Browsing by Author "Getaneh, Worash (PhD)"

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    Assessing the Quality, Mining and Processing Techniques of Bombawuha Kaolin Deposit, Southern Ethiopia
    (Addis Ababa University, 2018-06-02) W/Maryam, Tilahun; Getaneh, Worash (PhD); Desta, Zerihun (PhD)
    Bombawuha kaolin deposit is a residual type deposit formed by weathering and hydrothermal alteration of granite and pegmatite units. The present study was designed to assess the quality, mining and processing techniques of Bombawuha kaolin deposit by physical observations of the site and different analytical methods. For this purpose, samples of the source rock, kaolin deposit, run of mine, and processed kaolin were collected for analyses. Chemical, and mineralogical (thin section) analyses were applied to examine the source rock of the deposit. For kaolin deposit, and processed kaolin chemical, mineralogical (XRD), and physical properties were investigated. A chemical analysis was also carried out to investigate the composition of run of mine. The result of the study revealed that the source rock of the deposit is composed of higher SiO2 (72.1%), coloring impurities (1.88% Fe2O3, and 0.13% TiO2), fluxes (5.765 alkalies, and 0.38% alkali earth oxides), and lower Al2O3 (16.3%) and loss on ignition (3.85%) values compared to its altered product. It is composed of quartz, k-feldspar, plagioclase, biotite, muscovite, and opaque minerals. The kaolin deposit has light gray to white color, higher grits (79.9-96.7%>63μm), pH (6.27-6.37), lower plasticity (<10%), linear shrinkage (0-3), and specific gravity (2.53-2.60) values. The deposit is constituted by higher SiO2 (51.5-70.5%), and lower Al2O3 (18.1-33.4%) comparing to ideal pure kaolin 46.6 and 39.5% respectively. It also has higher Fe2O3 (1.09-1.92%), and lower TiO2 (0.03-0.17%). The XRD result revealed that kaolinite and quartz are the major minerals of the deposit with minor k-feldspars and illite. Specifically, kaolinized granite and kaolinized pegmatite have different physical and chemical characteristics. The kaolinized granite has higher grits, lower plasticity, and linear shrinkage values. It also has higher SiO2 (68%), Fe2O3 (1.65%) and TiO2 (0.13%), and lower Al2O3 (20.19%) and LOI (7.84%) values compared to the kaolinized pegmatite. Mineralogically, it is composed of kaolinite, halloysite, quartz, and k-feldspar. Kaolinized pegmatite contains quartz, mica (illite), and kaolinite minerals. Although these two units have different characteristics, they are mined together by simple open pit mining method. A run of mine having higher SiO2 (71.2%), Fe2O3 (1.88%), and lower Al2O3 (17.95%) is produced for processing. The wet processing method enhanced the quality of kaolin product by producing higher Al2O3 (35.5%), lower SiO2 (45.8%), and Fe2O3 (0.99%). It reduced SiO2 and Fe2O3, and increased Al2O3 by 36%, 47% and 98% respectively from its crude state. The processed kaolin contains major kaolinite, and minor orthoclase and muscovite minerals. Based on findings of this study, it is concluded that Bombawuha kaolin product can be used in ceramics (bricks, pottery, floor and wall tiles), plastics, paint and rubber filer productions after processing.
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    Characteristics and Genesis of Enkafela Manganese Deposit, Dallol Area, Northern Afar Depression
    (Addis Ababa University, 2018-05-30) Assen, Abate; Getaneh, Worash (PhD)
    The Enkafela manganese deposit is situated in the Afar Depression, northern Ethiopia, about 20km west of Dallol at the border with the western escarpment. The geology of the Enkafela area is characterized by marine formations of reef limestone, oolitic limestone, gypsum, conglomerates and basalt. The ore body is stratabound and lies between the reef limestone and basalt. The ore stratum is characterized by two distinctive manganese layers. The bottom is massive while the top layer is powdery/friable. The main purpose of this study is to understand the geochemical characteristics and genesis (origin) of the manganese mineralization. Geological, mineralogical and geochemical data are integrated to characterize the genesis of the manganese deposit. Based on XRD mineralogical analysis, Pyrolusite, Chalcophanite and Biernessite minerals are identified as the main ore minerals in the deposit. The geochemical analysis result indicate enriched MnO (av. 70.25wt %), Ba (>10,000ppm), Sr (>10,000 ppm) and depleted Fe2O3 (av. 0.37wt %) and transition metals. The total REE content of the massive manganese is 172.9ppm while the powdery manganese contains total REE of 7.84ppm. The massive manganese show higher REE content than the powdery manganese. Chondrite normalized REE plot show LREE enrichment for both manganese layers. The massive manganese layer shows enrichment in Ce and no anomaly in Eu. However, the powdery manganese shows depletion in Ce and Eu. The geochemical and mineralogical studies indicate that Enkafela manganese mineralization does not originate from a pure hydrothermal source or pure hydrogenic source. The massive manganese shows mixed sources, whereas the powdery manganese shows a hydrothermal source. The Ni-Co-Zn discriminating ternary diagram indicates the powdery manganese (top layer) has a hydrothermal origin and the massive manganese (bottom layer) has mixed origin (both hydrothermal and hydrogenic). Alternatively, the Fe-(Ni + Cu + Co)*10-Mn and Fe-Si*2-Mn discriminating diagrams indicate hydrothermal activity played the major role in the formation of both the powdery and massive manganese layers. Generally, the geochemical studies show the dominance of hydrothermal activity in the formation of the Enkafela manganese deposit, though seawater contribution is undeniable in the massive manganese deposit. The two manganese layers are similar genetically and formed successively from the same source.
