CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF THE STUDY

The interpretation of airborne magnetic maps in the past decade has moved from the interpretation of basement structures to detailed examination of structures and lithologic variations in the sedimentary section. Magnetic basement is an assemblage of rocks that underlies sedimentary basins and may also outcrop in places. If the magnetic units in the basement occur at the basement surface, then depth determinations for these will map the basin floor morphology and its structure). In many sedimentary basins, magnetic anomalies arise from secondary mineralization along fault planes, which are often revealed on airborne magnetic maps as surface linear features. Most mineral deposits are related to some type of deformation of the lithosphere, and most theories of ore formation and concentration embody tectonic or deformational concepts. Some lineament patterns have been defined to be the most favorable structural conditions in control of various mineral deposits. They include the traces of major regional lineaments, the intersection of major lineaments or both major (regional) and local lineaments, lineaments of tensional nature, local highest concentration our world is magnetic thus because of this natural fact, various applications of magnetics have become explorable to earth scientists. Understanding the magnetic effects associated with Earth materials require the knowledge of the principles of magnetism (Dobrin and Savit, 1988). These basic principles are fundamental to the applications of magnetics for oil gas and mineral explorations. The inherent magnetism of rocks called magnetic susceptibility is caused by changes in the subsurface geologic structures. Magnetic susceptibility of rocks is the fundamental parameter in the applications of magnetics for oil and gas explorations. In every case, the susceptibility of rocks depends on the amount of magnetite (Fe304) contained in the rock unit. The magnetic susceptibility (k) is the significant variable in magnetic playing the same role as density in gravity interpretation, although this property is represented as a range even for a particular rock and a wide overlap between rock types. The magnetic method is useful whenever the object of investigation has a contrast in the magnetic susceptibility or remanence that can be detected by the magnetometer and is measured in nanotesla (nT) or gamma (γ) units. Thus, the magnetic prospecting, the oldest of the geophysical exploration method is used for: Location and definition of Sedimentary Basin extent.

1.1.1 Geology of the study area

Detailed Geological field mapping is an indispensable exercise in geology as a result of the fact that geology as a discipline is field-oriented. It is the aspect that completes and gives life to the study of geology. An independent Geologic field mapping of the Somorika-Aiyetoro-Aiyegunle-Ogugu-Imiegba-Fugar-Okpekpe-Bawa Hill-Auchi area and their environs in parts of Etsako East local government area in the Northern part of Edo state, Nigeria, was undertaking by the 400 Level Geophysics students and 300 level students of the Department of Earth Sciences, Federal University of Petroleum Resources Effurun (FUPRE), Warri Delta state, Nigeria in partial fulfillment of the requirement for the award of Bachelor of science (B.Sc. Honours) degree in Geophysics. The field mapping exercise lasted for thirteen days (13 days). The Imiegba-Fugar-AuchiBawa Hill area are made up of sedimentary rocks and lies within the Benin flank of the Anambra basin.

The Somorika-Aiyetoro-Ayegunnle-Ogugu axis is made up of basically Igneous and Metamorphic rocks (schist belt). The Igneous rock is of the Pan – African Orogeny (600±150 mya) (Turner, 1989). The rocks found here are not the oldest igneous rocks in the African region. Interesting geologic features was seen such as contact metamorphism, Batholith, Xenolith, Vein Quartz amidst others.

1. STATEMENT OF THE PROBLEM

Studies of the geomagnetic field have a long history, particularly because of its importance in navigation. From the point of view of geomagnetism, the earth may be considered as made up of three parts namely: crust, mantle and the core. Convection processes in the liquid part of the inner core give rise to a dipolar geomagnetic field that resembles that of large bar-magnet aligned approximately along the earth’s axis of rotation. The mantle plays little part in the earth’s magnetism, while interaction of the geomagnetic field with the rocks of the earth’s crust. Secondly there have been series of studies on airborne magnetic data but not even a single study has been carried out on the determination of source parameters using airborne magnetic data within auchi and its environs south-south Nigeria

1.3 AIM AND OBJECTIVES OF THE STUDY

The main aim of the research work is to examine the determination of source parameters using airborne magnetic data within auchi and its environs south-south Nigeria. Other specific objectives of the study are:

1. to examine the efficiency of airborne magnetic data in the determination of source parameter in auchi and its environs south-south Nigeria
2. to investigate on the factors affecting the use of airborne magnetic data in the determination of source parameter in auchi and its environs south-south Nigeria
3. to determine the application of  airborne magnetic data in auchi and its environs south-south Nigeria
4. to proffer solution to the above stated problems

1.4 RESEARCH QUESTIONS

The study came up with research questions so as to ascertain the above stated objectives of the study. The research questions for the study are:

1. What is the efficiency of airborne magnetic data in the determination of source parameter in auchi and its environs south-south Nigeria?
2. What are the factors affecting the use of airborne magnetic data in the determination of source parameter in auchi and its environs south-south Nigeria?
3. What are the uses of airborne magnetic data in auchi and its environs south-south Nigeria?
4. What is the way forward to the challenges faced in the use of airborne magnetic data in the determination of source parameter in auchi and its environs south-south Nigeria?

1.5 SIGNIFICANCE OF THE STUDY

The study on the determination of source parameters using airborne magnetic data will be of immense benefit to the entire Auchi and its environs south-south Nigeria in the sense that the study will be able to determine the efficiency of airborne magnetic data in the determination of source parameter in auchi and its environs south-south Nigeria, the factors affecting the use of airborne magnetic data in the determination of source parameter in auchi and its environs south-south Nigeria and the uses of airborne magnetic data in auchi and its environs south-south Nigeria. The study will serve as a repository of information to other researchers that desire to carry out similar research on the above topic. Finally the study will contribute to the body of the existing literature on the determination of source parameters using airborne magnetic data

1.6 SCOPE OF THE STUDY

The study on the determination of source parameters using airborne magnetic data will be limited to Auchi and its environs south-south Nigeria because of her population and good weather condition for the study.

1.7 DEFINITION OF TERMS

Aeromagnetic survey: An aeromagnetic survey is a common type of geophysical survey carried out using a ... Aeromagnetic data was once presented as contour plots, but now is more commonly expressed as thematic (colored) and shaded computer generated 

Magnetic field: A magnetic field is a vector field that describes the magnetic influence of electric charges in relative motion and magnetized materials