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Abstract Nuweibi area is located in the Central Eastern Desert, 30 km north of Marsa Alam and about 33 km west of the Red Sea coast. It lies between latitudes 25○ 10\ 30\\ and 25○ 15\ 15\\ N and longitudes 34○ 29\ 00\\ and 34○ 38\ 29\\ E, covering an area of about 135 km2. It is mainly covered by metasediments, serpentinites, metagabbros, grey granites, albite granites, post and pre-albite granite dykes. The Nuweibi albite granite is one of 14 Known Sn-Ta-Nb bearing granitoids ( Hawashis, Umm Naggat, Umm Samra, Nuweibi, Ineiga, Humer Waggat, Igla, Zabara, Muweilha, Nugrus, El Gharabiya, Nikeiba and Humr Akarem) in the Eastern Desert of Egypt. Nuweibi area is drained by two main wadis, the first one is Wadi El-Nabi located at the north while the second is Wadi El-Nuweibi at the south. The Nuweibi albite granite was divided by N-S fault into two unequal parts, Eastern (with dimension of about 950m*400m with elevation of about 300m) and Western parts (with dimension of about 1.37km*1.33km with elevation of about 450m). The present study concerned with the Eastern part and the stream sediments of both wadis. The area has been studied geologically, minerlogically, chemically, geophysically and stream sediment analysis. Structurally, from Structural Lineament Statistical Analysis there are three sets of faults controlling the regional framework of the study area. They are E-W, NNW-SSE and NNE-SSW respectively. They are controlling the distribution of albite granite, mafic and intermediate dykes. The area of study characterized by different rock unites represented by serpentinites, metasediments (schist), metagabbros, grey granite, prealbite granite dykes, albite granite and post-albite granite dykes. The grain size analysis of both wadis shows that, the sediments of Wadi El-Nabi are a mixture of gravelly sand and sandy gravel while Wadi El-Nuweibi sediments is gravelly sand. The statistical sedimentological parameters shows that, the sediments of Wadi El- Nabi are very coarse and coarse sand size, very poorly sorted, coarse skewed and platykurtic, while the sediments of Wadi El-Nuweibi are very coarse and coarse sand size, poorly sorted, coarse skewed and mesokurtic. Consequently, the sediments of Wadi El-Nabi and Wadi El-Nuweibi displays river characters that deposits in fluviatile environment. Mineralogically, The distribution of total heavy fraction in Wadi El-Nabi shows that, the fine sand size display relatively high content of the total heavy minerals. The total heavy minerals in Wadi El-Nabi also does not show regular trend along the stream, on contrast the distribution of total heavy minerals in Wadi El-Nuweibi are slightly enriched in upstream than downstream. The obtained data reflected that, the spot surface samples attain total heavy minerals greater than that in trench samples. The concentration of magnetite in Wadi El-Nuweibi and its spot surface samples are greater than that in Wadi El-Nabi and its spot surface samples. the average magnetite content in Wadi El-Nabi is nearly a half of its content in Wadi El-Nuweibi in the three fraction sizes. The heavy minerals were identified and described by microscopic examination. The heavy minerals recorded in the area are: The opaque minerals represented by magnetite, ilmenite, hematite, goethite, chromite, leucoxene, tantalite-columbite, molybdinite, pyrolusite and the non opaque minerals represented by zircon, rutile, epidote, garnet, cassiterite, monazite, fluorite and sphene beside other minerals such as pyrite, barite, atacamite, apatite, autunite, allanite, REE bearing biotite and Less stable minerals such as pyroxenes and amphibole minerals group. Geochemically, the studied metagabbros are mainly calc-alkaline to slightly tholeiitic, originated in island-arc tectonic environment. The albite granite is mostly calc-alkaline, Itype and originated in within plate to post orogenic tectonic setting. the studied stream sediment samples plot in the greywacke field, in sodic field with high concentration of (Fe2O3 + MgO). According to the two discrimination functions diagram, the source of the studied stream sediments are mafic igneous provenance and intermediate igneous provenance. Geophysically, The Nuweibi granite is discriminated by their high radioactivity and the superimposed contour lines have two specific trends (NNE-SSW and NNWSSE). They controlling by E-W regional structural trend. The field radiometric survey revealed that; the potassium show the same concentration in both wadis either inside or outside the borehole. Uranium slightly highly concentrated in Wadi El-Nabi than that in Wadi El-Nuweibi, on the other hand thorium show remarked concentration in Wadi ElNuweibi than that in Wadi El-Nabi either inside or outside the borehole. The laboratory analysis do not show any remarkable variation between Wadi El-Nabi and Wadi El- Nuweibi either inside or outside the borehole. |