Environmental impact assessment inside and around Mahd Adh Dhahab gold mine, Saudi Arabia

Environmental impact of the mining activities in the Mahd Adh Dahab gold mine was examined through detailed chemical analyses of a number of samples represent the gold-bearing rocks, soils, dust, and plants from inside and outside the mine area and within the Mahd City as well as the surrounding areas. The obtained data were compared with the standard values of heavy metals concentrations in order to evaluate the pollution levels of these activities on the different systems around the mine area. The data of rock samples shows relatively high concentrations of Cu (up to 11.9%), Pb (up to 4.1%), and Zn (up to 14.2%), which attributed to the outcropping of the sulfide-bearing veins on the surface of the mine area. Soil samples inside the mine area show high concentrations of Zn, Cu, Cd, Pb, and As compared to those from outside the mine indicating pollution impact of the mine activities on soils from inside the mine with these elements. Dust samples collected from inside the mine have considerably high concentrations of Cd, Zn, and Pb compared to those from outside the mine. Values of heavy metals in the collected dust from outside the mine are comparable with those from many big cities including Riyadh City, Saudi Arabia, indicating contaminations with heavy metals to the dust from inside the mine at Mahd Adh Dahab City. Heavy metals concentrations in the stems and leaves samples of the various types of plants inside and outside Mahd Adh Dahab gold mine area show that they have relatively higher concentrations of Cu and Zn compared to other metals. Stem samples show relatively higher concentrations of Zn, Cu, Cr, and V compared to the leaves samples. Although values of most heavy metals in the plants, both stems and leaves, are comparable with those of the typical levels of heavy metals in plants, Co and Cr show relatively higher concentrations suggesting a pollution impact of the mine activities in plants with Co and Cr. As a conclusion, results indicated that the contamination effect of Mahd Adh Dahab gold mine activities are clear in soils and dusts inside the mine area with some metals such Zn, Cu, Cd, and Pb due to their relatively enrichment in mineralization. Therefore, careful treatments of the waste dump materials inside the mine area are recommended to protect soils and air contaminations and to prevent the extension of pollution outside the mine in the future.     

Engineering-geological and geotechnical investigation for risk assessment

Before construction activities could begin, engineering geological and geotechnical investigations had to be approved in order to establish a map with suitable areas for safe construction. The example used in this study is Tunis City which has complex geology and geomorphology. The risk analysis was based on a large-scale land-suitability map that was prepared using Geographic Information Systems (GIS). The approach used in this study combined physical data with the geotechnical properties of Tunis City. The adopted methodology and analyses were performed to assess the risk of urban expansion and landscape management. Results are presented as a zoning map that shows the suitable area for safe extension of the urban area. The data used and multi-criterion analysis of geotechnical and geological data seems to be useful for similar case studies and the adopted methodology can be used successfully for identifying similar cities for risk assessment.     

Paleoclimate record in the Nubian Sandstone Aquifer,Sinai Peninsula,Egypt

Sixteen groundwater samples collected from production wells tapping Lower Cretaceous Nubian Sandstone and fractured basement aquifers in Sinai were analyzed for their stable isotopic compositions, dissolved noble gas concentrations (recharge temperatures), tritium activities, and ¹⁴C abundances. Results define two groups of samples: Group I has older ages, lower recharge temperatures, and depleted isotopic compositions (adjusted ¹⁴C model age: 24,000–31,000 yr BP; δ¹⁸O: − 9.59‰ to − 6.53‰; δ²H: − 72.9‰ to − 42.9‰; < 1 TU; and recharge T: 17.5–22.0°C) compared to Group II (adjusted ¹⁴C model age: 700–4700 yr BP; δ¹⁸O: − 5.89‰ to − 4.84‰; δ²H: − 34.5‰ to − 24.1‰; < 1 to 2.78 TU; and recharge T: 20.6–26.2°C). Group II samples have isotopic compositions similar to those of average modern rainfall, with larger d-excess values than Group I waters, and locally measurable tritium activity (up to 2.8 TU). These observations are consistent with (1) the Nubian Aquifer being largely recharged prior to and/or during the Last Glacial Maximum (represented by Group I), possibly through the intensification of paleowesterlies; and (2) continued sporadic recharge during the relatively dry and warmer interglacial period (represented by Group II) under conditions similar to those of the present.     

