Browsing by Author "Asiedu, D.K."
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Item Assessing the impact of decreasing malaria transmission on parasite biology, disease pathogenesis and vaccine discovery(2017-03-23) Awandare, G.; Asiedu, D.K.The World Health Organization estimates that malaria still causes approximately 198 million cases annually worldwide, with 483,000 deaths, mainly in children below the age of 5 years and pregnant women. The most severe forms of the disease are caused by Plasmodium falciparum, which accounts for more than 90% of malaria cases globally. An effective malaria vaccine remains the optimal strategy for eliminating malaria. However, the use of vector control strategies such as long-lasting insecticide treated nets and inside residual spraying, combined with the use of the efficacious artemisinin combination therapy, have significantly decreased malaria transmission. Therefore, a comprehensive analysis of the impact of decreasing malaria transmission on parasite biology and disease pathogenesis is necessary to inform appropriate management of the disease, especially in children. Taking advantage of the significant differences in malaria transmission across ecological zones in Ghana as a model, we have been investigating the impact of decreasing transmission on P. falciparum biology, host immune responses, and clinical manifestations of malaria in children. The results of these investigations demonstrate that while parasite genomes are mostly similar, parasite invasion pathways vary significantly across transmission areas. In addition, patterns of clinical manifestations, immune responses and parasite tolerance change significantly with decreasing transmission intensity. Data from these investigations will be discussed, as well as research strategies for discovery of novel targets for vaccine development. In addition, progress made by the West African Centre for Cell Biology of Infectious Pathogens (WACCBIP) and its partners in training and building capacity for high quality, competitive biomedical research in Africa will be presented.Item Composotion and provenance of the upper Cretaceous to eocone sandstones in Central Palawan, Philippines: Constraints on the tectonic development of Palawan(Island Arc, 2000-12) Suzuki, S.; Takemura, S.; Yumul, G.P.; David, S.D.; Asiedu, D.K.Sandstones from the Upper Cretaceous to Eocene succession of Central Palawan are rich in quartz grains and acidic volcanic rock fragments. Potassium feldspar grains and granitic rock fragments are commonly observed. The moderate to high SiO2 and low FeO plus MgO contents of the sandstones support the proposal that clasts were derived from a continental source region. Southern China (Kwangtung and Fukien regions) is inferred to be the source area of the sandstones. The sedimentary facies of the Upper Cretaceous to Eocene succession consist of turbidite and sandstones, suggesting that they were deposited in the deep sea portions of submarine-fans and basin plains situated along a continental margin. These features indicate that the Upper Cretaceous to Eocene succession of the Central Palawan were derived and drifted from the southern margin of China. The tectonic history related to the formation of Palawan Island is also discussed.Item Crustal-scale transcurrent shearing in the Paleoproterozoic Sefwi-Sunyani-Comoé region, West Africa(Precambrian Research, 2012-08) Jessell, M.W.; Amponsah, P.O.; Baratoux, L.; Asiedu, D.K.; Loh, G.K.; Ganne, J.The Paleoproterozoic Sefwi-Sunyani-Comoé region that straddles the Ghana-Ivory Coast border in West Africa has been characterised as resulting from a combination of compression and simple shear with leucogranite intrusion either being prior to the compression or synchronous with late shearing. The analysis of regional magnetic datasets combined with field observations allows us to better define the geometry of the major lithostratigraphic packages and their structural contacts in this region. This analysis reveals a series of elongate rounded leucogranite intrusions enveloped by deformed metasediments. Recent finite element modelling of two-phase aggregates has shown that we can analyse the geometry of these systems both in terms of their finite deformation and their mechanical contrast. We interpret the geometries we see in the Sefwi-Sunyani-Comoé region as reflecting the activity of a major crustal deformation zone which was dominated by simple shear. The comparison with our modelling suggests a finite shear strain of approximately 5 gamma, which in turn implies a lateral displacement of 400. km parallel the Sefwi Greenstone Belt, which places Southern Ghana (EoGhana?) near eastern Burkina Faso prior to deformation. Our analysis also suggests that the leucogranites were already acting as more rigid bodies during the shearing, suggesting that their emplacement was predominantly pre-kinematic. © 2012 Elsevier B.V.Item Determination of rare earth elements by neutron activation analysis in altered ultramafic rocks from the Akwatia District of