Liberation-limited grade/recovery curves from X-ray micro CT analysis of feed material for the evaluation of separation efficiency

Procedures for 3D mineral liberation analysis by X-ray micro CT (XMT) are presented and discussed including the construction of liberation-limited grade/recovery curves for specific feed materials. In this way, actual separation efficiencies can be compared to what might be expected for a perfect separation limited only by the extent of liberation. It is shown that 3D mineral liberation analysis based on XMT is preferred to 2D section analysis which overestimates the extent of liberation. By way of example, procedures and experimental results are presented and discussed for feed material in the case of phosphate rock flotation.     

U–Pb TIMS age constraints on the evolution of the Neoproterozoic Meatiq Gneiss Dome,Eastern Desert,Egypt

Ages are used to constrain the temporal evolution of the Meatiq Gneiss Dome, Eastern Desert, Egypt, by dating (ID-TIMS) pre-, syn-, and post-tectonic igneous rocks in and around the dome. The Um Ba’anib Orthogneiss, comprising the deepest exposed structural levels of the dome, has a crystallization age of 630.8 ± 2 Ma. The overlying mylonites are interpreted to be a thrust sheet/complex (Abu Fannani Thrust Sheet) of highly mylonitized metasediments (?), migmatitic amphibolites, and orthogneisses with large and small tectonic lenses of less-deformed intrusives. Two syn-tectonic diorite lenses in this complex have crystallization ages of 609.0 ± 1.0 and 605.8 ± 0.9 Ma, respectively. The syn-tectonic Abu Ziran diorite, cutting across the tectonic contact between mylonite gneisses of the Abu Fannani Thrust Sheet and a structurally overlying thrust sheet of eugeoclinal rocks (“Pan-African nappe”), has a magmatic emplacement age of 606.4 ± 1.0 Ma. Zircons from a gabbro (Fawakhir ophiolite) within the eugeoclinal thrust sheet yielded a crystallization age of 736.5 ± 1.2 Ma. The post-tectonic Fawakhir monzodiorite intrudes the ophiolitic rocks and has an emplacement age of 597.8 ± 2.9 Ma. Two other post-tectonic granites, the Arieki granite that intrudes the foliated Um Ba’anib Orthogneiss, and the Um Had granite that cuts the deformed Hammamat sediments, have emplacement ages of 590 ± 3.1 and 596.3 ± 1.7 Ma, respectively. We consider formation of the Meatiq Gneiss Dome to be a young structural feature (<631 Ma), and our preferred tectonic interpretation is that it formed as a result of NE–SW shortening contemporaneous with folding of the nearby Hammamat sediments around 605–600 Ma, during oblique collision of East and West Gondwana.     

Efficiency of horizontal-to-vertical spectral ratio (HVSR) in defining the fundamental frequency in Muscat Region,Sultanate of Oman: a comparative study

Muscat region is the most important political, economic, and densely populated region in the Sultanate of Oman. The proximity of Muscat region to the Oman Mountains and Makran subduction zones controls the earthquake hazard for Muscat. Evidences indicate the occurrence of a nearby historical earthquake with moderate magnitude M _S?=?5.5 in 1883. This event led to the damage of some villages near Nizwa City. The main objective of the current study is to compare the site characteristics of the region of interest in terms of the fundamental frequency using microtremors measurements with the numerical analysis results using one-dimensional (1-D) shear wave profiles. The microtremor measurements were performed at 99 sites distributed over the study region in order to calculate the horizontal-to-vertical spectral ratio (HVSR). The numerical modeling of horizontal shear (SH) waves in soil at the selected 99 sites are assessed by carrying out 1-D ground response analysis using the program SHAKE91. The required shear wave velocity profiles for the numerical modeling of SH-waves were derived using multichannel analysis of surface waves profiles. The amplification spectra have been evaluated for the soil column at each site location and the fundamental frequency obtained using SHAKE91 and HVSR are compared. Results were found to be compatible with the general surface geology of the region of interest and in most cases the HVSR is proved to be suitable for calculating the fundamental frequency in Muscat region.     

Effect of municipal wastewaters on bottom sediment geochemistry and benthic foraminifera of two Red Sea coastal inlets, Jeddah, Saudi Arabia

Al-Arbaeen and Al-Shabab inlets are two Red Sea coastal inlets lying on the mid-coast of Jeddah City, Saudi Arabia. Forty-four surface sediment samples were collected from these inlets and surrounding areas during June 2010. Water depths and the overlying environmental parameters (temperature, salinity, pH and dissolved oxygen) of these samples were measured. Sediment samples were analyzed for variables, such as loss on ignition (LOI, organic matter), CaCO₃, heavy metals (Fe, Mn, Cu, Zn, Cd, Ni, Cr and Pb) and benthic foraminifera to assess any changes in the environment of the inlets and surrounding areas. Variables distribution patterns indicated that mud sediments dominated the inlets and enriched by LOI, heavy metals and Ammonia tepida–Quinqueloculina seminula assemblage, whereas coarse (sand–gravel) sediments dominated the substrates of surrounding areas and enriched by CaCO₃ and Coscinospira hemprichii–Peneroplis planatus–Varidentella neostriatula assemblage with low values of LOI and heavy metals. Highest concentrations of Cu, Zn, Cd, Ni, Cr and Pb were recorded inside the inlets, especially near the discharge points, and they were positively correlated with the LOI and mud fraction indicating their affinity to anthropogenic materials. However, highest concentrations of Fe and Mn were typically recorded in the whole study area. These metals were positively correlated with the LOI values of the surrounding area, but in the inlets they were negatively correlated with the LOI, indicating an existence of reducing conditions caused by limited dissolved oxygen conditions at bottom waters of the inlets. Changing the environment within the inlets, according to higher concentrations of heavy metals and LOI, is probably responsible for the existence of the low density and diversity of benthic foraminifera and the absence of (reefal) symbiont-bearing species.     

