ghanaopendata/ghanaian-research-english huggingface dataset:
Petrography and chemical evidence for multi-stage emplacement of western Buem volcanic rocks in the Dahomeyide orogenic belt, southeastern Ghana, West Africa

The volcanic rocks of the Buem Structural Unit in the Dahomeyide orogenic belt of southeastern Ghana, constitute a unique assemblage among the monocyclic sedimentary formations of this structural unit. Representative volcanic rock samples were collected from the Asukawkaw, Bowiri-Odumase and Nkonya areas which form a roughly north-south trend. The volcanic rocks comprise spherulitic, amygdaloidal, vesicular, phyric and aphyric varieties. Whole rock geochemistry shows that these volcanic rocks exhibit both alkaline and subalkaline characteristics. The alkaline varieties are relatively enriched in REE and incompatible trace element concentrations, similar to OIB; the subalkaline varieties show E-MORB and N-MORB REE and incompatible element characteristics. The rocks have low La/Nb (<1), low K/Nb (<450) and high Nb/U (averagely 47.3) values, suggesting no significant effect of crustal contamination. The key characteristics of these volcanic rocks are the distinct petrography and geochemistry, shown from the three separate localities, which may suggest source fractionation at different depths or modes of emplacement. The association of volcanic rocks of OIB, E-MORB and N-MORB affinities, with no significant crustal contamination, may suggest mantle derived magma that may have been related to rifting event and eventual emplacement at the eastern passive margin of the West African Craton.

Source: UG
Petrography and geochemistry of intraclastic manganese-carbonates from the ∼2.2 Ga Nsuta deposit of Ghana: Significance for manganese sedimentation in the Palaeoproterozoic of West Africa

Intraclastic Mn carbonate rocks occur in the marginal areas of the manganese-carbonate orebody (manganesestone) of the Palaeoproterozoic Nsuta deposit in the Birimian of Ghana. Macroscopically the intraclastic rocks display graded bedding and are typified by a matrix-supported fabric with subangular to subrounded particles less than a millimetre to ∼1.5 × 0.5 cm. Both clasts and matrix consist mainly of varying proportions of microcrystalline and microconcretionary carbonates, quartz, muscovite and subordinate pyrite. Within individual intraclasts, carbonate minerals (including distinctly zoned microconcretions) are essentially Mg kutnahorite and Mg-Ca rhodochrosite, similar to the carbonate minerals in the manganesestone. Whole rock chemistry of the intraclastic carbonates shows significant variability in the amounts of SiO2, Al2O3, MnO, MgO, CaO, Na2O and, to a lesser extent, K2O. Major element contents of the manganesestone similarly vary widely, except that these have, in particular, comparably higher MnO but less SiO2 and Al2O3 than the intraclastic carbonates and host rock Mn phyllite. Rare earth element (REE) concentrations in the intraclastic carbonates are approximately an order of magnitude higher than in the manganesestone. Whereas both rocks exhibit positive Eu anomalies, only the manganesestone shows a discernibly negative Ce anomaly. Petrographic and geochemical features suggest that the intraclasts are fragments of reworked Mn carbonate sediments derived from intraformational erosion and subsequent (mass flow) deposition as carbonate "turbidite" mud. Processes such as submarine slumping, sliding and other sediment gravity flows may have likely interrupted Mn sedimentation and transported partially consolidated manganiferous sediments down slopes into the early Birimian ocean. © 2007 Elsevier Ltd. All rights reserved.

