Spectral Analysis Of Aeromagnetic Data Research Articles

Spectral analysis of aeromagnetic data over parts of Southwestern Nigeria

This study endeavors to assess spectral depths, explore Basement structure variability, and deduce geothermal heat distribution by determining Curie point depth (Zb) through aeromagnetic data analysis across 14 sheets in Southwestern Nigeria. The depths to the shallow magnetic source (Zt) range from 0.14286 km to 1.02632 km, indicating sediment thickness, with the deepest point situated in the Northwestern region and progressively shallower towards the central and Southern portions of the study area. Depths to the deeper magnetic source (Z0) span from 1.08333 km in the North-central part to 3.23529 km in the Southwestern part. The primary sources of the first layer (Zt) depth are intrusions/outcropping Basement rocks, while the second layer (Z0) results from the intrusion of magnetic rocks into the basement, intra-Basement fissures, and deeper magma intrusions below the bedrock. Curie point depth ranges from 1.87380 km to 6.25629 km, with the North-central region exhibiting the shallowest depths, followed by the Northeast, Northwest, and Southeast. Shallow Curie point depth is attributed to magma upwelling and magmatic intrusion in highly fractured quartzite units and older granite units, while deeper Curie point in the Southwestern part may result from isostatic compensation/recovery. Given that Curie point depths are shallower than 10 km, the study area holds geothermal resource potential, particularly in the North-central region. The correlation between estimated spectral depths from aeromagnetic data and observed geothermal signatures in the study area promises to be advantageous in the pursuit of alternative energy generation, potentially mitigating the effects of global warming.

An attempt to calculate the curie point in the Eastern part of Egypt

A curie point depth (CPD) map of the selected area in Egypt (Safaga–Hurghada area along the Red Sea coast), was constructed from the spectral analysis of aeromagnetic data. It was chosen there because the Red Sea and the Gulf of Suez coasts are considered as two of the highest temperature geothermal potential in Egypt. The CPD values were estimated from 10 overlapping blocks, 90 × 90 km in size, using band-pass filtered of aeromagnetic data. The Curie point depth was calculated. The CPD for the region ranges between 26.69 km and 42.69 km.A corresponding heat flow map was also generated from CPD and thermal gradient estimation. The boundaries between the zones of the shallow and deep CPD's coincide well with faults trending NW direction (more or less parallel to the Red Sea) and NE direction. Deepening of CPD's (low heat flows) was detected in two parts, the first one at the northern part of the study area (NW part of Ras Gemsa region). The second, at the southern part (east of Qena).

Discussion about “estimation of curie depth, geothermal gradient and near-surface heat flow from spectral analysis of aeromagnetic data in the loum-minta area (centre-east cameroon)”

Discussion about “estimation of curie depth, geothermal gradient and near-surface heat flow from spectral analysis of aeromagnetic data in the loum-minta area (centre-east cameroon)”

DETERMINATION OF GEOTHERMAL POTENTIAL IN YANKARI GAME RESERVE, BAUCHI STATE, NIGERIA

The study deals with the determination of geothermal potential of Yankari Game reserve which involves; estimate of the Curie point depth, heat flow and geothermal gradient from spectral analysis of aeromagnetic data covering an area located approximately at longitude 9.7567 oN and Latitude 10.5094 oE. Radially power spectrum was applied to the aeromagnetic data of the study area divided into 4 square blocks and each block analyzed using the spectral centroid method to obtain depth to the top, centroid and bottom of magnetic sources. The depth values were subsequently used to evaluate the Curie-point depth (CPD), geothermal gradient and near-surface heat flow in the study area. The values of the curie point depths (Zb), range from 8.91 km to 10.11 km, with a mean value of 9.71 km, geothermal gradient, range from 57.37 oCkm-1 to 65.10 oCkm-1, with mean value of 60.10 oCkm-1 and heat flow (q), range from 143.43 mWm-2 to 162.75 mWm-2, with a mean value of 150.24 mWm-2. These results entails that the area under study has good geothermal potential for exploration.

