South Eastern Desert Research Articles

Remote sensing and geochemical investigations of sulfide-bearing metavolcanic and gabbroic rocks (Egypt): Constraints on host-rock petrogenesis and sulfide genesis

Field geology, geochemical analyses and multi-sensor remotely sensed data of Landsat-8, ASTER and Sentinel-2 were used to detect various types of hydrothermal alteration and sulfide-gold mineralization in Neoproterozoic metavolcanic and gabbroic rocks from Darhib and El-Beida areas in the South Eastern Desert (SED) of Egypt. We also used RADAR data of Sentinel-1 using PCI Geomatica software to decipher the structural lineaments that control this mineralization. Different styles of disseminated to massive sulfide deposits include: 1) undeformed magmatic disseminated ores in Darhib gabbros, metavolcanic rocks and metabasic dykes; 2) deformed (remobilized) massive ores mostly of a magmatic-hydrothermal origin in Darhib tremolite talc rocks along E-W shear zones; 3) hydrothermal sulfide ores along El-Beida NW–SE shear zones. Cu-Zn massive ores represent the main sulfides in the Darhib silicified tremolite-talc rocks and meta-andesites, and occur as bands, veins and patches along Darhib E-W shear zones. Discontinuous occurrences of sulfide ores-bearing tremolite-talc rocks indicate that major shear zones act as structural controls on mineralization. Sulfide ores consist chiefly of chalcopyrite, sphalerite, pyrite and galena as well as minor covellite and bornite. These ores are highly concentrated along E-W striking Darhib shear zones and resulted from granite-derived hydrothermal fluids that form/and or accumulate sulfide minerals from the sulfide-bearing metavolcanic rocks around shear zones. Two stages of hydrothermal alterations are recorded in the Darhib talc mine including pre- (talcification, amphibolitization and carbonatization) and syn- (silicification and chloritization) sulfide ore alterations. Disseminated sulfide mineralization hosted in Darhib gabbros, metavolcanic rocks and metabasic dykes is of a magmatic origin, similar to Cu-Ni sulfide deposits hosted in gabbroic varieties in worldwide mafic–ultramafic intrusions. On the other hand, El-Beida gold-sulfide-bearing quartz and quartz carbonate veins are hosted in ferruginated and silicified metavolcanics/ metavolcaniclastic rocks along NW–SE shear zones (Najd Fault System trend). These are spatially associated with regional convergent structures (high-angle convergent wrench structures), suggesting orogenic gold type mineralization. The E-W with minor WNW-ESE shear zones in Darhib and NW-SE trending shear zones in El- Beida structurally controlled sulfides and gold mineralization in the SED of Egypt. El-Beida sulfide mineralization occurs as disseminated ores that consist mainly of pyrite, chalcopyrite, covelite and chalcocite with occasional occurrence of gold. The spatial occurrence of native gold in ferrigenous alteration zones indicates the role of iron in gold precipitation through buffering of gold-bearing complexes. Mineralogical and geochemical data of Darhib and El-Beida sulfide-bearing rocks indicate that they crystallized from depleted mantle sources in a back-arc basin setting, starting with the generation of arc-like volcanic rocks in a nascent BAB stage followed by the emplacement of plutonic equivalent of MORB/OIB-like rocks such as gabbroic intrusions in a mature BAB.

Ore Genesis of the Abu Ghalaga Ferro-Ilmenite Ore Associated with Neoproterozoic Massive-Type Gabbros, South-Eastern Desert of Egypt: Evidence from Texture and Mineral Chemistry

