by Alexis Hamdja Ngoniri, Timoleon Ngnotue, Evine Laure Tanko Njiosseu, Patrick Ayonta Kenne, Sylvestre Ganno and Jean Paul Nzenti
Original Research
The Mbondo-Ngazi Tina area belongs to the Adamawa-Yade domain within the Pan-African Central Africa Fold Belt in Cameroon (CAFB). The basement of this area is dominated by metasedimentary rocks composed of sericite schist, chlorite schist and muscovite schist. Whole-rock geochemical compositions of these rocks were investigated in order to determine their provenance and tectonic setting. The studied metasedimentary rocks have SiO2 and Al2O3 contents comparable to the average composition of the Neoproterozoic upper continental crust (UCC). These rocks are strongly depleted in CaO, MgO, and enriched in K2O, Ba and Rb with respect to UCC, reflecting K addition during diagenesis. The CIA, CIW, PIA and the SiO2/Al2O3 and Th/U ratios indicated that these rocks had suffered varying degrees of weathering as the source rocks underwent mild to moderate chemical weathering. The PAAS-normalized REE patterns are almost flat with slightly LREE depletion with respect to HREE and null to weakly positive Eu anomalies. Their chondrite-normalized REE patterns are parallel to sub-parallel, LREE-enriched, and display distinct negative Eu anomalies and weakly fractionated HREE segments. Overall, they are geochemically mature and have suffered sedimentary recycling. They derived mainy from felsic to intermediate rocks with minor contamination of mafic rocks. The Mbondo-Ngazi Tina metasedimentary rocks show REE and trace element compositions similar to those of Archean sediments, suggesting that the continental crust of the study area during the early Proterozoic had chemical compositions similar to those of the Archean crust and were probably deposited in active to passive continental margin settings.
Journal of Geosciences and Geomatics. 2020, 8(2), 94-109. DOI: 10.12691/jgg-8-2-5
Pub. Date: November 17, 2020
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by Nicy Carmel Bazebizonza Tchiguina, Timothée Miyouna, Hardy Medry Dieu-Veill Nkodia and Florent Boudzoumou
Original Research
Several studies have stated the possibility of seismic hazards in the Congo Basin area. This study aims to conduct a morphometric analysis of the Inkisi Group which constitutes a part of the subsoil of the south-eastern Republic of Congo (RC) and the south-western part of the Democratic Republic of Congo (DRC), to detect neotectonic signatures. GIS and ASTER GDEM images have enabled the automatic extraction of morphometric indices, in particular the Hypsometric Integral (HI), the Relative Declivity Extension (RDE) index, along with the hydrographic network and its frequency density. Analysis of the hypsometric distribution of watersheds in the Congo Basin highlights two relief trends. The first relief trend is high (HI>0.5) and is represented by young and abrupt-type basins suggesting rejuvenated relief by neotectonics. The impact of neotectonics in this rejuvenation is evidenced by the RDE index, which reveals that the first order knickpoints in the drainage gradient are mainly located in these watersheds at HI>0.5. The second relief trend is low (HI<0.5) and encompasses the basins tending towards the "equilibrium" stage in which neotectonics is less active. The young basins constitute a NE-SW oriented strip that borders on both sides of the Congo River, thus revealing elevated seismic risk on these two banks. In the Republic of Congo, these young basins perfectly overlap the high lineament density network of the Inkisi group. Moreover, the densest areas of knickpoints in the drainage gradient are located along the course of the Congo River. Thus, the course of the Congo River corresponds with a tectonically active feature; the installation of seismographs along its borders is strongly recommended to better assess the seismic risk associated within it.
Journal of Geosciences and Geomatics. 2020, 8(2), 83-93. DOI: 10.12691/jgg-8-2-4
Pub. Date: October 11, 2020
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by Hart Lawrence and Victor Glory Ukwoma
Original Research
The traditional way of handling storm water runoff from cities has always been to drain it as fast as possible by means of drainages. Thus, in urban areas the natural water cycle is been influenced by infrastructures that hinders infiltration and concentrates storm water flows. This approach has been shown to cause several environmental problems as storm water from urban areas can be polluted by heavy metals, organic materials, suspended materials and nutrients when discharged to the nearest receiving river. The main thrust of this work is to modelled basic environmental and spatial parameters for the design of storm water canal that will serve as a means of collecting and conveying the urban runoff of the Greater Port Harcourt City. Consequently, the methodology deployed was terrestrial surveying techniques, bathymetric mapping and hydrological models in other to identify the optimal route for the canal, determination of the topography/configuration of the area, generation of the mathematical parameters of the proposed storm water design location in relation to the adjourning communities and to ascertain the proximal impact of the canal on the neighbourhood. The identified route for the canal covered a total distance of 6.47kms with 100m right of way/corridors in addition to a total of 14 transect lines at 700m on both side of the proposed route with no feasible development outside farmlands. Similarly, the receptacle river, covered a total distance of 750m while the width of river varies from 7.21m to 11.34m. The profile of the identified route presents a continuous gradual decrease in elevation data of 21.94m at SC 19 to 1.89m at SC 5 so also the 700m transects with elevation data decreasing gradually from 16.96m to 2.07m at the centre of the proposed canal. The average time of concentration, rainfall intensity and peak discharge for the various basins along the route were 10.719mins, 49.824mm/hrs and 0.826m3/s respectively, while for the GPH Phase area, the average time of concentration, rainfall intensity and peak discharge were 72.728mins., 13.001mm/hrs., and 1.824m3/s respectively. These are the basic and essential data required for the design of the storm water canal.
