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Neoproterozoic sedimentary basins are increasingly gaining hydrocarbon exploration attention globally following results of significant discoveries in these basins as a result of long, consistent and focused research and exploration efforts. The hydrocarbon prospectivity of the unexplored Mesoproterozoic–Early Paleozoic Voltaian basin is reviewed relative to global Neoproterozoic basins. Like the Voltaian basin of Ghana, global Neoproterozoic basins have experienced similar geological event of glaciation with accompanying deposition of marginal–shallow marine carbonates and associated siliciclastic argillaceous sediments. These carbonates and argillaceous sediments coupled with deep anoxic depositional environments, favored the preservation of organic matter in these sediments and carbonates globally making them source rocks and in some cases the reservoir rocks as well, to hydrocarbon occurrence. The hydrocarbon prospectivity of the Voltaian is highly probable with Neoproterozoic basins of similar geologic analogies, Amadeus basin, Illizi basin, the Tindouf and Taoudeni basins of the WAC, having proven and active petroleum systems with some listed as world class oil/gas producing basins together with other Neoproterozoic basins like South Salt Oman basin, Barnett shales and giant gas reserves of southwestern Sichuan basin of China.

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 SiO 2 and Al2O3 contents comparable to that of average Neoproterozoic upper crust . The metasedimentary rocks are strongly depleted in CaO, Na 2O, and Sr and enriched in K2 O, 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 La N/SmN = 3.68), significant negative europium anomaly (average Eu/Eu* = 0.61) and fairly flat heavy-REE (HREE) (average Gd N/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.

Petrographic and whole rock geochemical studies were carried out on sandstones and shales of the Devonian Accraian Group of southern Ghana to constrain their provenance and tectonic setting. Modal petrographic analysis on the sandstones show that the framework grains are sub-angular to rounded in shape. Upper continental crust normalized multi-element plots, as well as trace element ratios, suggests that the sandstones and shales were mainly derived from felsic and recycled sources. Modal mineralogy of the sandstones, and major and trace element geochemistry of sandstones and shales further suggest that they are of recycled orogenic provenance. Discriminant function based major-element diagram suggests that the Accraian sandstones and shales were deposited in a Passive margin setting. Weathering indices suggest high degree of source area weathering. It is of the view that the Accraian sandstones and shales, most probably, received sediment input mostly from the Paleoproterozoic Birimian metasedimentary rocks and their associated granitoids and/or the Neoproterozoic sedimentary rocks from the Volta Basin which are both positioned northwest and north, respectively, of the Accraian sedimentary rocks.

The Paleoproterozic Birimian Supergroup consists of sedimentary basins composed predominantly of wackes and argillites, and volcanic belts composed predominantly of basaltic rocks. Whole rock geochemical and Nd-isotopic studies were carried out on fine-grained sedimentary rocks (shales and fine-grained sandstones) from one of the Birimian sedimentary basins, the Kumasi basin. The sedimentary rocks are immature in nature, with very little recycled materials. Relative to average early Proterozoic upper continental crust, the Birimian sedimentary rocks are depleted in the alkalis and alkaline earth elements and the high field strength elements, and enriched in transition metals. Chondrite-normalized rare earth element (REE) plots for both the shales and sandstones show fractionated LREE patterns (average La N /Sm N = 3.45), with slight negative Eu-anomalies (average Eu/Eu ∗ = 0.79) and a slightly fractionated HREE patterns (average Gd N /Yb N = 1.84). Low to moderate degree of chemical weathering in the sediment source area is indicated by Chemical Index of Alteration values of between 52 and 80. Elemental ratios such as La/Co, Th/Co, Th/Cr, and Eu/Eu ∗ that are critical to provenance suggests that the sediments were derived from rocks of mixed felsic and mafic compositions. Mixing calculations based on the REEs indicate that, the shale is best modeled with a mixture having 62% TTG, 16% granite and 22% basalt whereas the sandstone is almost 100% TTG. The e Nd values for the analyzed samples, calculated at the age of deposition (i.e., 2.1 Ga), range from −1.69 to 1.07, suggesting derivation from an undifferentiated source. The Nd-isotopic compositions, together with Eu/Eu ∗ and Th/U values and other trace element characteristics suggest Young Undifferentiated Arc provenance, and this is in agreement with previous studies that show that the Birmian crust is juvenile and little amount of Archean crust is present in the sedimentary rocks. The geochemical and Nd-isotopic systematics further suggest that the bulk of detritus was supplied by adjacent Paleoproterozoic Birimian greenstone belts with only 10% or less contribution from the Archean crust. Trace element characteristics further suggest that deposition took place in an island arc setting.