Massif-type mafic intrusions (gabbro and anorthosite) are known for their considerable resources of vanadium-bearing iron–titanium oxide ores. Massive-type gabbroic and anorthosite rocks are frequently associated with magmatic rocks that have significant quantities of iron, titanium, and vanadium. The most promising intrusions that host Fe-Ti oxide ores are the gabbroic rocks in the south-eastern desert. The ilmenite ore deposits are hosted in arc gabbroic and anorthosite rocks. They are classified into three types, namely black ore, red ore, and disseminated ore. The black ilmenite ore is located at the deeper level, while the oxidized red ore is mainly located at or near the surface. Petrographically, the gabbro and ilmenite ores indicate a crystallization sequence of plagioclase, titaniferous pyroxene, and ilmenite. This reveals that the ilmenite is a magmatic deposit formed by the liquid gravity concentration of ilmenite following the crystallization of feldspar and pyroxene. Meanwhile, quartz, tremolite, zoisite, and opaque minerals are accessory minerals. The Fe-Ti ores are composed of ilmenite hosting exsolved hematite lamellae of variable sizes and shapes, gangue silicate minerals, and some sulfides. The X-ray diffraction (XRD) data reveal the presence of two mineral phases: ilmenite and hematite formed by the unmixing of the ferroilmenite homogeneous phase upon cooling. As a result, the ore is mostly made up of hemo-ilmenite. Using an electron microscope (SEM), as well as by observing the textures seen by the ore microscope, ilmenite is the dominant Fe-Ti oxide and contains voluminous hematite exsolved crystals. Under the scanning electron microscope, ilmenite contained intergrowths of hematite as a thin sandwich and lens shape. The formation of hematite lamellae indicates an oxidation process. Mineral chemistry-based investigations reveal late/post-magmatic activity at high temperatures. The examined ilmenite plots on the ferro-ilmenite line were created by continuous solid solution over 800 °C, whereas the analyzed magnetite and Ti-magnetite plot near the magnetite line and were formed by continuous solid solution exceeding 600 °C.

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.

Digital Map Simulation and Paleo-Stress Analysis of Post-Accretion Structures in the South Eastern Desert (Egypt): A Case Study from Wadi Kharit Shear Zone

Digital Map Simulation and Paleo-Stress Analysis of Post-Accretion Structures in the South Eastern Desert (Egypt): A Case Study from Wadi Kharit Shear Zone

Magnetic Signature of Gold Deposits: Example from Um Garayat Region, South Eastern Desert, Egypt

Magnetic methods of exploration have proved to be efficient and have potential in the gold mineralization industry. New magnetic processing technologies aid in improving the process of interpretation and gold opportunity identification. In this work, we show the possible application of combined digital magnetic filters to explore new gold mineralization localities with application to a well-known Au mineralization zone. Um Garayat (UG) region, southeastern desert, Egypt, is an ancient example of a potential area for gold mining. Modern analysis showed that other types of mineral concentrations are present. So, exploiting the magnetic signature of the area for future investment is of great interest. The old UG gold mine is characterized by volcanic and tectonic features such as faulting and folding that affect the arc sedimentary rock sequence of repeated deformation stages. A thorough geophysical effort has been carried out around the old gold mine in the UG area to explore the extension of mineralized ore deposits. A detailed geophysical survey using magnetics was carried out in this study together with the available aeromagnetic data. Field data sets on appropriate sites were measured, processed, and evaluated by suitable software. High magnetic anomalies were detected based on grid filter analysis and contact occurrence maps as marked as possible ore deposits after satisfying the geologic conditions for gold formation. An integrated understanding of attained results revealed that the new possible ore deposits are related directly to fault and fracture zones in the shape of lenses of variable thickness in this zone. Results show that newly detected mineral occurrences in the UG area are also controlled by major faults and hydrothermal solution enrichment along fault zones at a depth ranging from 20 to 70 m. Favorable fault/joint mineralized places were located. The relationship between the Au-quartz vein's strike direction compared with magnetic anomaly lineament analysis was studied. Search for new sources of Au and other mineral deposits in addition to quartz veins is needed as pockets of accumulated mineral-rich rock fragments are deposited in drainage wadis and fault/joint zones because of hydrothermal solution enrichment.

Petrological and Geochemical Characteristics of Wadi Sikait Lamprophyre Dykes, South Eastern Desert, Egypt: Implications for Petrogenesis and Crustal Contamination

Petrological and Geochemical Characteristics of Wadi Sikait Lamprophyre Dykes, South Eastern Desert, Egypt: Implications for Petrogenesis and Crustal Contamination

Mineralogy and Radioactivity of Stream Sediments of Wadi Abu Marw, South Eastern Desert, Egypt

Mineralogy and Radioactivity of Stream Sediments of Wadi Abu Marw, South Eastern Desert, Egypt

Critical raw material resources in Nugrus-Sikait area, South Eastern Desert, Egypt: Geological and geochemical aspects