Solid Mineral Potential and Geothermal Energy Reserve of Northern Basement Complex, Nigeria

Abstract in English The spectral analysis of aeromagnetic data over the study area (Northern basement complex, Nigeria) revealed the existence of two major source depths. The second segment of the spectrum layer shows shallow sources ranging in depth from 0.135 km to 0.201 km, with an average depth of 0.140 km. The depth to the basement or deeper source ranges between 1.655 km and 2.021 km, with an average depth of 1.882 km. The Precambrian basement is reflected in the deeper sources, beginning with the first segment of the power spectrum. Structural and topographic relief of the basement surface, lateral differences in basement susceptibilities, and intra-basement features such as faults and fractures contribute to the variation in basement composition. The mean thickness of sediments in the study area is represented by the D2 values obtained from the spectral plots. The depths revealed by this study appears to be reasonable and consistent with previous researchers’ findings. Tectonically active regions have a major impact on heat flows. The average heat flow in thermally normal continental regions is reported to be above 60 mW/m2. Values between 80 and 100 mW/m2 indicate a good geothermal source; values in excess of about 80–100 mW/m2 indicate anomalous geothermal conditions.

Determination of depth to basement using spectral analysis of aeromagnetic data over Azare segment of Chad Basin

The high-resolution aeromagnetic data over part of the Bornu basin (sheet 84) north eastern (NE) Nigeria, was processed and interpreted using spectral analysis to determine the depth to the basement. The study area is bounded between longitude 10⸰ 00’ 00’’E to 10⸰ 30’ 00’’ E and latitude 11⸰ 00’ 00’’ N to 12⸰ 00’ 00’’. Regional residual separation of the total magnetic field intensity (TMI) was performed using polynomial fitting method. The residual map was divided into nine square spectral blocks using the filtering tool of Microsoft excel software. The Microsoft excel program employed Fast Fourier Transform (FFT) technique. It transforms the magnetic field data into the radial energy spectrum for each block. Then the average radial energy spectrum is computed in MATLAB. The result shows that depth to the deeper magnetic source ranges from 4503.9m to 1948.3m. However, it can be observed that NN, NE, and NW are having less deep magnetic sources ranging from 1948m to 2459.7m. The deepest sources happened at the major towns of interest which are Bidawa , Matsango , Yakiri and Fatara areas, Katagum Bauchi state ranging from 2632.8m to 4503.9m The maximum depth of the sedimentary unit was estimated as 4.5km because the isolated value beyond this depth cannot be connected , and this depth occurs around Matsango and Bidawa. The shallow depth magnetic source map shows that SS, SW, SE are having least shallow depth, central to northern part of the study area are having shallowest depth to the magnetic source.

Geostatistical mapping of the depth to the bottom of magnetic sources and heat flow estimations in Mexico

The depth to the bottom of magnetic sources (DBMS) is widely used as a proxy for crustal thermal structures. In this study, the DBMS is calculated using the spectral analysis of aeromagnetic data for the whole territory of Mexico. By assuming the DBMS to be related to the Curie point depth, the heat flow distribution is estimated. The DBMS and heat flow maps were constructed using geostatistical simulations to quantitatively determine standard deviation as uncertainty. The results show a good agreement with the complex geologic and tectonic setting in Mexico. Small DBMS values (high heat flow) as expected appear in areas where recent volcanism occurs and at seafloor spreading zones. In contrast, large values are present in tectonically stable zones.

Estimation of Curie point depth and geothermal gradient in parts of the Bida Basin, Nigeria

The purpose of this work is to estimate the Curie point depth, heat flow and geothermal gradient from spectral analysis of aeromagnetic data over the Bida and Baro areas, Bida Basin, north central Nigeria. The area covered is approximately 6050 km2 and bounded by latitudes 8° 30′ and 9° 30′ north and longitudes 6° 0′ and 6° 30′ east. The aeromagnetic maps were digitised at an equal interval, and the regional values were removed using polynomial fitting. The resulting residual data were subjected to the upward continuation technique to suppress the short-wavelength components of the residual magnetic anomalies. The upward continuation residual map was divided into eight overlapping blocks, and each block was spectrally analysed. The estimated Curie point depth ranges from 13.6 to 27.2 km, the geothermal gradient ranges from 21.3 to 42.6°C/km with an average value of 34.4°C/km and the corresponding heat flow ranges from 53.2 to 106.6 mW/m2. The average value of the geothermal gradient of 34.4°C/km indicates the possibility of hydrocarbon maturation in the area. Areas of geothermal anomalies with gradients greater than 40°C/km may be prospective for geothermal energy usage in Nigeria for generation of electricity.

