Analysis Of Aeromagnetic Data Research Articles

Curie point depth, thermal gradient and heat flow along the Ethiopia Rift System and adjacent plateaus using spectral evaluation approach: implications for geothermal resources

The Ethiopia Rift System (ERS) is a section of the East African Rift System within Ethiopia extending from the Afar in the northeast to the Kenya border in the southwest. It is apparent that magmatism and magmatic intrusions influence the crustal shape in the ERS resulting in its thinning and the shallowing of magmatic sources at various locations within it. As a consequence, more than 31 volcanoes hosting hydrothermal structures with a conceivable potential to generate massive quantities of geothermal energy have been identified along the ERS. In this study, we map the Curie Point Depth (CDP) over the ERS based on the analysis of aeromagnetic data extracted from the World Digital Magnetic Anomaly Map. Spectral evaluation method was used to estimate the boundaries (top and bottom) of the magnetized crust. Reduced-to-pole (RTP) aeromagnetic records have been divided into 105 (50% overlap) square blocks of 200 × 200 km size. The Curie temperature (580 °C) of magnetite was used to determine the thermal gradient and the heat drift in the area. The depths obtained for the bottom of the magnetized crust are assumed to correspond to the Curie Depths, where the magnetic layer loses all its magnetization. The determined values of Curie Point Depth, geothermal gradient and heat flow for the 50% overlapped 105 blocks, respectively, range from 8.85 to 55.85 km, 10.38 to 65.54 °C/km and 25.96 to 163.84 mW/m2. Lower CPD (< 20 km) in the ERS was obtained between Mille and Gewane (southwest Afar), between Adama (Nazret) and Yerer (NMER) and between Wendo Genet and Koti (SMER) localities. These areas, showing low CPD, exhibit excessive geothermal gradient and high heat flow all of which indicate the presence of significant geothermal potential.

Correction to: Mapping of geological structures and sediment thickness from analysis of aeromagnetic data over the Obudu Basement Complex of Nigeria

Correction to: Mapping of geological structures and sediment thickness from analysis of aeromagnetic data over the Obudu Basement Complex of Nigeria

In-situ Location of Precious Stones using Magnetic Data and Pseudo-Gravity Transforms in Parts of the Nupe Basin Area of Nigeria

In-situ location of precious stones from the mineral-rich zones in parts of Lafiagi (Sheet 203) and Pategi (Sheet 204) areas of Bida basin, central Nigeria was carried out. It was aimed at identification of the structures that usually host precious stones and then locating them in these areas. This work involved the qualitative and quantitative analysis of aeromagnetic data and pseudo-gravity transforms using the 3-D Euler Deconvolution subroutine of Oasis MontajTM software and the geological information obtained from reliable sources in the structural interpretation and isolation work. The geological features in the studied region have been connected to the presence of gemstones known to associate with them making their location logical and easier than the hit- or-miss approach adopted by the artesian miners. The results have shown that the abundance of 2D and 3D structures that are commonly associated with precious minerals as well as the persistence and continual activities of artisanal miners explain why the study area is rich in mineral deposits. Keywords: Precious stones, Mineral-rich, aeromagnetic, pseudo-gravity transforms, 3-D Euler.

Delineation of structural features and hydrothermal alteration zones using integrated geophysical data of part of North-central Nigeria

Delination of possible structural features in part of Nigeria Northcentral region has been performed using high-resolution aeromagnetic and aero radiometric data. The objectives of this work are to identify and harness the factors responsible for alteration zones which can serve as a potential mineralized sources for exploration purpose in the area. To achieve this purpose, mathematical techniques such as First Vertical Derivative, Analytic Signal, and Centre for Exploration Targeting (CET) grid were performed on the aeromagnetic data analysis and interpretation; in addition, ratios of radioelements were obtained to support the mapping process. The results obtained showed that the area is dominated by structures trending Northeast-Southwest, Northwest, Northeast, Eastwest and Northsouth directions, although the structures trending Northeast-Southwest were found to be most predominant and considered as orientations of mineral deposits in the area. Also, aero radiometric analysis based on the concentrations of Potassium, Uranium, Thorium and their ratios revealed lithological units and hydrothermal alterations of the area. However, this study concluded by identifying and harnessing the factors responsible for alteration zones which can serve as a potential mineralized sources for exploration purpose in the area.