the Birim diamondiferous field, Ghana(Journal of Radioanalytical and Nuclear Chemistry, 2005-06) Dampare, S.B.; Asiedu, D.K.; Osae, S.; Nyarko, B.J.B.; Banoeng-Yakubo, B.Rare earth element (REE) analysis using instrumental neutron activation (INAA) was carried out on ultramafic rocks from the Akwatia District of the Birim diamondiferous field, Ghana, with the primary objective of investigating their kimberlitic characteristics. The total REE concentrations range from 113 to 1610 ppm and fall within the interval of those reported in the literature for kimberlites. Despite the marked difference in the REE contents, all the analyzed samples show similar REE patterns that resemble those of kimberlites. However, compared to most of the kimberlites, the ultramafic rocks have small negative Eu anomalies and low light-REE/heavy-REE ratios, suggesting that the rocks have been significantly assimilated by crustal rocks. © 2005 Akadémiai Kiadó.Item Dynamic interaction in tropical Africa: IGCP-616Y and IGCP 646 projects and events(2021) Kankeu, B.; Akaegbobi, I.M.; Asiedu, D.K.; Greiling, R.O.; Runge, J.; Fuanya, C.; Ganno, S.; Nzenti, J.P.; Bassahak, J.; Hell, J.V.The scientific objectives and research program of the IGCP-646 project (2015–2018) cuts across many disciplines and includes various aspects of continental basement geology, resource exploration (mineral, water and hydrocarbons), geohazard mitigation, and climate change, all of which are of critical importance to developing countries, particularly in parts of West Africa where population pressures are on the rise. Considerable emphasis was placed on capacity building, creation of opportunities for young scientists to undertake higher degrees programs, knowledge transfer and training. The SIDA-funded “pilot project” IGCP-616Y (started in 2012), focused on three objects (i) crustal architecture, tectonic evolution and regional geology of Central Africa and the connection with NE Brazil; (ii) the Mesozoic continental rifting and breakup leading to a better integration of the onshore and offshore geology; (iii) clarification and quantification of the links between basement structures, neotectonics, climate change and landscape evolution. The IGCP-616Y and IGCP-646 projects consisted of over 250 researchers, from different countries. In the course of the projects, six annual meetings, four field trips/workshops, as well as several training sessions were organized. Here we provide a summary of the scientific targets of the projects and a summary of the organized activities.Item Geochemical and Sr‐Nd isotopic records of Paleoproterozoic metavolcanics and mafic intrusive rocks from the West African Craton: Evidence for petrogenesis and tectonic setting(Geological Journal, 2018-03) Sakyi, P.A.; Anum, S.; Su, B.X.; Nude, P.M.; Su, B.C.; Asiedu, D.K.; Nyame, F.; Kwayisi, D.Metavolcanics and mafic intrusive rocks of the Paleoproterozoic Birimian terrane in the southeastern part of the West African Craton, Ghana, were analyzed for major and trace elements and Nd and Sr isotopic data to constrain the geodynamic evolution of the Birimian Supergroup. The metavolcanic rocks consist of metabasalts, meta-andesites, and amphibolites, whereas the mafic intrusions are mainly gabbros, hornblendites, and dolerites. The rocks are tholeiitic in composition and show the classic features of arc magmatism. The metavolcanics display significant enrichments in large ion lithophile elements (LILE) and light rare earth elements, relative to high field strength elements (HFSE) and heavy rare earth elements. The multielement patterns of the rocks also show positive Pb, Ba, Th, and Sr and negative Nb, Ta, and Ce anomalies that are typical characteristics of subduction-related magmas. They also have La/Nb ratios <3 and La/Ta ratios <43 that are similar to other Archean and Birimian greenstone belts in West Africa. The rocks have εNd (2.1 Ga) values of -0.96 to +2.60, and Nd model ages of 2.24-2.51 Ga (TDM1) and 2.16-2.45 Ga (TDM2), indicating their juvenile character with possible contributions from pre-Birimian crustal materials in their sources. The εNd values suggest a depleted source and further indicate that they were probably produced in an almost entirely oceanic environment with minor influence from the continental crust. The Nd isotopic results are consistent with the island arc model, which views Paleoproterozoic terranes of the West African Craton in the context of subduction-accretion processes. Accordingly, these processes may have played a role in the formation of the Columbia supercontinent during the Paleoproterozoic (2.1-1.8 Ga) orogenic events.Item Geochemical constraints on provenance and source area weathering of metasedimentary rocks from the Paleoproterozoic (~2.1 Ga) Wa-Lawra Belt, southeastern margin of the West African Craton(GEODINAMICA ACTA, 2019-09-27) Asiedu, D.K.; Agoe, M.; Amponsah, P.O.; Nude, P.M.; Anani, C.Y.The Wa-Lawra Belt which is situated in the northern part of Ghana consists of Paleoproterozoic Birimian fine metasedimentary rocks