scholarly journals Estimation of The Structural Pattern and Sedimentary Thickness Over Part Of Anambra Basin, Nigeria Using Aeromagnetic Data

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Priscilla E. Ikioda ◽  
Charles O. Ofoegbu ◽  
Etim D. Uko ◽  
Olatunji S. Ayanninuola
Keyword(s):  
Spectral Analysis ◽  
Analytical Techniques ◽  
Average Depth ◽  
Intensity Data ◽  
Aeromagnetic Data ◽  
Structural Pattern ◽  
Near Surface ◽  
Anambra Basin ◽  
Potential Depth ◽  
Magnetic Basement

AbstractAeromagnetic data acquired over part of the Anambra Basin is analyzed to determine the structural pattern and sedimentary thickness of the basin. The study area is covered by high resolution aeromagnetic data on sheets 301 (Udi), 302 (Nkalagu), 312 (Okigwe) and 313 (Afikpo), and lies between latitudes 5o30’0’‘-6o30’0’‘ and longitudes 7o0’0”-8o0’0”. The whole area was divided into 25 overlapping blocks of 37.2km2 each and a 2D energy spectral analysis was carried out. Total magnetic intensity data was subjected to filtering and analytical techniques to determine the structural pattern, mineralization potential, depth to the basement, variation in the sedimentary thickness. The structural map generated using the vertical derivatives shows that the major structural orientation of the area is in the ENE-WSW trend and the minor trend is the NW to SE direction widespread all over the area. These structures are as a result of the various near-surface magnetic intrusion within the study area. The spectral analysis result shows two depth layers, the deep and the shallow depth, the depth to magnetic basement for the deep anomalous source ranges from 3.3km to 4.8 4km with an average depth of 3.99km, while the depth to shallow magnetic sources ranges between 0.46km to 0.67km and an average of 0.56km within the area. The mineralization pattern in this area follows the ENE-WSW direction.

scholarly journals Subsurface Structural Mapping over Koton Karifi and Adjoining Areas, Southern Bida Basin, Nigeria, using High-Resolution Aeromagnetic Data

2019 ◽  
Vol 3 (2) ◽  
pp. 304-316
Author(s):  
E.B. Ikumbur ◽  
V.E. Ogah ◽  
M. Akiishi
Keyword(s):  
Spectral Analysis ◽  
Sedimentary Cover ◽  
Detection Methods ◽  
Hydrocarbon Generation ◽  
Average Depth ◽  
Aeromagnetic Data ◽  
Analysis Method ◽  
Near Surface ◽  
Spectral Analysis Method ◽  
Basement Surface

In this current work, we aim to delineate the subsurface structural trends, determine the depth to basement surface, and provide an illustrative 3D model for its subsurface structure. Four digitized aeromagnetic maps were acquired from the Nigerian Geological Survey Agency, Abuja. The total field aeromagnetic anomalies over Koton Karifi and adjoining areas have been evaluated. In order to map the subsurface structures and estimate the depth to basement surface the spectral analysis method was applied. To achieve such goals, a detailed analysis of the aeromagnetic data for the study area was performed. 2D interpretation was carried out for the aeromagnetic data. The processes used include contouring of the Total Magnetic Intensity (TMI) data, separation of regional and residual anomalies, structural detection methods such as analytic signal, vertical derivatives, and magnetic lineament mapping were used to map the contacts and faults within the study area. The first vertical derivative and the magnetic lineament maps show major geologic lineaments trending in East-West with minor ones trending Northeast-Southwest. In the south-eastern part of the study area, there is a dome-shaped linear feature. The result obtained using the spectral analysis method reveals two source depth models. The depths to deeper magnetic sources range from 2.81 km to 3.24 km with an average depth of 2.90 km. The deeper magnetic source bodies are identified with the magnetic basement. The shallower magnetic sources which range from 0.45 km to 1.81 km with an average depth of 1.13 km could be attributed to near surface magnetic sources which are magnetic rocks that intruded into the sedimentary formations or magnetised bodies within the sedimentary cover. Based on the sedimentary thickness range of 0.45 to 3.24 km, there is an indication that the possibility of hydrocarbon generation in the study area is feasible.

scholarly journals Estimation of Curie-point depths, geothermal gradients and near-surface heat flow from spectral analysis of aeromagnetic data in the Loum – Minta area (Centre-East Cameroon)

