africana Douvillé, Bournonia fourtaui Douvillé, Biradiolites lombricalis (d'Orbigny), Biradiolites zumoffeni Douvillé, Radiolites lewyi lewyi Parnes, Radiolites sauvagesi (d'Hombres‐Firmas), Durania arnaudi (Choffat), Toucasia carinata (Matheron), Toucasia sp., Neocaprina raghawiensis Steuber and Bachmann, Sellaea sp., Ichthyosarcolites sp. and Horoiopleura sp.. The Cenomanian deposits in the northern Eastern desert of Egypt only contain E. liratus. The domination of the Cenomanian rudist species in North Sinai, however, is attributed to changes in the platform, which passes mainly from carbonate in the north to siliciclastics in the south. The presence of Horiopleura sp. in the late Barremian–early Aptian deposits is documented for the first time, which suggests the expansion of taxa of the genus Horiopleura Douvillé to North Sinai during this interval. The age of the rudist species is documented from the late Barremian–Turonian formations, with their geographic distribution in the Mediterranean region considered.

Petrogenesis of contrasting magmatic suites in the Abu Kharif area, Northern Eastern Desert, Egypt: implications for Pan-African crustal evolution and tungsten mineralization

AbstractThe Abu Kharif area in the Northern Eastern Desert consists of contrasting granitic magma suites: a Cryogenian granodiorite suite (850–635 Ma), an Ediacaran monzogranite suite (635–541 Ma) and a Cambrian alkali riebeckite granite suite (541–485 Ma). Tungsten mineralization occurs within W-bearing quartz veins and a disseminated type confined to the monzogranite.Whole-rock geochemical data classify the granodiorite as a late-orogenic I-type with calc-alkaline affinity, while the monzogranite and alkali riebeckite granite represent respectively a post-orogenic highly fractionated I-type with calc-alkaline affinity and an anorogenic A1-subtype with alkaline affinity. Geochemical modelling indicates that the three intrusions represent separate magmatic pulses where the granodiorite was generated by ∼75 % batch partial melting of an amphibolitic source followed by fractional crystallization of hornblende, biotite, apatite and titanite. The monzogranite was formed by 62 % batch partial melting of the normal ‘non-metasomatized’ Pan-African crust of calc-alkaline granite composition followed by fractional crystallization of plagioclase, biotite, K-feldspar, magnetite, ilmenite, with minor apatite and titanite. The alkali riebeckite granite was generated by 65 % batch partial melting of metasomatized Pan-African granite source followed by fractional crystallization of plagioclase, K-feldspar, amphibole and biotite with minor magnetite, apatite and titanite. In general, the parent magmas of the three intrusions were originally enriched in W, but with different concentrations. This W-enrichment would be caused by magmatic-related hydrothermal volatile-rich fluids and concentrated within the monzogranite.

Petrogenesis and tectonic evolution of late Pan-African granitiods in the El Regita area, Central Southern Sinai, Egypt: With a synopsis about Th–U distribution and Cu mineralization

The Late Precambrian intrusives in the El Regita area, central Southern Sinai at the northernmost Arabian-Nubian Shield, signify the typical evolutionary Pan-African magmatic stages. Geochemical and mineralogical variation from calc-alkaline (I-type) quartz-monzonite and granodiorite to later mostly A-type monzogranite, syenogranite, and alkali-feldspar granite, indicates high fractionation and extensive magmatic differentiation of the same parent melt, derived from the mantle–crust interaction above the subducted oceanic plate influenced by partial melting processes. The compositional variation is linked to the tectonic evolution from regional compressional deformation to the continental crust's relaxation. The mineralogy of the studied granitoids, which are analogous to similar rocks that crop out in the North-Eastern Desert of Egypt, is consistent with the view that the Sinai region is an eastern extension of the northern Eastern Desert. Results from all geothermometers of the studied granitoids expected decreasing oxygen fugacity in the magma following temperature decrease. Based on the Al-in-hornblende geobarometer, the (I-type) granitoids represents hydrated granites emplaced at lower crustal levels than the monzogranite-syenogranite plutons. The El Regita area is characterized by structurally controlled mesothermal copper mineralization which has epi-genetic origin and is mainly related to the emplacement of granitoids in the late-collisional stage. Abnormal radioactivity levels in the El Regita area are structurally controlled and connected to highly sheared granodiorites. After leaching, uranium was redistributed and finally fixed or adsorbed by Fe-oxyhydroxides to form immobile secondary U-bearing minerals.