metamorphosed to greenschist facies, particularly, in the western part. A whole-rock geochemical study of these metasedimentary rocks was undertaken to unravel their source area weathering, provenance and tectonic setting. Geochemical characteristics of the studied shales show that they are immature in nature and first cycle in origin, with little or no recycled component. Compared to Post- Archaean Australian Shales (PAAS), the studied shales indicate reduction in Zr, Hf, La, Nb, Th and Ta being the high field strength elements and evidences of transition metal enrichments in V, Ni, Sc, Co, and Cr. Major element geochemistry indicates that the shales were subjected to slight potassium metasomatism after deposition. Pre-metasomatized Chemical Index of Alteration calculations indicates that weak to moderate degree of chemical weathering took place at the sediment source area. Co-Th-La-Sc systematics reveals a combination of mafic and felsic provenances for the shales. Eu/Eu* together with values of Th/U and some abundances of trace elements show that the shales were mainly derived from juvenile rocks. Average REE model calculations suggest that the source materials are composed of about 49% basalt, 16% TTG and 35% granite.Item Geochemical constraints on provenance and source area weathering of metasedimentary rocks from the Paleoproterozoic (~2.1 Ga) Wa-Lawra Belt, southeastern margin of the West African Craton(Geodinamica Acta, 2019-09-27) Asiedu, D.K.; Agoe, M.; Amponsah, P.O.; Nude, P.M.; Anani, C.Y.The Wa-Lawra Belt which is situated in the northern part of Ghana consists of Paleoproterozoic Birimian fine metasedimentary rocks metamorphosed to greenschist facies, particularly, in the western part. A whole-rock geochemical study of these metasedimentary rocks was undertaken to unravel their source area weathering, provenance and tectonic setting. Geochemical characteristics of the studied shales show that they are immature in nature and first cycle in origin, with little or no recycled component. Compared to Post- Archaean Australian Shales (PAAS), the studied shales indicate reduction in Zr, Hf, La, Nb, Th and Ta being the high field strength elements and evidences of transition metal enrichments in V, Ni, Sc, Co, and Cr. Major element geochemistry indicates that the shales were subjected to slight potassium metasomatism after deposition. Pre-metasomatized Chemical Index of Alteration calculations indicates that weak to moderate degree of chemical weathering took place at the sediment source area. Co-Th-La-Sc systematics reveals a combination of mafic and felsic provenances for the shales. Eu/Eu* together with values of Th/U and some abundances of trace elements show that the shales were mainly derived from juvenile rocks. Average REE model calculations suggest that the source materials are composed of about 49% basalt, 16% TTG and 35% granite.Item Geochemistry and provenance of Neoproterozoic metasedimentary rocks from the Togo structural unit, Southeastern Ghana(Journal of African Earth Sciences, 2019-03) Anani, C.Y.; Bonsu, S.; Kwayisi, D.; Asiedu, D.K.Neoproterozoic metasedimentary rocks of greenshist facies, consisting predominantly of quartzites, phyllites, and phyllonites, occur in the Akwapim range of the Togo Structural Unit (TSU) in Ghana. The geochemistry of the phyllites were studied to determine their provenance and tectonic setting. The major element analysis was carried out by the Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) and trace elements, including REEs, by the Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) method. The studied metasedimentary rocks have SiO2 and Al2O3 contents comparable to that of average Neoproterozoic upper crust. The metasedimentary rocks are strongly depleted in CaO, Na2O, and Sr and enriched in K2O, Ba and Rb with respect to average Neoproterozoic upper crust, reflecting K addition during diagenesis. Zr and Hf concentrations are significantly above Neoproterozoic upper crustal values. Chondrite-normalized rare earth element (REE) patterns are characterised by fractionated light-REE (LREE) (average LaN/SmN = 3.68), significant negative europium anomaly (average Eu/Eu* = 0.61) and fairly flat heavy-REE (HREE) (average GdN/YbN = 1.3). The geochemical data, particularly the high La/Sc, Th/Sc, La/Co, Th/Co, Zr/Sc, La/Th ratios, Eu/Eu* values, and high Zr and Hf concentrations, suggest that the metasedimentary rocks of the Togo Structural Units in the Akwapim range were derived mainly from recycled sedimentary sources. Comparison of geochemical signatures of the studied metasedimentary rocks with those of the Paleoproterozoic Birimian rocks suggests that the felsic materials in the Togo Structural Units (TSU) could not have been derived predominantly from the Birimian rocks, implying more distal sources. The studied metasedimentary rocks exhibit provenance characteristics similar to that of the Kwahu/Bombouaka Group of the Voltaian Basin, suggesting derivation from the same source, probably in the Amazon Craton. The metasedimentary