3D Magnetic Model Research Articles

2D structural and thermal models in southeastern Norway based on the recently drilled Årvollskogen borehole and 2D density, magnetic and thermal modelling

BackgroundWe have made an attempt to understand the main mechanism which controls the conductive heat transfer in the Årvollskogen borehole. This has been done in order to determine the 2D subsurface temperature distribution within the deep-seated crystalline rocks and, therefore, to estimate the geothermal potential in the Moss area near Oslo.MethodsAn integrated 2D density, magnetic and conductive thermal analysis has been performed in order to recognise the major structural features and thermal pattern of the crystalline crust.ResultsBased on 2D density and magnetic modelling, a 2D structural model has been constructed for the Moss area. This 2D model has been used during the 2D thermal modelling. The results of the 2D thermal modelling demonstrate that a significant decrease of the Earth’s surface temperatures during the last glaciations still affects the subsurface thermal field of the study area in terms of reduced temperatures within the uppermost crystalline crust. The modelled temperatures are characterised by almost horizontal isotherms without considerable vertical disturbances, reflecting the predominance of subhorizontal layering within the crystalline crust of the Moss area.ConclusionThe 2D density and magnetic modelling, with consideration of all available geological and structural data, allows us to reveal the deep structure of the crystalline crust within the Moss area. According to the results of the 2D thermal modelling, the predicted temperatures within the upper crystalline crust are in the range of expected values for this part of Fennoscandia.

Magnetic data, fault tectonics of consolidated earth crust and oil-and-gas content of the Dnieper-Donets avlakogen

Main perspectives to find oil-and gas deposits into crystal foundation and lower parts of sedimentary cover are related to the deep ruptures of different categories, to its crossings as well as to the presence of decompression and fracturing zones in it. In the article anomal magnetic field (AT ) a , its regional and local components as well as developed 3D magnetic model together with magmatism and fault tectonics scheme of Dnieper-Donets Aulacogene have been analyzed. On the basis of complex analysis and interpretation of obtained data the Earth's crust deep structure have been defined and eventual migration ways to the places of deep hydrocarbons agglomeration have been considered. That interpretation allowed to specify found hydrocarbons inflow locations in the Earth's crust of DDA as well as to indicate the new prospective ones. It also permitted to formulate regional geomagnetic signs oil-and-gas content in foundation and to identify probability to replenish the deposits of sedimentary cover by deep hydrocarbons. It has been defined that decompression and fracturing zones of sedimentary basins foundation located over deep magnetic blocks of DDA consolidated crust may be potentially gas-bearing while weekly magnetic zone of the Earth's crust among strongly magnetic blocks of Chernigiv and Lohvitsa segments is potentially oil-bearing.

자력자료를 이용한 몽골 우기누르 철-망간 분포 특성

한국지질자원연구원은 몽골 광물자원청과 공동으로 우기누르 철-망간 광화대에 대한 공동 연구를 수행하였다. 이의 일환으로 수행된 육상 자력탐사에서 획득한 자료를 바탕으로 3차원 자력 역산을 수행하였으며, 3차원 지질모델링 기술을 이용하여 철-망간 광화대에 대한 3차원 영상화 및 광체 평가를 위한 연구를 수행하였다. 총자력 이상의 분포 특성을 통해 연구지역의 광상에서 지표 노두로부터 수평적으로 연장되는 광체의 부존 가능성을 확인하였다. 또한, Fe 함량과 상관성이 높은 자기감수율 역산 결과를 토대로 연구지역의 제 1광상 및 제 2광상 모두에서 지표에서 드러난 광체가 지하 하부로 연장되어 있는 것으로 해석되어, 지표에 드러나지 않은 광체의 부존 가능성이 높은 것으로 판단된다. 시추 조사를 통해 일부 대표 지역의 광체 품위 자료가 확보되고 이번 연구결과와의 복합 해석을 수행한다면 효과적인 개발 가능성 평가가 가능할 것으로 판단된다. Korea Institute of Geoscience and Mineral Resources (KIGAM) and Mineral Resources Authority of Mongolia (MRAM) performed a joint survey on Ugii Nuur Fe-Mn mineralized area. Following the survey, we carried out magnetic survey and 3D magnetic susceptibility inversion. Based on the inversion results, basic feasibility study and 3D imaging of Fe-Mn mineralized area were performed using 3D geological modeling technique. Using the distribution of total magnetic field data, we were confirmed for the possibility of horizontal extension of ore bodies from surface outcrops. The 3D magnetic susceptibility model, which is highly related with Fe content, analyzed by inversion shows that the ore bodies of Deposit 1 and Deposit 2 are extended to the underground and ore bodies that are not exposed on the surface are largely distributed in the underground. If we perform the integration analysis using this magnetic susceptibility model and the ore grade data analyzed by drilling survey, it is possible to carry out the effective potential evaluation of Ugii Nuur Fe-Mn ore deposit.

