Blades M.L.,University of Adelaide |
Collins A.S.,University of Adelaide |
Foden J.,University of Adelaide |
Payne J.L.,University of South Australia |
And 5 more authors.
Precambrian Research | Year: 2015
The Western Ethiopian Shield (WES) forms a vast, underexplored, region of the East African Orogen. Lying towards the west of the orogen and between the dominantly juvenile Arabian-Nubian Shield in the north and the high-grade Mozambique Belt to its south, it holds a key position; vital in understanding the role of the East African Orogen in Gondwana formation. The WES is made up of a range of supra-crustal and plutonic rocks that formed in Tonian volcanic arc environments. The relative timing and duration of arc formation within the East African Orogen is still slowly being unravelled and we present new U-Pb and Hf isotopic data from zircons that help to define the maximum depositional age and provenance of the protoliths to meta-sedimentary units, as well as constrain the age of igneous intrusions located within the WES. Detrital zircons, obtained from a meta-sandstone, yield provenance age peaks at 2.8-2.4Ga, ca. 1.8Ga and 1.15-0.84Ga and a maximum depositional age of 838±13Ma. Hafnium isotopes from the same zircons demonstrate that both the oldest and youngest populations have broadly juvenile Hf isotopic values. However, the ca. 1.8Ga population shows significantly evolved Hf isotopic values. Sensitive High Resolution Ion MicroProbe (SHRIMP) U-Pb ages from two granites and a felsic granite and hornblende+biotite tonalite in the Nekempt-Ghimbi region of the Western Ethiopian Shield (Didesa and Kemashi Domains) indicate two pulses of magmatism at 850-840Ma and 780-760Ma. Partial melting and deformation in the Didesa Terrane occurred at ca. 660 Ma. Further west, the post-tectonic Ganjii granite yielded a 206Pb/238U age of 584±10Ma, constraining pervasive deformation in the area.Age constraints on orogenesis in the Western Ethiopian Shield (ca. 660. Ma) are similar to those in NE Uganda (ca. 690-660. Ma), but are older than the Ediacaran peak orogenesis reported from the Southern Ethiopian Shield, Eritrea and northern Ethiopia and from SE Kenya. This suggests that closure of the western Mozambique Ocean involved progressive volcanic-arc accretion to the active margin of Cryogenian-Ediacaran Africa. © 2015 Elsevier B.V.
Agency: European Commission | Branch: FP7 | Program: CSA-SA | Phase: ENV.2007.4.1.4.1. | Award Amount: 2.42M | Year: 2008
Africa, the largest single component of the African Caribbean Pacific (ACP) Group of States, despite its huge potential for development through both human and georesources, suffers in many places from poverty and underdevelopment. The sustainable use of its resources is a key issue, not only for development of the African countries, but also for the worlds future. Over the coming decades, these issues are likely to play an ever-increasing role due to the worlds growing population, rapid urban development and the rising demand for better infrastructure and services. The sustainable use of georesources requires a knowledge based on data, information and expertise. Thus, the availability, traceability, accessibility and processing using GIS technologies of heterogeneous data from multiple sources is essential. Such processing requires a qualified and experienced personnel and the definition of strategies for capacity building and training. In view of this situation, a recognised need has emerged for a shared, distributed, Internet-linked georesources observation system, based on open standards and interoperability developments, as a contribution to the sustainable development of African countries. The Support Action is the preparatory phase needed to design the African-European Georesource Observation System (AEGOS) capable of hosting and providing access to Africas geological resources, including groundwater, energy, raw materials and mineral resources. Its objectives are to define: i) operational procedures for data management (Spatial Data Infrastructure, metadata and data specification), ii) user-oriented products and services including the preparation of innovative spin off projects based on AEGOS and an evaluation of the input of Interoperability and interdisciplinary in support of GEOSS iii) the African- European partner network, iv) a geoscience contribution to GEOSS, in the context of INSPIRE
Admassu E.,Geological Survey of Ethiopia |
Worku S.,Reykjavik University
Transactions - Geothermal Resources Council | Year: 2015
The area of investigation, Tulu-Moye, is situated in the Main Ethiopian Rift (MER) northwest of Asela close to the eastern margin of the rift. It is a wide zone where tectonic and volcanic activities are concentrated. As a major part of the Koka magmatic segment, The Tulu-Moye area has depicted interesting characteristics of volcanism and geologic structural patterns. The formation and growth of faults in the area could be explained by three progressive phases of faulting. Two fault models are proposed to explain the sequence of faulting, fracturing and lava flow events. The volcanic activities of the area are mostly controlled by the active faults and extension fractures of the Wonji Fault Belt (WFB). A fault morphology survey exhibited the various nature of the fault and fissure morphology that was primarily controlled by strike variations in the geologic units. The fault kinematic data collected from selected localities indicated E-W direction (∼ 93°) extension, consistent with previous works conducted in other parts of the MER. A comprehensive relationship between Quaternary faulting and magmatism was realized in the Tulu-Moye geothermal prospect. In such a way that, cone-fault, cone-lava and lava-fault interactions were the most noticeable relationships between Quaternary faulting and magmatism in the area. The fault morphology, fault model, fault-magmatism relationships, suggests a progressive development of an extension fissure to a mature normal fault. Tulu-Moye has both favorable geological and structural features for a prospective geothermal resource, which however deserves detail geothermal investigations towards defining the area's major parameters.