Source: UG
Petrography of detrital zircons from sandstones of the LowerDevonian Accraian Formation, SE Ghana: Implications onproven ance

Integrated petrographic studies entailing quartz‐type analysis and zircon typologic studies were carried out on sandstones of the Lower Devonian Accraian Formation of southern Ghana to constrain their provenance and tectonic setting. The stratigraphic succession of the Devonian Accraian Group consists mainly of sandstones in the Lower Accraian Formation, shales in the Middle Accraian Formation, and sandstone–shale intercalations in the Upper Accraian Formation. Systematic sampling of sandstones was conducted in the Lower Devonian Accraian Formation. Modal petrographic analysis indicates that the sandstones are quartz arenites with their framework grains consisting on average of, 99.8% quartz, 0.14% lithics with little or no feldspars. They are subangular to subrounded in shape. Modal mineralogy of the sandstones suggests that they are of craton interior origin with an affinity to recycled orogenic provenance. Quartz‐type analysis was used to unravel distinct characteristic features of the quartz grain, namely its polycrystallinity, nonundulose, and undulose nature to constrain the source rock. This pointed to multiple sediment supply from both a plutonic origin and a medium‐ to high‐grade metamorphic terrain. Furthermore, a comprehensive zircon typology study on 298 zircon grains indicate multiple provenances of calc‐alkaline affinity. This study revealed that the Lower Accraian Formation sandstones probably received sediment input from the Paleoproterozoic Birimian Basin granitoids and their associated metasedimentary rocks and some additional supply from the Neoproterozoic sedimentary rocks from the Volta Basin which are inclusive of sediments derived from the Dahomeyide Belt of the Pan‐African Orogeny.

Source: UG
Petrological, geochemical and geochronological constraints on the origin of the Xiadong Ural-Alaskan type complex in NW China and tectonic implication for the evolution of southern Central Asian Orogenic Belt

The Xiadong mafic–ultramafic complex is located in the Central Tianshan Terrane, the southern part of the Central Asian Orogenic Belt. It is composed of dunite, hornblende clinopyroxenite, hornblendite and hornblende gabbro. Several dykes of hornblendite, hornblende gabbro and gabbroic diorite cut the main body. These rocks are characterized by adcumulate textures. The dunites contain high-Fo (92.3–96.6) olivines with rare orthopyroxene and plagioclase. Hornblende, chromite, and magnetite are common phases in all of the rock types. Geochemically, the rocks of the Xiadong complex display high MgO contents and extremely low trace element abundances. Although the rocks of the main body show higher MgO contents and lower trace element abundance compared to the dykes, both are characterized by flat REE patterns and enrichment of LILE relative to HSFE. These petrological, mineralogical and geochemical features indicate that the Xiadong complex is a typical Ural–Alaskan type complex. The cross-cutting and intrusive relationships of the rock units and their distinct geochemical features suggest that the main body represents a different pulse from the intrusive dyke. The positive whole-rock εNd(t) values, together with variable (87Sr/86Sr)i ratios, show a depleted mantle source metasomatized by subduction-related material. Zircon U–Pb dating on one hornblende gabbro from the main body of the complex yields a U–Pb 206Pb/238U age of 479 Ma, and zircons from three samples of the dykes yield ages of 477, 379 and 313 Ma. All the zircons have positive εHf(t) and slightly higher δ18O than normal mantle, and their Hf–O isotopic values are correlated to their ages. The older samples are comparable to those from the Permian mafic–ultramafic complexes in the Beishan Terrane, which were derived from a mantle source metasomatized by subduction of the South Tianshan ocean, while the younger samples are similar to those from the Paleozoic complexes in the Eastern Tianshan, which record the subduction features of the Junggar ocean. These results suggest that the Central Tianshan was a continental arc from at least the Ordovician to the Carboniferous. The lithospheric mantle beneath the Central Tianshanwas depleted in Sr–Nd–Hf isotopic compositions and was metasomatized by melts and/or fluids from the subduction of the South Tianshan and Junggar oceans in Paleozoic. The formation of the Xiadong Ural–Alaskan type complex was the product of arc magmatism via high-degree melting of the lithospheric mantle beneath the southern Central Asian Orogenic Belt.