rocks exhibit geochemical characteristics indicative of sediments derived from a passive continental margin. This inference supports previous studies that indicate that prior to the Pan-African Dahomeyide orogenic event, the southern margin of the West African Craton (WAC) was under passive margin settings.Item Geochemistry of Lower Cretaceous sediments, Inner Zone of Southwest Japan: Constraints on provenance and tectonic environment(Geochemical Journal, 2000-01) Asiedu, D.K.; Suzuki, S.; Nogami, K.; Shibata, T.A geochemical study was carried out on Lower Cretaceous sedimentary rocks of the Wakino Subgroup, Kenseki Formation, and Sasayama Group, distributed in the Inner Zone of Southwest Japan. The chemical characteristics of the Lower Cretaceous sediments indicate that these rocks are immature first-order sediments derived from igneous and/or meta-igneous rocks of predominantly felsic composition. The sediments from the Kenseki Formation and the Sasayama Group, however, show high Cr and Ni abundances, suggesting a significant contribution of detritus from ultramafic rocks. Weathering at the source areas was moderate. The high Th/U ratios (mostly >3.8), negative Eu anomalies (Eu/Eu(*) between 0.67 and 0.93) and Th/Sc ratios (mostly between 0.5 and 1) of the Lower Cretaceous sediments suggest their derivation dominantly from an old upper crust with minor amounts of young arc-derived detritus. The major, trace and rare earth element compositions imply that deposition took place in an active continental margin environment. The small amounts of young arc-derived material in the sediments support the inference by other workers that arc magmatism was not so prominent in Southwest Japan during the early Cretaceous.Item Geochemistry of Paleoproterozoic metasedimentary rocks from the Birim diamondiferous field, southern Ghana: Implications for provenance and crustal evolution at the Archean-Proterozoic boundary(Geochemical Journal, 2004-01) Asiedu, D.K.; Dampare, S.B.; Sakyi, P.A.; Banoeng-Yakubo, B.; Osae, S.; Nyarko, B.J.B.; Manu, J.Metagraywackes and metapelites from the Paleoproterozoic Birimian Supergroup in the Birim diamondiferous field, southern Ghana, were analyzed for their major and trace element contents. Compared to early Proterozoic crust, the metasedimentary rocks are enriched in ferromagnesian elements but depleted in rare earth elements (REE), high field strength elements (HFSE) (with exception of Zr), and Th. They show REE patterns similar to their Archean counterparts. The chemical data indicate that the sediments were derived from a local source of mixed felsic-mafic composition, with the latter dominating. The source rocks were the basaltic to dacitic volcanic rocks and granitoids within the Birimian greenstone belts. The chemical data further suggest their deposition in a tectonic setting comparable to modern island arcs, and that minimal old upper crust (i.e., pre-Birimian sources) was involved in their formation. The analyzed metasedimentary rocks have Eu-anomalies and GdN/YbN, Sm/Nd, Th/Sc, Cr/Sc and Cr/Th ratios that closely resemble those of their Archean counterparts, and therefore inconsistent with models suggesting abrupt compositional changes in upper crust at the Archean-Proterozoic boundary. © 2004 by The Geochemical Society of Japan.Item Geochemistry of Paleoproterozoic metavolcanic rocks from the southern Ashanti volcanic belt, Ghana: Petrogenetic and tectonic setting implications(Precambrian Research, 2008-05) Dampare, S.B.; Shibata, T.; Asiedu, D.K.; Osae, S.; Banoeng-Yakubo, B.Geochemical data are presented for Paleoproterozoic metavolcanic rocks from the southern Ashanti volcanic belt with the aim of inferring their petrogenesis and tectonic setting in which they were formed. The metavolcanic rocks, which are predominantly basalts/basaltic andesites and andesites, have high Cr and Ni contents, indicating that they have not undergone significant fractional crystallization from mantle-derived melts. Two types of basalts/basaltic andesites, Type I and Type II, were identified. The Type I basalts show flat to slightly LREE-depleted patterns with (La/Sm)N = 0.69-1.03, (La/Yb)N = 0.57-0.71 and minor negative and positive Eu anomalies (Eu/Eu* = 0.92-1.24). The Type II basalts/basaltic andesites show fractionated REE patterns with (La/Sm)N = 1.34-2.31, (La/Yb)N = 2.08-4.25 and minor positive Eu anomalies (Eu/Eu* = 1.09-1.13). The andesites also show fractionated REE patterns, (La/Sm)N = 1.97-2.78 and (La/Yb)N = 4.11-8.48 with minor positive to non-existent Eu anomalies (Eu/Eu* = 0.99-1.15). N-MORB-normalized, trace element patterns show that the Type II basalts/basaltic andesites and the andesites have geochemical patterns characterized by enrichment in LILE relative to HFSE and in LREE relative to HREE. The andesites and the Type II basalts/basaltic andesites exhibit characteristics of subduction zone-related magmas; i.e., the former displays strong Nb and Ti anomalies and relatively high Th/Nb ratios (0.69-95) whereas the latter displays strong negative