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Abstract The study area occurs at the South Eastern Desert to the south of Marsa Alam City along the Red Sea Coast and covers an area about 739.5 km2. The area is delineated by the latitudes 24º 20’-24º 30’ N and longitudes 34º 50’ – 35º 10’ E. It forms a part of the exposed Pan-African basement of the South Eastern Desert of Egypt. The area is relatively low to moderate hilly area. There are five main wadies run into the area; Wadi Abu Ghusun, Wadi Rumayt, Wadi Shawab, Wadi Umm Sayal and Wadi Abu Ghalqa. Field observations and relations in addition to using the landsat thematic mapper indicate that the area of Wadi Shawab is intensively sheared, depressed and principally affected by hydrothermal actions. The area is mainly covered (from older to younger) by rock varieties; metavolcanics, epidiorites, amphibolites, grey granites, gneissose granites, red granites and post orogenic dykes. Metavolcanics outcrop along Wadi As-Surubi and are surrounded by the grey granites whereas small partition is exposed along the eastern part of Wadi Abu Ghalqa. Metavolcanics are low hilly hard, highly sheared, massive, dense and fine grained rocks with blackish grey to grey colors. Epidiorites are located mainly along Wadi Abu Ghalqa; these epidiorites are the host rocks of ilmenite ore deposits (Abu Ghalqa ilmenite mine). Epidiorites are generally massive, medium to coarse grained with dark grey color and speckled with white patches. Epidiorites are metamorphosed, sheared and are invaded by felsites. Field relations clear that the epidiorites have intrusive contact with the surrounding grey granites. Amphibolites occur either as lens-shape masses associated with epidiorites or as dykes-like bodies protruding epidiorites. They are hard, dense and fine grained rocks with dark colors. Grey granites occur as an extended belts that trending NW-SE and occupy the north eastern and a part of the south eastern parts of the study area, whereas they are separated by Wadi Abu Ghusun which drained SW- NE. CHAPTER 7 SUMMARY and CONCLUSION 142 The grey granites form moderate relief with medium grained size and grey color while their altered surfaces show yellowish brown colors. These rocks are blocky and have no gneissose or foliation textures compared with the gneissose granite. Grey granites show ambiguous gradational contacts with the gneissose granites, whereas grey granites enclose enclaves of epidiorites ranging in diameter nearly about 5 cm to 20 cm. Gneissose granites form the main rock unit in the Wadi Shawab area that occupies the major part of the mapped area. They form mountainous chains with elevations increasing from east to west. Gneissose granites are represented by some mountains features such as Gabal Hashanit, Gabal Ushush and Gabal Shawab. They are deformed, foliated, exfoliated, highly sheared and weathered as they exhibit spheroidal and cavernous weathering. Occasionally the gneissose granites are intensively affected by hydrothermal solutions especially in the highly sheared places and along joint planes. They may show ambiguous gradational contact with the grey granites whereas they exhibit sharp contact with each of the epidiorite and red granite. Red granites occur as isolated pluton in the north east of the studied area at the end of Wadi Umm Sayal. It forms high ridged mountain with pink to slightly red colors. It has sharp intrusive contact with the gneissose and grey granites. Petrographiclaly metavolcanics are represented by meta-andesites. Metaandesites exhibit blasto- porphyritic texture. They mainly consist of porphyroblasts of saussuritized plagioclases, altered hornblende and some quartz in a fine grained groundmass of hornblende, laths of plagioclases and quartz grains. These rocks show considerable amount of amygdals which are filled with secondary quartz, epidote and chlorite. Petrographically epidiorites exhibit hypidiomorphic granular texture. They essentially consist of plagioclases, hornblende, ±quartz, ± tremoliteactinolite. Opaque minerals, zircon, fluorite, titanite and apatite are the common accessories. Secondary biotite, chlorite, epidote and saussurite are the alteration products. Amphibolites are essentially composed of hornblende and plagioclases. Opaque minerals, zircon and apatite are the common accessories. Biotite and epidote are the alteration products. Petrographically grey granites are classified into quartz diorite to tonalite and exhibit hypidiomorphic granular texture. Compared with the white gneissose granites, these rocks are highly deformed and barren of gneissosity. Grey granites mainly consist of highly turbid feldspars due to kaolinitization and saussuritization, quartz, hornblende, minor k-feldspar ± biotite. Opaque minerals, apatite, fluorite, zircon, allanite and titanite are the common accessories whereas saussurite, chlorite, carbonates and epidote are the alteration products. Gneissose granites are characterized by foliation textures and mainly composed of plagioclases, quartz, k-feldspar, and biotite. Opaques, titanite, zircon, apatite, fluorite and garnet are the main accessories. Muscovite, clinozosite, chlorite, sericite and carbonates are the alteration products. Red granites petrographically are graded from monzogranites to granodiorites. Red granites are generally medium grained rocks which are essentially composed of quartz, perthitized k- feldspar, plagioclases, muscovite and few biotites. Apatite, zircon, garnet and opaque minerals are accessories. Sericite and kaolinite are the alteration products. These rocks exhibit hypidiomorphic granular texture. Geochemically epidiorites and amphibolites are of igneous source with trends similar to that of early stage differentiates of basic igneous rocks. The epidiorites and amphibolites plot in the oceanic field with tholeiitic affinity. According to the differentiation trends, TiO2, Fe2O3total, MgO decrease with SiO2 increase from epidiorites to amphibolites, whereas Al2O3, CaO, Na2O, K2O and P2O5 show increase from epidiorites to amphibolites correlation