The Gabel Tarbtie ring complex represents important caldera style magmatism in the Egyptian Nubian Shield. The massive association formed from a migratory magmatic midst ex-position as circular entities in three adjacent sectors with analogous lithological and structural features: two sectors forming the Tarbtie South (TS) and the other forms the Tarbtie North (TN). The rocks forming the two rings occur as a wide spectrum of petrographic sets including nepheline syenite, biotite-amphibole - aegirine bearing syenite, carbonitized syenite, nordmarkite, syenogranite, carbonatite and pyroclastics. The whole association is injected by andesitic to basaltic dykes, and affected by fenitization processes. Geochemically, the Gabel Tarbtie rocks belong to anorogenic intraplate A1-type alkaline complexes. They have high amounts of alkalis and show enrichment in some HFS elements (i.e. Ba, Nb, Zr, Y), mainly having meta-aluminous ferrouan nature. It is believed that during the post-orogenic times tension and uplift could cause migration of the decompression portion, and advance partial melting which promotes magma generation. The Gabel Tarbtie association was developed as result of migratory magmatic pulses evolved over a 15 km along NW lineaments or deep-seated fractures. Subsequently, the mature caldera outline was influenced by NE structural trend.

Space-borne hyperspectral imagery data are known for their high spectral resolution in a number of narrow wavelength intervals, which makes these data useful for mineral mapping. However, the available free-of-charge hyperspectral scenes cover only narrow and scattered geographic areas. In contrast, multispectral imagery scenes have a nearly complete spatial coverage and wider wavelength intervals. The low spectral resolution of the multispectral data, however, limits their efficiency in the mineral mapping of small geological massifs or hydrothermal alteration halos. The present contribution presents a new transformation tool (SAM-HIT) to simulate the hyperspectral sensor responses in unscanned areas based on partially overlapping hyperspectral and multispectral scenes. Simulation or prediction of the pseudohyperspectral data is here accomplished by using the simulated annealing linear optimization algorithm, which allows the lowest possible mismatch between the original and predicted data. The high visual and numerical correlation of the resultant data confirms the reliability of the newly adopted transformation. Further, the application of the SAM-HIT to a well-exposed part of the Egyptian basement complex with available hyperspectral data showed high concordance and nearly identical band signatures, opening a new outlook for mineral exploration in vast areas by a nearly automated cost-free means.

El-Gezira ring complex represents an important alkaline association in the south Eastern Desert, Egypt display crescent-shaped bodies and vast diversity of lithologies. It consists of several concentric rings separated by arch-shaped bodies of alkali gabbros, pyroclastics and hybrid rocks. The outer ring of El Gezira is composed of metavolcanics and basaltic andesitic flows. The inner part comprises carbonate, pyroxene bearing syenite, monzosyenite, trachyte, trachy-andesite and trachydacite. Clinopyroxenes are the prevailing mafics components in most rocks varieties. Amphiboles and olivine are common in most basic units. El Gezira ring complex comprises a high fractures frequency. El Gezira ring complex is one of a major cluster of ring complexes aligned along an ENE transform fault in the extreme southern part of Egypt. Chemically, El Gezira rock-associations are mostly metaluminous, and show low concentrations of CaO, MgO and Sr. Moreover alkalis, Rb, Nb, Y, and REE are relatively high which is distinctive of anorogenic affinity. The alkali gabbros have flat REE patterns with slight positive Eu anomalies. The trachyandesite, trachydacite and monzosyenite all have weakly to moderately fractionated patterns with a general enrichment in LREE, and mostly possess a pronounced positive and negative Eu anomalies. Typically, El-Gezira alkaline associations are classified as within plate granites. It is suggested that the primitive mantle mafic magmas were emplaced into intracrustal magma chambers during extensional regime. The primitive magma underwent fractionation processes to give the highly evolved liquids. Influx of more hot primitive magma may promote dynamic convection, crustal assimilation and eruption of the volcanic alkaline association filling fractures during post orogenic regimes.