The current work aims to assess the critical raw materials (CRMs) in the Arabian-Nubian Shield in accordance with the European Union. CRMs are strategically and economically significant, but they are subject to supply shortages. CRMs, such as Nb, Ta, Zr, U, Th, Rb, Ga, Hf, Zn, Ba, Sr, Sn, Cu, and Pb, are concentrated in post-orogenic highly fractionated granitic plutons, such as Abu Dabbab, Abu Diab, Homrit Waggat, Um Naggat, and Nuweibi. They also occur in the gneiss rocks of the Nugrus-Sikait area. The present work sheds light on the CRM resources in the Nugrus-Sikait area in the South Eastern Desert, Egypt. Gneiss rocks, ophiolitic rocks (ultramafics, metagabbros, schists, and mélange), gneissose biotite granites, muscovite leucogranites, pink biotite granites, and post-granitic dikes and veins are the main exposed rock units in the target area. CRMs are abundant in the examined area and reach up to 1845 ppm Nb, 203 ppm Ta, 3212 ppm Zr, 1789 ppm Y, 278 ppm Hf, 3209 ppm Zn, ˃10000 ppm Pb, 941 ppm Sn, 1458 ppm Cu, 3551 ppm U, 2233 ppm Th, 144 ppm Sr, 1416 ppm Rb, and 121 ppm Ba. Therefore, it's recommended to shed light on CRMs distribution due to their economic importance and strategic uses.

Mapping of gold mineralization using an integrated interpretation of geological and geophysical data—a case study from West Baranes, South Eastern Desert, Egypt

The current study is mainly devoted to the integration, analysis, and interpretation of the available geologic, remote sensing, and potential field data (mainly magnetic) to delineate the subsurface geologic structural elements controlling the western part of Baranes, South Eastern Desert, Egypt, and its relation to the southwestern desert structural regime. Additionally, to detect potential mineralization zones for future mining plans in the study area. The Western part of Baranes has not had enough geomorphological mapping, consequently, potential discoveries of mineralization zones are very low. So, in this paper, an attempt is initiated to better understand the evolution of the geomorphology and structural regime of the region and construct a digital geological map and structural patterns showing the possible locations of mineralization zones based on the previous knowledge from similar potential sites and focus on the future economic importance of the region. To achieve this purpose, processed Landsat-8 images successfully revealed the lithological contacts and fault zones helping in distinguishing between the different rock units; moreover, the aeromagnetic data available in the area is used and several filters are applied including reduction to the pole, Euler homogeneity equation, analytic Signal (AS), and advanced grid filtering are sequentially used aiming to detect the possible subsurface distribution of mineralization zones from the integrated interpretation of magnetic susceptibilities and available geologic and remote sensing data.

Natural Radioactivity Assessment and Radiation Hazards of Pegmatite as a Building Material, Hafafit Area, Southeastern Desert, Egypt.

Sixty-seven sites of Hafafit pegmatite from the Southeastern Desert of Egypt were investigated radiometrically in the field using an in situ γ-ray spectrometer to determine eU, eTh, and K contents. The obtained results ranged from 0.4 to 6 ppm for eU with a mean value of 2.5 ppm, from 0.2 to 32 ppm for eTh with a mean value of 6.7 ppm, and from 0.7% to 5.4% for K with a mean value of 3.3%. Consequently, the radiological effects from these rocks were estimates by determination of the environmental parameters: gamma activity concentration index Iγ, external hazard index Hex, internal hazard index Hin, external absorbed dose rates in outdoor, and external absorbed dose rates in indoor air. The results obtained in this study showed that values U, Th, and K lie in the range of the acceptable world values. In addition, the calculated radiation hazard parameters (Iγ, Hex, and Hin) have values lower than the world values, while the calculated external absorbed dose rates (Dair) have values higher than the world and Egyptian permissible levels.

Occurrences and genesis of emerald and other beryls mineralization in Egypt: A review

Beryl and others gem varieties represent the most valuable gemstones due to their good appearance and high hardness (after diamond and ruby). Beryl is a rare mineral due to lack of Be abundance in the upper continental crust. The present work aims to state the occurrences, chemistry, fluid inclusions and genesis of Egyptian emerald and other beryls mineralization. They are recorded in the South Eastern Desert (Zabara-Um Kabu, Homret Akarem- Homret Mikpid) and south Sinai (Ghazala and Sidri) in addition to less significant concentrations in the central Eastern Desert (Igla, Abu Dabbab, Nuweibi and Mueilha granitic rocks). Among all of the Egyptian beryls, Homret Akarem beryl has the highest SiO2 (65.49 wt%), Al2O3 (16.52 wt%), FeO (1.5 wt%) contents. All the recorded beryl and emerald in the Eastern Desert and Sinai are sodic. Emerald and others beryl mineralization of Egypt are found to be formed in tectonic magmatic-related (where beryl is disseminated in tectonic related alkali feldspar granite as a result of Be-bearing fluids from a hidden-granitic intrusion as in Wadi Ghazala, Homret Mikpid and Homret Akarem) and into tectonic metamorphic-related (where emerald and other beryls are formed in mica schists as a result of Be-bearing fluids from tectonic related (Nugrus thrust and related shear zones as in Zabara-Um Kabu district); where muscovite leucogranite and its related pegmatites and quartz veins intrude and interact with Cr, V-bearing mafic-ultramafic rocks).

