Eastern Desert Of Egypt Research Articles

Sites with Holocene dung deposits in the Eastern Desert of Egypt: Visited by herders?

The Tree Shelter and Sodmein Cave are two sites in the Egyptian Eastern Desert with stratified archaeological deposits. In Middle Holocene contexts of both sites, dated to the 7th millennium BP and later, animal dung has been found, in the shape of small concentrations of pellets at the Tree Shelter and of large accumulations at Sodmein Cave. The combination of several lines of evidence, including the size and weight of the excrements, the dimensions of the dung layers from Sodmein and the presence of hearths and artefacts inside them, and the species represented in the bone assemblages from Sodmein and the Tree Shelter, indicates that the dung was mostly deposited by herds of domestic ovicaprines. Sodmein Cave and the Tree Shelter belong to the oldest sites of the African continent where evidence for domestic small livestock has been attested. The importance and size of the herds seems to have been greater than would be suspected from the scant bone remains that were found. The visits to the caves were probably short but repeated over a long time period. Macrobotanical remains recovered from the dung suggest that these visits took place after seasonal winter rains.

Mineralogical and Geochemical Characterization of Beryl‐Bearing Granitoids, Eastern Desert, Egypt: Metallogenic and Exploration Constraints

AbstractMineral chemistry and geochemical characteristics of beryl‐bearing granitoids in Eastern Desert of Egypt, were examined in order to identify the metallogenetic processes of the host granitoids. The investigated Be‐bearing granitoids and type occurrences are classified into two groups: (i) peraluminous, Ta ≥ Nb + Sn + Be ± W‐enriched, Li‐albite granite (e.g. Nuweibi and Abu Dabbab); and (ii) metasomatized, Nb >> Ta + Sn + Be ± W ± Mo‐enriched alkali feldspar granite (i.e. apogranite; e.g. Homr Akarem, Homr Mikpid and Qash Amir). In these two groups, beryl occurs as stockwork greisen veins, greisen bodies, beryl‐bearing cassiterite ± wolframite quartz veins, dissemination, and miarolitic pegmatites. Beryl of the Be‐granitoids, particularly those of miarolitic pegmatites, contains appreciable contents of Fe, Na, and H2O. An important feature of the Be‐apogranites is the occurrence of white mica as the sole mafic mineral in the unaltered alkali feldspar granite in lower zones. Presence of white mica as volatile‐rich pockets suggests that the melt underwent disequilibrium crystallization, rapid nucleation rates, and exsolving and expulsion of volatiles.

Epigenetic BIF-hosted gold lodes at the Abu Marawat area, Eastern Desert, Egypt: integrated mineralogical, structural control and fluid inclusion studies

