Structural and Tectonic Interpretation of Nkalagu and Environs Using High-Resolution Aeromagnetic Data

Research Article

Austin J Earth Sci. 2022; 6(1): 1028.

Structural and Tectonic Interpretation of Nkalagu and Environs Using High-Resolution Aeromagnetic Data

Igbokwe SC¹; Agbodike IC²; Ejiogu BC³*

¹Department of Physics, Kingsley Ozumba Mbadiwe University Ideato, Imo State, Nigeria

²Department of Physics Imo State University, Owerri, Nigeria

³Alvan Ikoku University of Education, Owerri, Nigeria

*Corresponding author: Ejiogu BC Alvan Ikoku University of Education, Owerri, Nigeria Tel: +2348064568294 Email: blessingchikaodilie@yahoo.com

Received: September 11, 2023 Accepted: November 06, 2023 Published: November 13, 2023

Abstract

The aeromagnetic survey carried out by the Geological Survey of Nigeria between 2003 and 2010, provided high-resolution aeromagnetic data used in this study. The study area is Nkalagu and its environs. It lies within latitudes N6o00 and N6o30 and longitudes 8o00 E and E. The geology of the study area is predominantly the geology of the Lower Benue Trough. The purpose of the study is to determine the depth of the basement and delineate the basement morphology and structural features associated with the subsurface of the study area using the structural and tectonic interpretation of aeromagnetic data. This will create indebt knowledge of the geology of Nkalagu and its environs. The Aeromagnetic data obtained were subjected to various data preprocessing enhancement techniques these include relief imaging, vertical and horizontal derivatives, analytic signal, apparent susceptibility mapping, automatic gain control, and spectral analysis. Results of the study revealed lineament with trend directions in the N-S, NE-SW, NW-SE, and E-W, with the NW-SE trend being dominant. When subjected to 2-D spectral analysis, it revealed a two-layer depth model; the shallow magnetic sources and the deep magnetic sources with average depths of 1.041 km and 3.574km respectively. Similarly, the average sedimentary thickness of the study area was estimated at approximately 3.6km.

Keywords: Benue trough; Spectral analysis; Sedimentary; Magnetic; Aeromagnetic data

Introduction

The release of the aeromagnetic maps of Nigeria has turned the application of aeromagnetic surveys primarily, from interpretation of solely basement structures to detailed examination of structure and lithological variations in the sedimentary basin. Magnetic anomalies often result from secondary mineralization along fault planes in most cases and are revealed on aeromagnetic 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 [1,4,11,12,17]. 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, between echelon lineaments, and lineaments associated with circular features. Linear features are very observable on aeromagnetic maps and often indicate the form and position of individual folds, faults, joints, and other geologic features which can lead to the location of individual mineral deposits. Similarly, a Magnetic basement is an assemblage of rocks that underlies sedimentary basins and may also outcrop in places. When magnetic units in the basement occur at the basement surface, then depth determinations for these will map the basin floor morphology and its structure, [16]. Thus, the aeromagnetic method utilizes the power of interpretation of images captured to delineate and thus map out the structural pattern of a study area, its structural trend, and the possibility of locating minerals in such area. This is unique in that it has the potential to cover areas that other methods may not find assessable. This research was carried out in order to delineate the structural trend of the study area, determine the morphology of the study area and, the depth to the basement of the study area, it was also meant to determine the possibility of locating commercial minerals in the study area.

Location, Geology, and Geomorphology of the Study Area

The study area is Nkalagu and its environs. It is located within the lower Benue trough. The Benue trough which is conventionally subdivided into lower, middle, and upper Benue troughs is a linear NE-SW trending trough with a length of approximately 800km and opens into the Gulf of Guinea where the Cenozoic Niger Delta has built out upon oceanic crust.

The major towns and cities in the study area are; Enugu, Emene, Amangunze, Ezillo, Ndiaguowo, Okposi, and so on. It lies between latitude 6o20 N and 6o45 N and longitudes 7o30 E and 8o00 E (Figure 1).