Nb anomalies but relatively smaller Ti anomalies and lower Th/Nb ratios (0.35-0.37). The Type I basalts/basaltic andesites are generally moderately enriched in LILEs and depleted in HFSEs and HREEs relative to N-MORB. Like the andesites and the Type II basalts/basaltic andesites, the Type I basalts/basaltic andesites display subduction-related trace element characteristics of positive Ba and Sr anomalies together with slightly negative Nb-Ta anomalies. The low Th/Nb ratios of 0.06-0.11 coupled with their MORB-like REE patterns indicate no or negligible amount of sedimentary component in the Type I basalts/basaltic andesites. Crustal contamination may be ruled out as the cause of the negative Th and HFSE anomalies observed in the basaltic and andesitic rocks. Rather the anomalies are interpreted, on the basis of Th-Nb-La-Ce, to reflect a recycled slab-derived lithosphere component. The LREE-depleted tholeiitic Type I basalts/basaltic andesites exhibit back-arc basin geochemical signatures. The calc-alkaline andesites and the Type II basalts/basaltic andesites show intra-oceanic island arc signatures. The high Mg basaltic/andesitic rocks may, however, have evolved in a forearc setting. We, therefore, infer an intra-oceanic island arc-forearc-backarc setting for the Paleoproterozoic Birimian metavolcanic rocks from the southern Ashanti volcanic belt. REE modeling indicates that the magma from which the Type I basalts were formed was generated by about 17-30% partial melting of a depleted mantle (DMM) composed of spinel lherzolite in an extensional marginal basin. The parental magmas of the high Mg calc-alkaline basaltic/andesitic rocks were produced in the forearc by about 20-30% partial melting of the metasomatized mantle, and the Type II basalts/basaltic andesites and the andesites are related by fractional crystallization. © 2007 Elsevier B.V. All rights reserved.Item Geoscience Education in Ghana and Sustainable Development(University of Ghana, 2018-10-11) Asiedu, D.K.Geoscience is the study of the Earth. It involves the study of the materials of which the Earth is made up of, the structure of these materials, the processes acting upon them, and the organisms that have inhabited the Earth. It also includes the study of how Earth’s materials, structures, processes and organisms have changed over time. Geoscientists study the Earth to understand the history of our planet. This is very important because the better we can understand Earth’s history the better we can foresee how events and processes of the past might influence the future. Geoscience is fundamental to us as humans because it deals with Earth, the planet we live on, and its resources. Earth materials such as sand and gravel are used to make concrete to build, for example, houses and roads. Rocks are made up of aggregates of minerals and mineral products surround us in our ordinary daily life; minerals can be found in mobile phones, personal computers, cables, cars, makeup products, paints, papers, batteries, etc. Basic knowledge of Geoscience is essential to meeting the environmental challenges and natural resource limitations of the 21st century. Understanding the causes and potential societal consequences of natural Earth processes (e.g., earthquakes, floods, landslides, tsunamis, volcanic eruptions, weather, and global climate change) and the production, availability, and potential depletion of natural resources (e.g., water, soil, mineral, and energy) are of particular importance because they impact our economy, our security, and the safety and sustainability of our environment. Geoscience has an important role to play in helping to achieve the SDGs, through the efforts and contributions of Geoscience workforce which includes educators, researchers, industry professionals, students, public servants and policymakers, to ensure sustainable and equitable foundations for future global development. Their knowledge of the Earth’s structure, the materials it is made of, and the processes acting upon it can be used to inform many important areas of sustainable development such as access to clean water and safe sanitation, food security and agrogeology, disaster risk reduction, energy supply and management, improved infrastructure and access to basic services, and environmental and biodiversity management and conservation. The critical needs of the Ghanaian society include the following: (i) ensuring reliable energy supplies, (ii) providing sufficient supplies of water (ii) managing waste to maintain a healthy environment, and (iv) mitigating risk and building resilience from natural and human-made hazards. Given the importance of Geoscience in our everyday lives, it is vital to, on regular basis, inform and educate the general public on Geoscience issues that are related to the critical needs of the Ghanaian society. However, the level of Geoscience literacy in the country is very low. To address this issue there is the need to train more Earth scientists. Despite this glaring need for Geoscience literacy the science