Applying Source Parameter Imaging (SPI) to Aeromagnetic Data to Estimate Depth to Magnetic Sources in the Mamfe Sedimentary Basin

Aeromagnetic data over the Mamfe Basin have been processed. A regional magnetic gridded dataset was obtained from the Total Magnetic Intensity (TMI) data grid using a 3 × 3 convolution (Hanning) filter to remove regional trends. Major similarities in magnetic field orientation and intensities were observed at identical locations on both the regional and TMI data grids. From the regional and TMI gridded datasets, the residual dataset was generated which represents the very shallow geological features of the basin. Processing this residual data grid using the Source Parameter Imaging (SPI) for magnetic depth suggests that the estimated depths to magnetic sources in the basin range from about 271 m to 3552 m. The highest depths are located in two main locations somewhere around the central portion of the study area which correspond to the area with positive magnetic susceptibilities, as well as the areas extending outwards across the eastern boundary of the study area. Shallow magnetic depths are prominent towards the NW portion of the basin and also correspond to areas of negative magnetic susceptibilities. The basin generally exhibits a variation in depth of magnetic sources with high, average and shallow depths. The presence of intrusive igneous rocks was also observed in this basin. This characteristic is a pointer to the existence of geologic resources of interest for exploration in the basin.

Characteristics of fault structures in the south coastal zone of Taizhou based on aeromagnetic data

The south coastal of Taizhou lies on the magmatic rock belt along the southeast coast of China,which has a complex regional geological structures,intense tectonic movement,and frequent magmatic activities.On the basis of the latest aeromagnetic data,combined with regional geology,gravity,and magnetic susceptibility information,integrated interpretation of the regional aeromagnetic anomalies and their refl ected faults was completed.According to the block features in diff erent zones of the reduction to the pole aeromagnetic data,the magnetic field characteristics and relationship with the structure division were described in detail.The different characteristics of the magnetic field are the concentrated reflection of tectonic movements,magmatic activities,and stratigraphic distributions;the fault structure,especially deep and large fault structures,was inferred and studied.The fault structures were mainly distributed in the NE,NNE,and NW directions,with approximately equal spacing between them.The magnetic anomaly is mainly characterized by the boundary,gradient zones,and beaded anomalies in a different magnetic field.The faults are not only important tectonic boundaries in this region but also tectonic belts that control the distribution of mineralization.Under the interaction of these faults,they form the basic structural pattern of the east-west zone and the north-south block.The NE faults have the largest scale and obviously control the diff erent magnetic fi elds and magmatic activities.The results can provide a reference for further study of the distribution and activity characteristics of magmatic rocks in the coastal zone.

Characteristics and Geological Significance of Aeromagnetic Data in Taiyuan,Shanxi,China

The study area is located in the central part of Shanxi Province,between Qinling Tectonic Belt and Yinshan Tectonic Belt,which is an important part of North China Platform;General direction of the structural line is NNE,with clear geological structure outline and developed structural features.The study area has complex regional geological structure,intense tectonic movement and frequent magmatic activities.Based on the latest high-precision aeromagnetic data,integrated interpretation was completed,combining with the existing geological and geophysical research results.According to the block features in different zones of the RTP aeromagnetic data,this article thoroughly studied the characteristics of aeromagnetic anomalies and found the relationship between aeromagnetic anomalies and surface geological information,and the fault distribution,magmatic rock distribution and magnetic characteristics in this area are discussed.

Interpretation of Aeromagnetic Data on the Area around Aswan-Berenice Road, Southeast Aswan, Egypt

The area around Aswan-Berenice Road southeast Aswan is geophysically studied to delineate the subsurface structures and to evaluate the tectonic framework of the basement rocks and the overlying sedimentary cover. This area comprises a variety of igneous, metamorphic and sedimentary rocks, ranging in age from Precambrian to Quaternary time. The interpretation of the aeromagnetic data around Aswan-Berenice Road was carried out using GM-SYS modeling technique. Many methods were performed to the RTP aeromagnetic map of the study area such as filtering and trend analysis techniques. The tracing upward and downward of the deduced subsurface structures was investigated using trend analysis for the surface geology and filtered magnetic maps. The locating and determination of the approximate depth of the causative bodies were done using Euler deconvolution, Werner deconvolution and 2.5 dimension magnetic modeling techniques. The obtained results indicate that the most significant tectonic trends are N-S and E-W, which they are in accordance with the local trends of River Nile and Kalabsha fault respectively. Less common trends as NW-SE and NE-SW directions are also detected. Also, the depth to the basement rocks ranges from 0 km at the exposed parts to 1.4 km at the covered parts.

Litho-Tectonic Architecture of the Dialafara Area, Kédougou-Kéniéba Inlier, Integration of New Field Data and Geophysics

The Dialafara area is part of the highly endowed Kédougou-Kéniéba Inlier (KKI), West-Malian gold belt, which corresponds to a Paleoproterozoic window through the West African Craton (WAC). This study presents, first of all, an integration of geophysical data interpretation with litho-structural field reconnaissance and then proposes a new litho-structural map of the Dialafara area. The Dialafara area shows a variety of lithology characterized by volcanic and volcano-sedimentary units, metasediments and plutonic intrusion. These lithologies were affected by a complex superposition of structures of unequal importance defining three deformation phases (DD1 to DD3) under ductile to brittle regimes. These features permit to portray a new litho-structural map, which shows that the Dialafara area presents a more complex lithological and structural context than the one presented in regional map of the KKI. This leads to the evidence that this area could be a potential site for exploration as it is situated between two world-class gold districts.