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    Characterization and Genesis of Kulfamba Manganese - Iron Occurrence, North Wollo, Ethiopia
    (Addis Ababa University, 2020-06-03) Zemelak, Adise; Getaneh, Worash (PhD)
    The Kulfamba Manganese-Iron occurrence is located in the top parts of Wollo plateau, northern Ethiopia, about 83 km west of Woldia. The main purpose of the research is to characterize and determine the origin of the ore body. To accomplish this secondary data collection, field observation, rock and ore analysis, and data presentation and interpretation methods have been applied. The geology of the study area is mainly characterized by presence of volcanic rocks and terrestrial sedimentary rock such as sandstone and mudrock. The ore body occurs within the volcano-sedimentary sub-basin associated with most probably late Oligocene intertrappean beds. In order to define the genesis of the ore body, field observation, petrographic and geochemical examinations were undertaken. The field observation informs that the ore body is found in the form of stratabound - stratiform, vein, concretion and coating. From these, the layered ore is prominent over the other morphology. Based on petrographic observation, manganese oxide (mainly pyrolusite), hematite and goethite have been identified as ore minerals. Similarly, colloform growth banding, well developed crystals, vein fillings structures and secondary replacement are the ore mineral textures. Geochemically, the mean Fe/Mn ratio of the upper and lower parts of the ore body shows strong fractionation of Fe and Mn, which are 0.045 and 20.52 respectively. The concentration of Ba is also high in the Mn-rich part, which is >10000 ppm. Contrary, the average concentrations of heavy metal such as Co, Ni and Cu have been very low in the ore body. The mean ΣREE concentrations of Mn and Fe ore body are extremely high, which is 1839.8 and 3056.2 ppm respectively. Likewise, the ΣLREE/ΣHREE ratios of the ore body exhibit high concentrations of LREE over HREE. The primitive-mantle-normalized diagram of both whole rock and ore body samples reveals the presence of slight negative Eu anomalies, and both positive and negative Ce anomalies. Therefore, the different investigation suggests that Kulfamba Mn-Fe occurrence is formed by mixing of hydrothermal and sedimentary processes. In addition, the occurrence of Mn - Fe ore in the form of concretion and coating reveals a contribution of secondary weathering process later on.
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    Characterization of the Genesis of Belessa Kaolin Occurrences, Hosaina Area, Central Main Ethiopian Rift
    (Addis Ababa Universty, 2017-06) Bedassa, Gemechu; Getaneh, Worash (PhD)
    Belessa kaolin occurrence is situated in the Western margin of Central Main Ethiopian Rift (CMER) near Hosaina town which is about 230 km from Addis Ababa. Geology of the kaolin district is composed of Miocene to Quaternary age acidic igneous rocks consisting of pyroclastic tuff, ignimbrite and rhyolite. Based on petrographic study, the main minerals identified in these volcanic rocks include quartz, k-feldspar and plagioclase. The kaolin occurrence is located in the central part of the study area and it is associated with rhyolite. The host rock has been partly and completely transformed to kaolinite. The main aim of the present study is to characterize the genesis of this kaolin occurrence. An integrated study combining geological, mineralogical and geochemical data were carried out in order to characterize the genesis of alteration (supergene or hypogene). Data obtained from morphological study and available physical property tests were also examined to see the possible industrial applications. Moreover, Landsat 8 OLI and ASTER images were enhanced using two techniques (band ratio and band composites) to discriminate lithological units, host rock and vegetation. Spectral signature curves of Belessa kaolin are also compared with other kaolinite spectral curves to produce preliminary model of spectral curves for kaolin occurrences associated with volcanic rocks in the MER. Results from geological, mineralogical and geochemical studies indicate that supergene alteration has played a great role to the formation of Belessa kaolin. The absence of quartz veining and alteration zones with high temperature minerals implies the lack of significant hypogene alteration process. The Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) result also showed that the host rock has experienced a strong alteration and weathering process that resulted in the formation of kaolinite. Furthermore, the higher Ce + Y + La values correspond to the supergene type alteration. The low P and high Cr + Nb concentrations also support supergene origin. From digital image processing, ASTER RGB band combinations of (7, 2, 1), (7, 3, 1) and band ratios of 9/4 showed better contrast on geologic units, vegetation and kaolinite host rock respectively. Moreover, the comparison of kaolinite spectral reflectance curves shows that the spectral curve of Belessa kaolinite can be used as a preliminary model to the kaolin occurrences in the MER. Studies from technological properties like physical tests, chemistry, mineralogy and crystal morphology indicate that Belessa kaolin could have potential applications in paper coating, filler (in paper, rubber, plastic and paint), ceramics, pharmaceuticals and cosmetics. Key words: Applications, Belessa, genesis, kaolin, supergene, technological property.
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    Determination of Genesis of Orogenic Gold and Sulfide Prospects at Ashashire Western Ethiopia
    (Addis Ababa University, 2020-09-29) Yenesew, Sewagegn; Getaneh, Worash (PhD); Alene, Mulugeta (PhD)
    Orogenic gold also known as (“shear zone hosted”, “Mesothermal”, “greenstone-hosted quartz-carbonate vein” deposit). The Ashashire area is also orogenic gold prospect area and source of placer deposit that used as an income source for artisanal gold miners. The study area is part of Proterozoic terrains that related to the East African Orogeny (EAO), a N–S elongated mega collisional structure stretching from Israel to Madagascar and found between West and East Gondwana. It is located in western Ethiopia in Benishangul Gumuz region at Kurmuk Woreda within the Western Greenstone belt of Precambrian volcano-sedimentary belt, near the Sudan border locally called Ashashire. Gold is an important commodity of the world. Due to this exploration work in gold including its genesis made worldwide by many scholars and well developed in developed countries. But not well developed in developing countries including Ethiopia. Some reports and exploration works show that Ethiopia is endowed by precious metals including gold in different parts of the country. As a result, the main objective of this research work is to characterize the genesis of the gold and the associated sulfides. To accomplish this objective geological field observation and data analysis including 15 doubly polished and 3 thin section petrographic samples and 20 geochemical samples both for ore and host rock characterization has been conducted. The geochemistry held by fire assay and ICP-MS. The petrographic investigation involves characterization of host rock and ore body. The host rock is mainly composed of greenschist to amphibolite facies metamorphic minerals such as chlorite, carbonate, sericite, amphibole, epidote, and quartz; the ore petrography investigation shows pyrite, pyrrhotite, magnetite, sphalerite, chalcopyrite, galena and gold. The ore microscopic and geochemical analysis indicates that gold mineralization has got strong spatial association with alteration features, such as carbonitization, silcification, sulfidation and sercitization. The concentration of gold increases with sericitized, carbonitized silicified and sulfidized host rocks. The host rock geochemistry Zr vs TiO2 shows that the tectonic setting lays within volcanic arc setting means that the formation of the deposit is related to subduction related activities. The ore geochemistry result shows the Ashashire area is target area for gold deposit ranges upto 10.3ppm that hosted in chlorite-sericite-carbonate schist in carbonate-quartz veins. The ore components possibly originated from dehydration, decarbonation and devolatilization of hydrated mafic rocks and carbonated rocks during prograde regional metamorphism and precipitates in retrograde conditions. The strong association of gold and carbonate-quartz vein with intense wallrock alteration indicates that gold is precipitated from hydrothermal solutions. The source of solution is still in debating, however the geological, petrographic and geochemistry result of the study indicates that hydrated mafic volcanic rocks and carbonated sedimentary rocks are possible sources.