To characterize paleoenvironmental changes and examine the response of calcareous nannoplankton to climatic warming during the Paleocene-Eocene Thermal Maximum (PETM), an integrated high-resolution study of calcareous nannofossils, mineralogy, and geochemistry was carried out on PETM sediments from Taramsa, west of Qena, in the central Nile Valley of Egypt. The PETM interval in the Taramsa Section is characterized by the following: (1) an extraordinary shift in δ13Corg, δ13Ccarb, and δ18Ocarb values and carbonate contents (−28.30‰, −8.75‰, −10.43‰, and 8.60%, respectively) accompanied by an abrupt decrease in calcite contents and an increase in both detrital input (quartz and phyllosilicate) and apatite content; (2) a dominance of K-mode genera such as Ericsonia, Coccolithus, Thoracosphaera, Discoaster, Rhomboaster, and Tribrachiatus, dwarfing of bony fish, "malformed" nannoliths in Discoaster multiradiatus, and a decrease in diversity to only three taxa (Coccolithus spp., Thoracosphaera spp., and Discoaster spp.) at the peak of the carbon isotope excursion (CIE). The asymmetric species Discoaster araneus and D. anartios thrived during the PETM interval and likely took shelter from environmental changes in order to adapt to the elevated temperatures and scarcity of nutrients. Dwarfism in bony fish and malformations in Discoaster multiradiatus appear to have been a response to changes in the environment that prevailed at the beginning of the Eocene, thus reflecting increasing environmental stress during the PETM interval.

The present work deals with geologic adaptation of Wadi Kharit shear zone based on field, petrographic, remote sensing and structural data. Neoproterozoic basement cover of Wadi Kharit includes, island arc metasedimentary association, metagabbro-diorite complex, syn-late to post-tectonized granites, and Nubian sandstone. The major structural orientation of the area is 270°‒ 280° N. The microstructure and paleostress analyses reveal a dextral sense of the shear zone. Such orientation indicates either the greater Najd-related Wadi Kharit–Hodein shear zone was overprinted by a dextral event subsequent to the main sinistral sense shear, or that Wadi Kharit shear can be considered as a separate high strain zone showing neither geometric nor kinematic relations with Wadi Hodein shear zone.

This article describes a 135-m-thick sequence collection from the lower Eocene limestones of the Dungul Formation that caps the Sinn El-Kaddab Plateau in the Kurkur area. A sedimentological evolution model of these limestones has been constructed for the first time primarily based totally on lithology, microfacies analysis, SEM microscopy, and EDAX microchemical analyses. This carbonate sequence has been subdivided into three shallowing-upward facies. The hemipelagic facies at the base is dominated by foraminiferal wackestone, unconformably overlain by shallow offshore facies dominated by larger benthic foraminiferal grainstone and packstone, and capped by middle ramp facies dominated by bioclastic grainstone and packstone. These facies are analog of the Eocene facies of the Tethys Sea that had been formerly defined from Libya, Tunisia, Spain, and Kirkuk oil field in Iraq. Results suggest deposition in a basin characterized by oscillation in relief, in response to tectonic uplifting coupled with eustatic sea fluctuations associated with and the Syrian arching system. The limestones exhibit four successive diagenetic stages. The first stage is early marine diagenesis with the formation of micrite rim cement and preferential micritization of some skeletal grains. The second stage is shallow burial diagenesis, compaction, drusy calcite cement, and silicification. The third stage is meteoric diagenesis, the formation of isopachous calcite rim cement, dissolution and formation of blocky cement. The fourth stage is vadose diagenesis which includes karstification and ferrugination with iron oxy-hydroxides impregnation.

