Department of Earth Science
Permanent URI for this collection
Browse
Recent Submissions
Item Mineral Prospectivity Modeling over Julie Tenement of Northwestern Ghana using Geophysical Datasets(Journal of Mining and Environment (JME), 2024) Amponsah, P.O.; Forson, E.D.This study was set out to delineate prospective zones of gold mineralization occurrence over the Julie tenement of Northwestern Ghana using two spatial statistical techniques, namely information value (IV) and weight of evidence (W of E) models. First, 110 locations, where gold (Au) mineralization has been observed, were identified by field survey results derived from highly anomalous geo-chemical assay datasets. Of these 110 locations, 77 (representing 70% of the known locations, where gold has been observed) were randomly selected for training the aforementioned models, and the remaining 33 (analogous to 30% of the known Au occurrence) were used for validation. Secondly, eleven mineral conditioning factors (evidential layers) comprising analytic signal, reduction-to-equator (RTE), lineament density (LD), porphyry density, potassium concentration, thorium concentration, uranium concentration, potassium-thorium ratio, uranium-thorium ratio, geology, and arsenic concentration layers were sourced from geophysical, geological, and geo-chemical datasets. Subsequently, by synthesizing these eleven evidential layers using the two spatial statistical techniques, two mineral prospectivity models were created in a geographic information system (GIS) environment. Finally, the mineral prospectivity models produced were validated using the area under the receiver operating characteristics curve (AUC). The results obtained showed that the IV model produced had a higher prediction accuracy in comparison with the mineral predictive model produced by the W of E with their AUC scores being 0.751 and 0.743, respectivelyItem Estimation of natural background and source identification of nitrate-nitrogen in groundwater in parts of the Bono, Ahafo and Bono East regions of Ghana(Groundwater for Sustainable Development, 2021) Manu, E.; Afrifa, G.Y.; Loh, Y.S.A.; et al.The identification of the chemical status of groundwater is a prerequisite for sustainable management and development of groundwater resources. A better assessment of the chemical status of the groundwater requires the knowledge and understanding of the natural background concentrations to establish threshold values of chemical pollutants in groundwater. The aim of this study is to estimate the natural background levels, the threshold value (TV) of nitrate-nitrogen (NO3) − -N) and to identify its source in the groundwater in the Bono, Ahafo and Bono East regions of Ghana. A total of 165 groundwater samples were taken from the crystalline and sedimentary aquifers in the study area. iterative outlier removal technique and a Gaussian mixture model were then used to assess the natural background and threshold nitrate-nitrogen concentrations in the groundwater. Chloride data was then used to trace the NO3 - source in the groundwater. The estimated NBL of NO3 − -N in the area ranges from [0.001–3.9] mg/L, with an expected value of 1.25 mg/L and calculated TV of 6.95 mg/L. The data suggest that NO3 − –N concentrations are homogeneous across all the lithologies underlying the study area. The results showed that agricultural, domestic, and denitrification contribute significantly to the loading of NO3 − –N concentration in the groundwater. The estimated threshold range of NO3 − –N provides the baselinenitrate-nitrogen concentration for future studies in the region. However, the results are inconclusive, and we recommend using isotopic detection. 15N-NO3 − and 18O-NO3 − ) in future studies through comprehensive and sustainable regional monitoring of the aquifer system in order to further limit the source of nitrate and nitrogen in the groundwater system.Item Mineralizations of Nb-Ta-Rb-Zr and rare-earth elements in Boziguoer, South Tianshan, NW China: Geochronology and geochemistry of monazite and bastnasite(Ore Geology Reviews, 2024) Xie, M.; Fan, H.; Sakyi, P.A.; et al.The Boziguoer alkaline intrusion is located in the South Tianshan Orogenic Belt on the northern margin of the Tarim Craton. The intrusion is entirely mineralized and forms a super-large rare metal (RM) and rare-earth element (REE) deposit dominated by Nb-Ta-Rb, accompanied by Zr-REE. The primary RM minerals include pyrochlore, astrophyllite, and zircon, while the main REE minerals consist of fluocerite, monazite, xenotime, and bastnasite, ¨ which are commonly present as granular aggregates or singularly filling the interstices between gangue minerals. Through a combination of geochronological and