http://ir.bdu.edu.et/handle/123456789/14102 Tue, 13 Oct 2026 04:02:08 GMT 2026-10-13T04:02:08Z http://ir.bdu.edu.et/handle/123456789/17357 Petrography, and Stratigraphy of Volcanic Rock of Gishe Rabel Area, North Shewa, Central Ethiopia Lema, Awel The study area is a part of the NW Ethiopian Plateau, is presented in this thesis. The study area is located in the North Shewa district, specifically around Gishe Rabel, in central Ethiopia. The main objective of the study is to provide a complete lithostratigraphy of the research area based on a thorough field investigation (mapping and description), stratigraphic sampling, and petrographic (thin section) description of representative samples. Various techniques were used to achieve the research objectives, including field observation, remote sensing, and petrographic description. Furthermore, the study attempts to integrate these data to relate them to regional studies on geochemical, geochronological, and magma emplacement behavior data about the volcanic provinces of Ethiopia and fill the scarce in a detail volcanic history of the study area. Three volcanic lithostratigraphic units, Lower Basalt, Rhyolitic Lava Flow, and Upper Basalt, are identified in this study as part of the Cenozoic continental flood basalt sequence. The basaltic lava flows (fissural flows) are the dominant products, with interlayered ash and tuff; the felsic products dominate the middle part. These stratigraphic units are separated by a considerable time gap marked by an alteration/erosional surface, paleosol, or sediments, which are related to a decrease in magma flux in the system. The petrographic characteristics of basaltic units in the study area display a range of textures, including aphyric, mildly phyric, and porphyritic varieties. In the lower basaltic rocks, the principal phenocrysts are pyroxene and olivine, accompanied by opaque. In contrast, the rhyolitic ignimbrite samples are dominated by alkali feldspar (sanidine), quartz, and lithic fragments set within a glassy groundmass. The predominance of alkali feldspar phenocrysts in the felsic units suggests a relatively low magma flux during their formation. The upper basaltic rock is dominated by plagioclase phenocrysts. The occurrence of plagioclase in the upper basaltic rocks indicates that crystal fractionation took place within the shallow upper crust. Meanwhile, the presence of olivine and clinopyroxene (Olv + Cpx) mineral assemblages in some basaltic lavas suggests that fractionation also occurred at deeper crustal levels or near the crust–mantle boundary. Mon, 01 Jun 2026 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/17357 2026-06-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/17205 Geology, Petrography and Geochemistry of Granitoid rocks in the Koli-Gomer area of Wemberma Woreda, Western Ethiopia Tesfa, Gizeaddis Petrographic and geochemical data are provided for the Koli-Gomer area granitoids, which is a part of the Blue Nile Gorge in western Ethiopia. The petrography and geochemistry of the KoliGomer area granitoid rocks have not been studied. The present research work aims to analyze and interpret the geological, petrographic, and geochemical characteristics of granitoid rocks by using the whole rock geochemical analysis method integrated with petrographic and field observation. Field observation shows that the studied area is dominated by plutonic rocks with some metamorphic rocks, and the area is affected by different geological structures like veins, joints, faults, dykes, and foliation. Petrographically, the studied granitoids are mainly composed of alkali-feldspar minerals, quartz, plagioclase, biotite, hornblende, pyroxene, opaque minerals, and other accessory minerals. From geochemical data, the negative correlation of SiO versus other major oxides like Al 2 O 3 , MgO, CaO, FeOt, TiO 2 , P 2 O and trace elements like V, Ti, Sc, and Cr shows decreasing trends that indicate the characteristics of mineral fractionation trends in the early crystalizing phase that controls the evolution of magma. Their tectonic setting is volcanic arc granitoid, which resembles a subduction zone arc environment. The negative Eu anomaly and depletion in Sr, P, and Ti anomalies imply the fractionation of plagioclase, apatite, and titanite crystals, respectively. The variation in compatible and incompatible trace elements integrated with different binary plots suggests that most of the studied area's granitic rocks are Itype and some S-type granites, which were formed through partial melting of crustal involvement and/or by fractional crystallization from source magma that originated in the mantle. Further findings show that the granitoids in the study area consist of gabbroic to granitic units, some ferroan to magnesian, sub-alkalic magma series, and metaluminous to peraluminous magma sources. The Koli-Gomer granitoids are the one features of the East African orogeny. 5, 2 Mon, 01 Jul 2024 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/17205 2024-07-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/17204 Petrographic and Geochemical Characteristics of Medium to Highgrade Metamorphic and Associated Intrusive Rocks in the Konso Zone (Kholme Cluster Tebelana & Quchele Kebele) Mulatu, Hana This study investigated the petrographic and geochemical characteristics of metamorphic and intrusive rocks in the Kholme Cluster, Konso Zone, Southwestern Ethiopia. Fieldwork, petrographic analysis, and geochemical evaluations were employed to achieve this objective. The dominant geological units in the study area are high- to medium-grade metamorphic rocks, including granitic gneiss, amphibole gneiss, and biotite gneiss. Additionally, intrusive granite rocks are present. Petrographic analysis revealed compositional banding within the gneiss units. Hornblende, plagioclase, biotite, and quartz were identified as the primary mineral assemblage, with minor amounts of opaque minerals. Field observations and structural measurements indicated various geological structures, such as foliation, folds, joints, dikes, boudinage, veins, and veinlets. These structures are attributed to multi-phase deformation events and play a significant role in the metamorphic processes. Geochemical analysis revealed that most granitic gneiss units fall within the calc-alkaline series on the AFM ternary diagram, except for amphibole gneiss, which plots within the tholeiitic series. All studied rocks, except one sample, displayed geochemical signatures indicative of igneous origins. And exhibited geochemical characteristics suggestive of a sedimentary source. The enrichment of large-ion lithophile elements (LILE) relative to high-field-strength elements (HFSE) in both gneisses and granitoids points towards subduction zone enrichment and crustal contamination of the source region. Harker diagrams for the granite units did not reveal a clear geochemical trend, although they suggested the influence of crystal fractionation processes. The scattered trends are likely due to the pervasive metamorphic alteration within the area. Geochemically, the granites are characterized as high-potassium, calc-alkaline, and peraluminous, indicating magma activity derived from mixed sources. The rare earth element (REE) patterns displayed a slight enrichment in heavy rare earth elements (HREEs), reflecting the acidic nature of the rocks. The negative europium anomaly observed in the granites suggests plagioclase fractionation. Discrimination diagrams utilizing Rb-(Y+Nb), Ta-Yb, Rb-(Y+Nb), and Nb-Y ratios suggest that the granites formed in a volcanic arc or syn-collisional granite (syn-COLG) tectonic setting. However, one sample was plotted within the within-plate granite (WPG) field. Mon, 01 Jul 2024 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/17204 2024-07-01T00:00:00Z http://ir.bdu.edu.et/handle/123456789/15178 “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 Tue, 01 Feb 2022 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/15178 2022-02-01T00:00:00Z