Granitic rocks surrounding Nasb-Zurar intrusion at North West Wadi Allaqi comprise two varieties: tonalite and granodiorite of older granite (OG), and monzogranite of younger affinity (YG). Plagioclase crystals in OG are generally zoned and range in composition from andesite to oligioclase with An (21.0–46.4), Ab (52.9–78.1), and Or (0.7–1.1); meanwhile, they have albite composition in YG with Ab (87.4–93.3). Alkali feldspars are perthitic microcline and orthoclase. Muscovite has phengite composition with Si:Aliv being greater than 3:1. Biotite varies between Al-poor biotite end-members annite and phlogopite. Chlorite in OG has ripidolite composition, while that from YG is brunsvigite. The OG granite has SiO2 wt.% of 67.7 to 71.9, with high Al2O3 wt.% of 12.9 to 16.2 and low TiO2 wt.% of 0.26 to 0.52, MgO wt.% of 0.47 to 2.07, Fe2O3 wt.% of 1.91 to 4.5, P2O5 wt.% of 0.05 to 0.13, CaO wt.% of 2.01 to 3.92, K2O wt.% of 0.36 to 3.63, and Na2O wt.% of 3.63 to 5.64. YG is rich in SiO2 wt.% (73 to 75), and Al2O3 wt.% ranges 13.3–14.4, K2O wt.% elevated between 3.7 and 4.6, CaO wt.% ranges 0.18–1.59, and Na2O wt.% is high (3.52–4.18), while TiO2, Fe2O3, and MgO wt.% contents show relatively lower values. All studied granites have peraluminous characters and evolve as I-type granites within volcanic arc environment. The OG are believed to form by melting of metagreywackes surrounding the area at about 680 °C; meanwhile, the YG is supposed to crystallize under relatively lower temperature (average ~ 630 C°) by re-melting and differentiation of OG.

Poly-deformed late-Proterozoic metamorphic domains covering Um Ashira area at the western segment of Wadi Allaqi shear zone, South Eastern Desert of Egypt, show evidences of inverted Barrovian metamorphism. They exhibit four metamorphic zonal patterns, arranging progressively from chlorite, biotite, garnet, to sillimanite zones. The higher grade metamorphic domains appear at higher structural levels with general dipping toward the North East. Four deformational phases (D 1 –D 4 ), associating with major planar structures (S 1 –S 4 ), and four mesoscopic and microscopic folds are recognized. The pervasive fabric, growth of metamorphic minerals and peak metamorphism were linked to D 2 deformation phase. Structural, petrographic, microchemical, and thermobarometric data along South-North profile show possibility of inverted Barrovian metamorphic pattern with an increase in the metamorphic grade toward the North. The established structural sequence and tectonic modeling suggest that the apparent inversion coexists due to the main F 2 folding phase.

The Neoproterozoic basement complex of the western segment of the Allaqi Shear Zone (ASZ) in the extreme southern part of the Egyptian Nubian Shield comprises four main lithologic units: gneisses, amphibolites, island arc metasediments, and intrusives. In the present study, these units investigated at the outcrop scale, as well as petrographically and geochemically. Gneisses are subdivided into three types: hornblende, muscovite, and biotite gneisses. The hornblende and muscovite gneisses have para-gneissic origin, while the biotite gneiss has igneous protolith. Amphibolites have intermediate andesitic to basaltic andesite composition, with igneous origin, and were formed in island-arc environments. The metagabbros are subalkaline and have within-plate geochemical characteristics. The metasediments involve graphite-muscovite, albite, chlorite, biotite-muscovite, carbonate, and tremolite-actinolite schists, in addition to metagreywackes. The bulk chemistry of metasedimentary succession revealed their formation within active continental margin setting with pelitic to semi-pelitic and psammitic precursor. The previously mentioned lithologic units are poly deformed and intensively affected by shearing and thrusting. These structures strike in various direction: WNW-ESE, NNE-SSW, NW-SE, NW-SE, and E-W, which are consistent with the automatic and manual principal component analyses (PCA) lineament extraction.