United Arab Emirates limestones: impact of petrography on thermal behavior

The thermal behavior of selected limestones from representative localities of the United Arab Emirates is investigated for their suitability for soft-burnt lime production. The limestone samples were collected from the Ghalilah, Musandam, Shauiba, Muthaymimah, Dammam and Asmari formations. The samples were characterized for petrography, mineral and chemical composition, together with physico-mechanical characteristics. Investigative methods included transmitted light microscopy (TLM), cathodoluminescence (CLM) and scanning electron microscopy (SEM), as well as X-ray micro-tomography (μ-CT), XRD, XRF and Archimedes method. The limestone samples were fired in an electrical muffle furnace for 0.25, 0.5, 1 and 2 hours at 800, 900, 1,000 and 1,100 °C. After firing the lime grains were tested to determine their hydration rate and microfabric. The Ghalilah and Musandam limes show the lowest and highest maximum hydration rates, respectively, due mainly to the impure nature of the former, and the smaller lime crystallites and dominance of post-calcination micro-cracks of the latter. The Dammam and Asmari limes preserve a “ghost” microfabric of the original limestone. Higher allochem contents impose lower activation energy requirements for calcination, which implies earlier calcination of the allochems. The Musandam, Shauiba and Muthaymimah limestones may be useful for the production of reactive soft-burnt lime under the applied firing conditions, however, the Dammam and Asmari limestones need more advanced calcination conditions than the applied ones. The Ghalilah limestone was found to be unsuitable for the production of lime.     

Trace and REE element geochemistry of fluorite and its relation to uranium mineralizations,Gabal Gattar Area,Northern Eastern Desert,Egypt

Uranium mineralizations occur and form in a broad range of geologic setting and age, including magmatic to surfacial conditions, and there are numerous controls on their transportation and deposition, such as redox, pH, ligand concentration, complexation, and temperature. These temporal and spatial variations have caused a range of ore deposit mineral assemblages. Consequently, understanding their conditions of formation is still in its infancy. This research reports rare earth elements (REE) and trace elements of fluorite associated with hexavalent uranium mineralizations and tests of genetic models for the deposits. These data contribute to a better understanding of the variables controlling fluorite formation and uranium ore composition through understanding the evolution of these ore-forming hydrothermal systems. Fluorite in Gabal Gattar granite occurs as disseminations and/or thin veinlets and encrustations filling some uranium mineralized fissures and fractures along the northern margin of host granite mass. In the U-poor samples, fluorite forms well-developed large crystals that are commonly zoned. The zones are represented by alternating colorless and violet zones, and the outer zones are frequently dark violet. In the U-rich samples, fluorite is usually anhedral, unzoned, and has a dark violet color. The results of analysis of REE and trace element contents of fluorites using laser ablation inductively coupled plasma mass spectrometry indicate that total REE in the anhedral unzoned fluorite are elevated compared to the well developed zoned fluorite, and also total REE in dark violet zones of zoned fluorite are elevated with respect to the colorless zones. The fluorites and host granite are generally characterized by strongly negative Eu anomalies and slightly negative or chondritic Ce anomalies. Accordingly, REE patterns of the fluorite and host granite are roughly alike, indicating that the source of REE and trace elements of hydrothermal fluids is the host granite leached by fluids. Y/Y*, Ce/Ce,* and Eu/Eu* patterns show that fluorite clearly records the compositional evolution of the hydrothermal solutions that have transferred trace and REE from host granite during the fluid–wall rocks interactions. The high uranium contents of fluorite in Gabal Gattar granite suggest that parent fluids bearing fluorine have interacted with host granite to leach uranium from the accessory minerals of granite and tetravalent uranium minerals in reduced or weakly oxidized zones.     

Determination of potential runoff coefficient for Al-Baha Region,Saudi Arabia using GIS

The curve number (CN) is a hydrologic parameter used to describe the stormwater runoff potential for drainage areas, and it is a function of land use, soil type, and soil moisture. This study was conducted to estimate the potential runoff coefficient (PRC) using geographic information system (GIS) based on the area’s hydrologic soil group, land use, and slope and to determine the runoff volume. The soil map for the study area was developed using GPS data carried on to identify the soil texture to be used in building a soil hydrological groups map. Unsupervised and supervised classifications were done to Landsat 5/7 TM/ETM image to generate land-use and land-cover map. This map was reclassified into four main classes (forest, grass and shrub, cropland, and bare soil). Slope map for Al-Baha was generated from a 30-m digital elevation model. The GIS technique was used to combine the previous three maps into one map to generate PRC map. Annual runoff depth is derived based on the annual rainfall surplus and runoff coefficient per pixel using raster calculator tool in ArcGIS. An indication that in the absence of reliable ground measurements of rainfall product, it can satisfactorily be applied to estimate the spatial rainfall distribution based on values of R and R ² (0.9998) obtained. Annual runoff generation from the study area ranged from 0 to 82 % of the total rainfall. Rainfall distribution in the study area shows the wise use of identifying suitable sites for rainwater harvesting, where most of the constructed dams are located in the higher rainfall areas.     