geochemical analyses of different types of monazite and bastn¨ asite in the mineralized alkaline rocks, this study elucidates the role of magmatic hydrothermal evolution on the Boziguoer RM-REE mineralization and reconstructs the geochronological framework of alkalic magmatic-hydrothermal evolution and mineralization processes, as well as establishing mechanisms responsible for RM-REE enrichment. Petrographic observations and back-scattered electron (BSE) imaging revealed several types of monazite and bastnasite ¨ with different characteristics as follows: (1) type Ia monazite (Mnz-Ia) experienced intense hydrothermal alteration, forming residual cores of monazite mantled by apatite and allanite coronas; (2) type Ib monazite (Mnz-Ib) was partially eroded, forming concentric zoning patterns with a core of monazite, a mantle of apatite, and an outer rim of allanite coronas; (3) type II monazite (Mnz-II) is slightly modified, and commonly associated with fluorite; (4) bastnasite ¨ and fluocerite exhibit a core rim structure, with the core of fluocerite being brighter than the rim of bastnasite ¨ in BSE images. According to the paragenetic relationships and compositional variations, all two types of monazite are of primary magmatic origin, while bastn¨ asite is of hydrothermal origin. In addition, principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) results indicate that Mnz-Ia and Mnz-Ib belong to the same group, different from Mnz-II. The latter has higher (Ce/Gd)N and (Th/U)N ratios, indicating relatively low-temperature crystallization of Mnz-II at late stages. In-situ LA-ICP-MS U-Th-Pb dating of monazite and bastn¨ asite show that Mnz-Ia and Mnz-Ib have ages of ca. 290 Ma, consistent with the zircon age of the intrusion, whereas the Mnz-II and bastnasite ¨ have younger ages of ca. 280 Ma, representing a post-magmatic hydrothermal mineralization event at Boziguoer. These new ages indicate that both magmatic and subsequent hydrothermal processes played critical roles in the RM-REE mineralization in this deposit. The latest findings also support the model that the formation of the alkaline belt where the Boziguoer ore-bearing intrusion was temporally and spatially linked to the Tarim Large Igneous Province that is genetically related to a mantle plume.Item Farmers’ maladaptation: Eroding sustainable development, rebounding and shifting vulnerability in smallholder agriculture system(Environmental Development, 2021) Asare-Nuamah, F.; Dick-Sagoe, C.; Ayivor, R.Adaptation has become crucial in developing economies due to climate change impact, especially on agriculture, which is the backbone of many economies and the main source of livelihoods and food security. Some adaptation strategies applied in the context of developing countries, however, produce maladaptive outcomes, which are usually ignored in the planning phase of adaptation policies and programmes. This mixed methods study therefore explores adaptation strategies and the associated maladaptation outcomes of smallholder farmers in rural Ghana. The study administered questionnaire survey to 378 farmers and 41 key informants were interviewed. The major adaptation strategies of farmers included crop and livelihood diversification, agrochemi cals application, and reduction in the number and size of meals. However, farmers’ adaptation strategies result in maladaptation outcomes through the release of greenhouse gases, environ mental degradation, and contamination of water bodies as well as resource conflicts and increasing pressure on lands, among others, which affect their capacity to respond to future climate change. Adaptation policy makers and development practitioners should prioritize the minimization of maladaptation outcomes through intensive review and modification of pro grammes prior to their implementation and extensive education on best practices among small holder farmers.Item Assessment of groundwater quality and the main controls on its hydrochemistry in some Voltaian and basement aquifers, northern Ghana(Groundwater for Sustainable Development, 2020) Loh, Y.S.A.; Akurugu, B.A.; Manu, E.; Aliou, A-S.Groundwater resources play the single most important role in the delivery of potable water to rural communities in northern Ghana, especially during the long dry season and where surface water sources are polluted or non existent. This study sought to assess the quality and main controls on groundwater chemistry in parts of Sawla Tuna-Kalba District in the Savannah Region of Ghana. Multivariate statistical analysis and conventional hydrochemical plots were employed in the analysis of 112 groundwater samples from the study area. Conven tional graphical