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.

Mapping of geological structures and sediment thickness from analysis of aeromagnetic data over the Obudu Basement Complex of Nigeria

Abstract In this study, geologic structures, as well as attendant orientations and sediment thickness, in the Nigerian Obudu Complex were delineated using the Centre for Exploration Targeting (CET), and depth determination methods such as source parameter imaging (SPI) and standard Euler deconvolution (SED). The CET, SPI, and SED procedures were applied on the total magnetic intensity data. Also, the enhanced TMI data using analytic signal, first-vertical derivative, total-horizontal derivative, and tilt-angle derivative filters were further subjected to CET operation, with the aim of mapping both subtle and prominent lineaments. In general, mapped geologic structures trends in the NE–SW, NNE–SSW, E–W, and N–S directions. Overall, the dominant geologic structural orientations of NE–SW and NNE–SSW reflect the regional strike orientation. The regional striking of the lineation, which is caused by the Pan-African orogeny and subsequent post-orogenic processes, has an impact on these orientations. The N–S and E–W structural deviations from the main NE–SW and NNE–SSW trends are initiated by the YGS of the post-orogenic events. Overall, these complex geologic structures are probable sites for metallogenic minerals.

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).

Curie Point Depth from Spectral Analysis of Magnetic Data in Potiskum and Environs, Yobe State, Nigeria

The area under investigation, is part of Chad basin of northeastern Nigeria, located between latitudes 11o00´ to 12o00´N and Longitudes 11o30´ to 12o30´E, with the objective to discover more about the thermal structure of the crust in the area, a research was carried out over Potiskum and surrounding regions in Yobe State, Nigeria to estimate the curie point depth, geothermal gradient, and heat flow using spectrum analysis and empirical formula of aeromagnetic data. To acquire the regional and residual data, polynomial fitting was applied to the high-resolution digital aeromagnetic data. In order to calculate the depth to the centroid and the depth to the top boundary, the upward continued residual data was processed to produce the upward continued data, that was subjected to spectral analysis. The depth to the centroid is between 10.50 and 11.50 kilometers, the depth to the top boundary is between 5.90 and 7.16 kilometers, the depth to the Curie point is between 14.84 and 16.83 kilometers, the geothermal gradient is between 34.462 and 39.083 oCkm-1, and the heat flow is between 86.135 and 97.707 mWm-2. The Curie point depth inferred from the study indicates that the crust is thinning due to thermal upwhirling of magma and is moderately decreasing toward areas of volcanic activity that occurred in the area during the Tertiary Period. The Geothermal gradient shows that the area is a moderate temperature zone, which could likely result in partial thermal maturation of sediments and hence probable oil generation as time goes on with an increase in temperature. In the research area, the geothermal gradient is proportional to the heat flow, whereas the connection between curie depth and heat flow is inversely linear. These findings are in line with the geotectonic regime that is now in effect in the research area. However, this analysis shows that the heat flow that was obtained from the study is sufficient to be utilized as a geothermal energy source.

Predictive Mapping of Prospectivity for Gold in the Central Portion of the Tapajós Mineral Province, Brazil

This work aims to model mineral prospectivity for intrusion–related gold deposits in the central portion of the Tapajós Mineral Province (TMP), southwestern Pará state. The scope includes experimentation and evaluation of knowledge and data-driven methods applied to multisource data to predict potential targets for gold mineralization. The radiometric data processing allowed to identify a hydrothermal alteration footprint of known gold deposits, providing information in regions with little or no field data available. The aeromagnetic data analysis prompted the identification of high magnetic zones, which are probably related to hydrothermal fluid transport. Linear features extracted from digital elevation data revealed an NNW–SSE general trend, which is consistent with the main structural control of deposits. The data were integrated through three modeling techniques—fuzzy logic (knowledge-driven), weights of evidence (WofE, data-driven), and a machine learning algorithm (SVM, data-driven)—resulting in three prospective models. In all models, the majority of indicated prospective regions coincide with the known deposits. The results obtained in the models were combined to generate an agreement map, which mapped the overlapping of their highest prospective scores, indicating new areas of prospective interest in the central portion of the TMP.