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

The Buem Structural Unit (BSU) of the Pan-African Dahomeyide orogenic belt, southeastern Ghana, is characterized by the occurrence of clastic and chemical sedimentary rocks, volcanic rocks and mafic-ultramafic rocks. The mafic rocks, comprising mainly gabbros occur in smaller proportion within the BSU. Representative samples of the gabbros have been analyzed petrographically and geochemically to infer their mode of emplacement, petrogenesis and tectonic setting. Two distinct gabbro types have been identified from petrography and whole-rock major and trace elements geochemistry, namely the B1 and B2 gabbros. The gabbros are generally phaneritic, holocrystalline and composed of plagioclase and clinopyronexe which have been replaced either completely or partially by sericite, chlorite and epidote. On the whole, B1 gabbros are deformed, altered, alkaline in nature, show no significant effect of crustal contamination and has affinity to OIB/E-MORB. The B2 gabbros, are relatively less deformed, subalkaline, akin to N-MORB and show arc signatures with minimal crustal contamination. The geochemical characteristics of the B1 gabbros are similar to the Buem volcanic rocks. The similarity of the B1 gabbros to the volcanic rocks may suggest a similar source and tectonic setting. Thus, the B1 gabbros may be related to rifting and emplacement at the eastern margin of the West African Craton (WAC). The effect of minimal crustal contamination and the arc nature of the B2 gabbros may suggest subduction related magmatism. Taken together, the occurrence of the gabbros may be related to rifting and subduction-collision at the eastern margin of the WAC.

The Obuom Gold Prospect is located in the central part of the Paleoproterozoic Birimian Ashanti belt of southwest Ghana. The prospect is approximately 45 km 2 and is underlain by basalt, andesite and dacite volcanic beds, graphitic and chlorite phyllites of sedimentary origin and granites. Published works on the Obuom geological terrane, using gravity models, showed that, the structures are more complex than previously thought and may involve multiple thrust slices. This research identified two deformational episodes; the first has a remarkable sinistral sense probably synchronous with an Eoeburnean event with the second, an overprint of dextral shearing during the Eburnean event. The first episode, Do 1 is characterized by NW-SE compression which resulted in subvertical NE-SW trending S 1 axial plane metamorphic foliation in tight to isoclinal F 1 folds with NW-SE trending L 1 lineations. The second episode, Do 2 indicates continuous shortening which produced nearly upright F 2 folds with east-west striking axial planes, slight plunging hinges and associated subparallel crenulation cleavages. The first deformational event Do 1 which represent NW-SE compression is observed affecting only the Sefwi Group. The Do 2 resulting from N-S compression affected both the Sefwi and Kumasi Groups.

The ‘Bongo-type’ granitoids intrude the northern portion (where it cross cuts the Tarkwaian), central and south-central portions of the Bole–Nangodi greenstone belt in Ghana. The non-foliated, porphyritic granitoids are characterised by microcline (5–18 mm), often set in a medium to fine grained matrix of quartz and plagioclase, contains granular quartz and show incipient development of mymerkites under thin section. The major mafic phases are a brownish-green variety of hornblende ± biotite, with sphene, epidote and apatite occurring as accessory minerals. The pink looking ‘Bongo-type’ granitoids are classified as granites with subordinate granodiorites and quartz monzonites. Whole-rock geochemical analyses show that the granitoids are magnesian and metaluminous to weakly peraluminous. On the basis of their Th–Co–K2O and SiO2 contents, the granitoids classified as high-K calc-alkaline and shoshonite series rocks. They show enriched LILE trends, decoupled LILE–HFSE patterns, negative Ta–Nb anomaly, pronounced negative Ti anomaly and variable positive and negative Sr anomalies. The K-rich granitoids from the middle and south-central portions of the Bole–Nangodi belt show the lowest concentrations of LILE and some HFSE with the most prominent negative Ti and Si anomalies. The ‘Bongo-type’ granitoids show I-type characteristics. Based on Ba–U–Th concentrations, they are interpreted to have had some interaction with crustal materials or some influence of subducted sediments. The granitoids unequivocally show subduction-related signatures and mimic high silica adakites (HSA). They show evidence of being emplaced in a volcanic arc geotectonic environment. Their geochemical similarities to A-type granitoids, however, suggest an arc–back-arc tectonic setting.

Major and trace elements, including rare earth elements (REEs) data are presented for metavolcanic rocks of the Paleoproterozoic Birimian Sefwi belt to determine the geochemical characteristics as well as the possible tectonic setting of emplacement of these rocks. In order to accomplish the aim of the study, the petrographical characteristics of the rocks were examined coupled with analysis of the rocks for their whole-rock major and trace elements contents by ICP-AES and ICP-MS methods respectively. The rocks have been classified as basalt/basaltic andesites and dolerites based on their textural and mineralogical compositions. It is observed that the rocks have suffered various degrees of alteration evident in the overprinting of primary minerals such as pyroxenes and plagioclase by chlorite, epidote, sericite and others. Generally, the rocks are moderately deformed and may have experienced at least greenschist metamorphism. The basalt/basaltic andesites are derivative magmas [Mg# (20–51), Cr (10–220 ppm) and Ni (5–137 ppm)], and show flat REE to fractionated REE patterns with (La/Sm) N = 1.36–3.90, (La/Yb) N = 1.17–5.32 and strong negative to non-existent Eu anomalies (Eu/Eu* = 0.51–1.03). N-MORB-normalised multi-element diagrams show that the rocks have geochemical patterns characterised by enrichment in LILE relative to HFSE and in LREE relative to HREE. The basalt/basaltic andesites exhibit characteristics of subduction zone-related magmas, such as pronounced negative Nb–Ta anomalies, slightly negative Hf and variable negative Ti anomalies. The dolerites do not vary much from the basalts and basaltic andesites. The MgO and Fe 2 O 3 values of the dolerite range from 2.97 to 6.93 and 5.98 to 14.35 wt.% respectively, corresponding to Mg#s of 38–62. LREEs enrichment over HREEs with (La/Sm) N ranging from 0.61 to 4.61 and (Gd/Yb) N ranging from 0.99 to 2.91 is also typical of these rocks. The dolerites also exhibit quite invariable Eu anomalies (Eu/Eu* = 0.81–1.00) and display a pronounced Nb–Ta trough and a minor negative Ti anomaly, suggesting arc characteristics. The metavolcanic rocks from the study area generally exhibit subduction-related setting characteristics with evidence of a sub-lithospheric contamination.