curricula of our elementary and secondary schools do not cover as many topics in Geoscience as they do in other science disciplines such as chemistry, physics or biology. Moreover, there is a shortage of teachers with an academic degree in Geoscience compared to other science disciplines. Conversely, it is critical that students understand how the Earth works as a system and how humans interact with the Earth. It is important that the study of Geoscience be made an integral component of science education in schools at all levels, from primary through to senior high school, and that highly qualified Earth science teachers provide the instruction. Earth science is an integrated science, bringing together chemistry, physics, and biology as they apply to the workings of the Earth. The applied and visual nature of Earth science helps learners to see the connections and relevance of science to their lives and their communities. Engaging students in learning about the Earth supports the development of problem solving and critical thinking skills and highlights the importance of science, technology, engineering, and mathematics (STEM) careers to society. Given the critical need for a skilled Geoscience workforce and more robust Geoscience education in Ghana, the Government of Ghana, through its relevant agencies, should promote the following: • Provide incentives for both public and private universities running science programmes in education to include a Geoscience programme. • Provide incentives for both public and private universities to introduce compulsory general education courses in the Geosciences. • Introduce Geoscience courses in the science curriculum of the colleges of education. • Review the science curricula in our primary and secondary schools to include a substantial component of Earth science. • Provide greater support for scholarships, grants, and fellowships for students majoring in Geoscience at undergraduate and graduate levels. • Actively engage the Geoscience workforce in the achievement of the SDGs. • Empower and support the Geoscience workforce, led by the Ghana Institution of Geoscientists, to undertake regular public outreach and informal geoscience education in the news media (print, electronic, TV, social media), and at geotourist centres.Item Hydrogeological Conditions of a Crystalline Aquifer: Simulation of Optimal Abstraction Rates under Scenarios of Reduced Recharge(The Scientific World Journal, 2013) Yidana, S.; Fynn, O.F.; Chegbeleh, L.P.; Nude, P.M.; Asiedu, D.K.A steady state numerical groundwater flow model has been calibrated to characterize the spatial distribution of a key hydraulic parameter in a crystalline aquifer in southwestern Ghana. This was to provide an initial basis for characterizing the hydrogeology of the terrain with a view to assisting in the large scale development of groundwater resources for various uses.The results suggest that the structural entities that control groundwater occurrence in the area are quite heterogeneous in their nature and orientation, ascribing hydraulic conductivity values in the range of 4.5 m/d to over 70m/d to the simulated aquifer. Aquifer heterogeneities, coupled possibly with topographical trends, have led to the development of five prominent groundwater flowpaths in the area. Estimated groundwater recharge at calibration ranges between 0.25% and 9.13% of the total annual rainfall and appears to hold significant promise for large-scale groundwater development to support irrigation schemes. However, themodel suggests that with reduced recharge by up to 30% of the current rates, the system can only sustain increased groundwater abstraction by up to 150% of the current abstraction rates. Prudent management of the resource will require amuch more detailed hydrogeological study that identifies all the aquifers in the basin for the assessment of sustainable basin yield.Item Improving nutrition in rural Ghana: A glimpse at the first decade of the University of Ghana Nutrition Research and Training Centre(University of Ghana, 2020-03-17) Marquis, G.; Asiedu, D.K.Large disparities in nutrition persist in Ghana -- across regions and urban-rural settings as well as by sociodemographic classifications including sex, age, education, and wealth. Over the last 10 years, the University of Ghana Nutrition Research and Training Centre (NRTC) in the Eastern Region has provided support for national and international researchers to enhance the understanding of nutrition disparities and design interventions to improve rural lives. Nutritional status is affected by many determinants that must be addressed through coordinated activities in health, education, agriculture, finance, business, among other areas. Close collaborations through participatory research methodologies with stakeholders – from community residents to district directors – enhance the potential of sustainable intervention benefits. The projects at the NRTC work with local institutions to enrich the knowledge and skills of district staff to promote their services to