Journal of Geosciences and Geomatics. 2020, 8(2), 76-82. DOI: 10.12691/jgg-8-2-3
Pub. Date: October 07, 2020
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by Benoît Joseph Mbassa, Emmanuel Njonfang, Caroline Neh Ngwa, Michel Grégoire, Zénon Itiga, Pierre Kamgang, Mfomou Ntepe, Jesús Solé Viñas, Mathieu Benoit, Jacques Dili-Rake and Ferdinand Mbossi Eddy
Original Research
The Mbengwi Pan-African high-K calk-alkaline I-type plutonic rocks consist of granitoids and monzodiorites. These granitoids have a rather homogeneous mineralogical composition made up of calcic amphiboles, ferromagnesian and lithio-aluminous micas, quartz, feldspars, oxides, titanite and incidentally of sulphides, magmatic epidote, apatite, zircon, chlorites and carbonates. Plagioclase compositions range from Na-albite to andesine. Micas are Mg-biotite in monzodiorites and Mg-biotite, Fe-biotite, siderophyllite, lepidomelane, muscovite and phengite in granitoids. Magmatic amphiboles are made up of Fe-hornblende, Mg-hornblende, Fe-edenite, Mg-hastingsite or edenite whereas post-magmatic amphiboles are actinolite. Trace elements analyses reveal: i) low rare earth elements content in monzodiorites (average = 199.9 ppm) compared to granitoids (average = 404.65 ppm); ii) a weak to strong fractionation ((La/Lu)N = 4.5 - 102.96), iii) an enrichment in LILE and LREE relative to HFSE and HREE, and iv) negative anomalies in Rb, K, Sr, Ti, Eu and positive ones in Th and La. Mineralogical and whole rock geochemical results reveal that magmas were produced by vapor-present partial melting of one or several heterogeneous igneous protoliths relatively rich in potassium. The investigated rocks were emplaced between 4 and 34 km deep, at pressure ranging from 1.2 to 9.4 Kbars and were not subjected to post-magmatic alterations according to their Zr/Hf values (> 20). Their differentiation process is the combined result of fractional crystallization and multiple mixing and mingling.
Journal of Geosciences and Geomatics. 2020, 8(2), 58-75. DOI: 10.12691/jgg-8-2-2
Pub. Date: July 01, 2020
6447 Views983 Downloads
by Raoufou D. Ibrahim GNAMMI YORO, Gérard Alfred Franck d’ALMEIDA, Karim ALLEK, Christophe KAKI and Nicaise YALO
Original Research
Spectral geology and aeromagnetic data help geoscientists in mapping and prediction of potential mineral areas. This paper aims to present structural features of the poorly studied Pako region of northern Benin using Landsat 8 OLI images and aeromagnetic data. Remote sensing technique led to the discovery of several faults of two main directions (N-S and E-W), resulting from great regional tectonics’ deformations. The other faults have NE-SW to NW-SE orientations. Among identified faults, N-S faults (N18°) gathering 14% and E-W (N92°) to NW-SE (N160°) fractures cumulating 61% limit the basin on both sides. Therefore, these faults could be interpreted as border fractures which have initiated the formation of Pako basin. Total magnetic field technique held to define anomalous zones and associate shears zones in order to identify potential corridors of mineralization. Field observations in Pako region have confirmed the existence of brittle deformations, as sociated to dextral and/or senestral detachment, and ductile deformations with rotational dextral components. The integration of our results with the regional geological context allow to propose a structural model of Pako region.
Journal of Geosciences and Geomatics. 2020, 8(2), 45-57. DOI: 10.12691/jgg-8-2-1
Pub. Date: June 22, 2020
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