Numerous massive and sheared, milky quartz veins cut a sequence of Neoproterozoic island arc metavolcanic/volcaniclastic rocks and related banded iron formation (BIF) at the Abu Marawat area, central Eastern Desert of Egypt. Sulphide-bearing quartz veins and related hydrothermal breccia masses display a range of textures including sheared, boudinaged and recrystallised quartz, quartz with open space filling and microbreccia, implying a complex history of crack-seal processes characterising the relationship between mineral deposition and a major N–S-trending shear zone, during a late brittle–ductile deformation event that affected the area at ∼550 Ma. Gold-base metal mineralisation is associated with brecciation and fracturing of the iron ore bands, close to silicified shears and related quartz veins. The auriferous quartz lodes are characterised by the occurrence of visible pyrite-chalcopyrite±pyrrhotite±sphalerite±galena mineralisation. Gold is refractory in pyrite and chalcopyrite, but rare visible gold/electrum and telluride specks were observed in a few samples. Hydrothermal alteration includes selectively pervasive silicification, pyritisation, sericitisation, carbonatisation that are confined to a delicate set of veins and altered shears, and a more widespread propylitic alteration assemblage (quartz+||chlorite+pyrite+calcite±epidote). The predominance of hydrated silicate phases (i.e. chlorite and sericite) within and adjacent to the shear zones points toward fixation of H2O during the shear zone development, while CO2 was consumed to form carbonate in halos around the chlorite-dominated zones, leading to variations in the H2O/CO2 ratio of the ore fluid with progression of the hydrothermal alteration.Ore textures, including hydrothermal quartz intimately associated with replacement of magnetite by pyrite, suggest the introduction of ore fluids via epigenetic conduits into the iron-rich wallrocks. Fluid inclusion textural and microthermometric studies indicate heterogeneous trapping of a low-salinity (1·4–6·7 wt-% eq. NaCl) aqueous solution that coexisted with a carbonic fluid. Evidence for fluid immiscibility during ore formation includes variable liquid/vapour ratios in inclusions along individual trails and bulk inclusion homogenisation into liquid and occasionally to vapour at comparable temperatures. The trapping conditions of intragranular aqueous-carbonic inclusions approximate 264–378°C at 700–1300 bar. Similar temperature estimates have been obtained from Al-in-chlorite geothermometry of chlorite associated with sulphides in the mineralised quartz veins. Fracturing enhanced fluid circulation through the wallrock and related BIF, allowing reaction of the S-bearing ore fluid with iron oxides. This caused formation of pyrite, a rise in Eh and concomitant Au precipitation, which was enhanced by fluid immiscibility as H2S partitioned preferentially into the carbonic phase. The ore fluids have probably originated from felsite intrusions, whereas Abu Marawat gold deposit and the post-Hammamat felsites is assumed in view of their communal relationship with the N–S fault/shear trend and high geothermal gradient calculated from the fluid inclusion data.

WITHDRAWN: Au–pyrite and Pt–Re–molybdenite associations in the sulphide mineralized younger granites in the Eastern Desert of Egypt

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Neoproterozoic diamictite in the Eastern Desert of Egypt and Northern Saudi Arabia: evidence of ~750 Ma glaciation in the Arabian–Nubian Shield?

The Neoproterozoic Atud diamictite in Wadi Kareim and Wadi Mobarak in the Eastern Desert of Egypt and the Nuwaybah formation in NW Saudi Arabia consist of poorly sorted, polymictic breccia, with clasts up to 1 m of granitoid, quartz porphyry, quartzite, basalt, greywacke, marble, arkose, and microconglomerate in fine-grained matrix. Stratigraphic relations indicate that the diamictite was deposited in a marine environment. Integrated field investigation, petrographic study and U–Pb SHRIMP zircon ages demonstrate that the Atud and Nuwaybah are correlative. The distribution of zircon ages indicate that ~750 Ma ages are dominant with a significant component of older materials, characterized by minor Mesoproterozoic and more abundant Paleoproterozoic and Neoarchean ages. Some matrix and metasedimentary clast zircons yield ages that are a few 10s of Ma younger than the age of the youngest clast (754 ± 15 Ma), suggesting Atud/Nuwaybah diamictite deposition ~750 Ma or slightly later, broadly consistent with being deposited during the Sturtian glaciation (740–660 Ma). The Paleoproterozoic and Neoarchean clasts have no source within the ensimatic Arabian–Nubian Shield. The distribution of the pre-Neoproterozoic ages are similar to the distribution of the pre-Neoproterozoic ages in Yemen and Saharan Metacraton, suggesting that these clasts have been transported hundreds of kilometers, maybe by ice-rafting. The Atud diamictite may represent important evidence for Cryogenian “Snowball Earth” in the Arabian–Nubian Shield.

Occurrence of Uraniferous Iron Grains at Gabal Gattar, El Missikat and El Erediya Granites in Eastern Desert of Egypt

AbstractUraniferous iron grains occur in some radioactive granite plutons in the Eastern Desert of Egypt. Modal analysis of these grains indicates that weight abundance of uraniferous grains amounts to 17.50%, 18.00% and 26.00% of the total accessory heavy minerals of the uranium‐mineralized samples of Gabal Gattar, El Missikat and El Erediya, respectively. These grains are mainly restricted to shear zones associated with strong hematitization, and occur either as fracture fillings or as interstitial grains among the main rock‐forming minerals. Uraniferous iron grains are mainly composed of uranophane and β‐uranophane coated and stained with limonite. These grains represent the main radioactive minerals in addition to the bright canary yellow to yellow uranophane and β‐uranophane mineral grains. The data obtained on scanning electron microscopy and electron microprobe analysis confirm the abundance of iron in the darker colored varieties with respect to the light colored varieties. This mode of occurrence of the uranium minerals requires special consideration during mineral processing by physical means.