Conventional graphical techniques, mass balance geochemical modelling, and multivariate statistical methods were jointly applied to hydrogeochemical data of groundwater from the fractured rock aquifer system, and surface water in the Bosumtwi and surrounding areas to reveal evolutionary trends and the characteristics of evolving groundwater in the area. Four clusters distinguished from the Q-mode hierarchical cluster analysis (HCA) comprised three main groundwater associations and one surface water group (lake water). Although both water resources are of low mineralization (TDS Mg HCO 3 − , evolves to Ca Mg and mixed cations HCO 3 − water types at the lower reaches. The lake water on the other hand is Na HCO 3 − water type. Results from principal component analyses (PCA) and other geochemical interpretations distinguished three sources of variations in the hydrochemistry. Saturation indices of possible reactive mineral phases show groundwater undersaturation relative to albite, anorthite, aragonite, barite, calcite, chlorite, chrysotile, dolomite, gypsum, k-felspar and talc, and supersaturation with respect to gibbsite, kaolinite, Ca-montmorillonite and k-mica in the area. The PCA and other geochemical interpretation identify weathering of feldspars and carbonate mineral dissolution as predominantly influencing the hydrochemistry of the groundwater. Hydrolysis of the aluminosilicates causes the groundwater to reach equilibrium with kaolinite. In addition to dissolution of silicates, the chemical composition of the lake water has been influenced by evaporation and consequent carbonate saturation.

The depositional histories of trace metals (Pb, Cu, and Zn) in sediment cores from three Ghanaian estuaries were reconstructed using radioisotope-derived ( 210 Pb and 137 Cs) geochronologies. A core collected from each of the Amisa, Sakumo II and Volta estuaries was analyzed for trace metals and radionuclides. Lead-210 and 137 Cs dating via gamma spectroscopy, and trace metal analysis via inductively coupled plasma mass spectrometry (ICP-MS) were used in deriving sedimentation rates, geochronologies and accumulation trends of trace metals. The sedimentation rates in all three estuaries (in the range of 0.54–0.83 cm yr −1 ) were greater than the predicted sea level rise (∼0.33 cm yr −1 ) for the Accra Coast of Ghana. The 210 Pb depositional rates of 6.83 dpm cm −2 y −1 , 2.74 dpm cm −2 y −1 and 1.75 dpm cm −2 y −1 estimated for the Amisa, Sakumo II and Volta estuaries, respectively, are higher than those recorded in other latitudes. Trace metal analysis revealed differences in the concentrations of Cu, Pb and Zn between deeper and surficial layers of each core to be in the range of 10–20%, which is well within the natural variations attributed to geochemical factors. Relative to the Amisa and Volta estuaries, the temporal profiles of Al-normalized metal concentrations and estimated fluxes suggest anthropogenic processes augmented the natural fluxes of trace metals, particularly Zn into the Sakumo II estuary during the last 7 years.

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 (

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.

The original version of this article unfortunately contained a mistake in the article title.

Total sediment concentrations of Cd, Cu, Pb, Zn, As, and Hg obtained from the Ankobra, Sakumo II, and Volta estuaries in Ghana were used to generate contaminant probability density distributions and species sensitivity distributions in AQUARISK. Results of the tier 1 assessment showed Cu, Cd, Zn, and Pb were not of concern in the Ankobra as their measured values and the 99th percentile of the fitted distributions were lower than the SQG low-trigger values. Mercury (Hg) and As were however, identified to be of concern in this estuary. In the Sakumo II estuary, Cu, Cd, Pb, and Hg have been identified to be of concern because their concentrations are higher than the SQG low-trigger values. Hg has been identified as the only metal of concern in the Volta estuary. The total proportion of species likely to be affected by the combined concentration of Cd, Cu, and Zn measured from Ankobra, Sakumo II, and Volta were 14%, 16%, and 12%, respectively, according to the Bur III distributional analysis of the ecotoxicology data. The measured median sediment concentrations of As and Hg in the Ankobra estuary greatly exceeded the median sediment concentration targets to achieve a 5% or less exceedence of the SQG low value. Similarly, in the Sakumo II estuary, the measured median sediment concentrations of Cu, Pb, and Hg greatly exceeded the median sediment concentration targets to achieve a 5% or less exceedence of the SQG low. For the Volta estuary however, other metals except Hg fall below the target values.