Sofiya A.,Tohoku University |
Sofiya A.,Geological Survey of Ethiopia |
Ishiwatari A.,Nuclear Regulation Authority |
Hirano N.,Tohoku University |
Tsujimori T.,Tohoku University
International Geology Review | Year: 2016
Serpentinites (massive and schistose) and listvenite occur as tectonic sheets and lenses within a calcareous metasedimentary mélange of the Tulu Dimtu, western Ethiopia. The massive serpentinite contains high-magnesian metamorphic olivine (forsterite [fo] ~96 mol%) and rare relict primary mantle olivine (Fo90–93). Both massive and schistose serpentinites contain zoned chromian spinel; the cores with the ferritchromite rims preserve a pristine Cr/(Cr+Al) atomic ratio (Cr# = 0.79–0.87), suggesting a highly depleted residual mantle peridotite, likely formed in a suprasubduction zone setting. Listvenite associated with serpentinites of smaller ultramafic lenses also contain relict chromian spinel having identical Cr# to those observed in serpentinites. However, the relict chromian spinel in listvenite has significantly higher Mg/(Mg+Fe2+) atomic ratios. This suggests that a nearly complete metasomatic replacement of ultramafic rocks by magnesite, talc, and quartz to prevent Mg–Fe2+ redistribution between relict chromian spinel and the host, that is, listvenite formation, took place prior to re-equilibration between chromian spinel and the surrounding mafic minerals in serpentinites. Considering together with the regional geological context, low-temperature CO2-rich hydrothermal fluids would have infiltrated into ultramafic rocks from host calcareous sedimentary rocks at a shallow level of accretionary prism before a continental collision to form the East African Orogen (EAO). © 2016 Informa UK Limited, trading as Taylor & Francis Group
Zacek V.,Czech Geological Survey |
Rapprich V.,Czech Geological Survey |
Sima J.,Aquatest a.s. |
Skoda R.,Czech Geological Survey |
And 3 more authors.
Journal of Geosciences (Czech Republic) | Year: 2015
Kogarkoite, anhydrous monoclinic sodium fluorosulphate, was identified as a white granular coagulate in the Shalo hot spring situated between the towns of Hawasa and Shashemene, in the central part of the Main Ethiopian Rift in southern Ethiopia. The mineral crystallizes together with trona, Na3(HCO3)(CO3)·2H2O, and opal as white stratified sinter covering the surface of rhyolite chips semi-immerged in Na–HCO3 type thermal water with temperatures of up to 96°C. The determined chemical composition of kogarkoite is close to the ideal formula Na3(SO4)F and the refined unit-cell parameters are a = 18.089(2) Å, b = 6.965(1) Å, c = 11.457(1) Å, β = 107.72(1°), V = 1374.4(4) Å3. Increased concentrations of fluorine in groundwater were detected in the area of the rift floor of the central and northern parts of the Main Ethiopian Rift including the wider vicinity of the towns of Shashemene and Hawasa; however, this is the first described occurrence of fluorine-bearing mineral related to hot springs in Ethiopia. The presence of “free” fluorine both in cold groundwater (up to 17 mg/l) and in the Shalo hot spring (40 mg/l) is related to the prevalence of highly alkaline silicic volcanic rocks (namely pantelleritic obsidians) extremely poor in calcium and phosphorus. This prevents fixing of fluorine in apatite or in other stable minerals. © 2015, Czech Geological Survey. All rights reserved.