The Abu Dabbab rare-metal granite in the Eastern Desert of Egypt is a highly-evolved alkali-feldspar granite with transitional magmatic-hydrothermal features. Extreme geochemical fractionation and the associated significant Ta-Sn resource make the Abu Dabbab intrusion an important feature in the metallogenic evolution of the Arabian-Nubian Shield. U-Pb dating by laser ablation sector field (SF)-ICPMS analysis of igneous monazite yields a Concordia age of 644.7 +/- 2.3 Ma, identical within uncertainty to a lower intercept Tera-Wasserburg isochron age of 644.2 +/- 2.3 Ma obtained from hydrothermal cassiterite. Both ages place tight constraints on the timing of magmatic-hydrothermal processes in the Abu Dabbab granite which represents the oldest highly-evolved granite recognized so far in the Pan-African Arabian-Nubian Shield. Thus, the new ages also date the start of a period of late-orogenic metalliferous granite magmatism, when the basement of the Eastern Desert underwent a geodynamic transition from a compressive subduction-collision regime towards orogenic collapse in the late Cryogenian. (C) 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

The Abu Dabbab rare-metal granite in the Central Eastern Desert of Egypt is a peraluminous alkali-feldspar leucogranite stock with minimummelt composition of albite-rich haplogranite and is characterized by economic resources of columbite group minerals (CGM) and cassiterite. The bulk-rock trace element composition is characterized by very low Sr, Ba, REE+Y, Zr, Ti, Ni, Cr concentrations, elevated Li and F, and very high Sn, Ta and Ga. The non-chondritic, low Y/Ho ratios and extremely low Nb/Ta and Zr/Hf ratios of the Abu Dabbab granite are consistent with highly evolved peraluminous granites. The chondrite-normalized REE patterns with significant tetrad effects (TE1,3 ~ 1.6–2.6) and strongly negative Eu anomalies are indicative of the magmatic to hydrothermal transition. Heterogeneous 147Sm/144Nd (0.20411–0.51923) and 143Nd/144Nd (0.512968–0.514056) values of the bulk-rock reflect a disturbed Sm-Nd isotope system. Nevertheless, the initial εNd values calculated for a wide range of Neoproterozoic ages (500–700 Ma) are consistently positive, suggesting a juvenile source.Laser ablation ICP-MS analyses of the CGM, cassiterite, wolframite and Mn-ilmenite show elevated rare metal concentrations and complex REE tetrad patterns, reflecting fluid-melt interactions. The metasomatic fluids associated with the Abu Dabbab rare-metal granite were primarily low-salinity (<6 wt.% NaCl eq.), high-density (~0.8–0.9 g/cm3), CO2-rich aqueous fluids with up to ~50 mol% CO2 (+CH4). The minimum entrapment conditions of carbonic-aqueous inclusions are calculated as 2–3 kbar and 350–360°C, whereas aqueous inclusions in the granite and crosscutting quartz veins most likely correspond to lower-pressure conditions and fluid phase separation by decompression. The extreme level of fractionation and complex tetrad effects of the bulk-rock and ore minerals coupled with criteria indicating the magmatic-hydrothermal transition are in accord with regional seismic tomography and heat flow data. A much larger, unexposed parental granite system, from which the exposed Abu Dabbab rare-metal tip has fractionated, must be present at depth. The interaction between extreme fractionation and fluid-melt interaction at shallow crustal levels gave rise to economic-grade Ta-Nb-Sn±W mineralization in the granite body and associated quartz veins.

This study investigates physical and mechanical characteristics of Lower Eocene limestone exposed on the Sinn El-Kaddab Plateau, southwest of Aswan. The limestone successions belonging to the upper member of the Dungul Formation attain 120 m in the composite section of the area. Sedimentologically, these limestones are composed of three lithofacies; hemipelagic facies at base composed mainly of wackstone, followed upwards by shallow marine nummulitic packstone and grainstone, and middle ramp facies at top composed mainly of bioclastic grainstone. The average values of the investigated physical properties include true density (2.70 g/cm(3)), bulk density (2.40 g/cm(3)), apparent specific gravity (2.66 g/cm(3)), apparent porosity (10.32%), and water absorption (4.44%). The average investigated mechanical properties values include Schmidt rebound attains (27.46), maximum stress (27.82 N/mm(3)), and compressive strength (283.77 kg/cm(2)). Unconfined uniaxial compressive strength and abrasion impact values were derived mathematically from equilibrated curves using Schmidt rebound values. Both limestones of Naqb Dungul and Kalabsha localities are suitable for uses in construction and ornamental purposes as dimension stone such as in floor tiles, interior and exterior cladding, production of bricks and mosaics, and possible non-constructional uses include fillers and pigments. Low values of both abrasions impact value obtained results; unconfined compressive strength and confined compressive strength of the lower facies refer to unsuitability as wear abrasive or road aggregates.