Ultra‐thick Triassic dolomites control the rupture behavior of the central Apennine seismicity: Evidence from magnetic modeling of the L'Aquila fault zone

AbstractHigh‐resolution tomography from the 2009 L'Aquila extensional seismic sequence has shown that the Mw 6.1 main shock and most of the aftershocks occurred within a high velocity body (6.6 ≤ Vp ≤ 6.8 km/s), located between depths of 3 and 12 km. The nature of the high‐Vp body has remained speculative, although exhumed mafic deep crustal and upper mantle rocks (serpentinites) have been favored. We used 3D magnetic anomaly modeling to investigate the plausibility of these favored sources for the L'Aquila body. The modeling does not support the presence of high‐velocity serpentinites with a 30–50% serpentinization degree and gabbros. Accordingly, we conclude that the high‐Vp body may represent non‐magnetic upper Triassic and possibly lower Liassic dolomites that have been drilled in neighboring wells for 2–4 km. This conclusion is also consistent with the lack of a coherent gravity anomaly for the body. We speculate that ultra‐thick Triassic dolomites reaching a thickness of 8 km may have been deposited in syntectonic wedges formed at the northern margin of the Ionian Sea, where oceanic spreading occurred in mid‐late Triassic times.

Magnetic field and radiative transfer modelling of a quiescent prominence

Aims. The aim of this work is to analyse the multi-instrument observations of the June 22, 2010 prominence to study its structure in detail, including the prominence-corona transition region and the dark bubble located below the prominence body.Methods. We combined results of the 3D magnetic field modelling with 2D prominence fine structure radiative transfer models to fully exploit the available observations.Results. The 3D linear force-free field model with the unsheared bipole reproduces the morphology of the analysed prominence reasonably well, thus providing useful information about its magnetic field configuration and the location of the magnetic dips. The 2D models of the prominence fine structures provide a good representation of the local plasma configuration in the region dominated by the quasi-vertical threads. However, the low observed Lyman-α central intensities and the morphology of the analysed prominence suggest that its upper central part is not directly illuminated from the solar surface.Conclusions. This multi-disciplinary prominence study allows us to argue that a large part of the prominence-corona transition region plasma can be located inside the magnetic dips in small-scale features that surround the cool prominence material located in the dip centre. We also argue that the dark prominence bubbles can be formed because of perturbations of the prominence magnetic field by parasitic bipoles, causing them to be devoid of the magnetic dips. Magnetic dips, however, form thin layers that surround these bubbles, which might explain the occurrence of the cool prominence material in the lines of sight intersecting the prominence bubbles.

Geophysical Evaluation for Evidence of Recharging the Pleistocene Aquifer at El-Nubariya Area, West Nile Delta, Egypt

With ever increasing demands on water resources, Egypt is facing increasing water needs, demanded by a rapidly growing population, by higher standards of living and by an agricultural policys. West Nile Delta represents a new agricultural area where the reclaimed lands are irrigated with groundwater in addition to surface water. The evaluation of groundwater aquifers in West Nile Delta area requires information about the extension, depth and distribution and source of recharging these aquifers. In this work, an integrated study using geoelectric, geomagnetic, hydrogeologic and hydrochemistry investigations has been applied to evaluate groundwater aquifers and to delineate subsurface structures predominant in the basement rocks at El-Nubariya area, West Nile Delta, Egypt. Thirty-five Vertical Electrical Soundings (VES) have been applied to identify the subsurface geoelctric layers predominant in the study area. As well as a detailed land magnetic survey has been carried out along the study area using two automatic proton precession magnetometers with an accuracy of 1 nT. These surveys allowed us to establish the subsurface structures and their relation with the detected aquifers. The geoelectric results are illustrated along seven geoelectric profiles and correlated with the lithologic and hydrogeologic data of drilled wells. The third geoelectric layer represents the water saturated zone (aquifer) with thickness varies from 14 m to 58 m, increasing to east and southeast directions. The hydrchemisty anlysis shows that the salinity of the water aquifer ranges from 600 ppm in the southeast to 3900 ppm in the south. The major dominant dissolved salt is Nacl. In the east and southeast, the water type becomes more NaSO4 which refers to dissolution of gypsum in addition to fertilizers. The magnetic data have been analyzed using horizontal gradient and 3D magnetic modeling along the locations of geolectric profiles. The results indicate that the fault structures are trending in E-W, NW-SE and NE-SW directions. These faults confirm the results obtained from the well geolectric interpretation. These fault structures act as recharging paths from lower brackish to upper fresh water aquifers.

