GEOLOGY AND PROVENANCE OF CLAY DEPOSITS IN PARTS OF CENTRAL BIDA BASIN, NIGERIA
GEOLOGY AND PROVENANCE OF CLAY DEPOSITS IN PARTS OF CENTRAL BIDA BASIN, NIGERIA
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Date
2017-04
Authors
ALABI, Adekola Amos
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Abstract
Systematic geological, mineralogical and geochemical investigations of clay deposits in central Bida basin and part of its adjacent northwestern basement complex area were carried out. Ten representative rock samples from the basement area and thirty clay samples from the central Bida basin were analyzed using Inductively Coupled Plasma mass spectrometer (ICP – MS) and X-Ray Fluorescence (XRF) to determine major oxides, trace and rare earth elements composition, X-ray Diffraction (XRD) to determine mineralogical composition, while petrography analysis was used to study mineralogical compositions and the minerals optical features of the basement rocks using transmitted petrographic microscope. A topographic base map covering the study area was generated from mosaic topographic map of Minna, Mokwa, Lafiagi and Baro on a scale of 1:250,000. Part of the basement rocks mapped is composed of migmatitic-gneiss, mica schist, phyllite and Older Granite. Metasedimentary rocks mapped in the study area include; muscovite schist, biotite schist, amphibole schist and quartz schist. In the field, contact between mica schist, amphibole schist and Zungeru mylonite gnies is sharp, while in some area gradational contacts were observed between the mica schist and phyllite. The Older Granite occur as ridges and inselberg, andas minor intrution in the mica shist and migmatitic gneiss. The mapped basement rocks are part of Ushama Schist Formation, Kushaka Schist Formation and Birnin Gwari Schist Formation. Modal and petrographic analyses suggest that the rocks are enriched in felsic minerals. Major oxides, trace and rare earth elements composition also reveal that the basement rocks were formed from upper continental crust while the positive Ce anormaly observe in schist and phyllite suggest clay rich sediments protholith for these rocks. The clays deposits in the central Bida basin are white and fine grained from center of the basin to dirty white towards the
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margin, red tint colour observed in the clay is inherited from overburden ironstone/laterite through percolating water. Vertical thickness of the clay ranges between 4 and 8 meters.Thus suggesting non-uniformity in the supply of clay minerals to the basin. Kaolinite is the dominant clay mineral in the study clay deposits (66.2 – 22.1%) with concentration increasing from the basin margin to the center. The increase in kaolinite composition compared to quartz composition is suggestive of the high velocity of transporting energy of clay materials from the source area to the basin. Plots of Na2O/Al2O3 against K2O/Al2O3 for basement rocks suggest that the phyllite, quartz schist, mica schist, and amphibole schist were of sedimentary origin while migmatitic gneiss and mylonite gniess are of igneous origin. Also, provenance discrimination plots of Th/Co versus La/ Sc, Sc versus Th, Cr versus V, Fe2O3 versus MgO and K2O/Al2O3 versus log MgO/Al2O3 suggest that the studied clays werefrom felsic continental material. The cross plot ratio of V/Cr, La/Th and authgenic uranium ratios value of 1.5 ppm for studied clays suggest fluvial environment of deposition (flood plain, alluvial fan and braided channel) in the Bida basin which were further weathered/altered in-situ in the basin prior to the last phase of marine incursion that deposited the Enagi siltstone Formation during the upper Maastrichtian. Major oxides elements compositions of the clays suggest that clays in Sake and Shegba can be utilized for the production of refractory bricks, pottery production and ceramics while clays in Batati, Kpaki, Lemu, Kutigi, Gubaji, Nami, and Nakama require beneficiation for upgrade to meet specific industrial application. Elemental compositions of the studied clay deposits, suggest that the clays do not meet recommended dietary allowance for medical applications.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA; IN PARTIAL FULFILMENT OF THE AWARD OF A DEGREE OF DOCTOR OF PHILOSOPHY (Ph.D) IN GEOLOGY
DEPARTMENT OF GEOLOGY,
FACULTY OF SCIENCE, AHMADU BELLO UNIVERSITY, ZARIA
Keywords
GEOLOGY,, PROVENANCE,, CLAY DEPOSITS,, PARTS,, CENTRAL BIDA BASIN,, NIGERIA,