Meshesha D.,Geological Survey of Ethiopia |
Shinjo R.,University of Ryukyus
Journal of Mineralogical and Petrological Sciences | Year: 2010
This paper presents new hafnium isotope data for the Bure volcanic rocks from the northwestern Ethiopian plateau to constrain the nature of mantle sources within the broad mantle upwelling. The 176Hf/177Hf values range from 0.282901 (εHf = 4.79) to 0.283206 (εHf = 15.71) for the Oligocene transitional tholeiite and 0.282915 (εHf = 5.45) to 0.283069 (εHf = 10.85) for the alkaline basalts; these ratios are distinct from MORB but typical to OIB sources. The εHf values correlate positively with εNd. The scattered variation between εHf and contamination indices (such as Nb/La and Ce/Pb) for the transitional tholeiites implies that most tholeiitic basalts are affected by crustal contamination processes. Components 1 (C1) and 2 (C2), which are proposed to be the end-member components for the Afar mantle plume, have a Hf isotopic signature of εHf = 15-17 and 5-9, respectively. The diversity of these compositions relies on the proportion of recycled materials in the deep source, its formation age, and proportion of sediments relative to oceanic crust in the recycled materials.
Lanzarone P.,University of Georgia |
Lanzarone P.,British Petroleum |
Garrison E.,University of Georgia |
Bobe R.,University of Santiago de Chile |
Getahun A.,Geological Survey of Ethiopia
Geoarchaeology | Year: 2016
The Fanta Stream site is an archaeological and paleontological locality in Addis Ababa, Ethiopia. The site contains a rich assemblage of fossil mammals and Acheulean artifacts of approximately 600 ka located in a rare high-altitude context. A ground-penetrating radar (GPR) survey was conducted in order to provide three-dimensional imaging of the subsurface, which the authors use to interpret the geometry and distribution of fossil-containing stratigraphic units. Utilizing the stream's natural cut bank exposure, we calibrate GPR data to known geologic units through radar facies analysis. Shallow, high-amplitude coherent reflection geometries are attributed to volcanic tuff deposits, as these units exhibit subparallel continuous reflections consistent with planar stratified sedimentary deposition. Deeper, discontinuous reflection packages are interpreted as conglomeritic, fossil-containing deposits. The results of the GPR survey outline the location of the Fanta Stream's paleodepositional features as well as suggest the extent of fossiliferous stratigraphic units for use in future excavations. © 2016 Wiley Periodicals, Inc.
Kebede S.,Geological Survey of Ethiopia
Transactions - Geothermal Resources Council | Year: 2014
Surface explorations for geothermal resources in Ethiopia began over three decades ago. The geothermal explorations so far have identified over 22 areas that have geothermal resources suitable for electricity generation, with a total potential of 10,000 MW. These resources are considered to have high quality in terms of temperature and chemistry. Despite the countries long term geothermal exploration and huge potential, the progress of development of geothermal resources has been slow. Deep drilling has been conducted only in two prospects and only a 7.2 MW pilot plant has been installed so far. However, since recent years the country has adopted, a renewable energy mix policy, geared towards the advancement of geothermal resources development, including other renewable energy resources. Accordingly both the public and private sector geothermal projects are being implemented at larger scale than before. The public sector has focused in developing, the two most explored prospects in the country, the Auto Langano and Tendaho geothermal fields. Under the public sector, geothermal power plants planned for commissioning by 2020 include: (i) 70 MW plant at Aluto Langano and 100 MW plant at Tendaho Additional geothermal power plants are expected to be commissioned at Corbetti geothermal field by private sector involvement, with a total capacity of 1000 MW, to be developed under various phases. Despite the recent efforts to advance geothermal development in Ethiopia, there are challenges that include: (i) high upfront capital costs required and availability of sufficient finance, (ii) risks associated with the exploration phase, and (iii) limitations in local human resource capacity and low level of experience in institutional set up, a legal and regulatory framework. Copyright © (2014) by the Geothermal Resources Council.