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    Environmental Impact Assessment of Quarrying Activity and Aggregate Production in Dire Dawa Administration Eastern Ethiopia
    (Addis Ababa University, 2021-09-14) Tamiru, Getachew; Getaneh, Worash (PhD)
    Quarries are open cast excavations from which fairly massive and deep deposits of hard or soft rocks are extracted, usually for the production of aggregates. the destructive nature of quarrying together with poor management of quarry sites has a serious environmental impact leading to a serious threat. This study focuses on the environmental and social impact of quarrying activity and aggregate production. Interviews & focused group discussion, observation, and reconnaissance surveys were utilized to evaluate the overall activity of quarry operation in the study area. Both close and open-ended type concentrated questionnaires were prepared to deal with the impact of quarry on workers and residents. A Focus group dissociation was made with the selected representatives to get information about the impact of the quarry activity. Maximum likelihood classification was applied to map land use/land cover and the transition was evaluated using spatiotemporal data between 2006 and 2021. SPOT-6 data with a 6 m resolution corresponds to 2006, Sentinel-2 data with a 10 m resolution between 2016 and 2021 were used to map the land use land cover. GPS data was used to check the LU/LC classified image into different classes. A field survey was also conducted to gather GPS points to map the change in land use and land cover and precisely validate accuracy assessment based on ground truth as well as to classify the rock mass of the quarry slope stability. The discontinuity of the rock mass was determined with Burton's compass at ten slope section sites. Land use land cover maps for the years considered, as well as the net change between 2006 and 2021 showed that quarrying sites have grown by around 692.68 ha, while Shrubland has shrunk by 2,238.68 ha during the same period. According to the social impact evaluation, numerous issues such as dust, noise, vibration, and flaying rock from quarry sites caused the problem on quarry employees and residents within the immediate vicinity of the quarry sites. The focused group discussion showed that there is a tremendous effect on the environment due to lack of follow-up. Except for site 5 and site 10 the all eight sites were classified as fair rocks whereas sites 5 and 10 were classified as poor rock. Also, according to the land stability review stability of the area ranges from completely unstable (sites 1,3,4, and 7) to partially stable (sites 2,6,8, and 9). According to the study, quarrying activity in the area will continue to cause significant environmental and community harm unless an adequate mitigation approach is followed by all responsible bodies.
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    Evaluation of Limestone Quarry Quality, Planning and Slope Design in Dangote Limetone Quarry, Mugher Area
    (Addis Ababa University, 2018-06-05) Amberber, Belay; Getaneh, Worash (PhD)
    The study area is found in western Ethiopia in Oromia Region State Mugher area. It is covered by mostly sedimentary and few volcanic rocks. In open pit mining method most of the time the excavation process is mostly so random that it has its own impact on the quality and excavation time. Because of the random excavation process the limestone is mixed with quaternary basalt and large amount of overburden. And also some large limestone boulders affect the working area of logistics. Such problems can be solved by designing the slope stability of the site. Apart from this problem the quality of the limestone is one of the important factor to be considered. It’s based on these classification the possible industrial usage of the limestone is made. Thus the main objective of the research is to evaluate limestone quarry planning and slope design. Moreover, the research aims to make safe cut slope design and determine quality of rocks for different field of application. To achieve the research objectives, collecting samples of rocks, RMR data, were done based on lithology, color, and structure and area coverage of each exposed section collected from the mining places for slope design and quality evaluation. The data were treated with the help of Rocscience.RocPlane.v2.029 software for determine possible mode failure. Furthermore the slope design of the quarry site was done based on Datamine studio 3.21 software. The average result of RMR determination the result lays under fair rock mass classification (50 – 60%). According to the field data, it’s possible to conclude that all the joint sets could not affect the stability of the Dangote limestone quarry excavation. The simulation result shows that there is no possible mode of failure in every critical slope sections. Since the large amount of ore body is indicated from the northwest direction, the sequential direction of excavation have to start along northwest direction for the long term quarry planning and cost effectiveness. The average value of each major oxide mineral of rock from XRF results are: CaO < 47.6wt. %, MgO > 3wt. %, SiO2 > 2wt. %, Fe2O3 > 1wt%. Hence, according to BGS standard classification it lies under impurity limestone. Therefore, it used for Mineral wool and natural cements on (subject to the silica/clay mineral ratio)
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    Genesis of Magmatic Phosphate Mineralization in Gabbro Intrusive Rocks of Bikilal-Ghimbi area, Western Ethiopia
    (Addis Ababa Universty, 2013-12) Lemu, Tesfa; Getaneh, Worash (PhD)
    Western Ethiopia is underlain by proterozoic metamorphic belts that form parts of exposed Arabian Nubian shield. The metamorphic belt consists of high-grade biotite gneisses, low-grade volcanogic sediments and mafic ulteramafic complexes. Bikilal-Ghimbi gabbroic intrusive is an elliptical mafic body that intruded into the metamorphic gneissic body during Neoproterozoic time. It consists of olivine gabbro at its center, hornblende gabbro and hornblendite at its periphery. The olivine gabbros are very fresh and un deformed, while hornblende gabbro and hornblendites show slight weathering and with minor deformational structures. The Bikilal-Ghimbi gabbro intrusive has deserved wide attention due to its ore mineralization. Apatite, magnetite and ilmenite mineralization occurs in all this intrusive lithotypes with varying grades. Apatite occurs in the disseminated, lense and lenticular forms. Two main zones of phosphate mineralization, the upper and lower zones, were identified and delineated entirely based on phosphate (P2O5) assay values. The strike length of the upper zone is 1600m, while the strike length of the lower zone is 3000m having a thickness of 