The end of the Cretaceous is a dramatic period in the Earths history, when a catastrophic event known as the Cretaceous-Paleogene mass extinction event took place (66.043 +/- 0.011 Ma). During the early Danian a minor hyperthermal event, known as Dan-C2 event, was raised and caused a minor perturbation in the carbon cycle. These two events were coincident with the second and the last phases of Deccan eruption in India. In El-Beida section, Quseir area, Red Sea, Egypt, the (K/Pg) is placed in the middle part of Dakhla Formation on the contact between the Hamama and Beida Member and is determined based on the high occurrence HO of Nerphrolithus frequens (CC26), the abrupt shift in delta C-13(org) from -23.5 parts per thousand to - 24.3 parts per thousand, and Hg enrichment was observed just below KPB; the Hg reaches 63.5 ppb, the earliest Danian zones (NP1, lower part of NP2, P0 and P1a) are missing due to the KPB hiatus. Dan-C2 is placed at the top of the Cretaceous-Paleogene boundary hiatus, and coincident to the base of NP2 nannofossil biozone. In general, only the second carbon isotope spike of the Dan-C2 is present and is characterized by 1.5 parts per thousand negative shift in organic carbon isotope, a sudden drop in TOC content, and mercury enrichment coincident with the delta C-13(org) onset that may be linked to the Deccan volcanic eruption (phase-3).

Satellite-based multi-sensor data coupled with field and microscopic investigations are used to unravel the setting and controls of gold mineralization in the Wadi Beitan–Wadi Rahaba area in the South Eastern Desert of Egypt. The satellite-based multispectral and Synthetic Aperture Radar (SAR) data promoted a vibrant litho-tectonic understanding and abetted in assessing the regional structural control of the scattered gold occurrences in the study area. The herein detailed approach includes band rationing, principal component and independent component analyses, directional filtering, and automated and semi-automated lineament extraction techniques to Landsat 8- Operational Land Imager (OLI), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Phased Array L-band Synthetic Aperture Radar (PALSAR), and Sentinel-1B data. Results of optical and SAR data processed as grayscale raster images of band ratios, Relative Absorption Band Depth (RBD), and (mafic–carbonate–hydrous) mineralogical indices are used to extract the representative pixels (regions of interest). The extracted pixels are then converted to vector shape files and are finally imported into the ArcMap environment. Similarly, manually and automatically extracted lineaments are merged with the band ratios and mineralogical indices vector layers. The data fusion approach used herein reveals no particular spatial association between gold occurrences and certain lithological units, but shows a preferential distribution of gold–quartz veins in zones of chlorite–epidote alteration overlapping with high-density intersections of lineaments. Structural features including en-echelon arrays of quartz veins and intense recrystallization and sub-grain development textures are consistent with vein formation and gold deposition syn-kinematic with the host shear zones. The mineralized, central-shear quartz veins, and the associated strong stretching lineation affirm vein formation amid stress build-up and stress relaxation of an enduring oblique convergence (assigned as Najd-related sinistral transpression; ~640–610 Ma). As the main outcome of this research, we present a priority map with zones defined as high potential targets for undiscovered gold resources.

