Interpretation of High Resolution Aeromagnetic Data over Okigwe and some Adjoining Areas, South Eastern Nigeria.

ABSTRACT 

Digitized high resolution total field aeromagnetic data over Okigwe and environ (Sheet 312) was interpreted using the standard 3-D Euler de-convolution and spectral analysis in order to determine depth to the magnetic basement, delineate the basement topography and relief, and delineate the trend of the structural features associated with the basin. The aeromagnetic data were subjected to various data enhancement and transformation routines using the Geosoft Oasis MontajTM software. Results of the study revealed that the dominant structural trend of the study area is in the northeast-southwest (NE-SW) direction. Other lineament trend is in the northwest - southeast (NW-SE) direction. The Results of the 2-D spectral analysis revealed a two layer depth model. The shallower magnetic source (D1) has an average depth of 0.5338 km, while the deeper magnetic source bodies (D2) has an average depth of 2.2048 km. The shallower magnetic anomalies is as a result of basement rocks which intruded into the sedimentary rocks while, the deeper magnetic anomalies is associated with intra-basement discontinuities like faults. The windowed 3-D Euler de-convolution for the anomalous bodies using structural index (SI) of 0.0, 1.0, 2.0 and 3.0 shows the presence of intrusive bodies in the form of contacts, dykes and sills, vertical pipes and spheres which are located at various depths ranging from 0.25 km to 3.0 km in the northern part of the study area

TABLE OF CONTENTS

Title page i

Certification ii

Dedication iii

Acknowledgement iv

Table of contents v

List of figures vii

List of tables ix

Abstract x

1.0 CHAPTER ONE: INTRODUCTION 1

1.1 Aeromagnetic survey 1

1.2 Purpose of study 4

1.3 Location of study area 5

1.4 Geology of study area 8

2.0 CHAPTER TWO: LITERATURE REVIEW 10

3.0 CHAPTER THREE: THEORY OF MAGNETIC METHOD, DATA AND METHOD OF DATA ANALYSIS

3.1 Theory of magnetic of prospecting method 14

3.1.1 Magnetic pole 14

3.1.2 Earth’s magnetic field 14

3.1.3 Elements of magnetic field 15

3.1.4 The composition of the geomagnetic field 16

3.1.5 Induced and remanent magnetization 16

3.1.6 Relative permeability, susceptibility and magnetization 17

3.2 Data acquisition 18

3.2.1 Data reduction and processing 18

3.2.2 Source of data 20

3.3 Method of data analysis (post processing and enhancement) 20

3.3.1 Regional-residual separation 21

3.3.1.1 Data Filtering 21

3.3.1.2 Analytical signal 22

3.3.1.3 Polynomial fitting 23

3.3.2 Reduction to pole 24

3.3.3 Artificial illumination 24

3.3.4 Automatic gain control 25

3.3.5 Estimation of depth to magnetic basement 25

3.3.5.1 Standard 3-D Euler de-convolution 25

3.3.5.2 Spectral analysis 29

4.0 CHAPTER FOUR: RESULTS AND DISCUSSION

4.1 Introduction 32

4.2 Results 32

4.3 Discussion of Results 50

4.3.1 Qualitative interpretation 50

4.3.2 Quantitative interpretation 51

5.0 CHAPTER FIVE: CONCLUSION AND RECOMMENDATION

5.1 Conclusion 54

5.2 Recommendation 55

REFERENCES 56