Exploration of new gold occurrences in the alteration zones at the Barramiya District,Central Eastern Desert of Egypt using ASTER data and geological studies

The use of ASTER data and fieldwork supported by mineralogical and geochemical analyses enabled exploration of new gold occurrences in the alteration zones in the ultramafic–mafic successions at the Barramiya district. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) band ratios (4/8, 4/2 and 8/9 in R, G and B channels, respectively) helped in recognising of two listwaenite alteration zones (areas 1 and 2) promising for gold in the north-east and south-east of the Barramiya gold mine. Mineralogical studies and X-ray diffraction analysis revealed that areas 1 and 2 are characterized by variable concentrations of talc, ankerite, magnesite, quartz and calcite. Ore microscope studies revealed the sulphide minerals carry gold within these alteration zones; moreover, goethite and malachite are also observed. Fire assay results show Au contents in the range of 5.04 ppm in the graphite schist, 4.02 ppm in the quartz veins and 3.76 ppm in the listwaenite alteration. The atomic absorption analysis (AAS) of samples from area 1 yields an average Au content in the quartz-veins of 2.4 ppm, Ag content is 8.0 ppm and Cu content is 2.4 wt%. The listwaenite alteration gives an average Au content of 4.4 ppm and a Cu content of 2.8 wt%. In area 2, the AAS of the quartz-veins revealed an average Au content of 2.6 ppm, 6.2 ppm Ag and 1.9 wt% Cu. The listwaenite alterations of area 2 grade 3.5 ppm Au and 2.4 wt% of Cu. The Barramiya District is made up of ophiolitic ultramafic belts of serpentinites, talc carbonates and talc graphite schists, mainly thrust over the metavolcanic sequences. They include highly strained and tectonised parts enriched in sulphides, iron oxides and carbonates, with developed listwaenite alterations along the thrust contacts. Gabbro and granitic intrusions were intruded in the ultramafics and metavolcanic rocks. ASTER data are an accurate and helpful tool for detecting and mapping alteration zones for gold exploration.     

Structural and geomorphic features accommodating groundwater of Al-Madinah City, Saudi Arabia

Al-Madinah City is located in the western part of Saudi Arabia on the Arabian Shield. The area underwent several tectonic events that developed its structural and geomorphic features, such as the Infracambrian Najd strike-slip faults, development of the Cenozoic basaltic flows of Northern Harrat Rahat, and Cenozoic N–S and E–W transtensional faults, related to the Red Sea rifting. These successive events formed a deltaic-shaped basin of Al-Madinah. The Al-Madinah basin is part of a 400?×?150-km² Wadi Qanah–Al-Hamd watershed, which exhibits mainly parallel drainage pattern. Sub-basins, within the main basin, exhibit trellised and radial drainage patterns. The trellised drainage pattern reflects control of the Cenozoic faults, whereas the radial drainage pattern reflects volcanic-related system. Rotation of the Arabian Plate after several extensional events that lead to the opening of the Red Sea influenced the drainage flow to be going from east to west. This geological history that include eruption, normal faulting, and erosion prior to and during the Red Sea rifting formed relief inversion geomorphology of Tertiary basalts that cap Precambrian rocks of the Ayr and Jammah Mountains in western Al-Madinah. The groundwater in the central area is part of the northern Harrat Rahat basaltic aquifer in which the groundwater level rises up in the central area due to the blocking of groundwater flow by constructions below the central area and due to reduced groundwater abstraction. Building a dam 60 km northwest of Al-Madinah would preserve more surface water than the Al-Bayda dam, in which all main valleys join in at the suggested location.     

The prolate Bok globules evidence for the existence of dark matter sub-halo

Although the existence of dark matter is generally accepted by the mainstream scientific community, there is no generally agreed direct detection of it. Also, observations show that some Bok globules are prolate in some regions without suitable explanation for its cause. In this paper, we investigate the effect of dark matter sub-halo in transformation of the Bok globules from spherical to the prolate shape. We limit the investigation to a particular case that the magnetic field and turbulent effects are negligible through the Bok globule. We consider the gravitational effect of dark matter sub-halo on the isothermal Bok globule that is exposed to suitable distance of it. The results show that the dark matter sub-halo can justify the transformation of Bok globules in some regions. In this paper, we introduce a new method for proving the existence of dark matter sub halo.     

A short period trial detection of the flare star AD Leo

A Fourier analysis programme was applied on observational data taken in Stephanion Observatory, Greece, for flare star AD Leo. The purpose of this task is to try to register a short period variation in Johnson'sB-band in the star's brightness at quiet-state to confirm a result obtained by Pettersen (1980) inV-band of the flare star EV Lac. A negative result has been obtained.