Whole rock and mineral chemistry of the rare metals-bearing mylonitic rocks, Abu Rusheid borehole, south Eastern Desert, Egypt

Abu Rusheid area represents one of the typical rare metals-bearing rocks in the Northern Neoproterozoic Arabian-Nubian Shield. The current work reports a new detailed lithologic description, petrographic, and mineralogical studies integrated with a geochemical investigation of the borehole no.5 to discern the petrological features, rare metals enrichment and their origin. Abu Rusheid mylonitic rocks are composed mainly of quartz, K-feldspars (Or62-98), plagioclase (Ab98-99), primary muscovite, and neoformed biotite of annite type as well as some accessories such as zircon, columbite, tantalite, fluorite, allanite, xenotime, monazite, and kasolite. They have a noticeable high content of rare earth elements and a conspicuous enrichment of Zr (up to ∼ 4400 ppm), Nb (up to ∼ 2150 ppm), Ta (up to ∼ 270 ppm), Hf (up to ∼ 190 ppm), Zn (up to ∼ 5600 ppm), U (up to ∼ 175 ppm), Pb (up to ∼ 900 ppm) and Th (up to ∼ 1000 ppm) trace elements. REE patterns revel M-type tetrad effect (t1) with an absence of the W-type tetrad segment in the third tetrad (t3). Further constrains, lambda method (where τ2 can be detected) yield a positive values of τ1 (av. 0.534), τ2 (0.487), τ3 (0.498) and τ4 (0.28) for the examined rocks, reflecting M-type tetrads. The rare metals enrichment are related to magmatic as well as the extrusion of lamprophyre dykes yielding alteration processes that led to the remobilization and enrichment of these elements through joints, faulting and their deposition along contacts with the ophiolitic mélange.

Natural Radioactivity and Radioelement Potentiality of Mylonite Rocks in Nugrus Area, Southeastern Desert, Egypt

Natural Radioactivity and Radioelement Potentiality of Mylonite Rocks in Nugrus Area, Southeastern Desert, Egypt

Mineralogy and geochemistry of serpentinized peridotites of the Northern Nubian Shield: The origin of compositionally banded olivine and implications for Neoproterozoic supra-subduction zone metasomatism

A sequence of Neoproterozoic ultramafic rocks — serpentinized peridotite, serpentinite, and clinopyroxenite — outcrop in Wadi El-Mireiwa in the south Eastern Desert of Egypt. They represent the mantle and lowermost crustal section of a fragmented ophiolite, emplaced by thrusting above metasedimentary rocks and an island arc assemblage and later intruded by a granite mass. In samples of the serpentinized peridotite, back-scattered electron images of olivine reveal banded zoning, defined by straight and parallel Mg-enriched (Fo ∼ 96) lamellae within typically magnesian host crystals (Fo ∼ 89). The presence of clinopyroxene, the relatively low whole-rock Mg# (∼88), the low NiO content of olivine (0.1–0.32 wt%), and the relatively high TiO2 content of fresh Cr-spinel (∼0.3 wt%) are all consistent with a cumulate origin for the serpentinized peridotite and serpentinites. On the other hand, some associated serpentinite has higher whole-rock Mg# (92) and low TiO2 in Cr-spinel (∼0.01 wt%), consistent with a residual origin by high-degree melt extraction in the fore-arc region of a supra-subduction zone (SSZ) environment. The formation of Mg-enriched bands in olivine is attributed to the enhancement of metasomatic Mg-Fe exchange with high-Mg/Fe2+ fluids along crystallographically-oriented subgrain boundaries produced by high strain-rate dislocation creep. Such high-Mg/Fe2+ fluid metasomatism also explains reverse zoning of MgO in Cr-spinel, whereas the low whole-rock concentrations of REE and other trace elements exclude a significant role for melt-rock interaction. The evidence for high-Mg/Fe2+ fluid metasomatism in this suite indicates that SSZ fluids and high fore-arc strain rates affect not only the mantle wedge but also overlying ultramafic cumulates. The oxygen fugacity [ΔlogƒO2(FMQ)] values calculated from unmetasomatized (+2.48 to +2.67) and metasomatized (+3.75 to +4.53) samples reflect the oxidized nature of Neoproterozoic SSZ magma and the even more oxidizing character of the metasomatic fluids. Banded zoning has also been recorded in olivine from Mariana fore-arc peridotite and Phanerozoic SSZ ophiolites; the Neoproterozoic Wadi El-Mireiwa case shows that rapid mantle flow has been a persistent feature of the tectonic environment where fore-arc ophiolites develop.