Source: UG
Petrological, geochemical and geochronological constraints on the origin of the Xiadong Ural-Alaskan type complex in NW China and tectonic implication for the evolution of southern Central Asian Orogenic Belt

The Xiadong mafic-ultramafic complex is located in the Central Tianshan Terrane, the southern part of the Central Asian Orogenic Belt. It is composed of dunite, hornblende clinopyroxenite, hornblendite and hornblende gabbro. Several dykes of hornblendite, hornblende gabbro and gabbroic diorite cut the main body. These rocks are characterized by adcumulate textures. The dunites contain high-Fo (92.3-96.6) olivines with rare orthopyroxene and plagioclase. Hornblende, chromite, and magnetite are common phases in all of the rock types. Geochemically, the rocks of the Xiadong complex display high MgO contents and extremely low trace element abundances. Although the rocks of the main body show higher MgO contents and lower trace element abundance compared to the dykes, both are characterized by flat REE patterns and enrichment of LILE relative to HSFE. These petrological, mineralogical and geochemical features indicate that the Xiadong complex is a typical Ural-Alaskan type complex. The cross-cutting and intrusive relationships of the rock units and their distinct geochemical features suggest that the main body represents a different pulse from the intrusive dyke. The positive whole-rock εNd(t) values, together with variable (87Sr/86Sr)i ratios, show a depleted mantle source metasomatized by subduction-related material. Zircon U-Pb dating on one hornblende gabbro from the main body of the complex yields a U-Pb 206Pb/238U age of 479Ma, and zircons from three samples of the dykes yield ages of 477, 379 and 313Ma. All the zircons have positive εHf(t) and slightly higher δ18O than normal mantle, and their Hf-O isotopic values are correlated to their ages. The older samples are comparable to those from the Permian mafic-ultramafic complexes in the Beishan Terrane, which were derived from a mantle source metasomatized by subduction of the South Tianshan ocean, while the younger samples are similar to those from the Paleozoic complexes in the Eastern Tianshan, which record the subduction features of the Junggar ocean. These results suggest that the Central Tianshan was a continental arc from at least the Ordovician to the Carboniferous. The lithospheric mantle beneath the Central Tianshan was depleted in Sr-Nd-Hf isotopic compositions and was metasomatized by melts and/or fluids from the subduction of the South Tianshan and Junggar oceans in Paleozoic. The formation of the Xiadong Ural-Alaskan type complex was the product of arc magmatism via high-degree melting of the lithospheric mantle beneath the southern Central Asian Orogenic Belt. © 2013 Elsevier B.V.

Source: UG
Petrology and geochemistry of nepheline syenite and related carbonate-rich rocks in the Pan-African Dahomeyide orogen, southeastern Ghana, West Africa

Nepheline syenite and carbonate-rich rocks known as the Kpong complex occur as deformed layers within the Pan-African Dahomeyide suture zone, in southeastern Ghana. The dominant phases in the nepheline syenite are nepheline and feldspar, whereas the carbonate-rich rock is dominated modally by Sr-rich calcite and annitic biotite. Biotite, calcite and nepheline have similar compositions in the nepheline syenite and the carbonate-rich rock. The rocks of the Kpong complex are enriched in alkalis, Ba, Sr, and Nb, have high LREE/HREE ratios, and show large depletions in Zr and Hf relative to primitive mantle. These features are characteristic of carbonatitic and related alkaline rocks worldwide. Whole-rock major elements in the Kpong complex with respect to SiO2 in bivariate plots show coherent variations with linear trends. However, based on the low Mg number, low Cr and Ni contents in whole rocks, and on overall high TiO2, FeO, rocks of the Kpong complex appear to have crystallized from an evolved parent, rather than primary mantle-derived magma. The ubiquitous disaggregated enclaves within the carbonate-rich horizons, the linear compositional arrays defined in binary variation diagrams, and overlaps in major modal mineral compositions all suggest magma assimilation of country rock was involved in the evolution of the Kpong complex. © 2009 Elsevier Ltd.

Source: UG
Petrology And Geochemistry Of The Suhum Basin Granitoid Complex, Ghana: Implications For Crustal Growth During The Rhyacian Orogeny Of The West African Craton.