Description of Dietzia lutea sp. nov., isolated from a desert soil in Egypt

An actinobacterial strain YIM 80766 T was isolated from a soil sample collected from the eastern desert of Egypt, and its taxonomic position was investigated by a polyphasic approach. The organism was found to have a range of chemical and morphological properties consistent with its classification in the genus Dietzia. Phylogenetic analysis indicated that the levels of 16S rRNA gene sequence similarity between strain YIM 80766 T and the other type strains of recognized members of the genus Dietzia were 97.0–98.9%. However, DNA–DNA hybridization values and phenotypic characteristics revealed that the strain differed from the currently recognized species of the genus Dietzia. Therefore, strain YIM 80766 T represents a novel species of the genus Dietzia, for which the name Dietzia lutea sp. nov. is proposed. The type strain is YIM 80766 T (=KCTC 19232 T=DSM 45074 T=CCTCC AA 207008 T). The 16S rRNA gene sequence of strain YIM 80766 T has been deposited in GenBank under the accession number EU821598.

Geoturist attractions of the Eastern Desert in Egypt

The main aim of this paper is presentation of interesting sites and geological formations of the Eastern Desert in Egypt. The authors mention also samples of petrified wood, which were collected from an area of the Eastern Desert, about 30 km away from Cairo. Samples of wood were subjected to a series of mineralogical studies under the microscope. It appeared that fragments of wood were mineralized with secondary silica as well as iron and manganese compounds. The area of the Eastern Desert, like the whole Sahara Desert, is interesting for geologists and tourists.

Estimation of heat generation by radioactive decay of some phosphate rocks in Egypt

Radiogenic heat production data for phosphate rocks outcropping on the three main areas Eastern Desert, Western Desert and Nile Valley are presented. They were derived from uranium, thorium and potassium concentration measurements of gamma radiation originating from the decay of 214Bi ( 238U series), 208Tl ( 232Th series) and the primary decay of 40K. A low radioactive heat production rate (0.32±0.1 μW m −3) was found for Wadi Hegaza, whereas the highest value (19±4.1 μW m −3) was found for Gabel Anz, Eastern Desert of Egypt.

Monazite chemistry: evidence for a prehistoric journey

The chemistry of monazite from the black sand deposits of northern Sinai beach suggests that pegmatites and granites of the Eastern Desert of Egypt are the most likely source rocks. The floods associated with the pluvial periods prevailed in Egypt during the Pleistocene were able to erode the source rocks and liberate heavy minerals including monazite. The mineral grains were moved through several wadis and tributaries to the River Nile. At the confluence sites, these heavy minerals were mixed with the Ethiopian and central African heavy mineral assemblages. The grains continued to move together downriver until being deposited in their current locations.

Radiospectrometric and magnetic signatures of a gold mine in Egypt

The purpose of this research is to study the signatures of a gold mine (Um Salim), located in the Eastern Desert of Egypt, using aeroradiospectrometric and aeromagnetic data. To achieve this goal, reduction-to-pole (RTP), high-pass filtering and analytical signal techniques were applied to the aeromagnetic data. Besides, interpretation of the total-count (TC) radiometric map, the three radioelements (K, eU and eTh) maps and the ternary radioelement composite image were carried out. Moreover, a two-dimensional trend analysis for the structural lineaments as traced from the geologic, total-count radiometric and reduced-to-pole magnetic maps was conducted to define the relationship which might exist between location of the gold mine, lithologies and major structures of the area under consideration. The study revealed that the known gold mine is associated with a high positive magnetic anomaly that trends in the NE direction and a high-amplitude analytic signal. The Um Salim gold mine is associated with very low aeroradiospectrometric levels on the four maps (TC, K, eU and eTh). The location of the gold mine is controlled by the intersection of both NW and NE trends. There are other particular radiospectrometric ratio signatures for gold deposits (eU/eTh, eU/K and eTh/K). Ternary radioelement maps can discriminate also alteration zones in various degrees that correlate with the gold mine. These zones can be used as a diagnostic exploration guide for various types of non-radioactive mineral deposits (e.g., copper and gold). Four major tectonic trends were identified that have the following directions: NE, NW, N–S and WNW.