methods, R-mode Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) identified dissolution of silicates and the influence of agrochemicals and domestic wastewaters as the main sources of variations in the hydrochemistry in the study area. Q-mode HCA coupled with Stiff diagrams identified Ca–HCO3 water type in recharge areas, and Mg–Ca–HCO3 water type, which evolves into a Ca–Na–K–HCO3 water type in discharge areas in the groundwater flow regime. Mineral stability diagrams indicate the groundwater is stable in kaolinite, which suggests little or no restricted groundwater flow conditions. Groundwater quality for domestic purposes was assessed using the weighted arithmetic index approach. The computed water quality indices (WQIs) from the data suggest that 94% of the sampled boreholes provide groundwater of “excellent” quality for drinking purposes, whereas 5% and 1% present water of “good” and “poor” quality respectively. Spatial interpolation of the estimated WQIs suggests the quality of the groundwater in the study area is suitable for domestic purposes. The assessment of the groundwater quality for irrigation purposes suggests the water is of “excellent” to “permissible” quality and may be used for irrigation without prior treatment.Item Chemical Reactivity and Alteration of Pyrite Mineral in the Kubi Gold Concession in Ghana(Mining, Metallurgy & Exploration, 2024) Nzulu, G.K.; Högberg, H.; Nude, P.M.; et al.Pyrite is the most common among the group of sulfide minerals on Earth and abundant in most geological settings. This gangue mineral, in association with garnet, hematite, magnetite, and other sulfide minerals, acts as an indicator mineral in the Kubi concession of the Asante Gold corporation in Ghana. X-ray difraction (XRD), air annealing in a furnace, energy-dispersive x-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were applied to investigate the crystal structure, identify individual elements, permanence, transformation, and chemical/electronic properties of such pyrite. The study aims to identify individual elements and gain an understanding of the surface reaction mechanisms, as well as the properties of precipitated pyrite particles observed during the hydrothermal formation of the ore deposit. XRD shows that pristine and annealed samples contain some hematite and quartz, besides pyrite. Results from air annealing indicate that the relationship between pyrite and hematite-magnetite is controlled by temperature. EDX reveals that the sample has O and C as contaminants, while XPS in addition reveals Ba, Au, P, Al, and N. These elements are attributed to pyrite, that bonds metallically or covalently to neighboring ligands/impurity minerals such as oxides and chalcogenide sulfides, as well as the gangue alteration minerals of magnetite and hematite in the pyrite sample. These findings suggest that during the hydrothermal fow regime, pyrite, pathfinder elements, and impurity minerals and metals were in contact with quartz minerals before undergoing hematite transformation, which thus becomes an indicator mineral in the Kubi gold concession.Item Automated mapping of regolith units with support vector machine and artificial neural network using data from Landsat-8 OLI, ALOS PALSAR DEM, and Sentinel-1A radar images: the case of the Sissingué Gold Project, Northern Côte d’Ivoire(International Journal of remote sensing, 2023) Diaby, H. A.; Kouamé, F.; Saley, B.; Ansah, K. O.The Sissingué Gold Project is in Northern Côte d’Ivoire and part of the southern extension, a large peneplain of the landscape in South Mali. The area has experienced extensive weathering and erosion over a long time, resulting in a widespread and complex regolith cover. This diverse and vast regolith cover poses con siderable difficulties for exploration. To overcome this problem, we adopted mapping of regolith units using machine learning (ML) with support vector machine (SVM) and artificial neural network (ANN) algorithms. The main objectives were to (1) make the predictive regolith map of the study region using these algorithms with data obtained from Landsat-8 operational land imager, Advanced Land Observing Satellite Phased Array Type L-Band Synthetic Aperture Radar digital elevation model and Sentinel-1A; (2) show the method of pre-processing and processing the required data and (3) develop the regolith land form unit (RLU) map from the predictive regolith map and col lected data based on the Relict – Erosional – Depositional model. Tests using the SVM and ANN algorithms showed that both ML tools could accurately map regolith landforms. An innovative method of optimizing data using parameters is presented. The results showed that ANN outperformed SVM with an overall accuracy of 87.01% and a kappa coefficient