Stein A.,University of Twente |
Yifru M.Z.,Geological Survey of Ethiopia
Transactions in GIS | Year: 2010
This article combines stereology with image mining. Image mining identifies and models objects from a series of remote sensing images and communicates this information to stakeholders. Stereology is the science of deriving properties of objects from lower dimensional features. This article first applies stereology to quantify properties of crisp objects on single images. Next it addresses the development of an object in space and time. Finally, it quantifies uncertainty of fuzzy objects. The article is illustrated with a case study from Cambodia, where flooding regularly occurs along the Mekong River. Nine Landsat images have been mined to assess the size of the flooding in space and time. Areal estimates obtained with stereology from single images show a high precision. Estimates of a space-time volume of the size of flooding in space and time include uncertainty estimates that could be ascribed to atmospheric distortion and limited resolution. Finally stereology is applied to estimate the effects on area estimates of fuzzified boundaries. All information can be transferred to stakeholders, e.g. to quantify the size of a disaster. The article concludes that stereology successfully and concisely quantifies phenomena and their uncertainties in a remote sensing image mining context. © 2010 Blackwell Publishing Ltd.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 22.17K | Year: 2013
The volume of groundwater in Africa is more than 100 times the annual renewable freshwater resource and 20 times the amount of freshwater stored in lakes, but its productive use in sub-Saharan Africa (SSA) remains low. Global abstraction of groundwater increased tenfold between 1950 and 2000 and contributed significantly to growth in irrigation particularly in Asia. The global area equipped for irrigation has been estimated as 301 Mha of which 38% depends on groundwater, but for sub-Saharan Africa (SSA) only 5.7% of the irrigated area is supported by groundwater. Just as in Asia, rapid expansion of groundwater irrigation may be about to occur in SSA. Although evidence from Asia suggests that groundwater irrigation promotes greater inter-personal, inter-gender, inter-class and spatial equity than is found under large scale canal irrigation, there is a significant risk that rapid development of groundwater resources in SSA may lead to inequitable resource use. There is a need for research to deliver the evidence and appropriate tools to support sustainable resource management and to assure access to groundwater resources by poor people. This research will address the following questions: 1: How and at what rate is groundwater being recharged? Deliverable: improved understanding of recharge processes at local and catchment scale; including consideration of influence of land use and water harvesting. 2: Can a tool be developed to help decision makers manage the resource? Deliverable: tools developed and tested at local (community) and catchment scales to assist decision makers in managing groundwater resources. 3: What are the implications of changes in land use? Deliverable: improved understanding of evidence base for influence of land use, water harvesting and green water flows on groundwater recharge. 4: What are the implications of climate change? Deliverable: tools for downscaling climate data and constructing scenarios developed and likely influence on recharge processes investigated. 5: How can policy and practice assure livelihood benefits for poor people? Deliverable: improved understanding of issues affecting access to and control of groundwater for productive use in irrigated agriculture. 6: What governance approaches are most likely to deliver equitable and sustainable use of groundwater? Deliverable: participatory evaluation of institutional change required at local community level and at national/catchment level to achieve equitable and sustainable use of groundwater in irrigated agriculture. Preliminary research will be delivered over a 1 year period by a multi-disciplinary research team from Newcastle University and the International Water Management Institute together with local partners in Ethiopia, Ghana and South Africa. This will deliver a pilot study and build the research consortium. The pilot study in Ethiopia will address both technical and social/governance aspects of groundwater resource assessment and management from the regional to the local scale. Lake Tana basin has been selected as a suitable site. In parallel, additional exploratory research will be conducted in Ethiopia, Ghana and South Africa. Key stakeholders will be invited to participate in consultations at in-country workshops aimed at understanding current state of knowledge around groundwater resources. Critical knowledge gaps likely to influence design of follow-up research will be identified and in-country collaborators will be commissioned to carry out short term studies. At the end of the 1-year catalyst grant project collaborating scientists representing partners from SSA together with UNEW and IWMI will meet for 3-day workshop in Addis Ababa in order to review lessons learned and agree design of the follow-on 4-year research project.