with silica content. The values of Rb, Sr, Nb, Zn, Ni, Hf and Co decrease with the increase in the silica content, whereas the values of Ga, V, Cr and Sc increase with the increase of silica content. Harker variation diagrams of epidiorites and amphibolites together with their magma type insure their origin from one igneous source by differentiation processes. The epidiorites and amphibolites are characterized enrichment in large ion lithophile (LIL) elements (Sr, K, Rb and Ba) relative to high field strength (HFS) elements (Nb, Y, Hf, Ce and Ti). Geochemical data declare a distinct variation between the three granitic rock types which can be observed from major oxides as SiO2, Fe2O3, MgO, CaO and K2O. In general the grey granites seem to be the least differentiated than the gneissose granites, whereas the red granites are the most differentiated type. TiO2, Fe2O3total, MgO, CaO, MnO and P2O5 decrease with differentiation from grey granites to gneissose granites. Al2O3, Na2O and K2O slightly increase with SiO2 increase from the grey granites to the gneissose granites. The high values and scatter relation of Na2O of the gneissose granites may be due to Na- metasomatism. The red granites contain lower content of TiO2, Fe2O3total, MgO, CaO, MnO, P2O5 and Al2O3 than the older granitoids and higher K2O declaring its more differentiated magma. The negative correlation of CaO, MgO and Fe2O3total and positive correlation of K2O with SiO2 content favors an evolution of Wadi Shawab older granitoids (grey and gneissose granites) through fractional crystallization. The depletion of CaO and Sr with increasing SiO2 content and positive correlation of Sr and Cao are consistent for plagioclase fractionation. The older granitoids are enriched in LILEs (Rb, Ba and Th) and HFSEs (Nb, Hf, Zr, Y and Yb). The red granites are enriched in LILEs (Rb, Ba and Th) and HFSEs (Nb, Hf, Zr, Y and Yb). Red granites are more enriched in K relative to the primitive mantle normalizing values as the behavior noticed for older granites, but the red granites are more enriched in LILEs than the older granitoids. Grey granites and gneissose granites are calc- alkaline rocks, whereas the red granites are calk- alkaline to alkaline. The so-called older granitoids of Wadi Shawab area are metaluminous, whereas red granites are metaluminous to peraluminous. The studied older granitoids are I- type granitoids and the red granites are highly differentiated I- type granites. Grey and the gneissose granites are syn- collision to late orogenic, while the red granites tend to be post orogenic. Grey granites suggest the silification trend and gneissose granites follow Na-metasomatism trend according to K% vs. Na% variation diagram showing the alteration type for the altered granitoids. Fluid inclusions are studied in quartz of most investigated samples; only five representative samples are selected for detailed study; two samples of gneissose granite, one sample of red granite, and two samples represent mineralized quartz and pegmatite veins. Fluid inclusions in quartz of gneissose granite are high saline (brines) H2O fluid inclusions. The fluid inclusions occur as primary isolated idiomorphic form and secondary trails. Quartz contains two types of fluid inclusions. The first type is bi-phases fluid inclusions that consist of H2O liquid (L), and H2O vapor (V) or solid NaCl salt cubes. The second type is tri-phase fluid inclusions H2O liquid (L), H2O vapor (V) and solid NaCl salt cubes as daughter minerals. Quartz in red granite contains fluid inclusions that occur as isolated, idiomorphic, primary bi-phase and tri-phase fluid inclusions they occur as irregular, sub rounded and elongated form. The bi- phases fluid inclusions consist of H2O liquid (L), and H2O vapor (V). The tri-phases fluid inclusions composed of H2O (L), CO2 (L) and CO2 gas, (G). Also it contains few secondary trails of H2O and CO2 fluid inclusions that are intersected. Fluid inclusions in red granite are less saline than those in gneissose granite. Quartz in quartz veins contains primary and pseudo- secondary fluid inclusions. There are two types of primary fluid inclusions: a) saline fluid inclusion that contains about 2 to 4 salt cubes in the fluid and does not contain any opaques. b) Low saline fluid inclusions that contain about 1 to 2 salt cubes. Primary fluid inclusions are tri-phases that contain H2O (L), and H2O (V) and NaCl salt cubes. Fluid inclusions in pegmatite occur as idiomorphic negative crystal shape primary bi-phases CO2 (L) and CO2 (G), H2O (L.), H2O (V.) and salt cubes. Few mono-phase fluid inclusions are found in this sample. A general model for the fluid rock interaction is given, from this model it can be concluded that the measured P-T conditions of the intrusion of the red granite into the gneissose g - meteoric origin. The opaque minerals and copper ore minerals occur in the different rock units especially the gneissose granites and the quartz veins which dissected through them. Ore minerals are represented by Cu-Fe-sulphides, Cusulphides, Cu-carbonates and iron oxides minerals. The Cu-Fe- sulphides and iron oxides in gneissose granites are disseminated, fine to medium grains occasionally oriented parallel to the gneissosity, whereas the Cucarbonate minerals occurred mostly in quartz veins. They are medium to coarse grained which arranged along fractures and shearing. Ore minerals in the gneissose granites are represented by Cu-Fe-sulphides (by primary bornite, tetrahedrite and pyrite), Cu- sulphides (secondary chalcocite), whereas Cu- carbonates are mainly represented by malachite. Iron oxides are represented by magmatic magnetite, secondary hematite and few goethites. The only ore minerals in the epidiorites and amphibolites are the iron oxides minerals represented by magnetite and secondary hematite. Ore minerals in the quartz veins are considered chronologically secondary ores in relation to other ores in the different rock units. They are classified as Cu-Fe sulphides (bornite, atacamite), Cu-sulphides (covellite, chalcopyrite) and Cu-carbonates (malachite) |