Geochemical Conditions and Factors Controlling the Distribution of Major, Trace, and Rare Elements in Sul Hamed Granitic Rocks, Southeastern Desert, Egypt

Egypt is mainly covered by ophiolitic rocks, muscovite, and two mica granites, in addition to different types of acidic and basic dikes. Our field observations indicated that El Sela granites were subjected to alteration types such as silicification, kaolinization, and hematitization, which is associated with uranium mineralization. Petrographic investigations clarified that these rocks were affected by saussiritization, muscovitization, and silicifications as the main alteration types associated with uranium mineralization (uranophane and autunite). We carried out chemical analyses of our samples for major oxides and trace and rare earth elements using ICP-OES and ICP-MS. The studied altered granites had high silica, titanium, and phosphorous as major components, with enhanced amounts of trace elements such as Nb, Ta, Zn, Mo, Pb, and Re, in addition to REE, especially light ones. The average REE content was higher than that of worldwide granites with LREE enrichment. One sample had a strong M-type tetrad effect in the fourth type; other samples had weak W-type in the third type, indicating the effect of hydrothermal alteration processes in the altered granites. This was confirmed by calculating the ratios of most isovalents that deviated from the chondritic ratio in many values. Variation diagrams of U and some trace elements illustrated that U had a weak positive correlation with Y and a strong positive correlation with gold, while it had weak to moderate negative correlation with Hf and Zr/U. In addition, uranium had a weakly defined correlation with the other trace elements, indicating a weak to moderate effect of magmatic processes, while the post-magmatic processes surficial or underground water greatly influenced the redistribution of uranium and other elements.

Integrated geophysical, remote sensing and geochemical investigation to explore gold-mineralizations and mapping listvenites at Wadi Haimur, Eastern Desert, Egypt

Although the continuity of gold mining work since Pharaonic times till today, Wadi Haimur is still promised source for gold. Wadi Haimur is located in west Allaqi-Heinai-Suture (AHS), south Eastern Desert of Egypt. Gold mineralization is mainly confined within quartz-carbonate and sulphide-bearing quartz veins within sheared, altered rocks, while listvenitization plays a significant role in gold concentration along the Haimur area. Therefore, critical analyses of remote sensing data were applied to map alteration zones and delineate listvenites. Spatially enhanced images were processed to trace lineaments and weakness zones which may represent pathways of mineralized, ascended hydrothermal fluids. Ground geophysical, magnetic and geoelectric surveys were performed to study the depth-extension of mineralized bodies in the vicinity of the historical mines within Wadi Haimur. Interpretation of land-magnetic data indicates the presence of mineralized veins associated with narrow shear zones. Derivatives and high-pass filters were utilized to map shallow mineralized sources and deduce their trends. Upward continuation and low-pass filters were used to detect the deep sources. Depths to magnetic bodies were estimated using Power-Spectrum, Euler and inversion of single anomalies. Geochemical sampling was performed to test the results. According to the remarkable variation in resistivity and chargeability values of resistivity and induced-polarization tomography profiles, the subsurface lithology was classified and probable mineralized zones within the subsurface were detected. Encouraging results from regolith, trenching, rock-chip sampling and Reverse-Circulation (RC) drilling indicated the extension of auriferous anomalies within the bedrock. Good correlation of RC-holes auriferous anomalies depths and deduced depths from magnetic interpretation was revealed. HIGHLIGHTS Integrated geophysical, geochemistry and remote sensing data are used to delineate mineralized ore deposits. The estimated average depths of mineralized sources are 12.5, 48 and 463 m for shallow, intermediate and deep magnetic bodies, respectively. Massive sulphide-bearing zones ± gold concentrations were suggested for zones with low-resistivity and high-chargeability signatures.

