Potential field data inversion

The Teisseyre-Tornquist Zone (TTZ) is the longest European tectonic and geophysical lineament extending from the Baltic Sea in the NW to the Black Sea in the SE. This tectonic feature defines a transition zone between the thick crust of the East European Craton (EEC) and the thinner crust of the Palaeozoic Platform to the SW. The TTZ is evident from the seismic data as a perturbation of the Moho depth as well as from magnetic and gravity anomaly maps and heat flow distribution. For over a century, the TTZ has been considered a fossil plate boundary of the EEC corresponding to the limit of early Palaeozoic palaeocontinent Baltica. The results of quantitative interpretation of gravity and magnetic data, integrated with data from the new reflection seismic profiles crossing the TTZ, indicate the continuation of the Precambrian basement of the EEC and its lower Palaeozoic cover toward the SW underneath the Palaeozoic Platform. Potential field modelling also suggests the occurrence of a crustal keel underneath the TTZ. These results imply the location of a Caledonian tectonic suture, marking the site of the collision between Avalonia and Baltica, not along the TTZ, but farther SW, in NE Germany and SW Poland. Consequently, the extensive Permo-Mesozoic sedimentary basin of western Poland is established above the attenuated margin of the Baltica palaeocontinent.

The present research represents a new, fast and easy-to-apply semi-inversion technique for the direct separation of the Bouguer gravity anomaly to its corresponding depths or thicknesses of the prior known rock formations from a borehole (as a control point). As well as the possibility of tracing these formations on the profile points to the Bouguer gravity map according to their density contrasts with basement rock. The proposed method is based on the fact that the sum of the gravitational effect at a point on the Earth's surface is equal to the sum of the subsurface gravity effects arising from the points of masses of the causal bodies along the vertical line between the Earth's surface and the basement rocks. In this method, two sedimentary basin models were built based on the distribution of densities from a prior known borehole. Assuming that the depths of the pointed tops of these rock formations can be replaced by the centres of sphere bodies (or point masses) as causative sources of gravitational effect and by the use of a simple algorithm, it was possible to calculate the depths of the rock formations and trace them on the profile, using a new concept called the zero-offset gravity measurement. In this concept, the measuring gravity is vertically above the centre of the sphere-shaped body as it represents the causative source, and its depths are equal to the radius of the sphere body. The present method was assessed on hypothetical models and synthetic data and applied to two real data in field cases which vary in geological and lithological aspects. The first assessed location is Abu Roash Dome Area, southwest Cairo, Egypt, and the second location is the Mors Salt Dome, North Jutland, Denmark.

The aim of this work is the formulation of a 3D model of the Mt. Amiata volcanic complex (Southern Tuscany) by means of geomagnetic data. This work is shown not only as a real test to check the validity of the inversion algorithm, but also to add information about the structure of the volcanic complex. First, we outline briefly the theory of geomagnetic data inversion and we introduce the approach adopted. Then we show the 3D model of the Amiata volcano built from the inversion, and we compare it with the available geological information. The most important consideration regards the surface distribution of the magnetization that is in good agreement with rock samples from this area. Moreover, the recovered model orientation recall the extension of the lava flows, and as a last proof of validity, the source appears to be contained inside of the topographic contour level. The credibility of the inversion procedure drives the interpretation even for the deepest part of the volcano. The geomagnetic signal appears suppressed at a depth of about 2 km, but the most striking consequence is that sub-vertical structures are found even in different positions from the conduits shown in the geologic sections. The results are thus in good agreement with the information obtained from other data, but showing features that had not been identified, stressing the informative power of the geomagnetic signal when a meaningful inversion algorithm is used.

The Teisseyre-Tornquist Zone (TTZ) is the longest European tectonic and geophysical lineament extending from the Baltic Sea in the NW to the Black Sea in the SE. This tectonic feature defines a transition zone between the thick crust of the East European Craton (EEC) and the thinner crust of the Palaeozoic Platform to the SW. The TTZ is evident from the seismic data as a perturbation of the Moho depth as well as from magnetic and gravity anomaly maps and heat flow distribution. For over a century, the TTZ has been considered a fossil plate boundary of the EEC corresponding to the limit of early Palaeozoic palaeocontinent Baltica. The results of quantitative interpretation of gravity and magnetic data, integrated with data from the new reflection seismic profiles crossing the TTZ, indicate the continuation of the Precambrian basement of the EEC and its lower Palaeozoic cover toward the SW underneath the Palaeozoic Platform. Potential field modelling also suggests the occurrence of a crustal keel underneath the TTZ. These results imply the location of a Caledonian tectonic suture, marking the site of the collision between Avalonia and Baltica, not along the TTZ, but farther SW, in NE Germany and SW Poland. Consequently, the extensive Permo-Mesozoic sedimentary basin of western Poland is established above the attenuated margin of the Baltica palaeocontinent.