Geophysical Evaluation for Evidence of Recharging the Pleistocene Aquifer at El-Nubariya Area, West Nile Delta, Egypt

With ever increasing demands on water resources, Egypt is facing increasing water needs, demanded by a rapidly growing population, by higher standards of living and by an agricultural policys. West Nile Delta represents a new agricultural area where the reclaimed lands are irrigated with groundwater in addition to surface water. The evaluation of groundwater aquifers in West Nile Delta area requires information about the extension, depth and distribution and source of recharging these aquifers. In this work, an integrated study using geoelectric, geomagnetic, hydrogeologic and hydrochemistry investigations has been applied to evaluate groundwater aquifers and to delineate subsurface structures predominant in the basement rocks at El-Nubariya area, West Nile Delta, Egypt. Thirty-five Vertical Electrical Soundings (VES) have been applied to identify the subsurface geoelctric layers predominant in the study area. As well as a detailed land magnetic survey has been carried out along the study area using two automatic proton precession magnetometers with an accuracy of 1 nT. These surveys allowed us to establish the subsurface structures and their relation with the detected aquifers. The geoelectric results are illustrated along seven geoelectric profiles and correlated with the lithologic and hydrogeologic data of drilled wells. The third geoelectric layer represents the water saturated zone (aquifer) with thickness varies from 14 m to 58 m, increasing to east and southeast directions. The hydrchemisty anlysis shows that the salinity of the water aquifer ranges from 600 ppm in the southeast to 3900 ppm in the south. The major dominant dissolved salt is Nacl. In the east and southeast, the water type becomes more NaSO4 which refers to dissolution of gypsum in addition to fertilizers. The magnetic data have been analyzed using horizontal gradient and 3D magnetic modeling along the locations of geolectric profiles. The results indicate that the fault structures are trending in E-W, NW-SE and NE-SW directions. These faults confirm the results obtained from the well geolectric interpretation. These fault structures act as recharging paths from lower brackish to upper fresh water aquifers.

Magnetic anomaly patterns, fault-block tectonism and hydrocarbon related structural features in the Niger Delta basin

Gridded airborne magnetic data, 3D magnetic forward models in combination with filtered maps and derivative techniques such as analytic signal and directional derivatives were used to reveal basement structure and architecture of the study area in offshore Niger Delta. The generating mechanisms of the magnetic anomalies are boundaries (fault) of basement blocks of different compositions having different physical properties (susceptibilities and remanence) and horst/graben structures with associated normal faults and extensions. The intrabasement sources exhibit anisotropic susceptibilities and depth to basement (sedimentary thickness) is between 4000m to over 10,000m indicating deep depocenters. All these factors combined to influence magnetic anomaly patterns which have implications in hydrocarbon prospect target. The regional structural characteristics of the basement interpreted from the regional magnetic data sets show clear relationship between inferred rift-related basement structures and oil fields. Oil and gas discoveries appear to be located on the flanks of steep/faulted basement and on top of basement structural highs and lows. This study, therefore, is significant in understanding the petroleum system, contributes to basin modelling and can unravel areas of identical structural development in less well-explored sectors of the basin.

Collaborative discourse and the modeling of solution chemistry with magnetic 3D physical models – impact and characterization

A significant body of the literature in science education examines students' conceptions of the dissolution of ionic solids in water, often showing that students lack proper understanding of the particulate nature of dissolving materials as well as holding numerous misconceptions about the dissolution process. Consequently, chemical educators have explored several instructional strategies to address this issue including the use of multimedia, computer animations, and hands-on activities. In this paper, we describe the ways in which the use of physical 3D magnetic molecular models during a cooperative inquiry-based activity on chemical bonding prompted classroom discourse on what counts as chemically justifiable and appropriate representations of dissolved ionic solids in water. In so doing, we use the intersection of science education and technology to research the role of models in science teaching, the nature of classroom discourse initiated by modeling activities, and unfolding changes in student conceptions and ultimately student learning.