the community and expand residents’ ability to address the daily challenges to providing a nutritious diet and healthy environment for their families. A decade of training and research at the NRTC has demonstrated that multi-sector approaches can improve rural nutrition and well-being.Item Petrography and chemical evidence for multi-stage emplacement of western Buem volcanic rocks in the Dahomeyide orogenic belt, southeastern Ghana, West Africa(Elsevier, 2015-12) Nude, P.M.; Kwayisi, D.; Taki, N.A.; Kutu, J.M.; Anani, C.Y.; Banoeng-Yakubo, B.; Asiedu, D.K.The volcanic rocks of the Buem Structural Unit in the Dahomeyide orogenic belt of southeastern Ghana, constitute a unique assemblage among the monocyclic sedimentary formations of this structural unit. Representative volcanic rock samples were collected from the Asukawkaw, Bowiri-Odumase and Nkonya areas which form a roughly north-south trend. The volcanic rocks comprise spherulitic, amygdaloidal, vesicular, phyric and aphyric varieties. Whole rock geochemistry shows that these volcanic rocks exhibit both alkaline and subalkaline characteristics. The alkaline varieties are relatively enriched in REE and incompatible trace element concentrations, similar to OIB; the subalkaline varieties show E-MORB and N-MORB REE and incompatible element characteristics. The rocks have low La/Nb (<1), low K/Nb (<450) and high Nb/U (averagely 47.3) values, suggesting no significant effect of crustal contamination. The key characteristics of these volcanic rocks are the distinct petrography and geochemistry, shown from the three separate localities, which may suggest source fractionation at different depths or modes of emplacement. The association of volcanic rocks of OIB, E-MORB and N-MORB affinities, with no significant crustal contamination, may suggest mantle derived magma that may have been related to rifting event and eventual emplacement at the eastern passive margin of the West African Craton.Item Petrography of detrital zircons from sandstones of the LowerDevonian Accraian Formation, SE Ghana: Implications onproven ance(Geological Journal, 2019-08-22) Anani, C.Y.; Anim, R.O.; Armah, B.N.; Atichogbe, J.F.; Sakyi, P.A.; Mahu, E.; Asiedu, D.K.Integrated petrographic studies entailing quartz‐type analysis and zircon typologic studies were carried out on sandstones of the Lower Devonian Accraian Formation of southern Ghana to constrain their provenance and tectonic setting. The stratigraphic succession of the Devonian Accraian Group consists mainly of sandstones in the Lower Accraian Formation, shales in the Middle Accraian Formation, and sandstone–shale intercalations in the Upper Accraian Formation. Systematic sampling of sandstones was conducted in the Lower Devonian Accraian Formation. Modal petrographic analysis indicates that the sandstones are quartz arenites with their framework grains consisting on average of, 99.8% quartz, 0.14% lithics with little or no feldspars. They are subangular to subrounded in shape. Modal mineralogy of the sandstones suggests that they are of craton interior origin with an affinity to recycled orogenic provenance. Quartz‐type analysis was used to unravel distinct characteristic features of the quartz grain, namely its polycrystallinity, nonundulose, and undulose nature to constrain the source rock. This pointed to multiple sediment supply from both a plutonic origin and a medium‐ to high‐grade metamorphic terrain. Furthermore, a comprehensive zircon typology study on 298 zircon grains indicate multiple provenances of calc‐alkaline affinity. This study revealed that the Lower Accraian Formation sandstones probably received sediment input from the Paleoproterozoic Birimian Basin granitoids and their associated metasedimentary rocks and some additional supply from the Neoproterozoic sedimentary rocks from the Volta Basin which are inclusive of sediments derived from the Dahomeyide Belt of the Pan‐African Orogeny.Item Petrology and geochemistry of TTG and K-rich Paleoproterozoic Birimian granitoids of the West African Craton (Ghana): Petrogenesis and tectonic implications(Precambrian Research, 2019-10-14) Sakyi, P.A.; Addae, R.A.; Su, B.; Dampare, S.B.; Abitty, E.; Su, B-C.; Liu, B.; Asiedu, D.K.We conducted petrologic, geochemical and isotopic studies on Paleoproterozoic Birimian granitoids that intrude the Bole-Nangodi Belt in northern Ghana, in southeastern West African Craton (WAC), to constrain the geodynamic evolution of the Birimian Supergroup. The rocks are potassic (K)-rich granitoids (KRGs), tonalities, trondhjemites, granodiorites (TTGs), pegmatite and aplite. The K2O contents of the KRGs are up to 5 wt%, with generally high concentrations of Rb, Ba, Sr, Cr and Ni. They are highly fractionated calc-alkaline I-type granitoids, enriched in LILE and LREE relative to HREE and HFSE. Chondrite-normalized REE diagrams indicate fractionated LREE (average LaN/SmN=5.05) and HREE (GdN/YbN=4.56) patterns, with slight negative Eu anomalies (average Eu/Eu*=0.75). This may indicate an evolved magma source with varying