Crustal and thermal structure of the Permian – Jurassic Luangwa – Lukusashi – Luano Rift, Zambia: Implications for strain localization in magma – Poor continental rifts

This work uses aeromagnetic, satellite gravity, and ground gravity data to image the thermal and crustal structures beneath the NE-trending Paleozoic - Mesozoic Luangwa – Lukusashi – Luano (LLL) rift in southeastern Zambia. This rift extends between the Precambrian Irumide metacraton in the northwest and the Niassa craton to the southeast and is partially controlled by the NE-trending Mwembeshi suture zone between the two blocks. Although the LLL rift is suggested to have been reactivated by the Southwestern Branch (SWB) of the East African Rift System (EARS), this work did not find shallowing of Curie Point Depth (estimated from the spectral analysis of aeromagnetic data) that would be indicative of elevated heat flow beneath the rift. Three-dimensional inversion of the aeromagnetic data shows a number of magnetized bodies, the largest occurring beneath the central part of the LLL rift and extending to a depth of ~35 km. Spectral analysis of the satellite gravity data indicates a ~45 km thick crust beneath the southwestern and central parts and the northeastern tip of the LLL rift. Two-dimensional (2D) forward modeling of the ground gravity data indicates a ~200 km wide and ~12 km thick under-plated mafic body (UPMB). These results support limited reactivation of the LLL rift by the SWB of the EARS. Further, extensional strain localization during the onset of the LLL rifting is attributed to the accretion of the UPMB beneath the crust.

Magnetic sources in the Earth’s mantle

Since the 1970s, ferromagnetic minerals were believed to be absent in the Earth’s mantle and, even if present, the temperatures were considered too high for such phases to carry magnetic remanence. However, new experimental data, measurements on mantle xenoliths and an improved understanding of long-wavelength features in aeromagnetic data require that the magnetization of the mantle be revisited. In this Review, we examine mantle magnetism through the xenolith record, evaluate the latest experimental advances, assess detection methods of deep-seated mantle sources and identify salient, unsolved questions about magnetic sources in the Earth’s mantle. Critically, magnetic data on a worldwide collection of mantle xenoliths have revealed that pure magnetite is common in the uppermost mantle (<150 km), particularly in subduction zones and cratons. Furthermore, experiments on haematite and its polymorphs suggest that they could carry a magnetic remanence down to ~600 km, for example, in cold, subducted slabs. Finally, modern spectral analysis of aeromagnetic data confirms that a magnetized layer is present below the crust–mantle boundary in multiple tectonic settings. Future work needs to explore the magnetic minerals in the deepest available mantle xenoliths (150–660 km), in conjunction with experiments on mantle materials at pressures corresponding to these depths. Although it was assumed for decades that the Earth’s mantle could not be magnetic, recent evidence suggests that parts of the upper mantle have magnetic remanence. This Review critically revisits mantle magnetism, discusses recent magnetic data and identifies unresolved questions about the sources of this magnetism.

Correction to: MAGCPD: a MATLAB-based GUI to calculate the curie point-depth involving the spectral analysis of aeromagnetic data

The authors of the above published paper were notified by one of the authors referenced in their paper

Evaluation of geothermal potential in some parts of Bida Basin of Nigeria using Curie point depths and heat flow from spectral analysis of aeromagnetic data.

The Centroid method of Spectral Depth analysis was used to evaluate the Curie point depth (CPD), Geothermal Gradient and Heat Flow in some parts of the Bida Basin of Nigeria with a view to determining the energy potential of the area. The reduced-to-pole aeromagnetic data was divided into 16 overlapping ensembles and Fast Fourier Transformed to decompose the anomalies into their energy and wavenumber components using Oasis montaj software. The radial power spectrum was calculated for each of the grid points with the locations of the centres of the ensembles and a plot of Energy spectrum versus frequency was carried out to generate two different gradients: s&lt;sub&gt;1&lt;/sub&gt; and s&lt;sub&gt;2&lt;/sub&gt; representing different depth source models. These gradients were used to evaluate the average depth to the top of the deepest crustal block, Z&lt;sub&gt;t&lt;/sub&gt;, depth to the centroid of the deepest crustal block, Z&lt;sub&gt;0&lt;/sub&gt;, CPD, Geothermal Gradient and Heat flow. From the results obtained, the CPD varied from 2.59 to 8.23 Km while the thermal gradient and heat flow in the area revealed values ranging from 70.45 to 224.15 &lt;sup&gt;o&lt;/sup&gt;CKm&lt;sup&gt;-1&lt;/sup&gt; and 176.13 to 560.37mWm&lt;sup&gt;-2 &lt;/sup&gt;respectively. The results of the contouring in conjunction with the CPD, geothermal gradient and the heat flow values have shown that the area has a greater energy potential in the south-eastern block of Katonkarfi, with shallow CPD and high geothermal gradient and heat flow. These results could be incorporated in the GIS and available geological, geophysical and geochemical information of the area to facilitate selection of the optimum site for energy exploration.

