Structural, Petrographical and Geochemical Characterization of Tin-Tantalum Bearing Pegmatites from Chessu Area, North Central, Nigeria (Published)
Granodiorite, medium grain granite gneiss, medium grain banded gneiss with pegmatite intrusion, comprise the Basement Complex rocks of Chessu. The primary geological structures that emerge from the Pan Africa ductile and brittle deformation stages are fold, strike slip fault, dextral shear plane and fractures in Chessu and environs. Tin and tantalum containing pegmatites are found in the main E-W and NE-SW fault. Field observation demonstrate NE-SW, NNE-SSW and N-S structural trend with dipping values ranging between 19°-52° in accordance with data collected, displayed on rose plots and equally supported by lineaments. In terms of petrography, medium grained banded gneiss, medium grain granite gneiss and granodiorite all contain quartz, plagioclase, biotite and muscovite. Pegmatite contains muscovite, biotite, quartz and orthoclase among other opaque minerals. The protoliths of the gneisses, which may be from granite are revealed by the geochemical data used on Middlemost plots (Na2O + K2O vs SiO2), which suggest that the rocks are members of the granitoid family. The Harker’s variation Plots of SiO2 vs Na2O, K2O, CaO, MgO, TiO2, P2O5, reveals intense alteration and contamination during fractionation of the rock, as displayed by the scattered/non-linear trends. The primitive mantle (spider plot) indicates the depletion of some compatible less mobile elements (Ti, Y, Zr and Sr) and enrichment of incompatible elements (Th, Rb, Nb, Ta, Sr and Pb), which reveal the mineralization potential in these incompatible elements. The enriched elements Th, Nb, Ta and Pb are used as the pathfinder elements for Tin and Tantalum mineralization in Chessu area. The deformation processes and structures created in the latter phase of Pan Africa Orogenic event resulted in the pegmatite emplacement, this could infer a connection between the mineralizing fluid and the rocks.
Keywords: Chessu, enrichment, geochemical, mineralization, petrography
The Geology and Geochemistry of Kakafu Pegmatites: An Investigation for Lithium Ore Bearing Minerals (Lepidolite-Spodumene), Pategi North Central Nigeria (Published)
The preliminary investigation of the Kakafu pegmatites was conducted, with the aim of carrying out detail geological mapping and geochemical analysis to reveal common field and geochemical features that will lead to understanding the nature of the Kakafu pegmatites, for the purposes of identifying its lithium minerals potential. Geological mapping reveals three lithological units in the area, which includes; muscovite schist, biotite granite and pegmatite veins. Mineral composition observed in the field and as hand specimen are quartz, plagioclase and orthoclase feldspars, muscovite, biotite and tourmaline. Also the two lithium minerals recognized by the investigation; lepidolite and spodumene (kunzite) grades vertically with depth and along the veins in areas where the veins swells. The main lineament features (fractures, joints and folds) observed trends in the NE-SW, NW-SE, N-S and E-W directions, these directions correspond with orientations of the pegmatites in the study area. Geochemical plots of K vs Rb; K/Rb vs Rb; Li2O vs SiO2 and Ca O vs SiO2 show linkages amongst the pegmatites of the study area. Also the plots of A/CNK vs SiO2 and TiO2 vs SiO2 show all the pegmatites samples fall in the fields of S-type and igneous protolith respectively. These linkages amongst the Kakafu pegmatites suggest they are genetically related to one another, and have same origin (igneous protolith). In terms of mineral potential assessment, the plots of A/CNK vs SiO2; Li2O vs SiO2 and REE show that the Kakafu pegmaites are strongly peraluminous and hence potential for lithium ore mineralization. Furthermore, the concentrations of Li2O of Kakafu pegmatites ranges between (0.82-2.27wt%) and averagely all are above 1wt%. This suggests the Kakafu pegmatites to be moderately potential for lithium ore mineralization.
Keywords: Geochemistry, Pegmatite, geology, lithium ore, mineralization
Geology and Geochemistry of Lead-Zinc Mineralization in Ameri, Southeastern Nigeria (Published)
The Geology and geochemistry of Lead-Zinc Mineralization has been carried out in parts of Ameri, South eastern Nigeria. The study area was mapped and lithological units and structural features were identified and studied. A total of twenty-seven (27) samples from five (5) wells (AMR 014, AMR 036, AMR 038, AMR 048, and AMR 049) of the study area were collected, prepared and subjected to geochemical analysis for both major and trace elements using EDX3600B X-ray fluorescence spectrometer. The analytical data were statistically computed using principal component factor analysis PCFA, statical package for social science SPSS, descriptive statistics DS, correlation matrix CM and were also adopted for various geochemical plots using Excel Microsoft office, geochemical data kid GCD Kid and Suffer software for geological map digitization, to determine the geochemical characteristics of the Lead-Zinc ore, the host rock and the environment of formation. The geology of the study area is strategically part of the Lower Benue Trough of Nigeria, it is made up of shale intruded by several small to medium sized mesocratic – melanocratic, phaneritic intrusives which are alkaline in nature with a slight variation in their mineralogical and textural characteristics. Structurally, the fractured zones or veins marked along the Enyigba and Ameka lodes could also be responsible for the mineralization of the Ameri Lead-Zinc. The Lead-Zinc in Ameri is associated with other gangue minerals such as marcasite, pyrite, quartz veins, carbonate materials, chalcopyrite, siderites, sphalerites and it shows that the Lead-Zinc mineralization in the study area is hosted by shales, which are probably parts of the slightly deformed cretaceous sedimentary rocks made up of essentially Albian shales and subordinate siltstones. Values of lead within this shear zone ranges from 0.06% – 64.58%, 0.02% – 64.35%, 0.01% –0.14%, 0.03% – 0.11% for AMR 036, AMR 038, AMR 048, AMR 049 respectively, while Zn ranges in value from; 0.09% – 53.98%, 0.08% – 1.11%, 0.19% – 58.64%, 0.08% – 56.11%. The value of lead and zinc within the hanging wall are 0.06% and 0.08%, 0.03% and 0.06%, 0.04% and 0.12%, 0.04% and 0.13% for AMR 036, AMR 038, AMR 048, AMR 049 respectively. Paleo-redox condition of Low Cu/Zn ratios from 0.001-0324, 0.001 – 0.307, 0.075-0.424, 0.001-0.309 and 0.001-0.321 for AMR 014, AMR 036, AMR 038, AMR 048, AMR 049 indicate more oxidizing conditions. This is confirmed by the Ni/Co ratio of 0.00-58.50, 0.00- 43.625, 0.00- 35.333, 0.00-1.704, 0.211- 1.472 for AMR 014, AMR 036, AMR 038, AMR 048, AMR 049 respectively mostly below the ratio indicated to be oxidic with little anoxic environmental affinity. The total Alkalis versus Silica plot from the intrusaive revealed their basic to ultrabasic nature, as the bivariate plots of the analyzed samples shows positive and /or strong relationship between the trace elements in the Ameri lodes and their respective certified concentration values which is also an indicator that the elements are probably from same hydrothermal source with the Lead-Zinc of the study area.
Keywords: Ameri, Geochemistry, geology, mineralization, paleo-redox and structure.