The provenance and tectonic setting of sandstones from the Bombouaka Group of the Voltaian Supergroup, in the northeastern part of Ghana, have been constrained from their petrography and whole-rock geochemistry. Modal analysis carried out by point-counting sandstone samples indicates that they are quartz arenites. The index of compositional variability values and SiO2/Al2O3, Zr/Sc, and Th/Sc values indicates that the sediments are mature. The sandstones are depleted in CaO and Na2O. They are, however, enriched in K2O, Ba, and Rb relative to average Neoproterozoic upper crust. These characteristics reflect intense chemical weathering in the source region as proven by high weathering indices (i.e., CIA, PIA, and CIW). In comparison with average Neoproterozoic upper crust, the sandstones show depletion by transition metals and enrichment by high field strength elements. They generally show chondrite-normalized fractionated light rare-earth element (LREE) patterns (average LaN/SmN = 4.40), negative Eu anomalies (average Eu/Eu* = 0.61), and generally flat heavy rare-earth elements (HREE) (average GdN/YbN = 1.13). The sandstones have La/Sc, Th/Sc, La/Co, Th/Co, Th/Cr, and Eu/Eu* ratios similar to those of sandstones derived from felsic source. Mixing calculations using the rare-earth elements (REE) suggests 48% tonalite–trondhjemite–granodiorite and 52% granite as possible proportions for the source of the sandstones. Both the petrographic and whole-rock geochemical data point to a passive margin setting for the sandstones from the Bombouaka Group.

In Ghana the West African Craton is represented by Birimian and Tarkwaian rocks with extensive granitoid bodies. Granitoids from Asamankese area of the Kibi-Winneba volcanic belt, southern Ghana were analysed for major and trace element contents and found to be characterised by highly-fractionated REE, enrichments, in LILE, and depletion in Nb, Ta and Sr. The LILE enrichment relative to strong Nb–Ta depression, indicates that these granitoids were emplaced in an active margin. Based on field relations, geochemical composition and geochronological data, the granitoids from the Kibi-Asamankese area can be divided into three types, namely; the Eburnean biotite granodiorite (2133–2127 Ma) and hornblende granodiorite (2147 Ma), and the Pre-Eburnean gneissic biotite granite (2193 Ma). The geochemical data of the studied rocks plot in the tholeiitic field, whereas on the A/CNK–A/NK diagram, they generally fall within the metaluminous field, with A/CNK values between 0.69 and 0.88. U–Pb dating of zircons in the granitoids yielded ages ranging from 2193 to 2127 Ma, which are among the oldest ages obtained from the granitoid plutons in Ghana. Such high-precision geochronological data indicate that magmatism occurred over a time-span of about 70 Ma. This provides further evidence that the period 2.1–2.2 Ga was one of the important stages of Birimian magmatism that led to the generation of the granitoids. From the above-mentioned ages, it is possible to link the geological activities to crustal processes and establish the cyclic geotectonic evolution in the West African Craton over time as part of an arc-back-arc basin system.

A transient finite difference groundwater flow model has been calibrated for the Nasia sub-catchment of the White Volta Basin. This model has been validated through a stochastic parameter randomization process and used to evaluate the impacts of groundwater abstraction scenarios on resource sustainability in the basin. A total of 1500 equally likely model realizations of the same terrain based on 1500 equally likely combinations of the data of the key aquifer input parameters were calibrated and used for the scenario analysis. This was done to evaluate model non-uniqueness arising from uncertainties in the key aquifer parameters especially hydraulic conductivity and recharge by comparing the realizations and statistically determining the degree to which they differ from each other. Parameter standard deviations, computed from the calibrated data of the key parameters of hydraulic conductivity and recharge, were used as a yardstick for evaluating model non-uniqueness. All model realizations suggest horizontal hydraulic conductivity estimates in the range of 0.03–78.4 m/day, although over 70 % of the area has values in the range of 0.03–14 m/day. Low standard deviations of the horizontal hydraulic conductivity estimates from the 1500 solutions suggest that this range adequately reflects the properties of the material in the terrain. Lateral groundwater inflows and outflows appear to constitute significant components of the groundwater budgets in the terrain, although estimated direct vertical recharge from precipitation amounts to about 7 % of annual precipitation. High potential for groundwater development has been suggested in the simulations, corroborating earlier estimates of groundwater recharge. Simulation of groundwater abstraction scenarios suggests that the domain can sustain abstraction rates of up to 200 % of the current estimated abstraction rates of 12,960 m3/day under the current recharge rates. Decreasing groundwater recharge by 10 % over a 20-year period will not significantly alter the results of this abstraction scenario. However, increasing abstraction rates by 300 % over the period with decreasing recharge by 10 % will lead to drastic drawdowns in the hydraulic head over the entire terrain by up to 6 m and could cause reversals of flow in most parts of the terrain.