2018 ◽  
Vol 27 (4) ◽  
pp. 1291-1299
Author(s):  
Jean Aimé Mono ◽  
Théophile Ndougsa-Mbarga ◽  
Yara Tarek ◽  
Jean Daniel Ngoh ◽  
Olivier Ulrich Igor Owono Amougou
Keyword(s):  
Spectral Analysis ◽  
Heat Flow ◽  
Curie Point ◽  
Surface Heat ◽  
Aeromagnetic Data ◽  
Near Surface ◽  
Geothermal Gradients ◽  
Surface Heat Flow

Depth to magnetic basement in the Anambra Basin, Benue Trough of Nigeria from aeromagnetic data: A prelude for hydrocarbon exploration

2021 ◽  
pp. 1-57
Author(s):  
Olatunbosun O. Olagundoye ◽  
Chiedu S. Okereke ◽  
Aniekan E. Edet ◽  
Dominic Obi ◽  
Aniediobong Ukpong
Keyword(s):  
Depth Estimation ◽  
Data Transformation ◽  
Hydrocarbon Exploration ◽  
Hydrocarbon Generation ◽  
Depth Range ◽  
Aeromagnetic Data ◽  
Benue Trough ◽  
Anambra Basin ◽  
Magnetic Basement ◽  
Fault Structures

Data transformation, regional-residual separation, trend analysis, and Analytic Signal (AS) depth estimation were applied to aeromagnetic data covering the Anambra Basin, which is a major depocentre in the Benue Trough, southeast Nigeria with the primary objectives of accentuating attributes of magnetic sources and determining if sufficient sediment thickness exists for hydrocarbon generation, maturation, and expulsion. The application of data transformation techniques (such as map projection, merging, and reduction-to-pole) and regional-residual ensured the computation of a crustal magnetic field that would be suitable for magnetic analyses. Results indicate that the magnetic basement in the basin forms an undulating surface overlain by sediments with average thickness ranging between 4 km and 7.5 km, while maximum thickness reaches 8 km in some areas. This depth range suggests promising prospect for source-facies maturation and expulsion. We expect that areas in the study area with these appreciable sediment thicknesses, good preservation of graben-fill, and suitable areal closures or fault structures would be favorable for hydrocarbon prospectivity.

scholarly journals Interpretation of aeromagnetic data over Abeokuta and its environs, Southwest Nigeria, using spectral analysis (Fourier transform technique)

2016 ◽  
Vol 63 (4) ◽  
pp. 199-212 ◽  
Author(s):  
Oluwaseun T. Olurin ◽  
Saheed A. Ganiyu ◽  
Olaide S. Hammed ◽  
Taiwo J. Aluko
Keyword(s):  
Spectral Analysis ◽  
Fourier Transform ◽  
Ground Level ◽  
Magnetic Data ◽  
Depth Range ◽  
Aeromagnetic Data ◽  
Southwestern Nigeria ◽  
Southwest Nigeria ◽  
Below Ground ◽  
Magnetic Basement

AbstractThis study presents the results of spectral analysis of magnetic data over Abeokuta area, Southwestern Nigeria, using fast Fourier transform (FFT) in Microsoft Excel. The study deals with the quantitative interpretation of airborne magnetic data (Sheet No. 260), which was conducted by the Nigerian Geological Survey Agency in 2009. In order to minimise aliasing error, the aeromagnetic data was gridded at spacing of 1 km. Spectral analysis technique was used to estimate the magnetic basement depth distributed at two levels. The result of the interpretation shows that the magnetic sources are mainly distributed at two levels. The shallow sources (minimum depth) range in depth from 0.103 to 0.278 km below ground level and are inferred to be due to intrusions within the region. The deeper sources (maximum depth) range in depth from 2.739 to 3.325 km below ground and are attributed to the underlying basement.