Geochemistry and geothermobarometry of the Um Eleiga Neoproterozoic island arc intrusive complex, SE Egypt: genesis of a potential gold-hosting intrusion

Gabbro-diorite-tonalite±granodiorite complexes, derived from subduction-related, calc alkaline magmas represent a distinct unit in the Precambrian basement of Egypt. These intrusive complexes are commonly intruded into ophiolitic mélange, schistose or gneissic rock assemblages. Well-constrained geological mapping of the Um Eleiga complex, combined with geochemical studies, should enable a better understanding of its genesis, especially its potential as a host for gold mineralisation. This complex represents a composite pluton intruded into the allochthonous, ophiolitic Abu Dahr massif and its associated undifferentiated metavolcano-sedimentary mélange matrix in the southern Eastern Desert of Egypt. Field and petrographic investigations have revealed a compositional continuum from gabbro to granodiorite through diorite and subordinate tonalite. Petrography and bulk rock geochemical data have been used to determine the magma type and tectonic setting of the Um Eleiga complex, whereas the electron microprobe data were valuable for the purpose of determining the pressure–temperature and oxygen fugacity conditions. The compositional continuum, pattern of zonation, shallow magma origin and marked common negative Nb anomalies suggest that a close petrogenetic relationship between the gabbro, diorite, tonalite and granodiorite units of the Um Eleiga complex. Subducted upper mantle wedge is proposed as being the source region for the gabbroic magma, whereas zoning of the complex is attributed to interplay of fractional crystallisation and assimilation. Pressure estimates based on the Al(iv)-in-hornblende geobarometry indicate that the gabbroic and dioritic rocks crystallised under 4–5 kbar, whereas tonalite and granodiorite were formed at 3–4 kbar. The hornblende-plagioclase thermometer indicates a formation temperature range of about 720 to 880°C for the complex. Varied oxidation states are inferred from the mineral assemblages, including magnetite, titanite and ilmenite and checked by Fe/(Fe+Mg) ratios of biotite in the granitoid rocks. The tectonic setting, mineralogical, geochemical characteristics and varied redox state of the Um Eleiga intrusive complex are typical for arc-related intrusives potential for hosting intrusion-related gold in a collisional environment.

A failed invader in the North Atlantic, the case of Aglenus brunneus Gyll. (Col., Colydiidae), a blind flightless beetle from Iceland

The occurrence of an occasional pest of mouldy stored product residues, the blind flightless beetle Aglenus brunneus Gyll., in samples from the medieval farm at Reykholt in Iceland, along with several other strongly synanthropic beetles, is considered in relation to its fossil record. The species is dependent on man for its dispersal and survival and it probably had its primary habitat in the warm, decaying litter of the undisturbed forest floor in Europe. Now virtually cosmopolitan, it had been introduced to a remote site in the eastern desert of Egypt by the Roman period and was widespread in medieval northern Europe. The processes by which such an apparently stenotopic species could have invaded are discussed in relation to other evidence for anthropochorous dispersal.

Granitoid evolution in Sinai, Egypt, based on precise SHRIMP U–Pb zircon geochronology