3D magnetic modelling and inversion incorporating self-demagnetisation and interactions

Self-demagnetisation can significantly reduce the amplitude and alter the orientation of magnetisation in highly magnetic bodies, thereby modifying the observed magnetic field, sometimes substantially. In tabular bodies, for example, the transverse magnetisation is reduced, with the result that the magnetisation vector rotates towards the plane of the body. Furthermore, when highly magnetic bodies are in close proximity, the assumption of uniform inducing field is violated. Highly magnetic bodies can modify the local magnetic field appreciably, with the result that the magnetisation induced in one susceptible body is affected by the magnetisations of all its neighbours. It is important to take such interactions between highly magnetic bodies into account. Potential field modelling and inversion software “VPmg” has been upgraded to account for self demagnetisation and interaction between magnetic bodies. The algorithm computes H-field perturbations at the model cell centres in two stages: initialisation and optimisation. During initialisation, a demagnetisation tensor is estimated for each cell, from which a first estimate for the H-field perturbation is derived. During optimisation, the H-field field estimate is refined iteratively via an inversion procedure. Remanence is taken into account as well as induced magnetisation. The algorithm has been validated for homogeneous spheres, spheroids, slabs, and cylinders. It has also reproduced magnetic interactions between two horizontal cylinders, previously published by Hjelt. Explicit verification for complex heterogeneous bodies requires a suitable independent algorithm for benchmarking. The application to inversion in a highly magnetic environment is illustrated in a field data example.

Evaluation of Groundwater Potential of Baikin Ondo State Nigeria Using Resistivity and Magnetic Techniques: A Case Study

A combined electrical resistivity and Magnetic surveys was carried out to locate fissured zones and associated groundwater-bearing media at Baikin Area in Ondo State, Nigeria that is known to have acute groundwater supply shortage. One Hundred (100) Vertical Electrical Soundings were acquired along ten traverses using the Schlumberger array with maximum half current electrode spacing (AB/2) of 200 m. Magnetic data were acquired along the traverses at station interval of 10 m using the Proton Precession Magnetometer. Four geologic layers were delineated. These include the topsoil, weathered layer, fractured basement and fresh basement bedrock. The thickness of the topsoil ranged from 0.2 to 1.1 m while the resistivity values varied from 29 to 455 Ωm. The weathered layer thickness varied between 0.2 and 12.6 m while its resistivity ranged between 13 and 307 Ωm. The fractured basement delineated had resistivity value of 61 Ωm. The fresh basement resistivity ranged between 941 and α Ωm. The overburden thickness ranged between 1.1 and 12.9 m. The weathered and fractured aquifers constituted the main aquifer units. Aquifer thickness varied between 0.2 and 12.6 m. Quasi 3D magnetic models also showed that depth to bedrock in the study area was shallow. The study concluded that the groundwater potential of Baikin Area was generally low.

Gravity and magnetic modelling in the Vrancea Zone, south-eastern Carpathians: Redefinition of the edge of the East European Craton beneath the south-eastern Carpathians

A 2D gravity and magnetic data model has been constructed along a 71km densely observed profile, called DACIA PLAN GRAV MAN's. The profile crosses part of the nappe pile of the south-eastern Carpathians and includes the seismically active Vrancea Zone and was acquired with the objective to illuminate the basement structure and affinity in this area. The modelling approach was to create an initial model from well constrained geological information, integrate it with previous seismic ray tracing and tomographic models and then alter it outside the a priori constraints in order to reach the best fit between observed and calculated potential field anomalies. The results support a realignment of the position of the TTZ (Tornquist-Teisseyre Zone), the profound tectonic boundary within Europe that separates Precambrian cratonic lithosphere of the East European Craton (EEC) from younger accreted lithosphere of Phanerozoic mobile belts to its west. The TTZ is shown to lie further to the south-west than was previously inferred within Romania, where it is largely obscured by the Carpathian nappes. The crust of the EEC beneath the south-eastern Carpathians is inferred to terminate along a major crustal structure lying just west of the Vrancea seismogenic zone. The intermediate depth seismicity of the Vrancea Zone therefore lies within the EEC lithosphere, generally supporting previously proposed models invoking delamination of cratonic lithosphere as the responsible mechanism.