Palynofacies analyses from Bonyere Well No. 1 in the Tano basin, western Ghana has revealed five palynofacies associations (I – V) based on the percentage relative abundances of the sedimentary organic matter (SOM). The palynofacies associations reflect deposition in a fluvio-deltaic (oxic) environment, a distal dysoxic-anoxic shelf environment, a proximal dysoxic-suboxic environment, nearshore (oxic) and a fluvio-deltaic/nearshore environment with high oxygen levels and low preservation rates respectively. Based on marker palynomorphs, Campanian – Maastrichtian age has been assigned to sediments within the interval (1800-10 ft) – (90-100 ft), Turonian – Lower Senonian (Santonian) age between (3160-70 ft) – (1980-90 ft) and Aptian age between the interval (8140-50 ft) – (3340-50 ft). The absence of the elater-bearing pollen which are typical Africa-South America (ASA) elements for the Albian – Cenomanian age is indicative of an unconformity between the Aptian and Turonian sediments.

The Paleoproterozoic Sefwi-Sunyani-Comoe 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-Comoe 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.

The provenance of sandstones derived from theLower Voltaian Kwahu-Morago Group and the Middle Voltaian Oti-Pendjari Group of the Neoproterozoic Voltaian basin are discriminated by their Sm-Nd Isotopic compositions. Plots from the Sm-Nd data suggested provenance of the Kwahu-Morago Group to be from the Birimian metasediments and associated “basin type”granitoids. The Sm-Nd studies have further revealed an average TDM model age of whole rock samples in the Kwahu-Morago Group to be 2.2 Ga which shows that this portion of the Voltaian Supergroup represents eroded remnants of “basin type” granitoids. Sm-Nd data from the Oti-Pendjari Group suggested provenance from the Birimian volcanic rocks and probably with contribution from the Pan African rocks. Its average TDM model age of whole rock samples was 2.0 Ga, which generally falls in the range of the model ages for the basement Birimian volcanic rocks as well as the model ages for the granitoid rocks and thus suggests the major source rock of the Oti-Pendjari Group as coming from the volcanic belts. The model ages for both groups seem to indicate clastic supply from an early Proterozoic crustal provenance. This study shows that whole rock isotopic analyses can also be complementary in providing an insight into the origin and development of sedimentary successions.

This study demonstrates the application of multivariate statistical methods in definition of groundwater recharge and discharge areas in a sedimentary basin in Ghana. Q-mode hierarchical cluster analysis (HCA) was applied to 57 hydrochemical data from the Buem formation in the northern part of the Volta Region in Ghana. R-mode HCA and R-mode factor analysis were then applied to the same dataset to reveal the processes controlling the hydrochemistry of groundwater from this hydrogeological formation. Results of both the Q- and R-mode analyses were backed by graphical methods. The analyses revealed two major water types, differentiated by salinity levels into four spatial groundwater associations. The characteristics of the four groundwater types are discussed. The recharge areas are characterized by CaHCO3 low salinity waters which evolve through rock–water interactions to NaHCO3 high salinity waters in the discharge areas. This study finds that the hydrochemistry of groundwater from this formation is mainly controlled by the weathering of minerals, principally silicates in the aquifer matrix. The effects of the chemistry of recharging precipitation are higher in the recharge areas, while mineral weathering tends to be severe close to the discharge areas in the groundwater flow regime. All the four spatial groundwater associations have low sodium content, but salinity levels increase towards the discharge areas, such that some of wells in the discharge areas may not be acceptable for irrigation on grounds of high salinities which might affect the osmotic potentials of plants. Copyright © 2011 John Wiley & Sons, Ltd.

The hydrologic cycle plays an important role in carbon cycling, due to the coupling of vapour release and CO2 uptake during photosynthesis. This coupling, expressed as water use efficiency of transpiration ratio, can provide an inexpensive alternative for estimating the Net Primary Productivity (NPP) of terrestrial ecosystem. Stable isotopes of hydrogen and oxygen and long-term hydrologic and meteorological data together with stoichiometric relations of water and carbon are used to constrain water and carbon balances for the Volta River watershed. Soils annually respire 0.199 Pg C, and the balance of these fluxes or Net Ecosystem Productivity (NEP) is +0.029 Pg C Yr-1, implying an annual flux of CO2 to the atmosphere. Annually, the Volta river watershed receives about 380 km3 of rainfall. Approximately 50% of this volume of water is returned to the atmosphere through plant transpiration. Associated with annual transpiration flux is a carbon flux of 0.170 × 1015 g C yr-1 or 428 g C m-2 yr-1 from the terrestrial ecosystem. Modeled estimates of heterotrophic soil respiration exceed slightly the NPP estimate, implying that carbon flux to and from the Volta river watershed is close to being in balance or the watershed is a small annual source of carbon dioxide to the atmosphere. In addition to terrestrial carbon flux, the balance of photosynthesis and respiration in Volta Lake is also examined. The lake was found to release carbon dioxide to the atmosphere, although the magnitude of the flux is smaller than that of the terrestrial ecosystem. Key words: Hydrologic cycle, carbon cycling, Volta river basin, isotope mass balance relation, carbon sink

