http://ir.bdu.edu.et/handle/123456789/14100 2001-01-13T05:52:43Z 2001-01-13T05:52:43Z Zemenu Molla http://ir.bdu.edu.et/handle/123456789/15178 2023-03-13T06:34:02Z 2022-02-01T00:00:00Z

“Geology, Petrography and Geochemistry of Volcanic Rocks Of Koma-Andabet Areas, North Western Ethiopian Large Igneous Province Zemenu Molla This study is aimed to investigate the petrological, geological and geochemical characteristics of magmatic rocks in the study area. To achieve this objective, detailed field work, geological, lithostratigraphical, cross sectional mapping, petrographical and geochemical analyses of 15 and 10 samples respectively was done. The geology of the study area has been classified into five lithological units: Aphanitic and porphyritic basaltic rocks, Gabbroic rock units, felsic pyroclastic rocks and unwelded ignimbrites. The low Ti basalts of the study area display sub ophitic texture and together with the presence of glomerophyric aggregates of pyroxene and plagioclase minerals denote a tholeiitic tendency. The correlation of MgO and CaO is positive and is an indicative of co-fractionation of olivine and clinopyroxene. The chondrite normalized values of the REE pattern shows enrichment in LREE, (La/Yb)N of 9.4 to 18 than MREE ( La/Sm N =1.38-1.86) and HREE (Dy/Yb =1.39-1.72) and there is fractionation of these HREE and MREE. The Nb/U ratio of the study area largly ranged from 13.91 to 37.1, which is an indicator for the contamination nature of the outpouring magma from the source crustal materials. The Koma-Andabet magmatic suits have similar trace element patterns and trace element ratios as Zr/Nb (12.95-14.37), Zr/Ce (4.53-5.23) and Hf/La (0.26-0.33) indicating originated from the same magmatic source. The low CaO/Al2O3 ratio (0.50-0.80) and the relatively flat pattern of HREE ((Dy/Yb) =1.39-1.72) and the HREE value is above 10 times greater than the chondrite values is a clue for the source of the Koma-Andabet magmatic rocks to be spinel containing mantle rather than garnet sourced. N N

2022-02-01T00:00:00Z Atinkut Kelemu http://ir.bdu.edu.et/handle/123456789/15175 2023-03-10T06:55:23Z 2022-03-01T00:00:00Z

Deformation and Metamorphic History of Basement Rocks from Blue Nile Gorge, Around Kuch Area, Western Ethiopian Shield Atinkut Kelemu Deformation and metamorphic studies were carried out on the Blue Nile basement rocks near the Kuch area, western Ethiopian shield. The study aimed to investigate and reconstruct the deformation and metamorphic history of the area. Field investigations, petrographic analysis, structural analysis, and microstructural interpretations were used to characterize the different phases of deformations and to identify the nature of the metamorphism of the rocks in the area. The area is part of the western Ethiopian shield containing metamorphic rocks ranging from highgrade gneisses to migmatites, medium-grade schist to low-grade phyllites, and granitoid rocks. The analysis showed that the Blue-Nile basement rocks experienced at least four phases of deformation and two paths of metamorphism. The first phase of deformation (D1) was compressional stress that resulted from NW-directed shortening of the original formation forming strong S1foliation and associated F1 folds. The second phase of deformation (D2) is also compressional stress-directed NNW (clockwise shift of D1) that further shortens the D1 structures but not coaxial to D1, which resulted in further tightening of the F1 folds and shaping in different geometries. The third phase of deformation (D3) was a shear force that resulted in different types of strike-slip faults, shear zones, and having characteristic brittle-ductile nature. Different kinematic indicators suggest D3 deformation was a combined effect of both sinistral and dextral sense of shear. D3 is also manifested by the development of penetrative NE to NNE striking shear zone. The fourth phase of deformation (D4) was brittle deformation which might be due to the stabilizing of the area after the extrusion of post tectonic magmatic intrusions, erosion, and uplift. D4 resulted in large normal faults and smaller localized faults and fractures which were later filled by hydrothermal veins. Metamorphic mineral assemblages on metamorphic rocks of the area are characteristic green schist to upper amphibolite facies. The mineral assemblages of clinopyroxene, plagioclase, hornblende, and garnet are inferred to be formed at the highest grade metamorphic conditions (upper amphibolite facies) which is regarded as peak metamorphic path (M1) in association with D1/D2 event. The retrogressive metamorphic path (M2) was mainly responsible for the formation of chlorite, muscovite/sericite, and epidote minerals which are characteristic green schist facies and interpreted to be associated with the D3.