Impact of Carpet Waste Fibre Addition on Swelling Properties of Compacted Clays

Municipalities and recycling and environmental authorities are concerned about the growing amount of carpet waste produced by household, commercial and industrial sectors. It is reported that 500,000 tonnes of carpet waste fibre are plunged into landfills annually in the UK. In the United States of America, around 10 million tonnes of textile waste was generated in 2003. In geotechnical engineering, expansive clay soils are categorised as problematic soils due to their swelling behaviour upon increase in the moisture content. The problematic nature of such soils is intensified with the increase in the plasticity index. This paper presents results of a comprehensive investigation into utilisation of carpet waste fibres in order to improve the swelling characteristics of compacted cohesive soils. Therefore, two different clay soils with markedly different plasticity indices (i.e. 17.0 and 31.5 %) were treated with two different types of carpet waste fibre. Waste fibres were added to prepare specimens with fibre content of 1, 3 and 5 % by dry weight of soil. Soil specimens with different dry unit weights and moisture contents were prepared so as to the swelling behaviour of fibre reinforced compacted clays is completely attained under various scenarios. The results indicated that the behaviour of the fibre reinforced soils seems highly dependent on the initial compaction state and secondary on the moisture content. It was found that the swelling pressure drops rapidly as the percentage of fibre increases in samples prepared at the maximum dry unit weight and optimum moisture content. Reducing the dry unit weight, while maintaining constant moisture content or increasing the moisture content at constant dry unit weight was found to reduce the swelling pressure.     

Silicifications de nappe dans les formations carbonatées tertiaires du piedmont atlasique (Hamada du Guir,Maroc)

Résumé

Les formations tertiaires du système de piedmonts atlasiques du Sud marocain montrent de nombreuses silicifications qui affectent les différents faciès de la série : les grès calcaires, les conglomérats, les calcaires lacustres, aussi bien que les faciès plus argileux. Les accidents siliceux sont de tailles et de faciès variés, allant d’échardes millimétriques à des masses pluri-décimétriques. Dans les faciès argileux (torba), ce sont des plaquettes et des tubules de silice translucide. Dans les calcaires, ce sont surtout des faciès silexoïdes, à morphologies variées et à contours irréguliers. Dans les grès calcaires, ce sont des silicifications scoriacées, quelquefois disposées suivant un réseau de conduits anastomosés,

La pétrographie révèle que les dépôts de silice dans les vides forment une part importante des silicifications. Les silicifications translucides des faciès argileux sont entièrement formées de concrétions de calcédoine. Dans les grès calcaires, les silicifications résultent de la cimentation des grains de quartz détritiques par des dépôts de silice fibreuse et d’opale, après dissolution du ciment calcaire primaire. Dans les calcaires, certaines silicifications correspondent à la cimentation de micro-brèches karstiques par des quartz géodiques; même les plages qui apparaissent très homogènes, formées de quartz microcristallin, révèlent une porosité primaire importante. Il y a alternance de phases de dépôt de silice et de dissolution de la matrice calcaire. A côté de ces dépôts dans les vides existent aussi des épigénies, c’est à dire le remplacement de la matrice calcaire avec préservation des structures, sans formation de vides. Néanmoins, ces épigénies sont limitées à la bordure de vides à dépôts de silice.

Les silicifications sont dues à des processus diagénétiques tardifs. L’essentiel de la silice est constitué par des dépôts dans des vides ce qui permet de faire des hypothèses sur la nature des solutions nourricières. La régularité des dépôts tout autour des vides indique un milieu saturé, au sein d’une nappe. En raison de la solubilité relativement faible de la silice dans les eaux superficielles, des débits importants sont nécessaires pour renouveler constamment la silice précipitée des solutions. Ceci conduit à envisager des climats relativement humides à l’époque de la silicification, ainsi que l’existence de reliefs et de paysages incisés pour générer les écoulements de nappe suffisants.     

