Spectrometric Prospecting, Geochemical Distribution and Mineralogical Investigation for Wadi Abu Rusheid Stream Sediments, South Eastern Desert, Egypt (original) (raw)

International Journal of Mining Science

Wadi (W.) Abu Rusheid area is located at the southern part of the Eastern Desert of Egypt, along and about 95 km of Marsa Alam city. The area could be reached from the Red Sea coast through W. El Gemal and then W. Nugrus along a desert track of about 45 km long. The area is characterized by low topographic features, where as the highest topographic features are about 509m above sea level, whereas the average wadi level is about 315 m above sea level. The area is dissected by Khour Abaleia, several gullies, NNW-SSE and ENE-WSW shear zones. The stream sediments are composite products of erosion and weathering and thus represent the source catchment area of the stream drainage network (Darnley, 1990 and Cocker, 1999). Stream sediments may be the natural sink of large amounts of chemical elements that derived from the drainage basin, where sediments possess a great capacity to accumulate and integrate those elements and their accumulate is dependent on the properties of the adsorbed chemical and the prevailing physicochemical conditions (El Nemr et al., 2007). The composition of clastic sedimentary rocks is controlled by several factors, which include source rock, weathering, erosion, deposition, transport, burial and diagenesis (Johnsson, 1993). The background levels of the rare metals; Sn, Nb, Y, Be and Li are higher than their corresponding world average abundance (Levinson, 1980) in normal soil. The high standard deviation values of Zr, Nb, Pb, Ga and Y reflect that these metals have wide concentration ranges. The abnormal Abstract: The loose stream sediments covering wadies of Abu Rusheid area are derived from the weathering of the different surrounding rocks. Thes are ophiolitic melange, consisting of ultramafic rocks and layered metagabbros set in a metasediment matrix; cataclastic rocks, including protomylonites, mylonites, ultramylonites, silicified ultramylonites; granitic rocks; and post-granite dykes (lamprophyre), pegmatite and quartz veins. The thickness of the stream sediments was determined by different geophysical techniques, which revealed that the depth to the surface of the basement rocks has an average value of about 21 m. Geochemical maps were constructed to delineate anomalous areas with abnormally high rare metal contents. The latter nearly the same as in the mineralized cataclastic rocks and lamprophyre dykes. The weak correlations between almost of these elements indicate that the element constituents are governed by many geochemical factors and are from different sources. According to the radiometric maps of the different radioactive elements, the high concentrations are close to the mineralized cataclastic rocks along the studied part of Wadi Abu Rusheid, especially in the upstream part. The investigated heavy minerals in the studied parts of the stream sediments can be classified according to their anion groups into the following: silicate minerals group (kasolite, uranothorite, zircon, garnet and titanite), phosphate minerals group (monazite and apatite), oxide minerals group (columbite, cassiterite, rutile, leucoxene, magnetite, hematite and ilmenite), carbonate mineral group (cerussite), sulfides minerals group (galena and pyrite). The preliminary assessment of some economic elements in stream sediments revealed that the ore metals in ton are: Zr (4936.93), Nb (978.98), Rb (1561.56), Zn (1297.3), Pb (1039.04), Y (1033.03) and Ga (240.24). Finally, this assessment need deeper investigations and requires more samples along grid patterns and at different depths.