3D magnetic model of the Korsun-Novomirgorod pluton and the Novoukrainka massif and its geological interpretation

Three-dimensional model of the upper and middle crust of the Korsun-Novomirgorod pluton and the Novoukrainka massif has been constructed applying the maps of anomalous magnetic field of a scale 1: 200 000, the data of gravity modeling and DSS. A specific feature of the Korsun-Novomirgorod pluton together with directly magnetized formations of gabbro-anorthosite complex is widely distributed rocks of this complex with inverse magnetization that is an evidence of their multiphase origin. It has been also revealed an asymmetry in distribution of magnetic formations of the pluton and of the deep structure of the Earth’s crust as to trans-regional separation zone of Kherson—Smolensk. According to the data of magnetic maps, magnetic model of the pluton has been supplemented by the distinguished semicircular structures that underline the individual character of development of each of the massifs in its limits and are considered as prototectonic faults related to multiphase formation of the pluton. The Novoukrainka massif is characterized by the development of rocks with different intensity, magnetized in direction of contemporary magnetic field. Formation of the massif is strongly related to large deep fault zones and trans-regional separation zone Kherson-Smolensk, which form an intersection knot at the base of the crust. Structural position of large dyke dolerite belts of the region has been analyzed showing that their formation occurred in the period between establishment of the Novoukrainka massif and the Korsun-Novomirgorod pluton.

Interpretation of airborne and ground magnetic and gamma-ray spectrometry data in prospecting for base metals in the central-north part of the Itabuna-Salvador-Curaçá Block, Bahia, Brazil

Interpretation of airborne and ground magnetic and radiometric geophysical data is fundamental to provide support for geologic mapping and exploration of mineral resources. This is particularly important of the Itabuna-Salvador-Curaçá Block component of the São Francisco Craton in the state of Bahia, Brazil, which bears important base metal mineralization in ultramafic intrusions. The interpreted airborne data covered part of the northern segment, and the ground data comprised an area of [Formula: see text] in the northern segment of that Archean block. The radiometric interpretation was only qualitative, and the magnetic interpretation was qualitative and quantitative. The qualitative interpretation defined distinct configurations of the geophysical signatures. So, it furnished possible regional and local geologic models and also helped to infer the distribution of magnetization and radiometric content in the rocks. The quantitative interpretation started with Werner deconvolution for a preliminary identification of the magnetic sources, and 2D magnetic modeling improved the definition of the anomalous bodies in terms of geometry, depth to the top, and magnetic susceptibility. The combined qualitative and quantitative interpretation allowed mapping of the rocks that contain magnetic and metallic minerals, as well as felsic lithology, such as granites and orthogneisses, and mafic lithology, such as gabbros and amphibolites. It also suggested that most of the northwest–southeast lineaments related to felsic and mafic magnetic intrusions. The analysis may extend to other areas of the block and be integrated with field and laboratory geologic, geophysical, and geochemical studies for an adequate exploration of nickel, copper, and chromium that are potentially present in the region.

Basement inhomogeneities and crustal setting in the Barents Sea from a combined 3D gravity and magnetic model

