Mineral Composition of Soil in Ado Ekiti Metropolis
Chapter One
Objectives of study
The objectives of this study is to examine the composition of mineral resources in Ado Ekiti.
CHAPTER TWO
LITERATURE REVIEW
The Older Granites (Pan African Granitoids)
The term “Older Granite” was introduced by Falconer (1911) to distinguish the deep-seated, often concordant or semi-concordant granites of the Basement Com- plex from the high-level, highly discordant tin-bearing granites of Northern Nigeria. The Older Granites are believed to be pre-, syn- and post-tectonic rocks which cut both the migmatite-gneiss-quartzite complex and the schist belts. They range widely in age (750–450 Ma) and composition. They represent a varied and long lasting (750–450 Ma) magmatic cycle associated with the Pan-African orogeny. The rocks of this suite range in composition from tonalites and diorites through granodiorites to true granites and syenites. Charnockites form an important rock group emplaced during this period. They are generally high level intrusions and anataxis has played an important role (Rahaman, 1981). The Older Granites suite is notable for its gen- eral lack of associated mineralization although the thermal effects may play a role in the remobilization of mineralizing fluids.
The Older Granites are the most obvious manifestation of the Pan-African orogeny and represent significant additions of materials (up to 70% in some places) to the crust (Rahaman, 1988). Attempt to classify the Older Granites with respect to timing during an orogenic event are valid over only short distances. Contact features between members of the Older Granites suite suggest the coexistence of sev- eral magmas. Compositionally, the granites plot in the field of calc-alkaline rocks on the AFM diagram and although they contain significant amount of alkalis, are also often slightly corundum normative. Dada (2006) was of the opinion that the term “Pan African Granitoids” be used for the Older Granites not only on the merit of age which was not available at the time they were named Older Granites, but because it covers several important petrologic groups formed at the same time.
The Basement Complex
The granitoids which outcrop with the schist belts in northwestern and southwest- ern Nigeria include biotite granites, biotite muscovite granites, syenites, chanock- ites, serpentinites and anorthosites.
Rahaman (1988) discarded the earlier classification of members of the Older Granites suite on the basis of their texture, mineraological composition and the rel- ative timing of their emplacement. In its place, members of the Older Granite suite were classified as follows, based mainly on the textural characteristics:
CHAPTER THREE
MATERIALS AND METHODS
Study Area
The study area Ado Ekiti is a town located between latitude 70 471 to 70 531 N and longitude 5o18’E to 5o24’E in Oye local government area of Ekiti State Southwestern Nigeria (Figure 1). The town is known to be the home of Ogun onire whom the Yoruba ethnic group of Nigeria recognizes as the “god of iron”. Ado Ekiti has naturally occurring and abundant clay deposits which are mined for different applications. Ekiti State is located between latitude 70 201 to 80 001 N and longitude 4o50’E to 5o50’E. The State is an upland zone rising over 250m above sea level and underlained by different rocks such as the gneisses, granite and charnockite.
Sample Collection and Preparation
Clay soil was collected with the aid of a hand auger from the basement complex of soil deposit in Ado Ekiti, Southwestern Nigeria. Both surface and subsurface clay samples were collected at four different cardinal points with equidistance of 500 m way from one another on the trial site. The samples were homogeneously mixed together and an adequate amount for use was taken as the representative sample. None soil sample was separated from the soil sample by hand picking and air dried at room temperature for 72 hours. Thereafter, the clay soil sample was stored in a black polyethylene bag prior to analysis.
CHAPTER FOUR
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RESULTS AND DISCUSSION
Physicochemical Properties of the Clay Soil
Table 1: Physicochemical Properties of the Clay Soil
CHAPTER FIVE
CONCLUSION
Ado Ekiti soil soil has been characterized by some suitable techniques order than XRD to evaluate the major mineralogical content of the clay for proper classification. The results from the techniques used in this study are consistent to one another. The results showed that kaolinite is the major clay mineral in the clay, indicating that the clay is typically kaolin. Also, the Ado Ekiti kaolin showed properties that indicated its potentials to be used as a pozzolana and industrial adsorbent for remediation of contaminants in wastewater. The results from this research therefore become an added value to existing data and information on mineralogical and physicochemical evaluation of soil soil and potential application of Ado Ekiti soil.
The lateritic profiles above pegmatite, granite gneiss and granite in Ado Ekiti and its environs are structurally related to the overlying weathering profiles. The mineralogy of the parent rocks greatly influenced and determined the textural characteristics and colour variation within and between profiles. The weathering profile over pegmatite and granite can be distinguished into top soil, iron rich laterite, clay and bedrock. The essential rock forming minerals in the basement rocks, such as feldspar, biotite, hornblende, have been chemically decomposed to clay minerals such as kaolinite. Hematite is the non- clay components, derived essentially from the lateritization of iron-bearing minerals such as biotite and hornblende, Close examinations of the whole rock geochemical data reveal that only Fe2O3, Al2O3 and TiO2 are relatively enriched in lateritic profiles above the basement rock. The other oxides, notably SiO2, MnO, MgO, CaO, Na2O, K2O, and P2O5 are depleted due to leaching. Studies of major element distribution shows relative enhancement of Al2O3 in the clayey zone and Fe2O3 in the laterized zone above pegmatite, granite gneiss and granite. These enrichments are reflected as kaolinite and hematite peaks in the relevant x-ray diffractograms. This shows that the weathering is towards lateritization than bauxitization. Among the three lithologies, pegmatite exhibits the highest degree of weathering.
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