Petro Chemistry of Major and Trace Elements Concentrations in the Stream Sediments of Awo Area and its Environs, Southwestern Nigeria.

Stream sediments are believed to record the environmental impact on fluvial system overtime and are often study to determine the overall pollution of an environment. This research work is aimed at mineralogical appraisal of various rock types through petro logical study, also to estimate the degree of enrichment of the element in the stream sediments and to determine if such enrichment has led to any form of pollution and also to produce a baseline geochemical data base for further geochemical investigation of the area under investigation. Ten soil samples were collected randomly within the study area and were analyzed for major and trace elements concentration using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) instrumentation techniques, while five rock types were selected for petro graphic studies. Thin section study shows that muscovite, biotite, microcline, and quartz are the main mineral assemblages present in the rocks of the study area. The result of the geochemical analysis were thereafter subjected to multivariate statistical analysis, the statistical plot from the result of major elements shows that Iron oxide (Fe2O3)  range from 9.30% - 1.60 %, with a mean value of 4.6865%. Aluminum oxide (Al2O3) range from 2.63% - 0.55% with a mean value of 1.6802%, Fe2O3 and Al2O3 are dominant major oxides within the study area and they show moderate enrichment in the environment under investigation.  From the result of the trace elements, Manganese [ Mn] with mean value of 3996.00 ppm, Zinc [Zn] with mean value of 272.40 ppm,  Copper [Cu]  with mean value of 628.10 ppm, Lead [Pb] with a mean value of 61.22 ppm, Nickel [Ni] with a mean value of 109.40 ppm and Cobalt [Co] with  mean value of  89.0 ppm have high concentration within the area of study, with Copper [Cu] having the highest degree of contamination factor 33%. The enrichment of Lead [ Pb] in the study area has been linked to anthropogenic  input of exhaust from motor bikes that ply the area, very strong positive correlation exist between V and Cr  (0.737), Co and Ni (0.648) while a positive strong correlation exist between Co and Cr (0.550), Mo and Ga  (0.535) indicating that they are from the same source. The conclusion drawn from the box plot study show that V, Cr, Co, Ni, Zn, Mn, As,  Rb,  Pb, Mo, Ga and Cd have values that are greater than zero, while Sr and  Zr have values that are less than zero. Copper [Cu] is the highest contaminating element within the study area, the presence of high amount of cupper in the study area may be probably due to geogenic factor, and in addition the  weathering of the associated rocks and precipitation of same within the environment and it can also be attributed to the mining operations going on in the study area; from this it can therefore  be deduced  that the study area range in the category of practically contaminated to moderately contaminated. Keywords: Sediment, Biotite, Enrichment, weathering, Geogeni

MINERALOGICAL AND GEOCHEMICAL STUDIES OF SANDSTONE IN IMOBI STUDY AREA AND ITS ENVIRONS, SOUTHWESTERN NIGERIA.

The combination of mineralogical and geochemical data of sedimentary rock can reveal the nature of source rocks, the tectonic settings of the sedimentary basins and the Paleoclimatic conditions. The aim of this research is to determine the geochemistry and mineralogy of the Imobi sandstones and to infer the provenance and possible depositional environment for these sand stones. Eight rock samples were collected from the study area, some portion were used for geochemical analysis to determine the chemical composition using X-ray fluorescence and the remaining portion were also used for mineralogical analysis to determine the mineralogical compositions and to estimate the modal percentages of minerals in the Imobi sandstone samples with the aid of the Petrological microscope. From the geochemical analysis, sixteen (16) elements and oxides were revealed and they includes SiO2, Al2O3, Fe2O3, CaO, V2O5, ZrO2, SO3, K2O, Br, P2O5, CuO, TiO2, MnO, Rb2O, As2O3, Cr2O3, while the mineralogical study show the presence of three minerals along with accessory minerals, they include quartz, iron oxide, microcline and accessory minerals. The presence of element and oxides like Br, V2O5, ZrO2, CuO, Rb2O, As2O3 and MnO (especially Br which occurred in a recognizable quantity of about 12%-27%) suggests the depositional environment of the Imobi sandstone to be a shallow marine or near marine environments.  However the abundance Of Fe2O3 infers the derivation of the sediments from a metamorphic source. The Petrography study reveals the presence of microcline, a feldspathic mineral commonly found in metamorphic rocks, and is consistent with the inference made from the geochemical composition that the provenance of these sandstones is from a metamorphic origin Key words: Geochemical, Sandstone, Aluminum, Bromine, Marine, Quartz, Provenance

PETROGRAPHY AND GEOCHEMICAL APPRAISAL OF AFOWO SANDSTONE FACIES, DAHOMEY BASIN, SOUTHWESTERN NIGERIA

Sandstones are sedimentary rocks formed by the cementation of sediment by material cements and they show a great deal of variation in mineral composition, degree of sorting and roundness. A petrographic and geochemical study of sandstones in the Afowo Formation of Dahomey basin southwestern Nigeria was carried out to infer the various elemental compositions, mineralogical composition, degree of sorting and degree of roundness of the sandstones in order to classify them. Seven (7) samples were collected and subjected to standard laboratory preparation and analytical method which include geochemical x-ray fluorescence for (trace and major elements analysis), and thin section petrography. The result of the geochemical analysis revealed the presence of some major elements (SiO2,Al2O3,Fe2O3,CaO,Br,and TiO2) and trace elements (V2O5,SO3,P2O5,CuO,MnO,Rb2O, and AS2O3) respectively. The mineral compositions obtained from the petrographical analysis are Quartz, Aluminum oxides, and high percentage of Iron oxides acting as the cementing material. The high percentage of Fe2O3 indicates that the sandstone is ferruginous while high concentration of Bromine ( Br) suggest a shallow marine environment of deposition of the sandstone. Key words: Petrography, Sand stone, Aluminum, Bromine, Marine, Quartz