The objective of this study was to determine the main controls on the hydrochemistry of groundwater in the study area. Mass balance modeling was used simultaneously with multivariate R-mode hierarchical cluster analysis to determine the significant sources of variation in the hydrochemistry. Two water types have been revealed in this area: (1) waters influenced more significantly by the weathering of silicate minerals from the underlying geology, and are rich in silica, sodium, calcium, bicarbonate, and magnesium ions, and (2) waters that have been influenced by the effects of fertilizers and other anthropogenic activities in the area. Mineral speciation and silicate mineral stability diagrams generated from the data suggest that montmorillonite, probably derived from the incongruent dissolution of feldspars and micas, is the most stable silicate phase in the groundwater. The apparent incongruent weathering of silicate minerals in the groundwater system has led to the enrichment of sodium, calcium, magnesium and bicarbonate ions as well as silica, leading to the supersaturation of calcite, aragonite, dolomite and quartz. Stability in the montmorillonite field suggests restricted flow conditions whereby groundwater residence time is relatively high, leading to greater contact of groundwater with the rock to enhance weathering. Cation exchange processes have also been determined to play minor roles in the hydrochemistry.

Conventional graphical and statistical methods were used with water quality indices to characterize the hydrochemistry of groundwater from the northern part of the Volta region of Ghana. The objective was to determine the processes that affect the hydrochemistry and the variation of these processes in space among the three main geological terrains: the Buem formation, Voltaian System and the Togo series that underlie the area, and to determine the suitability of groundwater from the area for drinking purposes. The Q-mode cluster analysis reveals three main water groups. The groups established from the Q-mode HCA appear to indicate different degrees of weathering which could further indicate varying levels of fracturing aquifer hydraulic properties. R-mode HCA and factor analysis (using varimax rotation and Kaiser Criterion) were then applied to determine the significant sources of variation in the hydrochemistry. This study finds that groundwater hydrochemistry in the area is controlled by the weathering of silicate and carbonate minerals, as well as the chemistry of infiltrating precipitation. Mineral activity diagrams for the CaO–Na2O–Al2O3–SiO2–H2O and CaO–MgO–Al2O3–SiO2–H2O systems plotted for the area indicate stability in the smectite field and attribute hydrochemistry to the weathering of silicate minerals. Silicate mineral weathering and the effects of precipitation appear to be pervasive among all the three main geological terrains, whereas carbonate weathering is localized among the Voltaian aquifers. Cation exchange does not appear to play a significant role in the hydrochemistry but mild Water quality indices (WQI) were calculated for the samples using the concentrations of Na+, Ca2+, Mg2+, Cl−, NO3 −, F−, and EC at the various sample locations. The WQI values indicate that groundwater from the study area is of excellent quality for drinking purposes. WQI values from groundwater samples are averagely higher than samples taken from surface water sources in the area. This implies that geology has had an impact on the WQI of groundwater in the area.

Hydrochemical data are presented for groundwater samples, collected from fractured aquifers in parts of northern Ghana. The data was collected to assess the groundwater suitability for domestic and agricultural use. Results of the study reveal that the pH of the groundwater in the area is slightly acidic to slightly alkaline. The electrical conductivity values, total dissolved solids (TDS) values and calcium, magnesium and sodium concentrations in the groundwater are generally below the limit set by the WHO for potable water supply. On the basis of activity diagrams, groundwater from the fractured aquifers appears to be stable within the montmorillonite field, suggesting weathering of silicate minerals. An inverse distance weighting interpolator with a power of 2 was applied to the data points to produce prediction maps for nitrate and fluoride. The distribution maps show the presence of high nitrate concentrations (50–194 mg/l) in some of the boreholes in the western part of the study area indicating anthropogenic impact on the groundwater. Elevated fluoride level (1.5–4 mg/l), higher than the WHO allowable fluoride concentration of 1.5, is recorded in the groundwater underlying the northeastern part of the study area, more specifically Bongo and its surrounding communities of the Upper East region. Results of this study suggest that groundwater from the fractured aquifers in the area exhibit low sodicity–low salinity (S1–C1), low sodicity–medium salinity (S1–C2) characteristics [United States Salinity Laboratory (USSL) classification scheme]. All data points from this study plot within the ‘Excellent to good’ category on a Wilcox diagram. Groundwater in this area thus appears to provide irrigation water of excellent quality. The hydrochemical results indicate that, although nitrate and fluoride concentrations in some boreholes are high, the groundwater in the study area, based on the parameters analyzed, is chemically potable and suitable for domestic and agricultural purposes.

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.