Late-stage Pan-African granitoids, including monzogranite, syenogranite and alkali granite, were collected from four separate localities in Sinai. They were selected to represent both the calc-alkaline and alkaline suites that have been viewed as forming separate magmatic episodes in the Eastern Desert of Egypt, with the transition to alkali granite at ~ 610 Ma taken to mark the onset of crustal extension. Although intrusive relations were observed in the field, the emplacement ages of the granitoids cannot be distinguished within analytical uncertainty and they all formed within a restricted time span from 579 to 594 Ma. This indicates that the two suites are coeval and that some calc-alkaline rocks were also likely generated during the late extensional phase. These ages are identical to those recently obtained from similar rocks in the North-Eastern Desert, confirming that Sinai is the northern extension of the Eastern Desert Pan-African terrane of Egypt. Rare inherited zircons with ages of ~ 1790 and ~ 740 Ma are present in syenogranite from northeastern Sinai and indicate that older material is present within the basement. A few zircons record younger ages and, although some may reflect later disturbance of the main zircon population, those with ages of ~ 570 and 535 Ma probably reflect thermal events associated with the extensive emplacement of mafic and felsic dykes in both northeastern and southern Sinai.

Characteristics and genesis of shear zone-related gold mineralization in Egypt: A case study from the Um El Tuyor mine, south Eastern Desert

Although gold production from orogenic deposits in the Arabian–Nubian Shield is currently relatively minor, extensive alluvial and lode fields were exploited by the ancient Egyptians along the western side of the Red Sea in Upper Egypt and northern Sudan. In the Eastern Desert of Egypt, numerous but small gold deposits are generally related to auriferous quartz veins commonly associated with brittle–ductile shear zones cutting the Neoproterozoic crystalline basement rocks. The Um El Tuyor gold deposit, in the extreme south of the Eastern Desert, consists of a series of quartz and quartz–carbonate veins, lenses and veinlets, along foliation-concordant and foliation-discordant fault segments. The orebodies are mainly quartz–carbonate (quartz + Fe-dolomite/ankerite + muscovite/sericite + sulfides ± gold/electrum) and laminated quartz veins (quartz + sericite/chlorite ± graphite ± free gold). Gold appears as microscopic blebs within arsenopyrite and pyrite or along fractures and grain boundaries in quartz veins and finely disseminated grains in mixtures of chlorite ± sericite and carbonate in the wallrock. The bulk vein system is controlled by a NNW- to NW-trending brittle–ductile shear zone, cutting sequences of pelitic metasediments (garnet–biotite schist with intercalations of metamudstone and metagreywacke). Pervasive sericitization, carbonatization and chloritization overprint the metamorphic assemblages in rocks adjacent to the mineralized quartz veins. Temporal and lateral evolution of the ore fluid composition through interaction with the wallrock is inferred from the concentric alteration pattern. Stages of increasing hydrothermal alteration are identified as initial, intermediate and advanced. Hydrolysis reactions by a near acid fluid, whose pH was buffered by the wallrock mineralogy, prevailed in the initial stage. The transitional stage involved intense carbonatization, sulfidation and redox reactions along with hydrolysis. During the advanced stage, intense sericitization consumed K +, released H +, and lowered the solution pH. Sulfidation continued, and unbuffered conditions were locally attained under high fluid/rock ratios. This collectively indicates that the ore fluids evolved progressively towards lower temperatures and sulfur fugacity with time. Clustered and intragranular trail-bound aqueous-carbonic [H 2O–NaCl–CO 2(± CH 4 ± N 2)] inclusions are common in cores of the less deformed quartz crystals, whereas carbonic [CO 2 ± CH 4 ± N 2] and aqueous [low salinity H 2O–NaCl] inclusions occur along intergranular and transgranular trails. The aqueous-carbonic and aqueous inclusions are common in the quartz–carbonate veins, whereas the carbonic inclusions are by far the dominant — or virtually the sole fluid inclusions — in most parts of the laminated quartz and quartz–carbonate veins. Clathrate melting temperatures indicate low fluid salinities (3 to 8 wt.% NaCl equiv.). Bulk densities and salinities of the aqueous-carbonic inclusions are high in the quartz–carbonate veins compared to those in the laminated quartz veins, further constraining interpretation of the field observations suggesting that the laminated quartz veins were formed through a fault–valve system and cyclic opening and annealing of reactivated quartz–carbonate reefs. Destabilization of gold–bisulfide complexes and lowering of gold solubility through interplay of fluid mixing (± unmixing), cooling, changes in pH and fO 2 along with fluid–wallrock interaction brought about gold deposition. In the quartz–carbonate veins, in which the highest T h total (336 °C) indicates a pressure range of 1.7 to 2.1 kbar using isochores for highest and lowest bulk density aqueous-carbonic inclusions. In the laminated quartz veins, gold deposition likely took place due to fluid mixing and fluid–wallrock interaction at ≤ 325 °C at pressures of 1.6 to 1.3 kbar. Gold deposition due to fluid–wallrock interaction (sulfidation) does not conflict with intermittent fluid unmixing or mixing, as the latter does not appear to have extended into the wallrock. Pressure estimates indicate depths of 6 to 8 km for quartz veining and gold deposition in the area, compatible with crustal conditions of greenschist metamorphism and brittle–ductile transition.