MAGCPD: a MATLAB-based GUI to calculate the Curie point-depth involving the spectral analysis of aeromagnetic data

The Curie point-depth, frequently related to the depth to the bottom of the magnetic source, is widely employed as an estimator of temperature at depth when borehole temperature data are not available. The Curie point-depth is calculated using the spectral analysis of the magnetic data derived from aeromagnetic or satellite surveys. In this paper, MATLAB user-friendly GUI are constructed to calculate the Curie Point Depth using the inversion of aeromagnetic data assuming 2D fractal magnetization and modeling the temperature at depth assuming a 1D steady-state conductive heat transfer model. The program, tested in synthetic and aeromagnetic data, is running under MATLAB 2020a or standalone application with these input parameters: Aeromagnetic data, fractal parameter, Curie temperature, surface temperature, thermal conductivity, surface radiogenic heat production and scaling length of surface radiogenic heat production. The radially averaged amplitude spectrum, scaled spectrum, modeled spectrum, Curie point-depth, and temperature profile at depth are the output parameters of the program. Finally, the program is tested with Texas aeromagnetic data, and the results of the Curie point-depth were compared with borehole data.

Study of Curie point depth and heat flow from spectral analysis of aeromagnetic data for geothermal potential of Gubio, Chad Basin, Nigeria

Aeromagnetic data of Gubio area, Chad Basin, northeastern Nigeria, were interpreted quantitatively by employing spectral analysis technique with the aim to estimate the Curie point depth, geothermal gradient and heat flow in order to determine the geothermal nature of the area. Data enhancement (reduction to pole, RTP and band pass filter) was performed on the total magnetic intensity (TMI) map of the area using oasis Montaj software. The enhanced map was divided into four overlapping blocks, and each block was subjected to spectral analysis. The results gave Curie point depth values ranging from 10.63 to 20.07 km, with deepest depth at the northeast, while the shallowest depth was observed to be conspicuous in the southeastern part of the study area. The estimated geothermal gradient ranges from 28.90 to 54.57 °C km−1 with an average value of 40.26 °C km−1, with low values in the northeast direction, and increases towards southeast. The average geothermal gradient of 40.26 °C km−1 indicates the possibility of hydrocarbon generation and accumulation in Chad basin. The estimated heat flow values range from 72.24 to 136.43 mW m−2 with an average value of 100.65 mW m−2, the highest values are found around southeastern part of the study area, and the lowest values are within the northeastern part. The areas of geothermal anomalies with gradient above 50 °C km−1 may be good areas for geothermal reservoir exploration for an alternative source for power generation.

Estimation of Curie point depth in southwestern Yemen from spectral analysis of aeromagnetic data

Curie point depths in southwestern Yemen were determined from radially averaged power spectra of the reduced to the pole aeromagnetic data by the modified centroid method. The results show that shallow CPD zones occurred in the western and southeastern parts of the area associated mainly with Tertiary and Quaternary volcanic regions, respectively. The distribution of hot springs and hot groundwater wells through the area is correlated well with the mapped shallow zones and thermal gradient regions around them. On the other hand, the deepest CPD zone is attributed to a hot mantle upwelling underplating the crust beneath the volcanic plateau and crystalline basement margins in the middle part of the area. This spot forming the most probable source of magma for the Quaternary volcanic activity in the area. The observed geothermal activity at Al Lisi–Isbil, Damt, and Al Qafr fields is ascribed to the heat derived from shallow magmatic bodies, with temperature less than Curie temperature of magnetite, and also to the heat transferred from the underlain hot mantle spot through a net of deep faults affected this region.