60m _200m.The mineable reserve of Soji-Bikilal phosphate deposit is estimated to be 181 million tons, at a grade of 3.5% P2O5. The major element geochemical shows that despite the difference in olivine and hornblende gabbro, there is no chemical contrast between the lithotypes, except for fluid mobile elements suggesting an origin from the same parental magma. Only the perimeter is affected by moderate metasomatism. An estimation of the parental magma composition by using trace element abundance analysia from fresh clinopyroxene and olivine gabbro bulk rock suggests intraplate-type tholiitic magma. The REE element analysis derived from apatite and host rocks show the same magmatic origin for the ores and silicate host rocks. The source of the magma may be linked to mantle degassing or to basic magmas derived by partial melting of the upper mantle. The ores were formed during magmatism as immiscible liquids which was separated from strongly differentiated magmas, aided by large volatile and alkali elements content. In this magma chamber, the phosphorous and alkali content probably led to the formation of a Fe–F, CO2–H2O–P–Na dominated immiscible melt which separated from a silica-rich melt. The breakdown of this late immiscible phase has resulted in the formation of magnetite–apatite melt and segregation of dense Fe-Ti-(P) rich melts which settled downward in a silicate crystal mush form net-textured and massive Fe-Ti oxide and phosphate ores as part of the cumulate sequence at this Bikilal-Ghimbi region. The immiscible phases of silicate and oxide- phosphates separation, breakdown, crystallization and Segregation might have occurred for more than two episodes resulting in the formation of different ore zones. The host rocks might have crystallized and segregated from the silicate rich melt which then invaded by the dense Fe-Ti-(P) rich melts which settled downward into a silicate crystal to crystallize and segregate together. The apatite free lithologies were crystallized during the less saturation of the Fe-Ti-(P) immiscible melt phase.
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    Geological and Geotechnical Considerations in Open Pit Planning and Design; a Case of Okote Gold Deposit, Southern Ethiopia
    (Addis Ababa University, 2019-05-06) Merga, Shibiru; Getaneh, Worash (PhD)
    This manuscript particularly presents the geological geotechnical factors and parameters to be considered for the designing and planning of Okote gold project which is located in Borena, southern Ethiopia. The deposit is currently under feasibility study by National Mining Corporation (NMiC). Geologically, the area lies within the southern extension of the Megado meta-volcano-sedimentary terrain. Carbonate amphibole schist, chlorite schist/ carbonate chlorite schist, metagabbro, metagranodiorite, metadiorite, are identified as the main lithological units. They are all aligned to the NNE-SSW direction and dipping to the west at about ~65-780. There are two distinctly identified mineralization types: chlorite schist hosted gold mineralization and metagranodiorite hosted mineralization. The resource estimation using ordinary kriging reveals the Okote gold deposit has 77 million tons of ore at 1.18g/ton average grade and 0.49 cut-off grade. Thus, the contained value is calculated to be 23,062Kg of gold. Geotechnical study shows that the rock mass in the area is strong enough for hard rock mining. According to the RMR89 classification system, waste and ore body are rated 65 and 65.5 respectively. All the factor of safety calculated for bench, inter-ramp, and overall slope angles for the proposed open pit range between 1.12 to 1.30 for dynamic condition and 1.27 to 1.43 for static condition. The bench face angle should not exceed 700. Bench height is 14m and has width of 7m. The selected ramp width is 18m (without ditch on both side of road, 2m each) depending on the preferred size of dump track. Depth of the pit is ~190m, that means starting from 1100m to 1290m. The calculated stripping ratio for the proposed open pit is 7.43 with 13 years of mine life. The pit has total enclosed volume of 89x106 m3 with longest diameter of 1.19Km.
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    Geology and Genesis of Gold Mineralization in Burikaro and Ejersa Areas, Guji Zone, Oromia National Regional State, Southern Ethiopia
    (Addis Ababa University, 2014-05-30) Ridwan, Munir; Getaneh, Worash (PhD)
    This study deals about geology and genesis of gold mineralization in Burikaro and Ejersa areas, which are located in the Neoproterozoic Adola gold field of southern Ethiopia. The area is not well explored and almost no research work has been done so far. Detailed review of the geodynamic evolution and mineralization history of the region, field description and geological mapping, rock and ore petrography, and surface sample chemical analysis were conducted. Secondary data from trench sample chemical analysis were also utilized in the study. The area comprises highly weathered and variably deformed upper greenschist to epidote-amphibolite facies metamorphic rocks like amphibolite, talc-tremolite-actinolite schist, graphite-quartz-mica schist, meta-conglomerate, and meta-sandstone. Intermediate to mafic meta-plutons such as meta-dolerite and meta-gabbro are also present intruding the amphibolite rock. A major N-S and two minor NW-SE and E-W trending shear zones; early- and late-tectonic quartz (± calcite) veins; and hydrothermal alterations like silicification, carbonatiztion, tourmalinization, and chloritization were observed. Besides its occurrence as a free gold, the gold mineralization of the study area is mainly associated with the hydrothermally altered major N-S trending shear zones containing late-tectonic quartz (± calcite) veins with associated sulfides and present mainly in the graphite-quartz-mica schist and meta-conglomerate/meta-sandstone. The ore minerals associated with gold are dominantly pyrite, magnetite, and ilmenite; minor amounts of hematite and chalcopyrite, and accessory mounts of sphalerite, covellite, and limonite chiefly occurring as open-space filling and replacement type mineralization. Based on texture, mineral association, and alteration a paragenetic sequence is suggested. The presence of not mineralized higher grade mafic metamorphic rocks at the base, the association of the gold mineralization with the lower grade meta-sediments, and the negative correlation between gold and metals like cobalt and nickel suggest that the possible source rocks of the gold are the underlying mafic rocks and metamorphic dehydration is the probable source for the hydrothermal fluids and leaching of gold from the mafic rocks. The association of gold mineralization with sulfides suggest that HS--or H2S-complexes were responsible for gold transport in the area.