To investigate the importance of factors influencing substrate availability for triacylglycerol biosynthesis on lipoprotein metabolism, the effects of two opposite-acting sulphur-substituted fatty acid analogues, tetradecylthioacetic acid and tetradecylthiopropionic acid were studied. Administration of tetradecylthioacetic acid to rats resulted in a reduction of plasma levels of triacylglycerols (44%) and cholesterol (26%). This was accompanied by a reduction in very-low-density lipoprotein (VLDL) triacylglycerols (48%), VLDL cholesterol (36%), low-density lipoprotein (LDL) cholesterol (36%) and high-density lipoprotein (HDL) triacylglycerols (50%), whereas HDL cholesterol levels did not change. Subsequently, the HDL/LDL-cholesterol ratio increased by 40%. The cholesterol-lowering effect was accompanied by a reduction in hydroxymethylglutaryl CoA (HMG-CoA) reductase activity (37%). Both mitochondrial and peroxisomal fatty acid oxidation increased (1.7-fold and 5.3-fold, respectively). Furthermore, there was a significant negative correlation between plasma triacylglycerols and mitochondrial fatty acid oxidation. Hepatic triacylglycerol synthesis was retarded, as indicated by a decrease in VLDL triacylglycerol secretion (40%), and by a reduced liver triacylglycerol content (29%). The activities of lipoprotein lipase and hepatic lipase in post-heparin plasma were not affected. Microsomal and cytosolic phosphatidate phosphohydrolase activities were inhibited (28% and 70%, respectively). Hepatic malonyl-CoA levels decreased by 29% and the total activity of acetyl-CoA carboxylase was reduced (23%). In hepatocytes treated with tetradecylthioacetic acid, mitochondrial fatty acid oxidation increased markedly (100%) and triacylglycerol secretion was reduced (40%). In tetradecylthiopropionic-acid-treated rats, a significant increase in both plasma and VLDL triacylglycerols was found (46% and 72%, respectively) but VLDL triacylglycerol secretion was unaffected. However, no effect on either plasma or lipoprotein cholesterol levels was seen. Mitochondrial fatty acid oxidation was decreased by 50% and hepatic triacylglycerol levels increased by 33%. In hepatocytes exposed to tetradecylthiopropionic acid, triacylglycerol synthesis increased (100%) while triacylglycerol secretion and fatty acid oxidation remained unaltered. The results illustrate that lipoprotein triacylglycerol levels can be modulated by changes in the availability of fatty acid substrate for triacylglycerol biosynthesis, mainly by affecting mitochondrial fatty acid oxidation. In addition, we demonstrate that suppression of rat hepatic HMG-CoA reductase activity during treatment with tetradecylthioacetic acid may contribute to a cholesterol-lowering effect.

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.

Radon gas emission from soils in parts of southeastern Ghana (Accra) have been measured to find a possible correlation of the gas emanation with faults and seismic activity in the area. LR-115 alpha track sensitive plastics were used for the detection of the gas at 47 sampling points within a 500 m × 500 m spaced grid. The obtained radon data was analyzed and superimposed on the geological and structural map to highlight the correlation between the gas emission and seismicity. In the highly faulted area, radon activity up to 115.00 kBq m −3 was measured; on the contrary in non-faulted areas radon activity was less than 20.00 kBq m −3 . In the highly faulted area radon activity above 50.00 kBq m −3 have been considered anomalous. The background level increased to 115.00 kBq m −3 before a magnitude 1.5 earthquake struck the area.

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.

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.

Tantalum, niobium, thorium and uranium contents of 21 columbite-tantalite minerals from the Akim Oda District of Ghana have been determined using epithermal instrumental neutron activation analysis (ENAA) with a conventional counting system. As thermal neutron filters, boron carbide was encapsulated in the irradiation vials during irradiation. The samples were irradiated at one of the outer irradiation channels in the Ghana Research Reactor-1 facility, and counted directly. Various elements were identified and quantified using 172 keV of 182mTa, 871 keV of 94mNb, 86.5 keV of 233 Th and 74.7 keV of 239U. The precision and accuracy of the method were evaluated using standard reference materials and the precision was found to be within 5% with comparable accuracy. The composition of columbite-tantalite minerals ranged from 33.1% to 59.2% Ta2O5 and 19.2% to 44.6% Nb2O5, ThO2 and U3O8 the levels were 0.024-0.045% and 0.014-0.048%, respectively.

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.

成羽地域に分布する下部白亜系を羽山層と命名して再定義した.本層はアルビアン期に河谷を埋めて堆積した河成層であり, 下部の礫岩が主体の枝礫岩部層と上部の泥岩が主体の空泥岩部層からなる.両者の境界は漸移的である.両部層とも流路から砂礫堆の堆積物である礫岩から氾濫原堆積物である泥岩へと上方細粒化するユニットの繰り返しからなる.古地形の解析から本層はほぼ南北に伸びる河谷を埋めて堆積していることがわかった.礫のインブリケート構造から北から南への古流向が復元される.空泥岩部層の泥岩は赤色化作用や鉄アルミナ富化作用等の強い土壌化を受けていないものの, 石灰質コンクリーションが形成されているため, 石灰集積作用を受けた程度の古土壌と考えられ, 当時乾燥した気候であったことが推定できる.本層は本来後背地にあたる山地内に, あるイベントによって堆積した地層である.その堆積をおこした要因には相対的海水準の上昇による堆積空間の増大と砕屑物の供給量の多さが関与したと推測される.

