MENVSC / Department of Mining and Environmental Gelogy / In the present study, the physico-chemical, applications, mineralogy, geochemistry and stable isotope of Lwamondo and Zebediela kaolin is documented, in order to understand the genesis, paleoenvironmental conditions and possible utilization. Mineral identification studies were conducted using X-ray diffractometer (XRD), Fourier transform infrared spectrophotometer (FTIR) and scanning electron microscope with energy dispersive X-ray micro analysis (SEM-EDX). Major oxides were identified by X-ray Florescence (XRF) whereas trace elements were identified by Laser Ablation Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Hydrogen and oxygen isotopic composition were determined by δ18O and δD isotopic measurements. Kaolinite was dominant mineral in all the kaolin samples whereas muscovite, quartz, goethite, hematite, smectite, anatase occurred in minor to trace quantities. The chemical data show that the kaolins are composed mainly of SiO2 and Al2O3 due to the presence of quartz and kaolinite, with minor to trace amounts of other elements such as Ca, Na, Cr, K, Fe, Mn, Mg, P and Ti which affected the kaolin application negatively. Lower concentration of Ca, Na, K, Fe, Mn, Mg, and Ti show the extent of the kaolinitisation. The samples were enriched in Ni and depleted in some other trace elements. The chondrite-normalised rare earth elements patterns show enrichmnent in Heavy Rare Earth Elements (HREE) than Light Rare Earth Elements (LREE) with slight positive Eu anomaly. The Rare Earth Elements (REE) pattern and the content of other trace elements show evidence of weathering processes related to kaolinitisatioon. Kaolin genesis is explained using kaolin mineralogy, particle morphology, structural order (functional group), major and trace elements geochemical data. The data suggest that kaolin is derived from the intensive chemical weathering of intermediate to mafic rocks deposited in non-marine environment. The stable isotopes were used to determine the paleoenvironmental conditions which influenced kaolinitisation of Lwamondo and Zebediela kaolins. Stable isotopes mean values for kaolinite from both Lwamondo and Zebediela were as follows: δ18O for Lwamondo= +18.57‰ and for Zebediela = +16.67 ‰ vii and δD for Lwamondo = -65‰ and for Zebediela = -64‰. The calculated mean temperatures were 26.94 ⁰C for Lwamondo kaolin and 36 ⁰C for Zebediela kaolin. Low temperatures were inferred from stable isotope values to have been involved in the kaolinitisation wherein hydrothermal processes were eliminated. The data suggests that kaolin was formed in a weathering environment. The kaolin is found to be suitable for brick making and based on the physico-chemical, mineralogical and chemical data it was suggested that the kaolin could also be used in producing low temperature ceramics, refractory materials, pottery and stoneware

PhDENV (Geology) / Department of Mining and Environmental Geology / The Cretaceous period marked the breaking up of Gondwana, giving rise to the separation of the African and South American continents with the subsequent emergence of the South Atlantic Ocean. Most correlation studies between the two continents with respect to paleoenvironmental conditions and tectonic settings during the Cretaceous- Tertiary periods have been concentrated more on the use of flora and fauna as indicators with less application of kaolinite as paleoenviromental proxies, hence, this study. The research involved the evaluation of paleoenvironmental conditions and tectonic settings of four (4) selected Cretaceous-Tertiary kaolin deposits with two (2) each from the Eastern Dahomey (Eruku and Lakiri) and Niger Delta (Awo-Omama and Ubulu-Uku) Basins in Nigeria. Representative kaolin samples collected from the selected deposits were analysed for physico-chemical, mineralogical, geochemical, isotopic, and geochronological data. The geochemical data obtained by x-ray fluorescence (XRF) spectroscopy and laser ablation inductively coupled plasma mass spectrometry (LAICPMS) were used in unraveling the provenance and tectonic settings of the kaolins. The kaolinite stable isotopic data for oxygen and hydrogen determined using a Finnigan Delta XP Mass Spectrometer were used to assess the paleoenvironmental and paleoclimatic conditions under which the kaolins were formed. The detrital zircon geochronological data acquired by laser ablation – single collector – magnetic sectorfield – inductively coupled plasma – mass spectrometry (LA-SFICP-MS) as well as kaolinite stable isotopic data were employed in constraining the probable timing of kaolinisation. The industrial applications of the kaolins were assessed based on the physico-chemical (Colour, particle