Some constraints on the form of the Welsh Basin from regional gravity and aeromagnetic data, with particular reference to Central Wales

1992 ◽  
Vol 129 (5) ◽  
pp. 515-522 ◽  
Author(s):  
R. M. Carruthers ◽  
C. J. N. Fletcher ◽  
A. J. W. McDonald ◽  
R. B. Evans
Keyword(s):  
Physical Property ◽  
Data Sets ◽  
Aeromagnetic Data ◽  
Near Surface ◽  
Magnetic Components ◽  
Major Fault ◽  
Magnetic Basement ◽  
Lower Palaeozoic ◽  
Regional Gravity ◽  
Geophysical Anomalies

AbstractGravity and aeromagnetic data sets provide systematic coverage over the whole of the Welsh Basin. Physical property information shows considerable overlap in densities within the Lower Palaeozoic and Precambrian formations, with relatively few units of the exposed succession being strongly magnetic. While the geophysical anomalies cannot be interpreted unambiguously in terms of these sources, the data can still be used to test different geological models and to indicate the range of possible solutions. The major fault zones are seen to influence the anomaly patterns in a variety of ways, reflecting a combination of differing near-surface contrasts and effects within the underlying basement. The general increase in gravity values towards Cardigan Bay may originate from the lower crust, and the large amplitude aeromagnetic low seen over Cardigan Bay indicates that a distinctive change in the character of the crust occurs here. Two-dimensional modelling in central Wales shows that a westward thickening of the Welsh Basin, to a maximum of about 10 km, may also be significant. It is necessary to postulate a separation of the base of denser, Lower Palaeozoic rocks from the underlying, more magnetic basement in order to account for offsets in anomaly source locations. This implies the presence of less dense Cambrian sediments and/or non-magnetic components of the Precambrian basement.

scholarly journals Delineation of Geothermal Energy Potentials in Parts of Calabar Flank, Southeastern Nigeria Using Aeromagnetic Data

2021 ◽  
Author(s):  
Elshalom Omokpariola ◽  
Emmanuel Anakwuba
Keyword(s):  
Spectral Analysis ◽  
Heat Flow ◽  
Geothermal Energy ◽  
Structural Parameters ◽  
Geothermal Gradient ◽  
Depth Range ◽  
Average Depth ◽  
Aeromagnetic Data ◽  
Southeastern Nigeria ◽  
3D Euler Deconvolution

Abstract In tackling energy-related challenges in Nigeria; the exploration of an alternative source of energy (Geothermal Energy) comes to the limelight as it is generated below the earth subsurface. This work focuses on the delineation of geothermal energy potentials in parts of Calabar Flank, in southeastern Nigeria using Aeromagnetic Data. The aim is to understand the geothermal energy potentials and structural of parts of the Calabar flank by studying the various geothermal, geological, and structural parameters using Aeromagnetic Data. The methodologies applied are quantitative for structural analysis and qualitative using spectral analysis and 3D Euler Deconvolution. The study area lies between within Latitude 5°30ʹ00ʺ N - 6°30ʹ00ʺN and Longitude 7°30ʹ00ʺE - 8°30ʹ0ʺE respectively. Results from the 3D Euler analysis revealed the depth range of 0.25 Km to 4.018 Km. the spectral Analysis revealed a depth range of Magnetic source (Zt) is (-)0.564 Km to (-)0.828 Km, the Zo is (-)4.261 Km to (-)5.999Km and the average depth to basement thickness is (-)4.825 Km. The Curie Point Depth, Geothermal Gradient, and Heat flow yield an average depth of (-)9.452 Km, a value of 61.893CKm-1, and 154.983 mWm-2 from the Spectral Analysis. Some structural features such as trending faults, and fractured basements was observed at the NE-SW of the study area and this correlated to the relatively high heat flow and geothermal gradient at the NNE-SSW part is associated with thermal structures, mineralogical and tectonic history from the NE-SW trending fault in the study area is suitable for geothermal energy exploitation.

Comparison of Ion-Milling Techniques For Cross-Sectional TEM of Semiconductors

1985 ◽  
Vol 43 ◽  
pp. 166-167
Author(s):  
Julia T. Luck ◽  
C. W. Boggs ◽  
S. J. Pennycook
Keyword(s):  
Analytical Techniques ◽  
Sample Surface ◽  
Ion Milling ◽  
Cross Sectional ◽  
Reliable Technique ◽  
Near Surface ◽  
Transmission Electron ◽  
Thin Region ◽  
Transient Thermal

The use of cross-sectional Transmission Electron Microscopy (TEM) has become invaluable for the characterization of the near-surface regions of semiconductors following ion-implantation and/or transient thermal processing. A fast and reliable technique is required which produces a large thin region while preserving the original sample surface. New analytical techniques, particularly the direct imaging of dopant distributions, also require good thickness uniformity. Two methods of ion milling are commonly used, and are compared below. The older method involves milling with a single gun from each side in turn, whereas a newer method uses two guns to mill from both sides simultaneously.

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