of 0.84, whereas the corresponding values for SVM were 86.69% and 0.84, respec tively. However, the validation data obtained from SVM-based prediction exhibited a better score than that of validation data obtained from ANN-based prediction. The Sentinel-1A radar band combined with Landsat-8 data reduced the vegetation-masking effect and improved the classification results. The RLUs of this area are composed primarily of relicts at 24.91%, including lateri tic residuum and soil, depositional material at 36.39% with exotic sediments and ferrierite and the remaining 38.7% of erosional material made of saprolite, colluvial fragments, and mottled zones on flanks.Item The search for plausible economic mineral deposits in the central parts of Tanzania; insight from stream sediment geochemistry, multivariate statistics and geostatistics(Heliyon, 2023) Nunoo, S.; Mvile, B.N.; Abu, M.; Kelimenze, D.Exploration success relies heavily on the data obtained, but, significantly on the type of analytical methods deployed and the interpretation reached. A poorly analyzed data may obscure the true reflectivity of the data, and thus, compromised the decision made. A combined data processing approach of descriptive statistics, enrichment-depletion data normalization, geospatial elemental distribution, and stacked overlayed comparison of elements have been used in this study. The prime purpose was to demonstrate potential elemental anomalies, and predict areas of higher degree of confidence for subsequent exploration and mineral resource evaluation. One-hundred and sixty-six stream sediment samples from the Dodoma Region of the Tanzania Craton have been examined; to reveal potential elements or mineral commodity that warrant further explo ration. Forty-three elements of target were examined, as this craton is globally known for its rich earth mineral commodity. Our result indicates an enrichment of transition metals (TMs) (Cu, Ni, Co, Cr, Mn and Zn), High Field Strength Elements (Y, Th, U, Zr, Nb, Hf, Ta and Pb), Large Ion Lithophile Elements (Ba and Rb) and Rare-Earth Elements (La and Ce), Platinum Group Element (Pd and Pt) and other metals (Au, As, Bi, W, Mo and Li). Obtained results point to a likely poly-metallic sources and processes; as the underlain geology is marked largely by pegmatite and migmatites, and moderate proportion of fine clastic sedi mentary rocks, and minor volcanic rocks mostly to the northern domain. Theoretically, the Large Ion Lithophile Elements (LILEs), Rare-Earth Elements (REEs) and Platinum Group Elements (PGEs) are associated with felsic rocks or variable stages of plutonic granitization. Although, the TMs are often associated with mafic-ultramafic rocks, the linkage of such metals with organic-rich shales been reported elsewhere. These rocks may equally contribute to the occurrence of other metals as stated in this paper. Its intriguing to note a strong positive correlation of Li with TMs, possibility of Li control by mafic minerals in pegmatite bodies. This work proposes a polymetallic enrichment controlled by the area geology. To suggest an alluvial mining potential of the above elements in the area, resource evaluation is a requirement. The geospatial maps reveal areas worth focusing for subsequent exploration. The adopted geostatistical methods and other approach utilized in this research are effective, indicative of handling bulk exploration data for decision and subsequent exploration.Item Cryogenian-Ediacaran Crustal Growth And Evolution Of The Active Margin Of The Dahomeyide Belt, Ghana(Geological Magazine, 2023) Kwayisi, D.; Nyavor, E.; Dzikunoo, E.A.; et al.The study presents detailed petrographical, geophysical, structural and geochemical data of the internal nappes zone to establish the deformational history, origin and tectonic setting and constrain the crustal growth and evolution of the active margin of the Dahomeyide belt. Two main lithological units, (i) deformed meta-granitoids (migmatites and gneisses) and (ii) undeformed granitoids dominate the internal nappe zone. Granitoids are generally I-type, metaluminous to weakly peraluminous, low-K tholeiite to high-K calc-alkaline and of tonalite, granodiorite, and granite affinity. The overall trace element patterns of the studied granitoids characterized by the enriched LILE and depleted HFS, with negative peaks of Nb-Ta, Sr, P, and Ti are indications of arc-related magmatism. Structural analysis reveals four deformation phases (D1-D4). D1 represents Northwest-Southeast (NW-SE) Pan African shortening associated with a continent-continent collision, resulting in westward nappe stacking. Progressive NW-SE shortening resulted in D2 and D3 top-to-the-NW dextral and sinistral thrusting