Organic Geochemical Analysis of Shaly Facies from Two Wells Within Anambra Basin, Southeastern Nigeria

Organic geochemical analysis of two selected wells penetrating shale facies of the Anambra basin was conducted with the view of evaluating the section in terms of quantity and quality of organic matter, genetic potential, organic matter type, thermal maturity as well as determining the type of hydrocarbon that could be generated. Geochemical parameters such as Total Organic Carbon (TOC), S1 (representing free and adsorbed hydrocarbons present), S2 (representing hydrocarbons generated directly from the kerogen), S3 (carbon dioxide CO2 present) and maximum temperature (Tmax) as well as Hydrogen Index (HI), Oxygen Index (OI), Production Index (PI) and Genetic Potential (GP) were derived and calculated from the pyrolysis data. Result indicated that Well 1 samples have an average TOC of 1.21 wt % which is considered good in organic matter quantity and fair in quality, while Well 2 samples are organically lean, poor in quantity and quality with average TOC value of 0.15 wt %. The Genetic Potential (GP) expressed as (S1+S2) for Well 1 and Well 2 averages 2.03 and 0.68 mg HC/g respectively, indicating, a poor generational potential. The HI, OI and S2/S3 values of Well 1 samples are 146.56 mg HC/g, 226.78 mg HC/g and 0.86 respectively which on plots suggest the kerogen as type IV although few samples fall within the type III area. This contrasts with Well 2 samples having HI, OI and S2/S3 values as 343.67 mg HC/g, 276.78 mg HC/g and 1.26 respectively. Thus making the kerogen type to be interpreted as type III. Judging from Tmax (average of 441.67°C for Well 1 and 470.44°C for Well 2) and PI (average of 0.13 for Well 1 and 0.24 for Well 2) values, Well 1 samples are within the oil generating window whereas Well 2 samples are overmatured generating dry gas. Deductions from the result of geochemical analysis show that the kerogen of Well 1 samples will generate oil while that of Well 2 samples have propensity to generate dry gas

Paleoenvironmental and paleodepositional architecture of SAMO field in Niger-Delta Basin of Nigeria using seismic and well log data

The use of Seismic data and well log data within the context of sequence stratigraphy is a valuable tool for the recognition of ancient cycles and sequences because they reflect information on the different processes that deposit sediments in different palaeoenvironment. An integrated geophysical well log data and seismic data from our wells within the SAMO field have been utilized to delineate the upper Miocene-Pliocene depositional environment parts of the Niger-Delta Basin. Identification of the different lithologies and depositional environment present in the penetrated borehole was achieved using gamma ray log. This enables the establishment of different rock units in the well from the gamma ray log values and signatures. Three succession signatures which include; the bell, cylindrical and the funnel being more prominent were identified from the log motifs in the different sand bodies attenuated in the wells from the field. The mapped sequences generated Low stand System Tracts (LST) progradational, Trangressive System Tracts (TST) retrogradational and High stand System Tract (HST) aggradational packages. All these reflect the depositional systems that dominated the different phases as a result of base level changes. Furthermore, values quantified from the logs revealed that porosity and permeability are more prominent in places where sand bodies accumulated in the slope channel setting indicative of slope-fills and turbidity fans. This deep-sea channels and switch complex fault system suggest good hydrocarbon bearing potential associated with the distal Niger-Delta province. Also a good quality reservoir was inferred from the sands of both LST and HST while the shale of the TST could serve as a good reservoir

Evaluation of hydrocarbon potential of shale outcrops in the flanks of Anambra Basin

The research aim is to determine the organic productivity and hydrocarbon potential of the exposed shale lithology along Uzebba road and Bawa hills near Auchi, Southwest Nigeria.Twenty two (22) shale samples were acquired from the study area; twelve (12) from the outcropping section along Uzebba road, and the remaining ten (10) samples obtained from Bawa hills. The samples were then subjected to organic geochemical analysis using Total Organic Carbon (TOC) and Rock Eval Pyrolysis to evaluate the organic enrichment, organic quality and thermal maturity espectively.Total Organic Carbon (TOC) content of the twentytwo samples ranges from 3.42 – 4.88 wt. %, affirming a high organic enrichment. Shale samples from Uzebba segment and Bawa hills falls within the Type I and Type II Kerogen class respectively. The former is indicative of immature – sub mature organic matter with no hydrocarbon formation prospect whilst the latter exhibits great hydrocarbon (oil) generation potential Thermal maturation assessment for both samples apparently ranges from immature to mature organic matter. From the Rock-Eval pyrolysis result, all the twenty-two (22) samples were confirmed to be organically enriched. However, the type I kerogen of Bawa at favourable geothermal gradient can potentially serve as a suitable source rock for petroleum generation