The South Eastern Desert, is the northern part of the Nubian Shield, characterized by abundant ophiolites, extensive high strain zones, and a multilayered structural architecture. Gold mineralisation is related to discrete occurrences of mesothermal quartz ± carbonate veins (< 100 m-long), cutting dismembered ophiolites and schistose metasedimentary-metavolcanic rocks. Though generally controlled by shear/fault zones, the mineralized quartz veins display a spatial association with granitoid-gabbroid intrusions exhibiting signs of forceful emplacement into the country rocks. In the areas where no intrusions are exposed, rhyolite and dacite dykes or granophyre sills appear to cut the structural trend in the host rocks and control the mineralized quartz veins. K-metasomatism is conspicuously associated with gold lodes, despite the variability of the host lithologies. Most of the mineralization is related to visible free-milling gold/electrum inclusions persistent in arsenopyrite or along pyrite fractures and grain boundaries, with subordinate invisible gold in As-pyrite. The mineralogy, fluid inclusions and stable isotope characteristics of several deposits in the region prove to reveal similar mineralization styles, ore fluids and isotope signatures, suggesting inherent similarities in the deposition process, fluid source and likely in the gold introduction related timing. Overheating by thrusting and concomitant calc-alkaline magmatism, along with metamorphic dehydration and devolatization promoted the circulation of hydrothermal fluids in a metallogenically fertile, mafic crust and deposited gold in accretionary and transpressional structures.

Field and structural studies supported by multi-sensor satellite-based imagery data are attempted to decipher the setting and controls of gold-bearing quartz veins in the central part of the greater Wadi Allaqi district in the South Eastern Desert of Egypt. Here, we assess the evolution of a complex part of the Neoproterozoic Allaqi-Heiani suture (similar to 730-700 Ma) with ample structures demonstrating the final Gondwanan collision. Abundant extensive N-trending folds, sinistral shear zones and oblate fold patterns and strain fabrics exemplifying an oblique convergence and torsion related to a regional similar to E-W compressional regime. In the Wadi Seiga area, the first order upright and overturned folds and thrusts (D1 structures) are mostly obliterated by intense NW-ward transpression, N-ward folding and transcurrent shearing assigned to as D2 and D3 structures. The domal crescentic and mushroom superimposed fold patterns suggest that Type 2 and Type 3 fold interference patterns were synchronous at some time during D2 or D3. Shear zones with abundant signs of plastic deformation and associated with quartz veins, within the axial planes of NNW- and NNE-trending F3 folds may imply gold mineralization during the third deformation stage (D3). The latter was supplemented or terminated by an episode of northward tectonic escape and slip reactivation of the pre-existing NW-trending faults. Integrated with field measurements, satellite-based radar and radiometer data abetted untangling the superimposed structures. Gold occurrences in the area are confined to domains of superimposed foliations, foliation deflection/steepening, foliation refraction and substantial strain partitioning, or at oppositely interfered plunging folds. The scattered small scale occurrences of <= 10 s g/t Au-bearing gold-quartz veins in such high strain zones, together with the lack of spatial association with a particular intrusive phase weigh with the metamorphic model for gold-only endowment in the area. The peak metamorphic conditions (amphibolite facies) in the central Allaqi-Heiani suture were attained not earlier than 630 Ma, during the collision of the Arabian-Nubian Shield with the Nile Craton to the west (provoked at 670-610 Ma). Gold-only endowment was complementing to the latest stages of deformation and terrane cooling between 610 and 585 Ma. Listvenitization of tectonized ophiolites and widespread sericite alteration of the island arc metavolcaniclastic rocks could have been promoted by the late-orogenic felsic intrusions (similar to 603 Ma) that filled oblate dilation spaces developed by structural transport to the north. The late orogenic timing of mineralization is one of many features making the Allaqi-Heiani suture comparable to well-documented global examples of accretionary metallogenic belts.

The groundwater contamination problem comes out from the ability of water to dissolve the aquifer materials, where any change in water acidity and alkalinity has an impact on this process. Iron and manganese are very sensitive to the water redox conditions. The present work attempts to characterize distribution and occurrence of Fe and Mn in the groundwater of Dakhla Basin, Western Desert of Egypt, their relationships with the acidity and alkalinity of groundwater, and the potential effect of oxidation-reduction conditions on their mode of occurrence. High concentrations of iron (Fe2+) and manganese (Mn2+) reductively dissolved from soil minerals have been detected in groundwater. Iron and manganese concentrations, as well as alkalinity and pH of groundwater were mapped in the study area. The concentrations of both elements are extremely high in the southern part of the study area (256 and 36 ppm, respectively) due to the high acidic character of groundwater. Two forms of Fe2+ are present (carbonate and sulfides), linked mainly to the level of the water-bearing layer depth. The iron carbonate is linked to the shallow water-bearing interval, whereas in the deep bearing water interval, Fe2+ tends to be in the sulfide form with the presence of sulfur-reducing bacteria (SRB). Mn behaves similarly as Fe but precipitated more rapidly, and the anaerobic bacteria play an effective role in concentration of both Fe and Mn in the studied samples. The long aeration time can help to drawdown the high Fe and Mn contents.