This thesis provided a new understanding of the lithospheric structural setting and anomalies observed in the greater Barents Sea.The Barents Sea has been focus of attention for geological and economical reason since the 70ies-80ies. The crustal and lithospheric evolution of this area has been poorly understood and relatively challenging because it involved a large number of different processes. During its evolution, plate aggregation and orogenesis have been alternated with episodic rifting and magmatic events. The final result is the present day continental shelf area formed by a heterogeneous crust and continental mantle, dominated by structural highs, platforms and structural lows (grabens, half graben and large sag basins). Although the general structures have been well outlined, numerous problems have been encountered in understanding the structure and evolution of the basins and the crust and their relation with the geodynamic evolution. Moreover the offshore propagation of Timanian, Caledonian and Uralian structures are still disputed.In this thesis, I have developed a new understanding of the lithospheric setting and properties of the Barents Sea using an integrated geophysical approach. The results have been obtained by combining gravity, magnetic and geoid potential fields with seismic, petrophysics and offshore observations. 3D magnetic anomalies inverse models have been developed first to define the distribution of magnetic crustal properties. The inversion results have been further integrated with 2D forward modelling and potential field analysis. The magnetic crustal units have been further refined by a 3D forward model which beside defining magnetic and density properties provided, major sedimentary interfaces, top basement, upperlower crust boundary and Moho depth. Finally, thermal and compositional models have been constructed to constrain the nature of the lithospheric mantle.The adopted integrated approach provides an enhanced regional understanding of the structure and devolution of the Barents Sea Four distinct Barents Sea basement types have been distinguished: Archaean-Paleoproterozoic, Timanian, Caledonian, and Uralian terranes. A distinction of the different allochthon nappes forming the Caledonian terranes is also proposed and a correlation with the onshore structures made. The crustal setting resulting from the models support the bifurcated extension model of the Caledonian into the western Barents Sea. The existence of a Svalbard micro-plate (Barentsia) has been identified as a thick and distinct crustal unit located in the northwest Barents Sea.The southeastern Barents Sea results to be the extension of the Timan-Pechora basement terranes, that are traced further north in the North Barents Basin. The lithospheric mantle velocity anomaly under the East Barents Sea has been interpreted as a relict Paleo-Proterozoic craton accreted toward Paleo-Baltica during the Timanian event.Thermal and compositional models of the lithospheric mantle provide also evidences of lithospheric-sublithospheric mantle interaction due to rifting and due to large magmatic events, as for example the magmatism on Svalbard and the opening of the North Atlantic.

Delineation the active subsurface structures at Fayoum-Cairo district, Egypt, using magnetic and magnetotelluric tools

In this work, we present a reconnaissance study to elucidate and delineate subsurface fault structures for an active tectonics area that lies between Cairo and El Fayoum provinces and consider major sources of seismicity in Egypt. Well logging, aeromagnetic, land magnetic, and magnetotelluric data have been used. The well-logging data were used for several drilled wells along W–E direction. The magnetic data were analyzed using trend analysis, 3D magnetic modeling, and Werner deconvolution techniques. The magnetotelluric data were interpreted using 2D (TM–TE) modeling techniques. The results show that there are eight major fault structures having E–W, N–S, and NW–SE directions. These faults extend downward for about 20 km at the Dahshour and Qatrani areas. The epicenter sources of the earthquakes are clustering around the intersections of these structures. The Kattaniya horst structure has been interpreted as a regional structure that exceeds the limits previously determined by geologists. The depth to this horst reaches about 1.8 km at the NW and more than 4.3 km at the southern parts. The interpreted values of magnetic susceptibility at the horst zone indicate that they are ultrabasic/basic intrusion bodies.

3D crustal structure and its tectonic implication for nile delta and greater cairo regions, egypt, from geophysical data

In the present study the crustal structures of Nile Delta, including Greater Cairo province, and its surroundings, were evaluated using 3D forward gravity and magnetic modeling. The interpretation is also based on the seismic reflection results, well logs data and previous density models. The present results allow to improve the understanding of both the crustal thicknesses and density distributions between the sedimentary cover and the upper mantle in the study area.The high Bouguer anomalies near the Mediterranean coast are mainly caused by deep-seated structures. The crust beneath the Mediterranean coastal region is typically continental, with a thickness of 24 km beneath Rositta and Damitta branches, which increases toward the south. The Greater Cairo province has been modeled with maximum crustal thickness of ca. 34 km. The negative gravity anomalies with minimum values are due to the effect of sedimentary cover and/or basement relief geometry.The main results of this work suggest that the study area...

Interpretation of Geophysical Data at EL Fayoum—Dahshour Area, Egypt Using Three Dimensional Models

