by Bravo Martin Mbang Bonda, Akumbom Vishiti, Mbai Simon Joel, Bayiga Elie Constantin, Ngon Ngon Gilbert François and Etamé Jacques
Original Research
The Sanaga magnetite bearing iron ore deposit is hosted in the eburnean Nyong complex which constitutes the northwestern edge of the Congo Craton. It is compose predominantly of magnetite bearing quartzite and magnetite-biotite gneisses related to charnockites and amphibole orthogneisses. In this study we use the composition of the magnetite bearing ore to determine their origin and ore formation process. A deposit model is also proposed for a better understanding of the emplacement of the iron ore. EMPA analysis on magnetite reveal variable amount of V, Ti, Al, and Mn. Most of the samples present Ti contents > 0.1%, this indicates a hydrothermal overprint. Although the texture and chemical composition of the magnetite bearing rocks neither represents typical skarn nor BIFs, on Ca + Al + Mn vs Ti + V and Ni + Cr vs Ti + V discrimination diagrams the magnetite reveals a double affinity for skarn and BIF. Elevated contents of Al, Mn and Mg in the magnetite signify crustal contamination while BIF signatures are related to hydrothermal activities. The variable content of V and Ti/V ratio suggests a mixture of reducing and oxidizing environments. On the Al + Mn vs Ti + V binary diagram the magnetite bearing ore reveal hydrothermal temperatures that vary between 200-300°C and 300-500°C. This suggests their precipitation from hydrothermal fluid with medium to high temperature and slight enrichment in Al and Ti. Integrating the data obtained from studies such as regional geology, ore geology and mineral microchemistry, we suggest that the Sanaga magnetite bearing iron ore deposit is similar to the Lake Superior iron ore type and was formed from transgression-regression in back arc basin or continental margin.
Journal of Geosciences and Geomatics. 2022, 10(1), 65-73. DOI: 10.12691/jgg-10-1-5
Pub. Date: April 08, 2022
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by Nowel Yinkfu Njamnsi, Njoh Oliver Anoh, George Ngiamte Lemewihbwen, Cheo Emmanuel Suh and Simon Fai Tamfu
Original Research
Hydrocarbon resources are still invaluable to the economic growth and social development of most producing countries. Keeping in pace with studies of global source rock development for resourcing future generations, exposed organic-rich, dark-grey mudstones were collected from the Koum Basin and on the basis of their total organic carbon (TOC) content, noted to range between 5.48-6.91 wt.%, organic matter (OM) was extracted and characterized in order to determine the OM source input, paleo-depositional conditions, thermal maturity, age, by which the hydrocarbon potential was deduced using gas chromatography (GC), medium pressure liquid chromatography (MPLC) and gas chromatography-mass spectrometry (GC-MS) techniques. The extract yield and bitumen composition range between 4291–5116 ppm which depicts a fair to very good source rock generative potential, dominated by saturates (41.86-45.96%), aromatics (9.36-26.36%), and resin/asphaltene (31.78-44.68%) pointing to normal paraffinic generated hydrocarbons. Source-related molecular markers indicate a mixed aquatic algae and clastic-rich terrigenous OM input, preserved under sub-oxic to oxic conditions, typical of fluvial-deltaic lacustrine systems. Gammacerane/Hopane ratios (0.26-0.27), support the fact that the lacustrine source rocks were likely developed under somewhat restricted circulation and moderate/low salinity. From maturity ratios of Ts/(Ts + Tm), C32 22S/(22S + 22R) homohopane, the 20S/(20S + 20R) and ββ/(ββ + αα) C29 and Methyl Phenanthrene Index with vitrinite reflectance value equivalent of 0.46-0.60%, it can give a conclusion that the analyzed extracts are from early thermal cracking of OM at the incipient oil window. Based on age-specific biomarkers, the extracts were probably derived from the Early Cretaceous. Accordingly, findings are comparable with some active Cretaceous lacustrine source rocks in some basins within the West Central African Rift system (WCARS) and therefore provide a better understanding of source rock development during the Cretaceous in a regional context. Nevertheless, the deeper unexposed organic-rich units of the Koum Basin may have a pod of active source rock.