Exhumed fault scarps and drainage modification as proxies of neotectonics at the Abu Dabbab area, Eastern Desert, Egypt

The basement rocks, Neogene sediments and Quaternary alluvial deposits in the Abu Dabbab area, Eastern Desert of Egypt, are deformed by N-S, NE-SW, NW-SE and E-W trending faults. Complex cross-cutting relationships show a complicated history of initiation and reactivation of these faults. The recent fault scarps demonstrate different morphologies, modes of formation and relative ages. Recurrent, step and successively reactivated faulting was likely responsible for the exhumation and neo-formation of the fault scarps. Capture, deep incision, offset and reversal in flow direction of streams are the main drainage modifications induced by active faults. The concealed and active faults are associated with high drainage density anomalies. Segmentation phenomenon is common for all fault trends. Microearthquakes are concentrated at the intersection zones of faults and caused by upper crustal strike-slip, oblique-slip, reverse and normal faults. The paleostresses are not consistent with the present-day stress fields. The present-day NE-SW extension across the Red Sea combined with a local multidirectional tension led to reactivation of old faults and initiation of new fault trends.

Petrogenesis of Gabal El kahfa Ring Complex, Eastern Desert of Egypt.

Petrogenesis of Gabal El kahfa Ring Complex, Eastern Desert of Egypt.

Hydrothermal alteration geochemistry of the Betam gold deposit, south Eastern Desert, Egypt: mass-volume-mineralogical changes and stable isotope systematics

Although there is relatively minor gold production from the Arabian–Nubian shield at present, extensive alluvial and lode fields along the western side of the Red Sea in Upper Egypt and northern Sudan were worked out by the ancient Egyptians for thousands of years. In the Eastern Desert of Egypt, numerous but small gold deposits are generally related to auriferous quartz veins commonly associated with brittle-ductile shear zones, generally cutting through the Neoproterozoic crystalline basement rocks and trending in different directions. Gold mineralisation at the Betam mine area, south Eastern Desert, is related to a series of milky quartz veins along a NNW- trending brittle-ductile shear zone cutting through successions of pelitic schists, next to a small granite intrusion. Gold-sulphide mineralisation (pyrite, arsenopyrite, galena, subordinate chalcopyrite and gold) is closely associated with a conspicuous hydrothermal alteration halo. Textural relationships, including replacement and crosscutting of mineral phases and quartz veins record a post-foliation alteration assemblage of quartz+sericite+chlorite+calcite±albite±epidote. The hydrothermal alteration halo alongside the auriferous quartz veins comprises three distinct zones, namely distal chlorite-calcite zone (chlorite+calcite±biotite±pyrite±sericite±epidote), an intermediate sericite-chlorite zone (sericite+chlorite+pyrite±biotite), and a proximal pyrite-sericite zone (quartz+pyrite+sericite±albite). These zones merge to each other gradually, ending outwards into the unaltered metasediments. The pyrite-sericite zone contains the highest gold grades, especially in zones thickly seamed with sulphide-rich quartz veinlets. Mass balance calculations have revealed that the pyrite-sericite zone experienced significant metasomatic changes relative to limited mass and volume changes for the chlorite-calcite zone. The overall picture of chemical gains and losses with increasing the intensity of hydrothermal alteration is indicative of addition of SiO2, K2O, Na2O, and volatile elements (S, CO2), removal of MgO, and relatively inert behaviour of Al2O3, TiO2, MnO, Fe2O3. CaO is variably mobile; slightly enriched in the chlorite-calcite and sericite-chlorite zones but depleted in the pyrite-sericite zone. Concentrations of the trace elements are variable in the different alteration types, but a notable increase in Au, As, Ba, Sr, Rb, V, and Ni in the intensively altered rocks is apparent. Investigation of the rare earth element (REE) behaviour reveals a little modification; heavy REE are more or less unchanged, whereas light REE are significantly mobile in all alteration types. New geochemical data provide evidence for progressive silicification, sericitisation, and sulphidation as a function of gold mineralisation. A proposed model for the hydrothermal alteration system for the Betam deposit includes fluctuation in pH and redox state (fO2), mainly during the wallrock sulphidation. This might have destabilised gold complexes and lowered gold solubility in the ore solution, and hence contributed at least partly in gold deposition in the study area. A decrease in the whole rock δ18O values from un-altered country metasediments to the distal, intermediate and proximal alteration zones, respectively, might be attributed to rock interaction with an isotopically lighter fluid. In addition, sulphur isotope data of pyrite-arsenopyrite pairs in the mineralised quartz veins and adjacent wallrock along with the calculated δ34S∑s values for the ore fluids suggest derivation from non-homogenous (mixed magmatic and metamorphic) fluids.