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    Geology and Genesis of Gold Mineralization In Kushmagane Area, Assosa Woreda, Western Ethiopia
    (2016-06) Amena, Leta; Getaneh, Worash (PhD)
    Geology of Western Ethiopian Shield is known by volcano-sedimentary terranes, gneissic terranes and ophiolitic rocks intruded by different granitoid bodies. This thesis study generally considered the geology and genesis of gold mineralization in Kushmagane area, a part of Western Ethiopian Shield and involved field investigations and petrographic and whole rock geochemical studies to determine genesis of gold and related processes. Kushmagane is covered by low grade metabasites and metagranitoids metamorphosed at greenschist facies. They consist of quartz veins which are both primary and metamorphic in their origin, the later lacking specific orientation. The metagranitoids are intruded by thin mafic intrusions that are oriented parallel to both regional foliation and the local contacts. They have high silica content (70.40–78.30wt %) and show increase in K2O and Na2O and decrease in Al2O3, MgO, MnO and Fe2O with increasing SiO2 which reflects the crystal fractionation in their evolution. Their REE pattern shows only slight variation between the abundances of LIL and HFS elements which indicates moderate percentage melting of the original material. The low content of Fe and Mg oxides in metagranitoids with their peraluminuous nature indicate crustal contribution. Mafic mineralogy and associated basic volcanic rocks on the other hand, infer mantle source. Therefore, the source for Kushmagane granitoids is likely both basaltic mantle derived parental magma and partial melting of continental crust. Kushmagane metabasites have high concentrations of MgO, Fe2O3 and CaO and low concentration of Na2O and K2O. Their REE abundance pattern shows nearly parallel trend in a negative general slope. Negative slopes combined with their tholeiitic nature infers that the Kushmagane basalts and andesites originated in the lower enriched mantle reservoir. The flat pattern in metabasalt suggests that the REE abundances in these rocks resulted from phases involving shallow fractionation (e.g., olivine), which do not fractionate the REE. Their tholeiitic nature and abundance of minerals like augite, pigeonite ad hypersthene with minor olivine indicates that the Kushmagane metavolcanics formed as oceanic slab subducted, reached sufficiently hot region and melted to leak into the crust. Gold mineralization in the area, is decorated by presence of sulphides like pyrite, pyrrhotite, chalcopyrite and covellite. Based on observed volcanic arc tectonic setting, ore petrography and alteration types, the mineralization is believed to be orogenic type hosted by metagranitoids and metabasites. The lower Au value in metabasites in the area may reflect that the rocks were also sources for metal and leached by hydrothermal fluids during metamorphism. The probable sources of fluids are proposed to be regional metamorphism of the mafic volcanic rocks, post to syn-tectonic intrusions and/or subducted oceanic crust.
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    Geology and Stability of Opal From Wegel Tena Area, Ethiopia
    (Addis Ababa University, 2017-11-01) Dagnachew, Selamawit; Ayalew, Dereje (Professer); Getaneh, Worash (PhD); Rondeau, Benjamin (Professer)
    Crazing (cracking) is a common opal destabilization which has not been studied in detail prior to this work. It is a major economic issue for the opal gemologic market and the industrial synthesis. The aim of this research is to understand cracking (crazing) phenomena of opals from Wegel Tena locality. To achieve this, opal samples are directly extracted from three different local mining sites of Wegel Tena opal deposit (Koke Wuha to the northeast of Wegel Tena town, Anset to west of Wegel Tena town and Chegen to the north of Wegel Tena town) from the host rocks of rhyolitic ignimbrites. The opal samples have been characterized under natural light, crossed polarizers and Raman spectra data. The opal samples were heated in order to accelerate the evacuation of the water. Hydrophanes opals (KOK01, CH01 bleach zone and AN02) have shown no development of cracks after heating. While non-hydrophanes opals (KOK04, KOK05, internal zone of CH01) develop crack pattern after heating regardless their transparency. All non-hydrophane samples at low Raman spectral resolution (3cm-1) showed significant variation at 780cm-1 peak (up to 13cm-1), which is an indicator for strong strain into the Si-O-Si bond. The average value for this shift is about 3.3cm-1 down after crazing (cracking) reflecting extensive stresses impact for crack development. Birefringence patterns (produce extensive local constraint) observed around the cracks between crossed polarizers. Abnormal birefringence figures appear with crazing: anisotropy is created around breaks. Opal stress distribution is dependent to opal surface irregularities and breaks distribution. Water loss triggers crazing into non-hydrophane opals. Crazing reorganizes stress distribution according to the new surface distributions. Generally hydrophanes opals (KOK01, CH01 bleach and AN02) have better resistance to cracking than non-hydrophanes opal (KOK04, KOK05, internal zone of CH01) even at high temperature. In Hydrophane opals water exist in molecular form.