Validate global mapping of internal lunar magnetic field

In this work, we report a global mapping of vector lunar magnetic field based on new method of separation of internal and external fields. The magnetic measurements collected during the lifetime of lunar prospector (LP) extended mission during 1999 were strongly disturbed by the solar wind, a period which coincided with a maximum of the 23 cycle activity. The multiscale wavelength external fields were analyzed using spherical harmonic transform. The external field determined by inversion was then removed from each magnetic field component for each half orbit. To map the vector magnetic crustal anomalies, all LP magnetometer data collected at low altitudes in the three different lunar environments: (1) geomagnetic tail, (2) solar wind, and (3) geomagnetic sheath were processed using this new approach. The results obtained using these selection criteria allow us to get a global coverage of the lunar surface by the vector magnetic field at variable spacecraft low altitudes. To validate our mapping, we have developed and applied a method based on properties of potential fields functions. This method can be used to determine both horizontal north and east components using only vertical component. The validated lunar internal magnetic measurements obtained at variable spacecraft altitudes were then continued to a common altitude of 30 km using an inverse method. This mapping confirms firstly the nature of the crustal sources of lunar magnetic field and clearly shows that the strongest concentrations of anomalies are associated with high albedo and/or located antipodal to large young basins (Orientale, Serenitatis, Imbrium, and Crisium) of age about 3.9 Ga.     

Cretaceous paleomargin tilted blocks geometry in northern Tunisia: stratigraphic consideration and fault kinematic analysis

New stratigraphic data, lithostratigraphic correlations, and fault kinematic analysis are used to discuss the basin geometry and sedimentation patterns of the northeastern Tunisia during Cretaceous times. Significant facies and thickness variations are deduced along the northeastern Atlas of Tunisia. The NW-SE 80-km-long regional correlation suggests a high sedimentation rate associated with irregular sea floor. The fault kinematic analysis highlights N-S to NE-SW tectonic extension during Early Cretaceous. During Aptian–Albian times, an extensional regime is recognized with NE-SW tectonic extension. The Cenomanian–Turonian fault populations highlight a WNW-ESE to NW-SE extension, and Campanian–Maastrichtian faults illustrate an NW-SE extension. The normal faulting is associated to repetitive local depocenters with a high rate of sedimentation as well as abundant syntectonic conglomeratic horizons, slump folds, and halokinetic structures. The sequence correlation shows repetitive local depocenters characterizing the basin during Early Cretaceous times. All the above arguments are in favor of basin configuration with tilted blocks geometry. This geometry is shaped by major synsedimentary intra-basin listric normal faults, themselves related to the extensional setting of the southern Tethyan paleomargin, which persisted into the Campanian–Maastrichtian times. The results support a predominant relationship between tilted blocks geometry and sedimentation rather than E-W “Tunisian trough” as it was previously accepted.     

Geomorphic and lithologic characteristics of Wadi Feiran basin,southern Sinai,Egypt, using remote sensing and field investigations

Wadi Feiran is an important drainage basin in southern Sinai Peninsula covering an area of about 1785 \(\hbox {km}^{2}\), its streams drain into the Gulf of Suez crossing variety of rocks and sedimentary units varied in age from Precambrian to Quaternary. Field investigations, geographic information systems (GIS) and remote sensing studies including Landsat-7 ETM+, Radarsat-1, and SRTM DEM were integrated to reveal its lithologic, geologic and geomorphic features. Besides the field investigations, rock units including basement and pre- and syn-rift sedimentary units were discriminated using band ratios and principal component analysis techniques (PCA). Such techniques revealed that the crystalline rocks covering W. Feiran are unaltered rocks lacking OH-bearing minerals. Radar data successfully displayed the structures and geomorphic features related to topography. Moreover, the techniques allowed the extraction of the dyke-like structures along faults and shear zones. This also characterized the topographic variations through analysis of the shaded terrain and the altitudinal profiles. The results of data integration, lineament analysis and lineament density maps revealed that the structural grain in the present study has four different trends: N20–45E, N30–45W, N–S and E–W. Based on analysis of radar data and geomorphic indices, W. Feiran is an asymmetrical basin, its left side occupies \(\sim \)34% of the total area that leads to a supposedly massive tilt towards the south which caused the southwestward slope.     

Groundwater contamination assessment in Al-Quwy’yia area of central Saudi Arabia using transient electromagnetic and 2D electrical resistivity tomography

Groundwater contamination is one of the most significant problems in arid countries. Al-Quwiy’yia region is an example of an area where the groundwater is contaminated as a result of infiltration of waste water in low-lying areas adjacent to inhabited zones. Such contamination poses significant environmental threats for the surrounding environment and groundwater. Surface observations and spatial distribution of contamination observed in the shallow aquifer indicate that the main contamination sources were from sewage as well as from waste water dumping. However, the main source of water supply for the whole area is groundwater abstracted from the relatively shallow aquifer. Therefore, the transient electromagnetic method (TEM) and 2D electrical resistivity tomography (2D ERT) have been applied close to the waste water dump site to characterize the response of pollution plumes. Both of these geoelectrical techniques are sensitive to electrical conductivity as well as to other physical properties, which are greatly influenced by the polluted groundwater. Therefore, it is possible to profile the contamination plumes, both vertically and horizontally, in the vicinity of the measured stations. The ERT profiles gave detailed information about the lateral distribution of the contaminated groundwater, whereas the TEM demonstrated the vertical extensions.