Comparison between the Structurally Controlled Radioactive Minerals at Felsic Granites of G. Abu Harba, G. Dara and G. Hamrat Al Jirjab Areas, Northern Eastern Desert, Egypt

Comparison between the Structurally Controlled Radioactive Minerals at Felsic Granites of G. Abu Harba, G. Dara and G. Hamrat Al Jirjab Areas, Northern Eastern Desert, Egypt

Palaeoecological and palaeoenvironmental analyses of Cenomanian–early Turonian macrobenthic faunas from the northern Eastern Desert of Egypt

The palaeoecology and palaeoenvironments of the Cenomanian–lower Turonian succession in the northern Eastern Desert of Egypt are interpreted, based on a detailed study of macrofaunal assemblages and sedimentary facies. The abundant molluscs and echinoids of the mixed carbonate-siliciclastic Galala and Abu Qada formations have been studied in three sections with ammonites that provide a well-correlated stratigraphical framework. Three unconformities (two Cenomanian sequence boundaries and a first Turonian one) bound two third-order depositional sequences. Facies development shows a strong relationship to the sequence architecture recognised. In addition, the facies characteristics indicate depositional palaeoenvironments ranging from lagoonal to deep subtidal settings on a homoclinal carbonate ramp that was proximally influenced by clastic input. The macrobenthic taxa identified in 51 samples, collected from the sections studied, are grouped into seven assemblages (A–G) that are described and interpreted as remnants of communities. The faunal distribution and trophic structure of most of the assemblages recorded confirm fully oxygenated and euhaline shallow-marine environments with mesotrophic productivity level, i.e., relatively stable and low-stress conditions. The trophic structure of some other assemblages, in contrast, reflects the influence of particular environmental parameters, dissolution of aragonitic shells and/or sample size effects. Environmental parameters controlling the faunal distribution include substrate consistency, bathymetry, water energy, surface-water productivity, rate of sedimentation and oxygen availability. The integrated litho- and biofacies results certify that the sequences were deposited during an interval dominated by different perturbations that resulted in a wide spectrum of depositional features and significant palaeoecological variations.

New insights into Cryogenian arc granitoids hosting Th-U mineralized Ediacaran syenogranite dikes, Ra’s Abdah area in the northern Egyptian Nubian Shield: Constraints from U‐Pb ages and zircon geochemistry

During the transition from compressional to extensional-related magmatism, at Ra’s Abdah area of the northern Eastern Desert of Egypt, Ediacaran uraniferous syenogranite dikes with complex morphology sent offshoots into Cryogenian arc granitoids. This study defines new tectonic environment of these dikes and suggests their emplacement timing before the Egyptian late-collision granite intrusions. U–Pb zircon dating for Ra’s Abdah dikes and arc granitoids yielded ages 597 ± 15 and 663.2 ± 8.4 Ma respectively; that extended the age of late Precambrian post-orogenic dikes in the Egyptian Nubian Shield to 597 ± 15 Ma. Zircons from dikes show significant enrichment of Th and U; while zircons from arc granitoids display typical igneous zircon patterns with Th and U enrichment but significant negative Nb, La, Pb and Sr anomalies. Average calculated zircon temperature crystallization of Ra’s Abdah dikes is 698 °C whereas of the granitoids is 713 °C. Similar geochemical behavior of some individual trace elements and REE in zircons from dikes and host rocks intimates identical magma source (partial melting of subducted oceanic crust and its overlying magmatic wedge intercalated with older continental crust). High fractional crystallization of the parent magma after the first pulse managed the change from arc granitoids magma with high fO2 values to syenogranite dikes phase with lower fO2 following the transformation from a transpressional to an extensional tectonic. Volatile complexing in late-magmatic stage, mineral fractionation and concomitant zircon crystallization would increase all REE in the residual melt with special HREE enrichment and LREE elimination in zircon of dikes. The radioactive mineralization of dikes (Averaging eU = 124.7 ppm; eTh = 263.9 ppm) are syn-genetic followed by supergene enrichment. Suggested model explains the multistage propagation of complex morphology dikes by filling, opening and increasing expansibility of inclined or perpendicular pre-existing fracture framework.