An analysis of aeromagnetic data of the Wulong gold deposit in Liaodong area: guide for structural identification and mineral exploration

An analysis of aeromagnetic data of the Wulong gold deposit in Liaodong area: guide for structural identification and mineral exploration

Subsurface structure of the Tarfaya-Laayoune-Dakhla basin (West African Craton Margin, Morocco) revealed from the analysis of aeromagnetic data

The Tarfaya-Laayoune-Dakhla basin is the largest coastal basin in the Moroccan Atlantic margin. It is filled by a thick Meso-Cenozoic sedimentary cover that overlies unconformably the NW margin of the West African Craton and its Proterozoic to Paleozoic peripheral orogenic belt. In this study, we aim to decipher the structure of hidden part of these terranes and discuss the tectonic evolution of the basin. To achieve these objectives, aeromagnetic data were processed by the application of edge enhancement and depth estimation operators. The combination of their results with geological information and boreholes data allowed the construction of a detailed structural map of the subsurface of the study area. The resulted map delineates three distinct tectonic domains: the Northeastern Domain, the Western Domain and the Southern Domain. These domains exhibit geological evidences of four major tectonic periods: the Eburnean, Pan-African and Variscan orogenies, and the Triassic rifting. The Eburnean dextral transpression event formed a shear-zone with a large magmatic body in the Western Domain. This domain was not affected by the subsequent Pan-African orogeny and the following Ediacaran intracontinental rifting phase. Meanwhile, this event led to the formation of an N- to NNE-trending large half-graben structure in the Northeastern Domain, and an Ediacaran bimodal magmatic series in the Southern Domain. The Paleozoic Variscan orogeny has reactivated the N- to NNE-trending normal faults, allowing thrusting in these domains. Eventually, the Central Atlantic opening event reworked pre-existing reverse faults resulting increases in depth in the Northeastern and Western Domains, meanwhile, the extension was reduced in the Southern Domain.

Favourable IOCG and polymetallic environs in Marwar - Khetri, NW Indian Shield imprints from aerogeophysical data analysis

The analysis of aeromagnetic data reveals two significant broad oval-shaped aeromagnetic anomalies oriented in the NE-SW direction, west of Laxmangarh and east of Fatehpur. These significant anomalies identified beneath sand-alluvium-covered areas of Rajasthan's Marwar region are of a low dominance nature. These magnetic signatures are associated with gravity gradients in the regional Bouguer gravity map. Magnetic anomalies and subsurface modeling revealed that the remanence source had a high magnetic susceptibility. The ground gravity profiles across the Laxmangarh anomaly show a high gravity variation of 5 mGal/km. The integration of geochemical distribution patterns, spectrometric elemental concentrations, different ratios, and composite image maps has brought out alteration/shear zones that are favourable for mineralization. The results of selective 2D-profiles, plate modeling, and 3D-inversion modeling of these anomalies reveal that the depth of the causative source varies from 300 to 1000 m. The higher-order magnetic susceptibilities, geochemical dispersion pattern, and spectrometric ratio maps and composite images distinguished hydrothermal alteration zones characterised by potassium enrichment. The results indicate the possibility of concealed source rocks with high magnetic mineral content (magnetite, maghemite, titanomaghemite, pyrrhotite, and franklinite?) and a relatively high density. The geophysical signatures observed around Fatehpur and Laxmangarh, with high magnetic contrast, low dominance, and remanence coupled with high gravity values, as well as hydrothermal alteration zones, appear to have striking similarities with the geophysical and geochemical scenarios of some of Australia's Iron Oxide Copper-Gold (IOCG) prospects in the Gawler, Arunta, Tennant, and Mount Isa regions. Therefore, these anomalous areas may be explored for the possibilities of an IOCG or polymetallic type of mineral.