The present work assesses the potential industrial uses of Paleocene limestone deposits, Garra Formation in Sinn El-Kaddab Plateau, South Western Desert of Egypt, based on their mineralogy and geochemical characteristics. Eighty-six limestone samples collected from ten stratigraphic columnar sections were analyzed using X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques. Petrographically, Garra limestone deposits consist dominantly of benthic foraminiferal wackestone and packstone microfacies. The XRD data revealed dominance of low-Mg calcite as essential carbonate mineral in the studied limestone. The bulk rock XRF results revealed CaO (29.28–55.75%) with an average of 52.74%. The CaO exhibits a strong negative correlation with MgO, SiO2, TiO2, Al2O3, and moderate negative correlation with Fe2O3 which indicates that the contribution of these elements is mainly due to detrital input. On the other hand, Al2O3 and Na2O contents exhibit significant negative correlation with loss of ignition (LOI) wt% indicating their incorporation within terrigenous matrix. The average Sr content attains 1297 ppm indicating deposition in temperate marine environment. The average molar CaCO3% values of bulk samples have been computed for individual columnar sections to determine the purity status of Garra limestone deposits. They range from impure (CaCO3% = 79.92%) to high-pure (CaCO3% = 97.76%) limestone. Therefore, Garra limestone deposits have extremely valuable uses in a wide spectrum of industrial applications including Portland cement, steel, ceramics, whiting, chemical uses, paper, and feed stuff.

Trace element composition of sulfides and O, C, Sr and S isotopic data are assessed to constrain the evolution and potential fluid and metal sources of the Um Garayat gold deposit. Ore microscopy and BSE investigations of quartz veins show blocky arsenopyrite and pyrite replaced in part by pyrrhotite, chalcopyrite, sphalerite, galena, and gersdorffite. Free-milling gold occurs commonly in close association with the late sulfides, and along fractures in pyrite. On the other hand, recrystallized pyrite is disseminated in host metavolcaniclastic/metasedimentary rocks that commonly contain carbonaceous material. In situ LA-ICP-MS analysis of sulfides shows the recrystallized pyrite enriched in most trace elements, while blocky pyrite contains only some traces of arsenic. Detected concentrations of gold (up to 17 ppm) were only reported in arsenopyrite disseminated in quartz veins. The δ 34 S values of blocky pyrite and pyrrhotite in quartz veins define a narrow range (1.6 to 3.7‰), suggesting a homogenous sulfur source which is consistent with the dominantly mafic host rocks. The recrystallized pyrite has a distinctive sulfur isotope composition (δ 34 S − 9.3 to − 10.6‰), which is rather comparable to diagenetic sulfides. Hydrothermal carbonate in quartz veins and wallrock have nearly constant values of δ 18 O (10.5 to 11.9‰) and δ 13 C (− 4.2 to − 5.5‰). Based on constraints from mineral assemblages and chlorite thermometry, data of six samples indicate that carbonate precipitation occurred at ~ 280 °C from a homogenous hydrothermal fluid with δ 18 O H2O 4.4 ± 0.7‰ and δ 13 C = 3.7 ± 0.8‰. Strontium isotope values of two samples ( 87 Sr/ 86 Sr = 0.7024 and 0.7025) are similar to the initial 87 Sr/ 86 Sr ratios of island arc metabasalts (~ 710 Ma) in the South Eastern Desert. The generally homogenous sulfur, C, O, Sr isotope data are suggestive of metamorphogenic fluids, likely produced from dominantly mafic volcanic rocks at the greenschist–amphibolite facies transition.