degrees of plagioclase fractionation. The KRGs share similar geochemical characteristics with the TTGs into which they intrude. Both rock types are characterized by Ba and Th enrichment and depletion in Nb‐Ta, Zr‐Hf, and Ti, which are typical characteristics of subduction-related magmas. The pegmatite-aplite association is slightly geochemically different and may have formed at a time later than the KRGs. The ԐNd(2.1 Ga) values range from+0.90 to+1.24 and −0.86 to+1.37 respectively for the TTGs and KRGs, with TDM1 ages of 2.34–2.38 Ga and 2.36–2.53 Ga and TDM2 ages of 2.21–2.24 Ga and 2.22–2.39 Ga respectively. These indicate their juvenile character, possibly a depleted mantle source with minor contributions from a pre-Birimian (or Archean?) crustal material in their source material(s). The TTGs and KRGs are volcanic arc granites (VAG) and syn-collisional (Syn-COLG) granites, with formation temperatures and pressures of ~640–750 °C and ~2–6 kbar respectively. Based on the high temperatures, I-type signature, calc-alkaline nature and other geochemical characteristics, we infer that the TTGs, KRGs and pegmatite-aplite association developed under high oxygen fugacity conditions in an orogenic tectonic setting related to subduction. Thus, our geochemical and isotopic results are consistent with an island arc tectonic setting arising from subduction–accretion processes, which are typical for the Paleoproterozoic terranes of the WAC. These processes may have contributed to the amalgamation of the Columbia (Nuna) supercontinent during the Paleoproterozoic (2.1–1.8 Ga) orogeny.Item Probabilistic seismic hazard assessment of southern part of Ghana(Springer Netherlands, 2018-05) Ahulu, S.T.; Danuor, S.K.; Asiedu, D.K.This paper presents a seismic hazard map for the southern part of Ghana prepared using the probabilistic approach, and seismic hazard assessment results for six cities. The seismic hazard map was prepared for 10% probability of exceedance for peak ground acceleration in 50 years. The input parameters used for the computations of hazard were obtained using data from a catalogue that was compiled and homogenised to moment magnitude (Mw). The catalogue covered a period of over a century (1615–2009). The hazard assessment is based on the Poisson model for earthquake occurrence, and hence, dependent events were identified and removed from the catalogue. The following attenuation relations were adopted and used in this study—Allen (for south and eastern Australia), Silva et al. (for Central and eastern North America), Campbell and Bozorgnia (for worldwide active-shallow-crust regions) and Chiou and Youngs (for worldwide active-shallow-crust regions). Logic-tree formalism was used to account for possible uncertainties associated with the attenuation relationships. OpenQuake software package was used for the hazard calculation. The highest level of seismic hazard is found in the Accra and Tema seismic zones, with estimated peak ground acceleration close to 0.2 g. The level of the seismic hazard in the southern part of Ghana diminishes with distance away from the Accra/Tema region to a value of 0.05 g at a distance of about 140 km. © 2017, The Author(s)Item Provenance and tectonic setting of Late Proterozoic Buem sandstones of southeastern Ghana: Evidence from geochemistry and detrital modes(Journal of African Earth Sciences, 2006-01) Osae, S.; Asiedu, D.K.; Banoeng-Yakubo, B.; Koeberl, C.; Dampare, S.B.The petrography, as well as major and trace element (including rare earth element) compositions of 10 sandstone samples from the Late Proterozoic Buem Structural Unit, southeast Ghana, have been investigated to determine their provenance and tectonic setting. The petrographic analysis has revealed that the sandstones are quartz-rich and were primarily derived from granitic and metamorphic basement rocks typical of a craton interior. The major and trace element compositions are comparable to average Proterozoic cratonic sandstones but with slight enrichment in high-field strength elements (i.e., Zr, Hf, Ta, Nb) and slight depletion in ferromagnesian elements (e.g., Cr, Ni, V) with exception of Co which is unusually enriched in the sandstones. The geochemical data suggest that the Buem sandstones are dominated by mature, cratonic detritus deposited on a passive margin. Elemental ratios critical of provenance (La/Sc, Th/Sc, Cr/Th, Eu/Eu*, La/Lu) are similar to sediments derived from weathering of mostly felsic and not mafic rocks. The rather high Eu/Eu* ratios (0.69-1.09) suggest weathering from mostly a granodiorite source rather than a granite source, consistent with a source from old upper continental crust. The granitoids of the Birimian Supergroup and/or the felsic gneisses of Birimian age exposed to the east and southeast of the Buem Formation appear the most likely source rocks. These results, therefore, support earlier studies that infer passive margin setting for the eastern margin of the West African Craton prior to the Pan-African orogeny. © 2005 Elsevier Ltd. All rights reserved.