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    Geology, Geochemistry and Genesis of Ula Ulo Nickel Deposit, Adola Belt, Southern Ethiopia
    (Addis Ababa University, 2018-05-30) Kebede, Wubegzier; Getaneh, Worash (PhD); Alene, Mulugeta (PhD)
    The study area is located in the Neoproterozic metavolcano-sedimentary assemblages of Megado belt within Adola belt of southern Ethiopia. Nickel mineralization is hosted and confined by serpentinites. The country rocks are tremolite talc schist and talc tremolite schists. Geochemistry of the host rock and country rocks is studied. All units shows LILE Enrichment (Ba/Yb)n is 2.92 (serpentinite), 1.2(talc schist), 3.84 (tremolite schist) and 3.2 (amphibolite). Because these LILEs are fluid mobile and easily assimilated from the subducting slab as compared HFSEs. REEt calculated as serpentinite (0.7 – 1.84 ppm), talc schist (2.69 ppm) and tremolite schist (2.79) while amphibolite has REEt (6.18). (La/Yb) c.n values are serpentinite (4.2), talc schist (6.6), tremolite schist (3.7) and amphibolite (8.1). Slight enrichment of LILE and LREE and depletion of HFSE and HREE for both serpentinite, talc tremolite schist and amphibolite is due to assimilation and dehydration of subducting slab. Magmatic evolution undergone without amphibole intervention and plagioclase crystallization. Both ultramafic and mafic rocks are crystallized from similar origin. The geochemical signature of both the mafic and ultramafic rocks is similar to alkaline thoeliitic and island arc thoeliitic bonnieite. Tectonic discrimination shows island arc boninite andesite affinity. Meta sedimentary rocks are also common in the study area. These are quartzite, meta psmmite and graphite schist. Both metavolcanic and metasedimentary rocks are metamorphosed to greenschist facies. Because the mineral assemblages are antigorite, lizardite, talc, tremolite, actinolite, chlorite, epidote, sericite and hornblende. The rocks are aligned NS and dips towards 700 towards W. The deposit is zoned into two. These are oxide zone and saprolite zone. Oxide zone is upper portion of the lateritic column while saprolite covers the lower part. The occurrence of the mineralization in these zones is variable. Inferred resources estimation is done for these zones separately. The source of the Ni is serpentinites. The metal is leached from oxide zone and serpentinites and precipitated in the saprolite as garnierites. The mineralogy of these garnierites is studied. Both serpentine-like and talc-like garnierites are observed. Other ore minerals observed are chromite and magnetite. The genesis is formulated based on geochemical and mineralogical characteristic of garnierites. The deposit model is ultramafic hosted lateritic nickel deposit hosted. Ore body Morphology, extent, mineralogy and geochemistry are studied and explained.
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    The Geology, Timing Event and Roles of Quartz Porphyry Intrusions, in Vms Gold Mineralization at Terakimti Area, North-West Shire, Northern Ethiopia
    (Addis Ababa Universty, 2016-06) Wudie, Gashaw; Getaneh, Worash (PhD)
    The volcanogenic massive sulfide gold and base metal mineralization at Terakimti area is part of the Southern Arabian Nubian Shield. This is one of the gold and base metal enriched area among many terrains in the shield and Northern Ethiopia. Many exploration companies and research groups are attracted to this area. The mineralization at Terakimti is intruded by several quartz porphyry intrusions. This work is conducted to determine the geology, the timing relation between the quartz porphyry intrusions with each other and with the VMS deposits and roles of the intrusions on the mineralization. Different methods are adopted to complete this work. These are geological mapping and structural description; thin section and polished section description of the lithologies; analysis and interpretation of the trace and major elements of major host rock units. More over the precious and base metal element interpretations is conducted. The major lithological units of the area includes basalts, rhyolits, some mafic and felsic volcanoclastics, several quartz porphyry intrusions, several quartz veins and gossans. The porphyry intrusions show homogenous characteristic of geological, mineralogical, structural and geochemical (major, trace, precious and base metallic) element. Based on the time of formation three types of mineralization are identified at Terakimti area. These are VMS deposits, mineralization in the quartz porphyry intrusions and supergene deposits The mineralization and the metallic elements of the VMS systems at Terakimti are remobilized by the late coming quartz porphyry intrusions. As compared to the VMS deposits, the quartz porphyries are weakly mineralized and it interrupts the continuity of the VMS deposits. The remobilization and relocation of the massive sulfide deposits and mineralized bodies causes slightly scattered distribution of the VMS deposits. The gossan is related to the two types of mineralization especially the VMS. Generally this work described the basic relation between the mineralization of Terakimti area and could have contribution to the scientific community and the exploration groups.
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    The Kilkile Emerald; Genesis, Mineralogy, Chemistry and Mining; Kilkile, Shakiso- Southern Ethiopia
    (Addis Ababa University, 2019-09-04) Abera, Girma; Desta, Zerihun (PhD); Getaneh, Worash (PhD)
    This study provides quantitative geochemical, petrological, and mineralogical data on major rock types and emeralds of the kilkile area. The meta-basic rocks containing 740ppm Cr provided the amount necessary for emerald mineralization. Emeraldhosting biotite schist is confined to the contacts of quartz- feldspar- muscovite pegmatite dykes/veins with meta-basics. The pegmatite dykes are genetically related to a fertile granite pluton within the Adola district. The formation of biotite schist from meta-basic rocks is associated with the introduction of pegmatitic components in to the meta-basics, causing enrichment with the pegmatitic composition. Quartz-feldsparmuscovite pegmatites of the kilkile area belongs to the rare-element pegmatites of the LCT family with common beryllium enrichment (12ppm). These pegmatite dykes/veins intruded the N-S orienting regional structures. The emeralds have higher MgO (0.26-4.08 wt. %), Fe2O3 (1.39-2.18 wt. %), Al2O3 (17.7- 20.1 wt. %), CaO (1.25- 3.85 wt. %), K2O (0.07-1.7 wt. %), P2O5 (0.02-1.88) and Be (527-1000 ppm) and lower Cr2O3 (0.01-0.09 wt. %) and SiO2 (59.13-61.79 wt. %) contents. The relatively higher value of iron and magnesium in the kilkile emerald might attribute for the ferromagnesian nature of the meta-basic rocks or aggressiveness of the brine solution in liberating Mg and Fe from meta-basic rocks. The low chromium content in the metabasic rocks contribute for chromium deficiency in the emerald. The high value of Fe2O3 depresses the green colour in addition to low Cr2O3. Compared to the Zambian, the meta-basic rocks in the case of Ethiopia have low magnesium and iron content. However, the relatively higher value of iron and magnesium in Ethiopian emerald might contribute for relative competency of magnesium and iron in occupying the aluminium site in the crystal structure of beryl. The higher value of K2O in the Ethiopian emeralds than in Zambian might suggest the role of potassium metasomatism at the pegmatite and meta-basic contact. The genesis of Ethiopian emerald holds the classical model for emerald mineralization, the condition in which pegmatites interact with the surrounding meta-basic rocks. The current mining activity at kilkile area requires vertical to horizontal ratio chances due to the overlapping of mining progress with direction with the dipping of the host rock units. Therefore, low vertical to horizontal ratio is recommended for the western berms of the mining pits.