The Suhum Basin granitoid complex is an important granitoid complex of the Birimian terrane of Ghana for unravelling the crustal growth and evolution of the West African Craton (WAC) during the Rhyacian Eburnean orogeny. Almost the entire Suhum Basin is occupied by an extensive granitoid complex, which contains useful information for constraining debatable plate tectonic issues, especially during the Archean-Paleoproterozoic transition period. We present petrography, whole-rock geochemistry, and mineral chemistry data of biotite, amphibole, and plagioclase to constrain the temperature-pressure conditions of emplacement, petrogenesis, tectonic setting, the evolution of the granitoids complex of the Suhum Basin, and its implications for the crustal growth and evolution of the WAC. Four lithological types; granite gneiss, migmatites, leucogranites, and mafic enclaves, characterise the granitoid complex of the Suhum Basin. Biotites from the granitoid complex have an annite-siderophyllite composition, and that, coupled with their calc-alkaline and I-type signatures, indicates crystallisation of the granitoid complex of the Suhum Basin under oxidised conditions. The medium-to high-K character of the rocks, together with the calc-alkaline nature, may be a reflection of the generation of magma in regions where the mantle wedge might have interacted with enriched fluids from the underlying plate during dehydration. The enrichment of LILE and LREE relative to HREE and HFSE and the negative Eu, Nb-Ta, and Ti anomalies of the granitoids complex may indicate derivation from enriched magma sources with varying degrees of fractionation in an arc environment. Amphibole-plagioclase thermobarometry indicates that the granitoid complex formed at P-T conditions of 600–712 ◦C and 5.2–7.2 kbar, signifying a deeper depth (19–27 km) of emplacement. The overall geochemical data suggest that the rocks formed during a single orogenic event related to a volcanic arc environment where subduction zone components played a role in the generation of their parental magmas. This finding is therefore consistent with the onset of “modern-style” subduction-related pro cesses during the Archean-Paleoproterozoic transitional period.

Source: UG
Petrology and geochemistry of TTG and K-rich Paleoproterozoic Birimian granitoids of the West African Craton (Ghana): Petrogenesis and tectonic implications

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.

Source: UG
Petrology and geochronology of Paleoproterozoic garnet-bearing amphibolites from the Dunhuang Block, Eastern Tarim Craton

The Dunhuang Block, located in the eastern margin of the Tarim Craton, possesses a wealth of information about the geological evolution of the Tarim Craton. In this study, we conducted detailed petrological, geochemical and geochronological investigations on garnet-bearing amphibolites as well as granites in the Dunhuang Block, which record important metamorphic and magmatic events that are poorly constrained. Based on field occurrence, geochronological and geochemical characteristics, the garnet-bearing amphibolites can be divided into two groups. Group I garnet-bearing amphibolite displays typical features of island arc basalts, which may formed at ~1.83Ga in a collisional setting during the assembly of the Columbia supercontinent, whereas group II has geochemical characteristics of ocean island basalt which may formed at ~1.61Ga in an ocean island setting. The ca. 1.83Ga amphibolite has positive e{open}Hf(t) values (+4.4 to +8.9), with TDM1 model ages of 2.02-1.83Ga, indicating an important addition of juvenile mantle-derived materials during the formation of its protolith. The ca. 1.61Ga amphibolite has e{open}Hf(t) values ranging from -0.6 to +5.6 and corresponding TDM1 model ages varying from 2.03Ga to 1.84Ga, which suggest that juvenile mantle-derived materials were dominantly contributed to the formation of its protolith but were later contaminated by crustal materials. The U-Pb ages obtained from the rims of the zircon grains in amphibolites and granites recorded a tectonothermal event at ca. 400Ma, which is coeval with the widespread magmatism in the Beishan orogen. We thus propose that these two groups of garnet-bearing amphibolites were possibly not related to each other during Paleoproterozoic time, and a late Paleozoic orogenic event brought them together during which both of them underwent metamorphism. © 2014 Elsevier B.V.

