Browsing by Author "Ajadi Jimoh"

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    Geochronology and Petrogenetic Studies of Alagbede Gold Deposit, Southwestern Nigeria.
    (PhD dissertation published in ProQuest Number 10930135, 2018) Ajadi Jimoh
    Geological mapping around the gold-bearing main quartz vein of Alagbede area, located about 25km northeast of the Kwara State University, Malete shows that the Basement Complex rocks comprised the biotite-gneiss, migmatitic gneiss, quartzite, quartz-mica schist, talc-tremolite-actinolite schist, porphyroblastic granite, porphyritic granite, porphyritic diorite, alkali granite, granodiorite, alkali syenite, pegmatite/aplite and vein quartz. The AFM chemical classification diagrams for common volcanic rocks revealed that the Alagbede granites exhibit volcanic arc granites (VAG) origin based on the (Rb) vs Log (Y+Nb) discrimination diagrams for tectonic interpretation. Electron Probe Micro Analysis (EPMA) and ore microscopic work has shown that Alagbede gold occurs mainly as small inclusions or microfracture-fillings in pyrite, chalcopyrite and arsenopyrite in the deposit and this suggest that the gold mineralization is coeval with the precipitation of the sulfide phases. The abundances of light REE relative to that of the heavy REE in the host quartzitic and granitic rocks, the presence of negative Eu anomaly on the chondrite-normalized REE spider diagram and the major element fractionation pattern argued for a metamorphic source accompanied by magmatic differentiation of granitic magma as the possible source for the ore fluids for the gold mineralization at Alagbede, consistent with other orogenic vein-type gold deposits. A process of fractional crystallization in which the latent heat of crystallization provides sufficient thermal energy to consume the wall-rock, is hereby proposed as the fractionation model for the major element chemistry of the igneous rocks in Alagbede area. The U-Th-Pb on zircon was dated by in situ Laser Ablation ICP-MS which yielded upper intercept crystallization ages with superimposed Pan African imprints for the gold mineralization. Alagbede gold deposit is hosted in the vein quartz (formed at 590+27 Ma) and fine grained syeno-granite (formed 596+28 Ma) that are sinistrally sheared by a NW-SE trending fault, linked to the transcurrent fault line of the Anka-Yauri-Iseyin schist belt. A Pan African age of 590+27 Ma is hereby proposed as the age of gold mineralization in Alagbede area.
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    Interpretation of Aeromagnetic and Geochemical Data for Tectonic and Structural Setting of Granitic Rocks Around Bishewa Area, Southwestern Nigeria
    (Springer, 2022) Ajadi Jimoh; Olasunkanmi K. Nurudeen
    High resolution aeromagnetic data of Bishewa area has been analysed to establish the geometry of its lithologic settings. Magnetic residualization of the total magnetic intensity (TMI) and derivative of resulting magnetic anomalies were enhanced using the fast Fourier transform of Oasis montaj geo-software. The reduced-to-equator residual anomaly varies within -174.9 to 111.9 nT which revealed the contrasting lithologic units viz: sedimentary and basement complex. The negative magnetic intensities (lows) in the southern and sparsely within the northwestern regions are associated with rocks of lower content of ferromagnetic minerals and are attributable to underlying igneous and metamorphic rocks or intrusive bodies within the schist. The positive anomalies coincide with the predominant migmatite gneiss complex. Structural relationships between the granites and metasedimentary host rocks suggest that the emplacement of the granitoids are associated with early, large-scale thermotectonic regional deformation within the Nigerian basement complex. It also revealed a transpressional regime that is characterized by WNW-ESE shortening and large-scale sinistral strike-slip faults associated with the regional NE-SW structural grains in the basement rocks of the area. Regional geologic features and structural correlation show that the area is underlain by the northwestern extension of the Ilesha schist belt in the western sector of the Nigerian basement complex.