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    Mineralization and associated structures of Okote prospect (Southern Ethiopia)
    (Addis Ababa Universty, 2005-06) Wube, Abu; Getaneh, Worash (PhD)
    Okote prospect area is the southern extension of the N-S striking auriferous structure, the Megado graben-syncline. Only a few of the numerous primary gold indications are identified in this structure. In the Okote area sulfide rich auriferous quartz veins of mesothermal mineralization occur along highly fracture contact zone between massive amphibolites and amphibole schist and to a minor extent along the schistosity planes of the chlorite carbonates schist. Lithologically, the Okote prospect area is constituted of transitional to basic metavolcanics in contrast to the northern half of the Megado graben-syncline, where both metasediments and metavolcanics occur. The Okote metavolcanics are bounded by granitic gneisses both in the eastern and western side and exhibit alterations comprising chloritization, silicification, epidotization, sulphidization and carbonetization. Within the Okote prospect five main lithologic units are recognized: - Epidote Quartz Chlorite Schist, Chlorite carbonates schist, Talc tremolite actinolite schist, Meta gabbro and Metagranodiorite. They are structurally overlain by mafic and ultramafic rocks consisting of mainly Meta gabbro & Talc tremolite actinolite schist. The granitoids occur in the form of lenses intruding in to the foliated metavolcanics. Four phases of deformation are described. The earliest D1, deformation has produced a pronounced local S1, schistosity. D1 deformation produced a regional S1 schistosity. The S1 is well developed parallel to the compositional banding in the epidote quartz chlorite schist and variably developed in the ultramafic rocks. Moderately to steeply NE and SW doubly plunging folds produced close to tight S1 schistosity. It was followed by the formation of NW trending faults, which characterized by sinistral brittle shear zones (D2). The D3 is open E-W sinisoidal F3 folds with N-S axial planes and D4 is linear E-W fractures. The D1 and D2 phases of deformations produced dilatational zone of intersection, which is most important for mineralization of gold. The auriferous veins are distributed in the Adola group of the upper complex, which is with in the axial trough of the geosynclines that gave rise to the Mozambique belt during the upper Proterozoic Generally the rocks of Okote prospect show characteristic of green schist facies metamorphism. Geochemical evidences showed that the rocks of Okote prospect are intermediate to basic composition. Chondrite normalized graph shows less fractionation of the host rocks. The gold occurred in quartz vein and alteration zones, the nature of the gold is very coarse that can be seen with the naked eyes. Visible gold particles are commonly encountered in boxwork association of fractured and limonitized pyrite structure. Two phases of mineralization have been recognized in Okote prospect, Gold-sulfide-quartz and sulfide-carbonate-quartz. The mineralization is controlled by shearing, with pinch and swell structures both along the strike and down dip. Okote prospect can be evaluated and falls in ordinary workable deposit or it is open to doubt. Gold and sulphides are the most common minerals in the area. The association of gold with sulfides in the quartz veins at Okote may be taken as the evidence of gold transport as bisulfide complex
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    Mineralogy, Geochemistry and Genesis of Mekane Selam Iron Occurrence in Tewa Area, Northern Ethiopia.
    (Addis Ababa University, 2020-10-02) Digafe, Belayneh; Getaneh, Worash (PhD)
    Iron is the fourth abundant metal in Earth’s crust and its ore minerals are concentrated as hematite, goethite, magnetite, siderite, illmenite and other sulfides. The Mekane Selam iron mineralization is part of the Northwestern plateau that bounded by Axum–Adigrat and Ambo lineaments of the N and SW. Mineralogy, geochemistry and genesis studies are main objective of this work. Geologic field work and mapping, X-ray diffraction, ore petrographic study of ore, geochemical analysis of host rock were applied methodologies. XRD and ore microscopic study reveals hematite, goethite, magnetite, kaolinite anatase and quartz are the principal ore minerals and associated gangue phases of ore while quartz and feldspars are petrographic composition of the host. Chemical analysis of major constituent show significant enrichment of SiO2, Al2O3 in the host and Fe2O3 in the ore with strong depletion of K2O, Na2O, MnO, MgO, CaO and P2O5. High value of CIA (88.46-99.44) with depleted content of K2O and Na2O suggests the area is subjected to intensive weathering process. Chondurite-normalized REE pattern show enrichment in LREE and relatively smooth pattern of HREE. The pattern is consistent with the characteristics of upper continental crust, protholith of sediments and weathered terrestrial is iron source. Positive Ce and negative Eu anomalies of analyzed samples suggest iron reprecipitation is occurring in weathered (supergene) oxidation leaching of REE. It indicates digenetic alteration and the absence of hydrothermal fluid inputs during mineralization. Concentrated detrital derived elements of Zr, Al and Nb with the oolithc textures of ore samples are the characteristic of digenetic modification in iron formation. The XRD results of goethite, hematite and kaolinites minerals indicate the genesis of Mekane Selam iron occurrence is laterite. SiO2-Fe2O3-Al2O3 ternary plot of ore and host rock samples show the ore is altered to hematite due to low–strong degree of lateritization while the host rock is as a result of kaolinization to kaolinite. Field observation and exposure measurement, mineralogical and geochemical data analysis suggests the iron occurrence of the area is classified as an indicated resource. Surface weathering, REE leaching, transportation and other physico-chemical conditions enrich iron. The digenesis and sediment recrystallization are significant iron ore formation and modification of the area.