Source: UG
Phallic Competence: Fatherhood and the Making of Men in Ghana

Popular notions of womanhood among most Ghanaian societies include the role of motherhood, particularly biological motherhood. There is an appreciation that women will be engrossed with thoughts of childbearing, and that no normal woman would give up motherhood voluntarily, except, perhaps, for religious reasons. Thus, if a couple is childless it is typically the woman who bears the brunt of pressure, taunts, and even abuse, both from her husband's family as well as, sometimes, her own. Men are generally felt to be able to avoid the stigma of being infertile. Thus, the contemporary literature on childbearing and parenthood, especially that coming out of sociology and demography/population studies, has focused on women. This is surprising given that family planning research since the 1980s has shown that programmes have not worked as well as they might have done because they failed to acknowledge men's fertility desires. An understanding of men's needs and desires around fertility and fatherhood are important for any discussion of gender, power, sexualities, and well being particularly around HIV/AIDS. The current study investigates the meanings and significance of biological fatherhood and their relationship to constructions of masculinity among a sample of urban Ghanaian men; particularly the associations men make among adulthood, marriage, manhood and biological fatherhood. We find that the associations made between biological fatherhood and manhood, as measured by notions of phallic competence, are so important for most of the men that they have implications for the stability of a marriage, as well as questions of remarriage and extra-marital relationships.

Source: UG
Phallic competence: Fatherhood and the making of men in Ghana

Popular notions of womanhood among most Ghanaian societies highlight the role of motherhood, particularly biological motherhood. It has been generally acknowledged, however, that family planning programs have not worked as well as they might have because they failed to acknowledge men’s fertility desires by focusing almost exclusively on women’s “unmet need.” The current study investigates the meanings and significance of biological fatherhood and their relationship to constructions of masculinity among a sample of urban Ghanaian men. Data are derived from interviews on reproductive preferences and decision making among 11 men in 11 monogamous husband‐wife dyads, held following a questionnaire survey among some 265 junior and senior staff/spouses of the University of Ghana in 1997 and 1998. It particularly addresses the associations men make among adulthood, marriage, manhood, and biological fatherhood. Results suggest that men’s associations between biological fatherhood and manhood, as indicated by notions of phallic competence, have important implications for marital stability, remarriage and extra‐marital relationships.

Source: UG
Pharmacoepidemiology of antiretroviral drugs in a teaching hospital in Lagos, Nigeria

OBJECTIVE: Prescribing, adherence, and adverse drug events to HAART in a large antiretroviral programme in Lagos was evaluated.DESIGN: A retrospective 5 year open cohort study.SETTING: The AIDS Prevention Initiative in Nigeria (APIN) clinic at LUTH is one of the United States Presidential Emergency Plan for AIDS Relief (PEP-FAR) funded centers for HIV relief program in Nigeria Participants The case files of 390 patients on HAART and attending the APIN clinic were reviewed sequel to random selection.MAIN OUTCOME MEASURES: Demographics of the patients and pattern of antiretroviral (ARV) combination drugs prescribed were extracted from their case files. The details of the adverse drug events (ADEs) were extracted from drug toxicity forms regularly filled for each patient. A Chi-square test with Yates correction was used to determine the association between adherence and therapeutic outcome.RESULTS: A total of 2944 prescriptions were assessed. Zidovudine + lamivudine + nevirapine (35.87%) and stavudine + lamivudine + nevirapine (35.63%) were the most frequently prescribed combinations. Over 2000 ADEs were reported with cough (13.3%), fever (8.75%) and skin rashes (8.01%) being the most frequently reported. Drug adherence was associated with good therapeutic outcome (χ(2) = 115.60, p<0.0001).CONCLUSIONS: Zidovudine + lamivudine + nevirapine was the most frequently prescribed ARV combination. Cough was the most frequently reported ADE. Interventions aimed at rational prescribing of ARV drugs and improving adherence to antiretroviral drugs is essential for good therapeutic outcome in the treatment of HIV infection.

Source: UG