Assessment of natural radioactivity and radon exhalation rate in Sannur cave, easterndesert of Egypt

Activity concentrations of 238U, 232Th and 40K in rocks and soil samples collected from Sannur cave, Beni Suef governorate, eastern desertof Egypt, were determined using the high-resolution gamma spectrometry technique. Theresults show that the concentrations of the naturally occurring radionuclides are the following:238U rangedfrom 8.51 ± 1.23 to 20.66 ± 2.12 Bq kg−1,232Th rangedfrom 7.69 ± 1.02 to 22.73 ± 1.60 Bq kg−1 and40K rangedfrom 185.74 ± 0.42 to2084.70 ± 23.30 Bq kg−1. The radium equivalentactivity (Raeq), the absorbeddose rate (D), and theexternal hazard index (Hex) were also calculated and compared to the international recommended values. The radonconcentration and radon exhalation rate from the rock and soil samples were measuredusing the Can technique. The average value of annual effective dose for cave workers is1.98 mSv y−1, while forvisitors it is 2.4 µSv per visit. The radon exhalation rate varies from0.21 ± 0.03 to1.28 ± 0.02 Bq m−2 h−1. A positive correlation has been observed between uranium content and radon exhalationrate.

Intrinsic and scattering attenuation in the crust of the Abu Dabbab area in the eastern desert of Egypt

Fifty-five microearthquakes recorded by a digital-temporary seismic network in the Abu Dabbab area in the Eastern Desert of Egypt were used to estimate the direct S-wave ( Q β), coda ( Q c), intrinsic ( Q i), and scattering quality factors ( Q s). Sato's [Sato H., 1977] single-scattering assumption was used to fit the amplitude envelopes of the coda at seven central frequency bands (1.5, 3, 6, 9, 12, 18, and 24 Hz), obtaining a Q c varying with frequency as generally observed in tectonically active areas. Lapse time dependence was also studied for the area, with the coda waves analyzed at window lengths ranging from 10 to 40 s starting from the onset of the S-wave arrival. The direct S-wave Q β was estimated using the coda normalization method [Aki, K., 1980a]. The frequency dependence of Q was investigated for the direct S-waves and coda waves. Results show a low quality factor and a high frequency parameter, indicating that the upper lithosphere of the Abu Dabbab area is seismically active and heterogeneous. Using the independent estimates of Q c and Q β, the intrinsic quality factor Q i was separated from the scattering quality factor. The results suggest that intrinsic dissipation plays a predominant role with respect to scattering phenomena in the area; the obtained Q values seem closer to those reported by analyzing volcano-tectonic earthquakes. This finding reflects that the cause of Abu Dabbab earthquake swarms might be igneous activity where the magma is ascending through joints or serpentinized joints that are dewatering.