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    Quality and QuanAssessments of Marble Deposit in Benishangual Gumuz, Regional State, Around Daleti Area.
    (Addis Ababa University, 2019-06-05) Mohammednur, Hafis; Getaneh, Worash (PhD)
    Daleti marble deposit is situated in the Western part of Ethiopia near Oda Beldeglue woreda, Daleti Keble, which is about 665 km from Addis Ababa and at an elevation of between 590 to 2491 m above mean sea level. Geology of the marble district is composed of metasedimentary schists, which are of low metamorphic grade; consist of intercalated greenschist, quartzo-feldspathic schist, graphite schist, phyllite, quartzite with lesser biotite schist, metaconglomerate and marble. Based on petrographic study, the main minerals identified in these basement rocks include calcite, muscovite and opaque mineral. The parent rock, calcite and dolomite have been partly and completely transformed to marble. The main aim of the present study is to assess the qualitative as well as quantative features of this marble deposit. An integrated study combining geological, petrography, mineralogical (XRD) and physical and mechanical test (compressive strength, porosity, water absorption, bulk density) data as well as cut and polish section were carried out in order to characterize the quality and quantity of marble deposit in the study area as well as to assess the environmental impact of mining. Data obtained from morphological study and available physical property tests were also examined to see the possible industrial applications. Usually the company uses highly sophisticated technologies where both cutting by diamond wire and water jet are applied. Marble is used in a variety of applications as flooring tiles in bedrooms, bathrooms, kitchens, restaurants and public places like hotels, public toilets churches and town halls. Therefore, these areas could be developed for dimension stone quarry and exploitation of these rocks could be as rough unprocessed building stone or better polished natural stones for a variety of uses.
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    Relationship Between Structure and Lithology and their Control on Gold Mineralization in Okote Area, Southern Ethiopia
    (Addis Ababa University, 2013-06-06) Tadesse, Yonatan; Getaneh, Worash (PhD)
    Okote gold field is found within Neoproterozoic greenstone terrains of southern Ethiopia. This greenstone belt trend in North-south direction, and characterized by Precambrian rocks comprising basic/ Ultrabasic and other older basement gneisses which form crustal scale shear zones extending for about 150 Km along its strike (Worku., et al., 1989). The belt is known for gold and other metallic and industrial minerals. The objective of this research is to use geological and structural mapping of the area and core logs to establish the inter-relationship between lithology and structure and to assess its control on the Okote gold deposit. Inorder to do that a pre-field study of the area using different literatures and reports was done, then during field work different kind of data collected like geological and structural mapping with important samples to identify the mineral assemblage of the area was done and after field works these gathered data from different literature and data from field work were used aiming to form a relationship between the data gathered to output the conclusion. The main rock units of the study area are chlorite-amphibolite schist, chlorite-carbonate schist, meta-gabbro, talc tremolite actinolite schist, granodiorite and quartz veins. The most common types of alteration in the area are; porpylitic alteration (includes Chloratization, Carbonitization and Epidotization), Pyritization, Silicification, Tourmalinization, and in small amount sericitization and feldspatization. The rocks of the study area has two kinds of strain, brittle and ductile strains which implicates the deformation takes place in the area is the same as that of the strain measurements of other localities. Gold in the study area is mainly related to chlorite-carbonate shist and meta-granodiorite. The ore body also relates to wall rock alteration like pyritization, carbonation and silicification. These ore bodies are confined by or found adjacent to the brittle-ductile shearzones These results implicates that the gold occurrence of Okote is controlled by lithologies and structures.
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    Some Features of Gold Mineralization i Worash in Southern Seken 1 Area (Worq Amba), Tigray
    (Addis Ababa Universty, 2000-06) Ofgaa, Temesgen; Getaneh, Worash (PhD)
    The geology of the study area is constituted by feldspar quartz sericite schist, muscovite chlorite schist , basic metavolcanics and granodiorite. The feldspar quartz sericite schist consists of thin intercalations of strongly silicified and chlorite talc schist . Additionally, granitic dykes and carbonate veins occur in this rock parallel to the regional foliation . The muscovite chlorite schist also has intercalations of quartz chlorite schist along its western margin. Major and minor quartz veins also occur in all major rocks. Foliations generally strike to the northeast and dip at moderate to steep angles to the west. Other geological structures evident in the study area include fractures and small tight folds. These folds may represent the earliest phase folds in the area . The rocks are strongly affected by hydrothermal alterations. Wall rock alteration types evident in the area include sericitization, silicification, carbonatization, chloritization, epidotization and sulfidation . Gold mineralization might have resulted from hydrothermal processes that caused the wall rock alterations. Open spaces along host rock fractures and foliations might have provided channel ways for the hydrothermal fluid. Gold has been detected in quartz and carbonate veins and altered feldspar quartz sericite schist, muscovite chlorite schist . The highest gold content has been obtained in chlorite talc schist that is intercalated in feldspar quartz sericite schist .Gold shows a slight positive correlation with cobalt. Though this result is not sufficient to suggest the source of the gold to be mafic- ultramafic rocks, it attracts attention for further studies in this regard . Some evidences from the granodiorite reveal that it is unlikely that the hydrothermal fluid emanated from this intrusive body.