2022-03-01T00:00:00Z Ali Eissa http://ir.bdu.edu.et/handle/123456789/15143 2023-02-28T08:00:36Z 2022-08-01T00:00:00Z

Hydrogeochemical Studies and Water Quality Analysis of Lower Bilate River Catchment, Southern Rift Valley of Ethiopia Ali Eissa The study area is found in the main rift valley of Ethiopia in which surface and groundwater are the main source for domestic and agricultur al purposes. The main objective of the study is to investigate the hydrochemistry and water quality of the area using graphical, multivariate and water quality analysis techniques. The spatial distribution of major cation and anions ions reveals in order of Na + > Ca 2+ and HCO 3 - > Cl - > SO 4 2- > F - > NO 3 - respectively. Na-HCO is the main hydrogeochemical facies resulting from deep rock-water interactions and long residence time. The principal component analysis shows that the first 3 factors explain 82.02% of the total variance of the hydrochemistry that shows hydrolysis of silicate minerals and to some extent, anthropogenic effects are the main factors that control groundwater chemistry. Water quality index values show the majority of the samples comprised very poor water (34.2%), distributed in the south-eastern parts of the study area, followed by excellent water (15.77%) in the western and good water (21.05%) in north western, north eastern and southern parts of the study area. The poor water types covers 21.05% and the remaing 8.10% is unfit water. The study result shows that the major drinking water quality problems in the area is fluorides concentration in which the values exceed the WHO standards with the average value of 8.3 mg/l . This water quality problem is high towards the discharge area with a parallel enrichment of F. In terms of irrigation water quality, the Sodium Absorption Ratio shows that the surface waters (Rivers) samples (SAR=2.57) were highly suitable for irrigation compare to groundwater with SAR value 22.4 . The sodium hazard versus salinity hazard of the entire surface water sample fall into category C 1 3 -S and shows very low electrical conductivity and sodium hazard index which is suitable for irrigation purpose The study result will be helpful for water managers and government offices to protect the local people from water quality problems,bone fluorosis and tooth decay on bones which is common in the area. Furthermore, This study, helps local farmers and agricultural activities in the extended rift valley farmlands

2022-08-01T00:00:00Z Mulutsega Mesfin http://ir.bdu.edu.et/handle/123456789/15142 2023-02-28T07:40:21Z 2022-08-01T00:00:00Z

Hydrogeological Characterization of Basement Rock in Assosa Area, Benishangul-Gumuz Regional State, Western Ethiopia Mulutsega Mesfin This thesis presents the hydrogeological characterization of basement Aquifers in the Assosa area, Benishangul-Gumuz Regional State, Western Ethiopia. The study area covers 863 Sqkm of Hoha and Selga rivers and is mostly covered by crystalline basement rocks (hard rocks) which are regionally known to be called aquicludes. Recent well drilling in the area shows that the well yield varies significantly (from abandoned to high discharge well). Currently, the water demand in the area is highly rising. However, limited groundwater investigation in the area causes well abandonment. To avoid the problem, combined geological, geophysical (electrical resistivity and magnetic methods), and pumping test methods, were carried out to investigate the hydrogeological system of the area. The study aims to characterize the expected aquifer zone / water-bearing units and map surface and buried geologic structures and weak zones. Twenty-one (21) VES data points and seven (7) 2D ERI survey data points with Schlumberger and Wenner configuration were conducted along Hoha and Selga river structures identified by satellite gravity and 364 magnetic data. The magnetic data and gravity data were processed using Oasis montaji 6.4.2 whereas IPI2win and Surfer were used for preparing pseudo-depth,geoelectric sections, and 2D ERI. According to this research work, the hydrogeological set up of the area is highly heterogeneous and mainly controlled by geological structures, weathering, and fracturing intensity.The aquifer is both intergranular and weathered / fractured volcanic and basement aquifer with secondary porosity. The study area has a localized shallow and deep confined and unconfined aquifer nature. Accordingly, the aquifer area is highly heterogeneous and mainly controlled by geological structures, weathering, and fracturing intensity for hard rock aquifers, however, granular porosity is dominant in the shallow alluvial aquifers. The transmissivity varies from 3.94 to 76.6m2/d, hydraulic conductivity ranges from 0.17 to 2.24 m/d. Secondary porosity and permeability that develop from secondary processes mainly control the aquifer productivity of the area.

2022-08-01T00:00:00Z