Application of Aeromagnetic Data Analysis and Interpretations to Investigate Solid Mineral Potential in Part of Bauchi, Northeast Nigeria

Abstract: The distribution of surface and subsurface magnetic materials within the study area, the delineation of geologic lineaments, and an estimate of the depth to magnetic sources were all determined by interpreting high resolution aeromagnetic data that covered a portion of Bauchi, northeastern Nigeria, lying between Latitudes 9040'00"N to 10010'0"N and Longitudes 900'0"E to 9040'0'E. The Aeromagnetic map, analytical signal, and horizontal derivative filters used on total magnetic intensity data after reduction to the magnetic equator (RTE) show that the Toro and its environs contain highly magnetic minerals thought to be potential deposits of iron ore. The lithological map and the lineament maps have a good connection. Further examination of the findings reveals that the research area has varying degrees of Ferro-, para-, and diamagnetic mineralization (of the iron and non-iron varieties). The geological source bodies are thought to be located between 177.389 and 991.626 meters deep, according to the Euler depth solution. This shows that during the orogenic process, a sequence of strong deformations were present alongside the Toro.

Detection of potential hydrocarbon accumulations at Qaret El-Soda area, Western Desert, Egypt, based on airborne geophysical survey data

Airborne spectral gamma-ray survey data were processed using Th-normalization technique for oil and gas exploration in the Qaret El-Soda area, Western Desert of Egypt. This technique was applied to suppress the effects of surface lithology, which are the main factors influencing the variation of radioelement content in rocks. Normalization of K and U by thorium yielded residual potassium and residual uranium estimates. Possible occurrences of new hydrocarbon microseepages were determined by mapping low values of residual potassium and high values of residual uranium relative to potassium, which are indicated as DRAD values, which were obtained by subtracting residual potassium from residual uranium values (eUresid – Kresid). Lower residual values of K, which were associated with higher DRAD anomaly values, highlight areas of prospective hydrocarbon accumulations. The obtained results from quantitative analysis and interpretation of aeromagnetic data show sufficiently thick sediments, probably suitable for the accumulation of hydrocarbons. This means that the study area may possess a potential for hydrocarbon exploration if supported by other detailed geophysical and geochemical exploration techniques.

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)”

EVALUATION OF DEPTH TO BASEMENT, HEAT FLOW, AND LEAD-ZINC MINERALIZATION FROM ANALYSIS OF AEROMAGNETIC DATA IN SOME PARTS OF SOUTHERN BENUE TROUGH

The techniques of aeromagnetic data analysis were employed to elucidate depth to magnetic basement sources, lead-zinc (pb-zn) mineralisation and heat flow in parts of Southern Benue Trough. The study area covers an area extent of about 18,150 sq. Km, latitude 05 0 30’N - 06 0 30’N and longitude 007 0 30’E - 009 0 00’E. The digital aeromagnetic data consisting of Total Magnetic Intensity with geospatial attributes covering six (6) sheets 302 (Nkalagu), 303 (Abakaliki), 304 (Dangha), 313 (Afikpo), 314 (Ugep) and 315 (Ikom) were used in this study. Several magnetic digital filtering methods such as reduce to pole, low/high pass, etc were applied on the data before analysis for lineaments, mineralisation, and depth to magnetic sources. Zones of broad magnetic anomalies were found in the north eastern and south eastern part of the study area like Otam-Izekwe, Enyigba, Uburu, Abakaliki, Ndieze Izzi, Isiagu, Obubra, Oturekpe, Mkpani, Idomi, Enona, Ugep, etc. Depth estimates to the magnetic basement sources from spectral analysis range from 0.65km to 1.155 km, while depth estimate from source parameter imaging (SPI) stretches from 0.679km to 7.723km. The north western part of the study area is the deepest. Pb-zn mineralization within the study area is found to be structurally controlled trending in NE-SW and NW – SE directions. The heat flow values range from 0.65 – 1.95Wm -2 , pb-zn mineralization is within 0.9 – 1.4Wm -2 and Curie point depth range from 0.75km to 2.1km. Keywords: Depth to basement, Heat flow, Lead-Zinc, Mineralization, Aeromagnetic data DOI: 10.7176/JEES/13-2-06 Publication date: March 31 st 2023

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.