Research on RTP aeromagnetic gradient data and its applicability in different latitudes

Aeromagnetic gradient data needs to be reduced to the pole so that it can be better applied to geological interpretation through theoretical derivation.In this paper,we conduct research on the morphological characteristics of the total and horizontal gradient modules before and after reduction to the pole and design models at different latitudes,with consistent and inconsistent magnetic field direction and geological body magnetization direction.We discuss how to use the total gradient module and horizontal gradient module in geological interpretation.The reduced-to-the-pole（RTP） method is required for the horizontal gradient module method but not for the total gradient module.Finally,the conclusions derived from the theoretical models are verified through analysis of real data.The position determination of a geological body using the total gradient method,gradient data,or total-field data works better without RTP,ensuring data primitive authenticity.However,the horizontal gradient module should be reduced to the pole to determine the boundary of the geological body.Finally,the theoretical model is verified by actual data analysis.Both the total and horizontal gradient methods can be applied to geological interpretation.

Study on deep structure in Ailaoshan region based on aeromagnetic interpretations

Linear and circular interpretation structure maps of different relative depths are obtained by processing 1:200000 aeromagnetic data to the pole in Ailaoshan region,interpreting upward extension of 4 heights,extracting a vertical second derivative line of 0 value and a series of calculations. Concealed boundary of deep magnetic rocks can be delineated according to the maps. On the basis of the conclusions above,a set of economical and practical methods to graph the deep structure are summarized. In addition,the relationship between deep structure and mineralization positions is discussed.

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.

Magnetic Applications to Subsurface and Groundwater Investigations: A Case Study from Wadi El Assiuti, Egypt

Wadi El Assiuti represents a promising area for agricultural development and building new communities far from the overpopulated areas in the Nile Val-ley. An integrated approach of satellite-based data and geophysical data with borehole data was used for defining the area of interest, the sediment thick-ness, delineating the subsurface structures, and mapping the depth to the basement rocks, and defining the groundwater aquifers. Findings are: 1) Dramatic changes are detected in the anthropogenic activities at the entrance area of the wadi, making stress and heavy exploitation of the groundwater resources. However, the central and northeastern regions show no development;2) Several structural trends in the directions of NNW, NW, NE, and E-W are cutting the basement rocks and sedimentary cover;3) The depth to the basement rocks is increasing eastward from ~2.24 km to ~4.84 km;4) Three groundwater-bearing reservoirs are represented by the shallow Qua-ternary, the fractured limestone, and the deep Nubian sandstone aquifers;5) The deep-seated faults are affecting the area and rising groundwater from the deeper Nubian aquifer along its sub-vertical trend;and 6) The results are in-formative and used to define the suitable sites for water well drilling.

Major Tectonic Lineaments Influencing the Oilfields of the Zagros Fold-Thrust Belt, SW Iran: Insights from Integration of Surface and Subsurface Data

The Zagros fold-thrust belt(ZFTB)formed from the progressive collision between the African-Arabian and Eurasian plates.This study focuses on the major tectonic lineaments concerned with the distribution of oilfields in the southern Dezful Embayment as an extremely rich hydrocarbon province in the ZFTB,SW Iran.Integration of surface,near-surface and sub-surface data(e.g.,remote sensing,overburden rocks,reservoir and aeromagnetic data)were used for locating major tectonic lineaments in the study area.The results show that the southern Dezful Embayment area was influenced by tectonic lineaments oriented in the NW-SE,NE-SW,E-W and N-S trends,which are possible fault indicators corresponding to surface,shallow subsurface and basement faults.The dominant N-S and E-W tectonic lineaments possibly highlight the stress regime inherited from old structures in the Arabian Shield basement while the NE-SW,NW-SE trends are interpreted as effects of the Zagros orogeny.Generally,these tectonic lineaments influenced both the basement and sedimentary rocks and are used here to divide the belt into several faulted blocks with different structural frameworks.A clear picture of the tectonic trends influencing the Zagros fold-thrust belt oilfields as well as guidance for delineating hydrocarbon reservoirs in the future are presented.

Using 3-D magnetic modeling to evaluate subsurface structures of the Siwa Oasis,Western Desert,Egypt

This work was designed to study the subsurface structures in the Siwa Oasis area of the Western Desert in Egypt and to determine their effects on surface geologic structures. A detailed land magnetic survey was performed in traverses covering about 400 km2 of the study area. The measured total magnetic field was corrected and reduced to the north magnetic pole. The reduction-to-pole aeromagnetic and Bouguer anomaly maps were used to obtain regional extensions of these subsurface structures, study the continuation of these structures in sedimentary rocks, and delineate the depths to the basement rocks. Data analysis was performed using trend analysis, Euler deconvolution, Werner deconvolution, the Hilbert transform of the analytical signal, and 3-dimensional magnetic modeling methods. The results indicate that the area is affected by tectonic forces in the E-W, N45°-65°E, and N35°-45°W trends, which are correlated with the directions of surface geologic lineaments. The depth to the basement rocks increases from 3.2 km in the southern part to about 3.6 km in the northern part of the area. The results are in good agreement with depths obtained from drill hole data in the area.