size distribution (PSD), pH, electrical conductivity, and Atterberg limits), mineralogical, and geochemical data. The mineralogical data were obtained through x-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, Thermogravimetric analysis and differential scanning calorimetry, and scanning electron microscopy (SEM). Correlative studies between selected Cretaceous African and South American kaolins were conducted. The results showed that the dominant colour in the studied kaolins was pale red (39 %) followed by pinkish and light grey (35 %) as well as reddish yellow, light pink, light brown, vii reddish brown, and pinkish white. The pH and EC values generally ranged from 4.27 to 5.29 and 0.2 to 13.1 μS/cm, respectively. The kaolins predominantly have clay to sandy clay textures with plasticity indices between 10 and 22 wt %. Bulk mineralogical quantitative results indicated that the Cretaceous kaolins have kaolinite, quartz, and muscovite present in that decreasing order with anatase, goethite, and hematite in traces whereas Tertiary kaolins have kaolinite and quartz present in that decreasing order with anatase and goethite in traces. In the silt fractions, kaolinite and quartz were the dominant mineral constituents, whereas in the clay fractions, the dominant clay mineral was kaolinite accounting for 69 to 99 wt % with the non-clay minerals like quartz, anatase, hematite and goethite accounting for percentages between 1 to 28 wt % in the Cretaceous – Tertiary kaolins. Morphologically, the studied kaolins were characterised by pseudohexagonal stacks to books and thin platy kaolinite particles with moderate structural order. The chemical compositions of the Cretaceous-Tertiary kaolin deposits were identical to hydrated alumino-silicates based on the dominance of SiO2, Al2O3 and LOI. The chemical index of alteration (CIA) and chemical index of weathering (CIW) values varied between 96.98 to 99.39 % and 98.95 to 99.89 %, respectively. The clay fractions were enriched in Cr, Nb, Sc, Th, U, V, Zr, and LREE and depleted in Ba, Co, Rb, Sr, and HREE, respectively, relative to the average Upper Continental Crust (UCC). The Th/Sc, La/Sc, Th/Cr, and Eu/Eu* ratios were within the range of sediments derived from felsic rocks. The TiO2 versus Al2O3 and La-Th-Sc plots indicated source rocks with granitic – granodioritic - gabbroic compositions. Geochemical discrimination plots showed that the Cretaceous and Tertiary kaolins were deposited in passive margin tectonic settings. The stable isotopic results indicated that the values of the Cretaceous kaolins ranged from – 47 to – 57 ‰ and 19.1 to 19.8 ‰, respectively, with paleotemperatures between 29.0 and 32.2 ˚C, whereas the δD and δ18O corresponding values for the Tertiary kaolins ranged from – 54 to – 66 ‰ and 20 to 21.5 ‰, respectively, with paleotemperatures between 17.0 and 23.9 ˚C. viii The U-Pb dating of the detrital zircons showed that the Cretaceous - Tertiary kaolins have inputs from rocks of Eburnean (2500 – 2000 Ma) and Pan African (750 – 450 Ma) ages. The age of maximum deposition determined from the least to statistically robust approach corresponds to the Ediacaran Period (645 – 541 Ma) of the Neoproterozoic Era (1000 – 541 Ma). The Cretaceous – Tertiary kaolins were formed under intense anoxic chemical paleoweathering conditions of predominantly felsic rocks in addition to contributions from intermediate and mafic rocks in passive margin tectonic settings. The Cretaceous kaolins were formed under warmer conditions relative to the Tertiary kaolins. The West African Massif rocks were the main sediment sources for the Cretaceous kaolins, whereas both the West African and Northern Nigerian Massif rocks were the major sediment sources for the Tertiary kaolins. The most probable timing of kaolinisation for the Cretaceous – Tertiary kaolins occurred between the Ediacaran (645 – 541 Ma) and Early Cretaceous Periods for the Cretaceous kaolins and between the Ediacaran Period (645 – 541 Ma) and Oligo – Miocene age for the Tertiary kaolins. The Nigerian and Brazilian Cretaceous kaolins formed under similar warm tropical paleoclimate. The study corroborated the occurrence of the Eburnean (Transamazonian) and Pan African (Brasiliano) orogenic events across the African and South American continents. Beneficiation of the Cretaceous – Tertiary kaolins will allow large scale industrial applications in paper coating, ceramics, pharmaceutical, and cosmetics industries. The major contributions from this study have been: the better understanding of the past environmental conditions and tectonic settings, the dating of the possible timing of kaolinisation, and improvement on the potential industrial applications of the Cretaceous – Tertiary kaolins. / NRF