events during the Pan-African orogeny. D4 is an extensional event likely associated with the orogenic collapse phase. The gneisses and migmatites, with dominant axial planar foliations point to their formation in a collisional setting or influence by the Pan-African collisional processes. Continental-arc signatures in these rocks imply continental subduction during their protolith formation. The intrusive granitoid and pegmatite are undeformed. meaning late- to post-orogenic emplacement. These findings suggest that the internal nappes zone archived the subduction-collision and post-collisional phase of the Pan-African orogeny and recorded large-scale migmatization and granitoid emplacement due to partial melting of thickened lower crust between the mid-Cryogenian and late Ediacaran.Item The geology and geochemistry of the Rhyacian Josephine gold deposit, Northwest Ghana(Applied Earth Science, 2023) Atanga, F.; Amponsah, P.O.; Nunoo, S.; et al.his paper focuses on the geology and geochemistry of the Rhyacian Josephine gold deposit in northwestern Ghana, where gold is primarily hosted in quartzites, with other lithologies observed, including granitoids, mafic intrusions, and gneisses. Four deformational events, DJO0, DJO1, DJO2, and DJO3, are observed. DJO0 is synonymous with the primary preserved sedimentary crossbedding in the quarzitic rocks. Gold mineralization within the deposit is mainly associated with the DJO1 NNW-trending dextral and steeply dipping sinusoidal shear zone. Gold occurs primarily as free gold and invisible gold within the lattices of the disseminated arsenopyrite along the shear foliation planes of the host rock. The ore body geometry is 15–40 m wide and strikes 800 m in the NNW direction. Silicification, sericitization, chloritization, and sulphidation are the main alteration assemblages associated with the gold mineralization zones within the Josephine deposit. Pathfinder elements for gold are stibnite, tellurium, sulphur, copper, silver, and LeadItem Pathfnder elements and indicator minerals of Au from the Kubi Gold ore deposits in Ghana(Environmental Earth Sciences, 2023) Nzulu, G.K.; Högberg, H.; Eklund, P.; Hultman, L.; Nude, P.M.; Yaya, A.; Magnuson, M.The Au mineralization in the Kubi Gold Mining Area in the Birimian of Ghana is associated with garnet (about 85 vol.%), magnetite, pyrrhotite, arsenopyrite, and sulfde minerals, as well as quartz with gold and calcite. These minerals and the included elements can act as indicator minerals or pathfnder elements. For the present work, we collected samples from drill holes at diferent depths, from the alluvial zone (0–45 m) to the ore zone (75–100 m). The distributions of minerals and elements in the rocks that act as indicator minerals and pathfnder elements in the concession area were investigated along the drill hole cross sections. X-ray difraction shows that the samples contain garnet, pyrite, periclase, and quartz as the main indicator minerals. By energy-dispersive X-ray spectroscopy, Fe, Mg, Al, S, O, Mn, Na, Cu, Si, and K are identifed as corresponding pathfnder elements. The results indicate that the Au mineralization in the Kubi Mine area correlates mostly with the occurrence of garnet, pyrite, goethite, and kaolinite in the host rocks, which show towards the surface increasingly hematitic and limonitic alteration in form of Fe(oxy-)hydroxides.Item Geospatial modelling of mineral potential zones using data-driven based weighting factor and statistical index techniques(Journal of African Earth Sciences, 2023) Amponsah, P.O.; Amponsah, P.O.Mineral prospectivity models (MPMs) are significantly essential in delineating target zones with the optimum likelihood of containing a particular sought-after mineral deposit. This present study carried out mineral po tential mapping over the Collette Prospecting Licence (PL) Area of north-western Ghana using bivariate data driven spatial statistical models composed of statistical index (SI) and weighting factor (WF) approaches. In the first instance, the geographic coordinates of variously known locations of artisanal mining operations as well as high Au concentration locations were mapped during a field survey. As a result, 181 known locations of Au occurrences were identified, out of which 127 (70%) were selected randomly for training and creating the mineral prospectivity models, whereas the remaining 54 (30%) were used to assess and validate the accuracy of the predictive models produced. The efficacy of mineral prospectivity models generated enormously depends on the appropriate selection of mineral-related factors. In this study, the following mineral-related condition factors (evidential layers) comprising analytic signal, lineament