Integrating mineralogy, geochemistry and aeromagnetic data for detecting Fe–Ti ore deposits bearing layered mafic intrusion, Akab El-Negum, Eastern Desert, Egypt

This study delineated the Fe–Ti oxide deposit concurrencies on the layered mafic intrusion in Gabal Akab El-Negum (GAN), South Eastern Desert, Egypt, using aeromagnetic mapping and chemical analysis of the hosted mafic rocks and mineralogical studies. Aeromagnetic data was improved using the enhanced horizontal gradient amplitudeto detect the primary structures (edges/contacts/faults) that control the distribution of Fe–Ti ore deposit. GAN layered gabbros are differentiated into troctolite, olivine–, pyroxene–, and hornblende–gabbros. These mafic rocks primarily comprise plagioclase, olivine, pyroxene, and hornblende with Fe–Ti ores (magnetite and ilmenite). The significant variation in Mg# of clinopyroxene between 0.70 and 0.82 indicates the importance of fractional crystallization in developing layered mafic intrusion. Clinopyroxene and plagioclase thermometry yielded low temperatures similar to the fractionated primary basaltic magma. The pairs of magnetite–ilmenite minerals in gabbros provide equilibrium temperatures of 539.44–815.56, and high fO2, reflecting various cooling and subsolidus reequilibration phases of minerals. The enrichment of GAN gabbros in light rare–earth elements relative to heavy rare–earth elements indicates the interaction between the Fe–Ti rich mantle and the fractionated tholeiitic magmas in the back-arc setting, generating Fe–Ti oxide ores.

Implementation of ASTER data for lithologic and alteration zones mapping: Derhib area, South Eastern Desert, Egypt

Derhib area is dissected by narrow E–W-trending shear zones that delineate the alteration zones accommodating the infamous structurally-controlled talc mineralization in the South Eastern Desert of Egypt. A multidisciplinary remote sensing approach using ASTER images integrated with field data and petrographic investigations have been used for mapping the alteration zones at the Derhib area. Band ratios composites, band ratio, selective Principal Component Analysis (PCA) have been used for discriminating rocks and mineralization zones. Iron oxide/hydroxides-, phyllic and propyllitic-rich alteration zones were mapped using band ratios and selective PCA. Fuzzy logic modeling was implemented to integrate the most informative thematic layers for generating mineral prospectivity map. Based on eigenvector loadings, the map was produced by merging the selected PC thematic layers using fuzzy AND operator. The present study is consistent with the recent literature and shows the capability of fuzzy model as a valuable cost-effective tool to produce mineral potential maps, especially at the reconnaissance stages of mineral exploration.

Petrogenesis of ilmenite-bearing mafic intrusions: A case study of Abu Ghalaga area, South Eastern Desert, Egypt

Neoproterozoic Abu Ghalaga ilmenite-bearing mafic rocks were subjected to geological, petrographical and geochemical studies integrated with mineral chemistry of ilmenite, pyrite and magnetite in order to deduce their petrogenesis. Abu Ghalaga mafic intrusions hosting the largest ilmenite reserve in the Egyptian part of the Arabian-Nubian Shield. Field observations revealed that the intrusions impound ilmenite ore, which occurs as interlayer of massive bands or disseminated within gabbroic rocks. Petrographically, Abu Ghalaga mafic intrusions include different kinds of gabbro; olivine pyroxene gabbro, pyroxene gabbro, pyroxene hornblende gabbro, altered gabbro and Fe-Ti-rich gabbro. They have calc-alkaline to tholeiitic magmas, which are depleted in high field strength elements (e.g., Ta, Nb and Th) relative to low field strength elements (e.g., Ba, Sr and Rb), and exhibit light rare earth elements enrichment relative to heavy rare earth elements with positive Eu anomaly (Eu/Eu*= 0.8-2.4). Variable mineralogical and wide variation of bulk rock geochemistry are ascribed to fractional crystallization and hydrothermal overprinting. Abu Ghalaga gabbroic rocks are derived from fractional crystallization of depleted mantle magmas that were modified by ascending fluids from subducted slab in volcanic arc setting. Fe-Ti oxides required high oxygen fugacity (ƒO2) and water contents by crystal settling of Ti-rich mantle which is applicable with subduction setting. It can be inferred that Abu Ghalaga mafic rocks are neither related to ophiolite nor to Alaskan type but to one of the layered intrusions hosting Fe-Ti oxides.

Using a Landsat-8 image for lithological mapping of basement rocks at southeast Aswan city, South Eastern Desert, Egypt.

Using a Landsat-8 image for lithological mapping of basement rocks at southeast Aswan city, South Eastern Desert, Egypt.