Sulaiman Alaabed

Veins, Dikes, and Pods of the UAE Mantle Peridotites: Possible Industrial Raw Materials

The northern extension of the Semail ophiolite in the UAE is dominated by tectonic mantle peridotites and gabbros. The peridotites are mostly harzburgite with little lherzolites and contain various intermittent veins, dikes, and pods. These veins, dikes, and pods can be divided into three rock categories: the ultramafic group that includes dunites, chromitites, and pyroxenites; the granitic dikes; and carbonate veins. Occurrences of these bodies are explicit and ubiquitous, but their distribution is not consistent throughout the sequence. Pyroxenites, chromitites, and granites occur in the upper half of the sequence, but more pronouncedly and dominantly close to the transition zone. Dunites pods and carbonate veins can be found at different stratigraphic levels. Magmatic signatures and monomineralic forms of the three ultramafic varieties are observed. Where it occurs, chromite-rich variety is always enveloped in olivine-rich pods. Coarse-grained mica-rich granites and pegmatites are well developed below and within the transition zone. Carbonates, and occasionally serpentine materials, impregnate through fractures and structures.

Erratum to: Mineralogical and geochemical aspects of the petrogenesis of Pan African Dokhan Volcanics at Esh El Mellaha Area—NE Desert, Egypt

The volcanic activities in the Eastern Desert of Egypt define two major magmatic episodes separated in time. The Dokhan Volcanics is the main representative of the later episode which commenced about 600 Ma and continued for about 25 Ma. These volcanics have been found to vary lithologically from mafic to felsic rocks. Mineralogical and geochemical signatures were used to examine a suite of Dokhan lithology from the Esh El Mellaha area of Egypt Eastern Desert with the aim of clarifying their petrogenesis and tectonic significance. The primary phases (e.g. pyroxene, amphibole, and plagioclase) of the Dokhan volcanics illustrate a progression from basalt to andesite to dacite. Enstatite component (En) of pyroxenes and anorthite (An) component of plagioclase decrease in modes from basalts to andesites to dacites. Whole rock geochemistry records similar trends. There is a wide range of SiO2 (43.62–63.91 wt.%), CaO (2.34–10.56 wt.%), Sr (110–908 ppm), and Zr (120–296 ppm) contents, and a moderate enrichment in incompatible elements. The fractionation index (FeOtotal/MgO) increases gradually from basalts through andesites to dacites (2.72, 2.89, and 4.03, respectively). These chemical variations support a model of fractional crystallization playing an essential role during the evolution of the Dokhan volcanic magma series. The enrichment of LILE (e.g. Rb, Ba, K, and Sr) and the relative depletion of HFSE (e.g. Nb, Zr, Y, and Ti) appear to be inherited from a mantle source. Compiling field relationships with mineralogical and geochemical data confirm three magmatic assemblages: tholeiitic basalts, calc-alkaline andesites, and dacites. The data is interpreted to indicate an island arc tectonic setting that may have been transitional to an active continental margin in a subduction-related environment.

Geoenvironmental Studies of Contamination of Bottom Sediments of Oman Gulf, United Arab Emirates

Heavy metals and grain size were determined in 23 bottom samples from Gulf of Oman, UAE. Analyses of grain size revealed that most of the samples in the studied areas lie between muddy sand to gravelly sand texture. The most standard deviations in the areas reflect moderately, well sorted grain size. The high percentages sediments of the four areas lie in saltation population rather than traction and suspension population this support the results that the sediments are mixed from different environments such as fluvial, beach and shallow marine. Studying the characteristic feature for all chromatographic pattern of four samples reflect typical to weathered crude oil. The concentrations of copper, zinc, lead, iron, manganese and vanadium vary between (9.00, 17.15 , 11.62, 19812.8, 281.1 and 19.40 µg/g) respectively which are being within the permission levels. This mean that no elements derived from pollutant sources. Nickel and cadmium concentration (497.4 and 5.57 µg/g) respectively of the studied samples are shown to be high level. The contaminations level were found due to petrogenic origin and their sources are either weathered or highly weathered crude oils and or used lubricating oil. Their detection gives an indication of recent and continuous petroleum inputs.