Journal of Geosciences and Geomatics. 2022, 10(1), 45-64. DOI: 10.12691/jgg-10-1-4
Pub. Date: March 23, 2022
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by Désiré Alphonse Rakotondravaly and Roger Randrianja
Original Research
Granitic rocks of the Ibity, Tsarasaotra, and Ambatofinandrahana areas of the Itremo domain, in the Precambrian basement of Madagascar were characterized by using the naked eye, microscopic observations, and whole rock chemical analyses with the aim of understanding their petrogenesis, their interrelations, and their membership in the known magmatic suites in the Itremo domain. The granitic rocks of this study are mainly composed of monzonitic rocks for the Tsarasaotra and granite for the other areas. Major minerals identified are alkali feldspars, quartz, plagioclase, and accessory minerals are amphiboles, micas, pyroxene, iron-titanic minerals, titanite, and epidote. Major element compositions are intermediate for the Tsarasaotra monzonitic rocks and felsic for the other rocks. All the studied rocks are silica-saturated with enough aluminum, ferroan, calc-alkalic to alkalic, metaluminous, rarely peraluminous, I-type granitic rocks. Transition elements contents are generally low for the granites and high for the monzonitic rocks, while the compositions of compatible elements are in general high. Chondrite-normalized patterns of REE show high enrichment of LREE and low to moderate enrichment of HREE. The behaviors of major elements (especially Ti, Al, Fe, Mn, Mg, and Ca oxides) and trace elements (Eu anomaly, La/Sm) in the studied rocks show magmatic differentiation signatures in relation to crystal fractionation. These rocks' magmatic sources were most likely enriched-MORBs that evolved through within-plate enrichment for the Tsarasaotra monzonitic rocks and Ifasina granite, and through subduction for the Ibity granite, Tsarasaotra granite dyke, and Antsahakely granite. The succession of these two different processes identified in the studied rocks reveals their membership in the Imorona-Itsindro. Although some of the studied rocks are adakite-like, their characteristics as well as their interrelations indicate magmatic differentiation signatures rather than slab-melting origin. This work is a contribution to the promotion of scientific and geologic research in Madagascar, and it is in perspective of its extension to the geochemical characterization of laterites and mineralization potential identification related to the studied rocks in the Itremo domain as well as in the Antananarivo domain of Madagascar’s Precambrian basement.
Journal of Geosciences and Geomatics. 2022, 10(1), 31-44. DOI: 10.12691/jgg-10-1-3
Pub. Date: March 17, 2022
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by Jay Bergi and Ratna Trivedi
Original Research
Water reservoirs as one of the sources for the supply of domestic water to Surat city are having extensive algal blooms that may contain species of toxic cyanobacteria. Current water treatment procedures do not detect or try to remove toxins possibly produced by these toxic cyanobacteria. These toxins are potent health hazard if present in drinking water. The aim of the present study was to study the presence of any such toxic cyanobacteria along with its diversity and their toxins in surface water of river Tapi. Detail analysis of nutrient pollution in surface water along with seasonal variation in cyanobacterial population was studied. Detecting genes responsible for toxin production in cyanobacteria that identify the possible health hazard of cyanobacterial toxins in drinking water reservoirs of Surat city.
Journal of Geosciences and Geomatics. 2022, 10(1), 18-30. DOI: 10.12691/jgg-10-1-2
Pub. Date: March 15, 2022
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by Primus Azinwi Tamfuh, Jean Pierre Temga, Emile Temgoua, Emmanuel Djoufac Woumfo, Philemon Zo'o Zame, Milan Stafford Tchouatcha, Georges Martial Ndzana, Dieudonné Bitom and Veronique Kamgang Kabeyene Beyala
Original Research
Although Vertisols have been highly documented owing to technological breakthroughs, numerous aspects are still not fully understood such as implication of geochemistry on source area-weathering, provenance, tectonic setting and sedimentary processes as well as problems of classification and management. This work aims to highlight the geochemical characteristics of Vertisols formed on alluvial deposits in the Benue Basin of North Cameroon and to highlight their source area-weathering, sedimentary processes, tectonic setting, taxonomic level and possible management strategies. The work was done in the field and in the Laboratory. The main results showed that smectite is the predominant clay mineral. Chemical composition revealed high Si, Al and Fe contents. Heavy minerals contents are of plutonic (augite, aegerine and aegerinic augerinic augite), metamorphic (kyanite, sillimanite and andalusite) and volcanic (tourmaline) origin. This agrees with the Al2O3/TiO2 ratio of 8.72 to 30.40 reflecting sediments from felsic rocks and minor mafic rocks. The CIA (chemical index of alteration: 70 to 85), PIA (plagioclase index of alteration: 66 to 82) and Ruxton’s index (SiO2/Al2O3: 2.27 to 3.55) suggest a warm and humid climate during moderate to intense chemical weathering probably prevailing during a more humid pre-depositional period. The K2O/Na2O ratio <1 suggests high sediments chemical maturity. The predominance of angular quartz grains suggests short fluvial transport distance and low sorting. The tectonic setting discrimination ternary diagram indicates that alluvial sediments, parent material of Vertisols, originate from an Active Continental Margin while the discriminant function-based multidimensional tectonic diagram indicates an arc-collisional setting suggesting that parent materials are from the Pan-African basement of the Central African Fold Belt. The Vertisols are classified as Ustic Haplusterts Clayey Isohyperthermic (United States Department of Agriculture) and as Gleyic Stagnic Vertisols (Pellic, Hypereutric, Clayic) (World Reference Base for Soil Classification).
Journal of Geosciences and Geomatics. 2022, 10(1), 1-17. DOI: 10.12691/jgg-10-1-1
Pub. Date: January 21, 2022
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