density, uranium-thorium ratio, uranium, potassium thorium ratio, potassium, reduction-to-equator, and geology were used. The aforementioned evidential layers were derived and sourced from geophysical and geological datasets, which were later prepared for the generation of the models in a geographic information systems (GIS) environment. Finally, the validation of the mineral prospectivity models generated was carried out by applying the receiver operating characteristics (ROC) curve. The estimated results based on the ROC plots obtained for the predictive models showed that the area under the ROC curve (AUC) scores obtained for the SI-based and WF-based mineral prospectivity models were respectively, 0.780 and 0.733. Hence, it can be concluded that both mineral predictive models created in this study produced reasonably good accuracy (AUC score greater than 0.7) in predicting the potential zones of gold mineralisation occurrences within the Collette PL Area of north-western Ghana. These MPMs can serve as essential models for mineral exploration programmes within the study area.Item Compositional characteristics of mineralised and unmineralised gneisses and schist around the Abansuoso area, southwestern Ghana(Applied Earth Science, 2023) Kazapoe, R.W.; Okunlola, O.; Arhin, E.; Olisa, O.; Kwayisi, D.; Dzikunoo, E.A.; Amuah, E.E.Y.Gold-bearing granitoid deposits have recently been discovered in the Birimian of Ghana but their mode of formation and ore genesis remain enigmatic. This study presents petrographic, and geochemical characteristics of mineralised and unmineralised (gold grade >0.05 and <0.05 g/t respectively) granitoids (now gneisses) and schists (metasedimentary) to evaluate their petrogenesis/provenance, and relationship to gold mineralisation in the Abansuoso area. The unmineralised rocks comprise biotite- and hornblende-biotite gneisses, sericite-quartz, carbonate-sericite, and biotite-quartz schist. The mineralised varieties are biotite-, muscovite gneiss, iron-carbonate-sericite, carbonate-sericite-quartz, chlorite carbonate, and biotite-carbonate schist. The mineralised and unmineralised gneisses are both metaluminous and peraluminous. Both mineralised and unmineraised gneiss and schist show Nb-Ta trough, depleted LILE and enriched HFSE although widespread overall trace element concentrations for the mineralised rocks on UCC-normalised multi-element diagram, suggestive of their formation in an arc setting. This suggests coeval granitic plutonism and sedimentation with subduction-accretion during the Eburnean orogeny, hence, mineralisation may be orogenic-type.Item Spatial heterogeneity in drinking water sources in the Greater Accra Metropolitan Area (GAMA), Ghana(Population and Environment, 2022) Tetteh, J.D.; Templeton, M.R.; Cavanaugh, A.; Owusu, G.; Yidana, S.M.; et al.Abstract Universal access to safe drinking water is essential to population health and wellbeing, as recognized in the Sustainable Development Goals (SDG). To develop targeted policies which improve urban access to improved water and ensure equity, there is the need to understand the spatial heterogeneity in drinking water sources and the factors underlying these patterns. Using the Shannon Entropy Index and the Index of Concentration at the Extremes at the enumeration area level, we analyzed census data to examine the spatial heterogeneity in drinking water sources and neighborhood income in the Greater Accra Metropolitan Area (GAMA), the largest urban agglomeration in Ghana. GAMA has been a laboratory for studying urban growth, economic security, and other concomitant socio-environmental and demographic issues in the recent past. The current study adds to this literature by telling a different story about the spatial heterogeneity of GAMA’s water landscape at the enumeration area level. The findings of the study reveal considerable geographical heterogeneity and inequality in drinking water sources not evidenced in previous studies. We conclude that heterogeneity is neither good nor bad in GAMA judging by the dominance of both piped water sources and sachet water (machine-sealed 500-ml plastic bag of drinking water). The lessons from this study can be used to inform the planning of appropriate localized solutions targeted at providing piped water sources in neighborhoods lacking these services and to monitor progress in achieving universal access to improved drinking water as recognized in the SDG 6 and improving population health and well-being.Item Impact of artisanal small-scale (gold and diamond) mining activities on the Offin, Oda and Pra rivers in Southern Ghana, West Africa: A scientific response to public concern(Heliyon, 2022) Nunoo, S.; Manu, J.; Owusu-Akyaw, F.K.B.; Nyame, F.K.The