Aeromagnetic Interpretation of Basement Structures and Geometry in Parts of the Middle Benue Trough, North Central, Nigeria

The research of an analysis of aeromagnetic data collected in the middle Benue Trough in north-central Nigeria is presented. A detailed analysis of basement structures is conducted in order to identify regions with high hydrocarbon potential that is different from those discovered by earlier researchers. Aeromagnetic data were filtered by using the Butterworth and Gaussian filters, transformed by engaging the reduction to the equator technique, and subsequently enhanced. To estimate magnetic basement depths at various places throughout the basin, the Euler deconvolution depth weighting approach was used. Eleven (11) sub-basins with depths ranging from –2000 m to –8000 m were also identified by Euler’s findings. The sub-basins trend in the NE-SW direction while the average sediment thickness is found to be more than 3 km. The extracted structural features indicate areas like Kadi Blam and Kado areas in the southeastern part and Ogoja and Obudu in the southern part of the study area as regions with high structural densities. These areas coincide with the areas delineated as the sub-basins. The cross-sections generated reveal depressions caused by the action of some tectonic activities in the area. This study identified undulating basement topography believed to be due to tectonic activities as well as five areas that are possible targets for hydrocarbon exploration.

Structural analysis of fracture networks controlling geothermal activity in the northern part of the Malawi Rifted Zone from aeromagnetic and remote sensing data

We investigated the relationship between the geothermal activity and fracture networks that control storage and fluid pathways of geothermal systems in the northern part of the Malawi Rifted Zone (MRZ). It is suggested that low to medium temperature geothermal systems in the MRZ are mainly non-magmatic and structurally controlled. However, structural controls and favorable settings of geothermal activity are poorly understood in this region. We used an approach of remote sensing and aeromagnetic data analysis to 1) identify and characterize fracture networks to better understand the structural controls of geothermal activity in the northern part of the rift, 2) quantify and identify permeable areas using topological analysis of fracture intensity and connectivity frequency proxies, 3) understand the role that inherited structures play in the geothermal systems of the northern part of the rift, and 4) build preliminary geothermal conceptual models of selected geothermal systems. Our findings show that fracture networks in the Karonga and Nkhata regions comprise a varying degree of complexity along strike. This structural complexity occurs mainly in favorable structural settings such as 1) two fault segments coalescing to form hard and soft-linked relays, 2) two different oriented fracture segments intersecting each other, and 3) on the tips of major normal faults. The hot springs are located where one or more of these favorable settings occur. The remote sensing analysis shows that Quaternary normal faults are the primary controlling structures of thermal waters at shallow depths in the Karonga (NW-SE to N-S strike) and Nkhata (N-S strike) regions. The aeromagnetic data revealed that permeable NW-striking foliation planes of the Precambrian Mugesse Shear Zone and WNW to ENE-striking foliation planes of the Mwembeshi Shear Zone are important structural controls of geothermal fluids at greater depths in the Karonga and Nkhata region, respectively. The Mwankeja-Mwesia and Chiweta geothermal systems in the Karonga region show favorable structural settings for geothermal fluids related to NNW and NW-striking normal faults segments that coalesce to form hard and soft-linked relay ramps and NW, and NNE -striking faults intersecting each other and NW-striking foliation planes. The Mtondolo geothermal area in the Nkhata region shows that the intersection of N-striking normal faults and ENE-striking foliation planes is the favorable structural setting that controls the emergence of hot springs through the surface. We conclude that high fracture intensity and connectivity are related to the location of the hot springs at the surface and can be used to determine permeable zones and hidden geothermal fluids together with other methodologies. The aeromagnetic data analysis suggested that buried faults and inherited structures (e.g., foliation planes) are controlling the geothermal fluids at depth. Additionally, our aeromagnetic analysis of magnetic basement depth estimation suggests that some of the geothermal reservoirs in the northern part of the MRZ could have an estimated depth of ~ 500 to 1000 m.b.g.l. Finally, the low-cost methodology applied in this study can reduce the risk of drilling non-productive wells in the early exploration stages and become an exploration strategy for similar geothermal systems in countries of the Western Branch of the East African Rift System.