Curie Point Depth Estimations for Northwest Iran Through Spectral Analysis of Aeromagnetic Data for Geothermal Resources Exploration

The northwest of Iran is considered as a promising geothermal zone owing to its geographical properties, tectonic features, and thermal activities, particularly in Sabalan geothermal field. Several large stratovolcanoes such as Sahand and Sabalan mountains in northwestern Iran, each of which has a vast central dome probably located on a tectonic plate, comprising of intrusive and effusive volcanic rocks. This study mainly aimed at performing the spectral analysis of aeromagnetic data to estimate Curie point depth (CPD), geothermal gradient and heat flow in the northwest of Iran using random magnetization (centroid method and forward modeling of the spectral peak method) and fractal magnetization (de-fractal method). The reduced-to-pole aeromagnetic data were divided into 55 overlapping blocks of 80 × 80 km. The derived range of CPD in the study area using the centroid method, forward modeling spectral peak method and de-fractal method were 9.2–13.9 km, 8.9–13.7 km and 7.2–12.9 km, respectively The derived values of heat flows in the study area using the above-mentioned methods were higher than 104 mW/m2, 105 mW/m2 and 120 mW/m2, respectively. The results of this study were found to have good correlations with wells data and resistivity measurements collected in the Northwest Sabalan geothermal field. Good consistency was also found between the CDPs and earthquake distribution. Moreover, the locations of hot springs and the maximum temperatures of the wells were associated with the variations in the modelled depth of the geothermal resources. Promising regions were in the northeast and southwest parts of the study area.

Applications of Aeromagnetic and Electrical Resistivity Data for Mapping Spatial Distribution of Groundwater Potentials of Dutse, Jigawa State, Nigeria

Optimal mapping of groundwater resource is usually accomplished using integrated geophysical survey in which two or more techniques are applied. In this work, spectral analysis of aeromagnetic data was used to map the topography of the magnetic crystalline fresh basement underlying the water bearing aquifer of Dutse, Jigawa State Nigeria. Vertical electric sounding technique was used to detect the spatial distribution of the depths to the top of the aquifer within the same area.&amp;nbsp; The overall goal of the work is to determine the groundwater potential of the area by mapping the spatial distribution of groundwater availability based on aquifer thickness and basement topography. The aquifer depth was found to be within the range of 5 to 15 m with a mean value of 10 m. The basement was found to be highly undulating having depths ranging from 6 to 69 m with a mean value of 24 m. The existence of isolated deep depressions within the basement which appears to be filled by water bearing sediments was thought to be favorable structures for groundwater accumulation. The spatial distribution of groundwater potential was therefore mapped in a reclassified image of three zones, high, moderate and low. The study therefore provides a vital tool for groundwater exploitation and management strategies.

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)

The current study deals with an estimate the Curie point depth, Heat flow and geothermal gradient from spectral analysis of aeromagnetic data in the Loum – Minta area, Centre-East Cameroun. Aeromagnetic data reduce to equator was divided into 5 blocks. All of the blocks overlapped with adjoining blocks by 50 percent and each block analyzed using the spectral centroid method to obtain depth to the top, centroid and bottom of magnetic sources. The depth values were subsequently used to evaluate the Curie-point depth (CPD), geothermal gradient and near-surface heat flow in the study area. The result shows that the CPD varies between 5.22 and 14.35 km with an average of 9.09 km, the geothermal gradient varies between 40.42 and 111.11 °C/km with an average of 72.24 °C/km, and the resulting heat flow varies between 101.05 and 277.77 mW m−2 with an average of 180.59 mW m−2. Such heat flow values are suggestive of anomalous geothermal conditions and are recommended for detailed geothermal exploration.

Determination of Geothermal Energy Sources in Masu Area Northeastern Nigeria Using Spectral Analysis of Aeromagnetic Data

The incessant power outage and power rationing in Nigeria has affected the economic development, hence the need to seek for other sources of electricity generation such as geothermal energy which is environmentally friendly and renewable. The wide range of geologic formations in the north-eastern Nigeria provides an avenue for exploration of geothermal energy. Hence, this work carries out an investigation of Curie point depth, geothermal gradient as well as heat flow in Masu, which is located within Nigerian sector of Chad Basin (lat. 12°00' to 13°00' N and long. 12°30' to 14°00' E) using spectral analysis. Application of minimum curvature in gridding the total magnetic field intensity data was done using the Oasis Montaj 6.4.2 software. First order polynomial fitting was applied in Regional-residual separation. The Curie point depth obtained ranges from 12.233 to 16.184 km with an average of 13.993 km, the geothermal gradient of the area varies from 35.838 to 47.413°C /km, with an average of 41.821°C /km, while the heat flow ranges from 89 to 117.80 mWm^-2, with an average of 104.551 mWm^-2. The 2D contour maps reveal that the Curie point depth is lowest in the southeast and increases towards the northwest, while the geothermal gradient and heat flow on the other hand are highest in the southeast and decrease towards northwest. The high geothermal gradient and heat flow values in the area are indications that the area might be suitable for geothermal energy generation as an alternative power supply in the area and in the country at large.

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