surface water systems of Ghana serve as a major source of drinking water, besides other multi-purpose benefit of hydro-electrical power generation and transportation. Thus, the dependence and benefits from such resources are of national interest. For instance, the Pra river of the South-Western surface water system of Ghana was a major consideration for a projected 5 billion m3 water demand in the year 2020 and “African Water Vision 2025”. In recent times, the colour state of the Pra river and similar surface water bodies of the Offin and Oda rivers has attracted intense public discussion. The prime issue relates to incessant illegal artisanal gold/diamond mining on or along these rivers. In order to assess the state of these rivers, water samples were taken, and analysed at the Council of Scientific and Industrial Research Laboratory (CSIR, Accra-Ghana) to investigate their physicochemical quality. The research objective was to assess the extent of their water pollution by measuring physico-chemical parameters of turbidity, colour, pH and content of selected metals. A total of 18 preserved bottled samples [(5 from Offin river and 2 boreholes), 5 from Oda river and 5 from Pra river and 1 borehole)] were analysed, and results compared with portable water standards as defined by the WHO and CSIR (GS-175-1) of Ghana. Results on turbidity, colour, mercury and iron from the river and water samples generally exceed WHO or GS 175-1 limit. The Pra river recorded the most alarming result; range for turbidity (2,010 to 2,745 NTU), colour (3,000 to 4,500 Hz), total suspended solutes (2,240 to 2,570 mg/L) and total dissolved solutes (97.80–99.60 mg/ L, excluding 319.00 to 25,440 mg/L). The Oda river shows lowest parameter values among the three rivers, as the areas have been dormant from illegal gold mining for 5 years. Current data suggests polluted river bodies and boreholes, and that none of these water resources meets the portable water consumption criteria unless treated prior to usage. As the current state of the water bodies may incur higher cost of water treatment or purification, an integrated water governance under Ghana's Ministry of Water Resource, Work and Housing, and the Minerals Commission and Environmental Protection Agency are recommended for the management of these valuable water resources.Item Syn-mineralization hydrous fluid activity in giant Jinchuan magmatic Ni-Cu sulfide deposit in North China Craton(LITHOS, 2023) Yuan, Q-H.; Su, B-X.; Cui, M-M.; Sakyi, P.A.; Jing, J-J.Giant magmatic Ni-Cu sulfide deposits in the world are hosted mainly in pristine gabbro-dolerite sills (e.g., the first largest in the Noril'sk region) and norite bodies (e.g., the second largest in Sudbury, Duluth, and Voisey's Bay), implying the petrogenic relationship between the giant deposits and anhydrous parental magmas. In contrast, the third largest Jinchuan deposit is hosted in dunite- and lherzolite-dominated peridotite bodies and characterized by the presence of hydrous minerals (e.g., hornblende and phlogopite) and intensive serpentini zation of olivine. The role of water in the formation of the magmatic Ni-Cu sulfide deposit remains unclear. To reveal the potential linkage between sulfide mineralization and ‘water’ (i.e., hydrous minerals), a detailed petrographic investigation of the Jinchuan deposit and the associated mineral chemistry analyses have been conducted in this study. The distribution of serpentinization of olivine in the Jinchuan deposit is unevenly, being more pervasive in the sulfide-bearing rocks compared to sulfide-free rocks. The degree of serpentinization de creases systematically in general sequence outwardly from the core net-textured dunite to the outer disseminated lherzolite at orebody-scale. In the sulfide-bearing rocks, the serpentinization is more intensively observed in the sulfide-rich portions compared to the sulfide-poor portions at thin section-scale. We consider sulfide content dependent serpentinization as ‘selective alteration’, which is distinct from post-magmatic modifications and should have occurred coevally with sulfide liquid emplacement and sulfide crystallization. The selective alter ation with dependence on sulfide contents is caused by hydrous fluids released from sulfide crystallization, because the crystallized sulfides cannot structurally accommodate hydrous components which previous latching onto the sulfide liquid. The olivine grains in sulfide-bearing rocks are reversely zoned with respect to Ni (Ni-poor cores, Ni-rich rims) and Co (Co-rich cores, Co-poor rims) which can be interpreted by stages of sulfide liquid olivine Ni-Co exchange and Fe-Ni exchange. Comparison of intra-grain elemental