EL Fayoum–Cairo district lies in the north western part of Cairo city. It is affected by several earthquakes. According to the Egyptian Network Seismology of National Research Institute of Astronomy and Geophysics (NRIAG), the last one occurred in July 2005 with a magnitude of 4.2 in Richter scale. The Bouguer and the aeromagnetic anomaly data as well as the detailed land-magnetic survey have been subjected to different techniques of processing and interpretation to better understand the tectonic setting of the study area. For example, different kinds of filters such as 2D spectral analysis, 3D analytical signal, and Euler deconvolution techniques have been applied. Finally, the 2D modeling has been used to simulate the subsurface configuration along some selected profiles at the area. It can be noticed from the obtained results that, the seismic events (Dahshour earthquakes) are closely related to a major NNW normal fault which has a deep extension and slightly lateral displacement, in addition to its NE-conjugate faults. The recent seismic activities in the study area are directly related and/or associated with the rejuvenation of the lateral movements. Three-dimensional interpretations of the magnetic anomaly and Bouguer anomaly maps of Fayoum, Cairo province area, Northern Western Desert of Egypt have been presented. In addition, a high-resolution 3D magnetic and gravity model constrained with the seismic results reveals a possible crustal thickness and density distribution of the northern part of Egypt between the sedimentary cover and the mantel. The results reveal that the basement has an irregular surface with depths ranging from 3,600 to 5,500 m. Faults of the NNW, as well as ENE and NE directions have predominated and affected both the basement and the overlying sedimentary cover. Furthermore, the 2D modeling technique across long gravity and magnetic anomaly profiles have emphasized the basement topography and its overlying sedimentary section. The agreement between the results of gravity and magnetic surveys and geology on the other hand, confirm the reliability of the chosen constraints of interpretation.

Crustal structure of the Antarctic Peninsula sector of the Gondwana margin around Anvers Island from geophysical data

We investigated the crustal structure of the northern Antarctic Peninsula (AP) — a composite magmatic arc terrane at the Pacific margin of Gondwana. It was formed in Mesozoic–Cenozoic by collision/accretion of allochthonous terranes to the Gondwana margin during subduction and progressive ridge collision of former Phoenix Plate under the AP. The AP is distinguished by belts of high-amplitude, gravity and magnetic anomalies, inferred to indicate the presence of plutons of mafic composition comprising the huge AP batholith. For a better understanding of the lithosphere structure and tectonic processes of the AP continental margin we performed 2D gravity and magnetic modeling along line III-III, which crosses the margin south of Anvers Island. Our model incorporates data on seismic refraction (DSS-13) and reflection (line 8545-03) profiles and physical property data.Our modeling shows that the crust of the AP margin near Anvers Island is of continental type and comprises two crustal domains, which were welded together during mid-Cretaceous collision. On the east there is a thick (~40km), high-velocity/density continental crust of the Gondwana margin, which occupies the AP inner shelf and mainland, and Larsen Ice Shelf. The space between the Gondwanian block and oceanic crust of the Bellingshausen Sea is occupied by thinner (~26km) crust of lower densities of supposed accreted terrane, characterized by gravity anomalies caused probably by accretional tectonics as a result of Cretaceous subduction. Two belts of magnetic anomalies forming the PMA (Pacific Margin Anomaly) probably belong to different crustal domains: the western belt of the PMA relates to accretional block, while the eastern belt of the PMA corresponds to the Gondwana margin block. This may represent an evidence that the PMA relates to a tectono-magmatic event occurred after collision of Gondwana margin and accreted terrane (in mid-Cretaceous) and had been imprinted on already formed continental margin.

Geophysical Models for the Cu-Dominated VHMS Mineralization in Katta District, Western Ethiopia

Volcanic hosted massive sulfides (VHMS) have been recognized for many years within the Arabian–Nubian Shield of western Ethiopia. The Shield is a collision belt formed when East and West Gondwana collided during the Neoproterozoic time. It covers NE Africa and the Middle East and is known to have hosted several economic mineral deposits. Situated within the Shield, the Katta VHMS mineralization is primarily made up of chalcopyrite, sphalerite, pyrite, pyrrhotite, and magnetite. These minerals are known to have contrasting values in resistivity, chargeability, and magnetic susceptibility with the enclosing host rocks. These physical attributes make resistivity, IP, and magnetic methods ideal to study and detect the mineralization and possibly delineate the ore body. Dipole–dipole DC resistivity and induced polarization data collected along parallel profiles are inverted to generate both 2D and 3D models of resistivity and chargeability. The chargeability model successfully delineates the zone of sulfide mineralization and the resistivity model gives information on the stratigraphic horizons and the structures. Magnetic data collected along more closely spaced profiles were also inverted to recover the 3D magnetic susceptibility model. The recovered model shows a linear magnetic anomaly that could be associated with the sulfides. This anomaly shows good spatial continuity and is in good agreement with the result obtained in the chargeability model. The geophysical inversion results indicate a NNW oriented mineralized zone of considerable strike length and extending to a depth of about 380 m. This study suggests the presence of exploitable VHMS presence in Katta district and that the inversion methodology is an important interpretation tool in guiding the exploration and exploitation of sulfide mineralization.