In people who do not have clinical immunity to malaria, infection with the malaria parasite could lead to severe complications. We describe a patient who had acute and severe lung injury from malaria. A 37-year-old woman had a 24-hour history of generalized weakness and chills 2 days after returning from Nigeria. She had received mefloquine as prophylaxis, but the patient did not take the medication. On admission, a thick blood smear revealed severe Plasmodium falciparum parasitemia. She was given doxycycline and quinine, but as her parasitemia resolved, dyspnea and hypoxemia developed and she consequently required placement of an endotracheal tube. Chest radiography results showed bilateral and diffuse infiltrate. This report shows that patients with P falciparum malaria should be monitored closely and transferred to an intensive care unit for additional management if respiratory distress develops. Physicians caring for patients who have recently traveled to malaria-endemic areas need to anticipate the possible development of malaria with all of its complications, including acute lung injury.

Modal analysis and phase chemistry of sandstones of the Lower Cretaceous Sasayama Group, Southwest Japan, indicate that the detritus were derived from heterogeneous sources that include medium- to high-grade metamorphic, mafic–ultramafic, and acidic magmatic rocks. Garnet geochemistry suggests their derivation from epidote-amphibolite to granulite facies metamorphic rocks. Sphene and chlorite geochemistry suggests their derivation from mafic rocks. Chemical compositions of chromian spinel indicate input from Alpine-type peridotite. The chemistry of the chromian spinel further suggests that the Alpine-type peridotite source was most probably formed under an oceanic back-arc basin setting rather than mid-oceanic ridge setting. Chemical compositions of chromian magnetite indicate that the Alpine-type peridotite provenance was subjected to metamorphism of up to the lower amphibolite facies prior to erosion and transport. The metamorphic and granitic rocks of the Hida–Oki Terrane, ophiolitic rocks of the Sangun–Renge Terrane, and rhyolitic rocks from uncertain terrane (Akiyoshi?) are most probably the major source of detritus to the Sasayama basin. The basin is most likely a strike–slip basin that formed along the eastern margin of the Asian continent.

The Wakino Subgroup is a lower stratigraphic unit of the Lower Cretaceous Kanmon Group. Previous studies on provenance of Wakino sediments have mainly concentrated on either petrography of major framework grains or bulk rock geochemistry of shales. This study addresses the provenance of the Wakino sandstones by integrating the petrographic, bulk rock geochemistry, and mineral chemistry approaches. The proportions of framework grains of the Wakino sandstones suggest derivation from either a single geologically heterogeneous source terrane or multiple source areas. Major source lithologies are granitic rocks and high-grade metamorphic rocks but notable amounts of detritus were also derived from felsic, intermediate and mafic volcanic rocks, older sedimentary rocks, and ophiolitic rocks. The heavy mineral assemblage include, in order of decreasing abundance: opaque minerals (ilmenite and magnetite with minor rutile), zircon, garnet, chromian spinel, aluminum silicate mineral (probably andalusite), rutile, epidote, tourmaline and pyroxene. Zircon morphology suggests its derivation from granitic rocks. Chemistry of chromian spinel indicates that the chromian spinel grains were derived from the ultramafic cumulate member of an ophiolite suite. Garnet and ilmenite chemistry suggests their derivation from metamorphic rocks of the epidote-amphibolite to upper amphibolite facies though other source rocks cannot be discounted entirely. Major and trace element data for the Wakino sediments suggest their derivation from igneous and/or metamorphic rocks of felsic composition. The major element compositions suggest that the type of tectonic environment was of an active continental margin. The trace element data indicate that the sediments were derived from crustal rocks with a minor contribution from mantle-derived rocks. The trace element data further suggest that recycled sedimentary rocks are not major contributors of detritus. It appears that the granitic and metamorphic rocks of the Precambrian Ryongnam Massif in South Korea were the major contributors of detritus to the Wakino basin. A minor but significant amount of detritus was derived from the basement rocks of the Akiyoshi and Sangun Terrane. The chromian spinel appears to have been derived from a missing terrane though the ultramafic rocks in the Ogcheon Belt cannot be discounted.

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.

The purpose of this research is to re-interpret the 1939 Accra Earthquake, explain the nature and cause of the recent seismicity of the Accra region, and assess the likelihood of occurrence of any major cyclic earthquake in the Accra region and southern Ghana. Combining re-interpretation of historical earthquake data of Ghana with new field data, the nature of the seismicity of the Accra region has been assessed. The results show that the 1939 Accra Earthquake was a shallow-focus tectonic event caused by high-angle submarine strike-slip faults along the eastern extension of the Romanche fracture zone 40 kilometres south of Accra. Recent seismicity in the Accra region has emanated from sources similar to those of the 1939 Accra Earthquake related to the offshore fault systems. The structural setting and mechanism of the 1939 earthquake, however, preclude the likelihood of occurrence of a major cyclic earthquake based on a regional cyclic earthquake phenomenon. The results, however, do not exclude the possibility of occurrence of any significant random earthquake striking Accra region or other parts of southern Ghana now or in the future, as there are many independent active fault systems associated with the fault systems of the region.