distributions of olivine grains shows that hydrous fluid activity enhanced elemental exchange between olivine and sulfide liquid. Interestingly, the presence of hydrous minerals, protects olivine from selective alteration, suggesting that the hydrous minerals were formed during syn-mineralization fluid activity. These features are linkage between the inferred fluids compounded with sulfide droplets in previous experiments and their transfer and fate in natural magmatic sulfide deposits. The selective alteration proposed here, formed during the syn-mineralization stage and indicate that the fluid activity is instrumental in the formation of magmatic sulfide ores. The selective alteration may be a common characteristic in ultramafic rock-hosted magmatic sulfide deposits and a pathfinder for mineral exploration.Item Amphibole as a witness of chromitite formation and fluid metasomatism in ophiolites(2022) Pan, Q.; Xiao, Y.; Su, B.; Liu, X.; Robinson, P.T.; Uysal, I.Here we present new occurrences of amphibole in a suite of chromitites, dunites, and harzburgites from the mantle sequence of the Lycian ophiolite in the Tauride Belt, southwest Turkey. The amphibole occurs both as interstitial grains among the major constituent minerals and as inclusions in chromite grains. The interstitial amphibole shows generally decreasing trends in Na2O and Al2O3 contents from the chromitites (0.14–1.54 wt% and 0.04–6.67 wt%, respectively) and the dunites (0.09–2.37 wt%; 0.12–11.9 wt%) to the host harzburgites (<0.61 wt%; 0.02–5.41 wt%). Amphibole inclusions in chromite of the amphibole-bearing harzburgites are poorer in Al2O3 (1.12–8.86 wt%), CaO (8.47–13.2 wt%), and Na2O (b.d.l.–1.38 wt%) than their counterparts in the amphibole-bearing chromitites (Al2O3 = 6.13–10.0 wt%; CaO = 12.1–12.9 wt%; Na2O = 1.11–1.91 wt%). Estimated crystallization temperatures for the interstitial amphibole grains and amphibole inclusions range from 706 to 974 °C, with the higher values in the latter. A comparison of amphibole inclusions in chromite with interstitial grains provides direct evidence for the involvement of water in chromitite formation and the presence of hydrous melt/fluid metasomatism in the peridotites during initial subduction of Neo-Tethyan oceanic lithosphere. The hydrous melts/fluids were released from the chromitites after being collected on chromite surfaces during crystallization. Different fluid/wall rock ratios are thought to have controlled the crystallization and composition of the Lycian amphibole and the extent of modification of the chromite and pyroxene grains in the peridotites. Considering the wide distribution of podiform chromitites in this ophiolite, the link between chromitite formation and melt/fluid metasomatism defined in our study may be applicable to other ophiolites worldwide.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 REE mineralization related to carbonatites and alkaline magmatism in the northern Tarim basin, NW China: implications for a possible Permian large igneous province(Springer, 2021) Xie, M.; Xiao, W.; Su, B.; Sakyi, P.A.; Ao, S.; Zhang, J.; Song, D.; Zhang, Z.; Li, Z.; Han, C.Permian magmatism occurred widely in the Tarim basin and adjacent areas of NW China, resulting in the emplacement of numerous carbonatite plutons and alkaline rock intrusions, which are likely to have been derived from mantle sources. In addition, at least one large igneous province (LIP) can be recognized in NW China; namely, the ca. 270–290 Ma Tarim LIP, and it can be inferred that the peak age of magma activity is~280 Ma. Therefore, the mantle plume is limited spatially within southern Tianshan and the Tarim Basin and temporally in the Early Permian. Age and feld evidence suggest a spatial and temporal relationship between the carbonatites and alkaline rocks within the Tarim LIP, and their genesis is related to the Tarim mantle plume. In this paper, we direct our attention to the mineral assemblages that are related to carbonatites and alkaline rocks which host REE deposits (Wajilitag, Boziguoer) in the northern Tarim Craton. Alkaline rocks typically are related to rifts and/or extensional tectonics, and we suggest that these magmatic and metallogenic events occurred during an extensional regime, possibly related to the Tarim mantle plume event that affected much of South Tianshan during the Permian.Item Corrigendum to “West Africa in Rodinia: High quality paleomagnetic pole from the ~860 Ma Manso dyke swarm (Ghana)” [Gondwana Res. 94 (2021) 28–43](Elsevier, 2021) Antonio, P.Y.J; Baratoux, L.; Trindade, R.I.F.; Rousse, S.; Ayite, A.; Lana, C.; Macouin, M.; Adu, E.W.K.; Sanchez, C.; Silva, M.A.L.; Firmin, A.; Dopico, C.I.M.; Proietti, A.; Amponsah, P.O.; Sakyi, P.A.