The Panjshir Fe-Polymetallic ore deposit is a valuable geological resource in Afghanistan, rich in iron and multiple essential metallic minerals, with substantial potential for industrial development. The exploration phase faces challenges related to the complex geological settings, high variability of mineral compositions, and the need for advanced geophysical techniques to accurately locate and assess valuable metallic resources. Considering the strong magnetic characteristics exhibited by Fe-Polymetallic elements, geomagnetic data were employed to analyze and map the likely prospectivity of Fe-Polymetallic deposits within the study area. Multi-scale edge detection techniques were employed to accurately map the boundaries of magnetic bodies by utilizing the upward continued analytical signal amplitude. The presence of a fault system on the geological map confirmed the structural information derived from our edge detection techniques. Advanced magnetic data inversion techniques were employed to create a three-dimensional representation of the distribution of magnetic bodies linked to Fe-Polymetallic deposits. In our efforts to reduce the impact of remnant magnetization in the study area, we adopted a comprehensive strategy by employing both magnetic susceptibility and magnetization vector inversion techniques. The use of a sparse and blocky norm regularization [0,1,1,1] is well-suited for magnetic susceptibility inversion, while a blocky norm [0000,0000,0000] is the appropriate choice for magnetization vector inversion in our study. Ultimately, the zones characterized by a high magnetic susceptibility and a high magnetization amplitude are considered promising areas for potential Fe-polymetallic occurrences.

This study is focused on the recognition of the geological structure of the southern part of the province of Sankuru in the D.R. Congo which covers the oil blocks 18 and 18b. Gravity and magnetic data were processed using the horizontal derivative and upward continuation methods. Note also that the Reduction yo Pole (RTP) was previously applied to the magnetic data in order to eliminate the distortions of the anomalies. Thus, we found that the region was affected by several tectonic phenomena, the most important of which was the rifting phenomenon that shaped this region by establishing a large collapsed central zone forming an NW-SE direction graben and raised peripheral reliefs forming horsts to the northeast and southwest. This study also revealed several faults, some of which, which are of the normal type, are parallel to the central graben and others are perpendicular to it. It should also be noted that the large negative gravity anomalies result from the salt domes located for the most part in the central graben. The integration of all the geological information from the interpretation of gravity and magnetic maps has enabled us to develop a structural map that improves our knowledge of the geological structures of major oil interests in this region.

This study is focused on the recognition of the geological structure of the southern part of the province of Sankuru in the D.R. Congo which covers the oil blocks 18 and 18b. Gravity and magnetic data were processed using the horizontal derivative and upward continuation methods. Note also that the Reduction yo Pole (RTP) was previously applied to the magnetic data in order to eliminate the distortions of the anomalies. Thus, we found that the region was affected by several tectonic phenomena, the most important of which was the rifting phenomenon that shaped this region by establishing a large collapsed central zone forming an NW-SE direction graben and raised peripheral reliefs forming horsts to the northeast and southwest. This study also revealed several faults, some of which, which are of the normal type, are parallel to the central graben and others are perpendicular to it. It should also be noted that the large negative gravity anomalies result from the salt domes located for...

This paper describes the updated stratigraphy, structural framework and evolution, and hydrocarbon prospectivity of the Paleozoic, Mesozoic and Cenozoic basins of Yemen, depicted also on regional stratigraphic charts. The Paleozoic basins include (1) the Rub' Al-Khali basin (southern flanks), bounded to the south by the Hadramawt arch (oriented approximately WE) towards which the Paleozoic and Mesozoic sediments pinch out; (2) the San'a basin, encompassing Paleozoic through Upper Jurassic sediments; and (3) the southern offshore Suqatra (island) basin filled with Permo-Triassic sediments correlatable with that of the Karoo rift in Africa. The Mesozoic rift basins formed due to the breakup of Gondwana and separation of India/Madagascar from Africa-Arabia during the Late Jurassic/Early Cretaceous. The five Mesozoic sedimentary rift basins reflect in their orientation an inheritance from deep-seated, reactivated NW-SE trending Infracambrian Najd fault system. These basins formed sequentially from west to east-southeast, sub-parallel with rift orientations-NNW-SSE for the Siham-Ad-Dali' basin in the west, NW-SE for the Sab'atayn and Balhaf basins and WNW-ESE for the Say'un-Masilah basin in the centre, and almost E-W for the Jiza'-Qamar basin located in the M. A. As-Saruri

The Panjshir Fe-Polymetallic ore deposit is a valuable geological resource in Afghanistan, rich in iron and multiple essential metallic minerals, with substantial potential for industrial development. The exploration phase faces challenges related to the complex geological settings, high variability of mineral compositions, and the need for advanced geophysical techniques to accurately locate and assess valuable metallic resources. Considering the strong magnetic characteristics exhibited by Fe-Polymetallic elements, geomagnetic data were employed to analyze and map the likely prospectivity of Fe-Polymetallic deposits within the study area. Multi-scale edge detection techniques were employed to accurately map the boundaries of magnetic bodies by utilizing the upward continued analytical signal amplitude. The presence of a fault system on the geological map confirmed the structural information derived from our edge detection techniques. Advanced magnetic data inversion techniques were employed to create a three-dimensional representation of the distribution of magnetic bodies linked to Fe-Polymetallic deposits. In our efforts to reduce the impact of remnant magnetization in the study area, we adopted a comprehensive strategy by employing both magnetic susceptibility and magnetization vector inversion techniques. The use of a sparse and blocky norm regularization [0,1,1,1] is well-suited for magnetic susceptibility inversion, while a blocky norm [0000,0000,0000] is the appropriate choice for magnetization vector inversion in our study. Ultimately, the zones characterized by a high magnetic susceptibility and a high magnetization amplitude are considered promising areas for potential Fe-polymetallic occurrences.

The integrated interpretation of the magnetic and gravity data allowed the depth configuration of the basement surface and gave a new picture of the sedimentary basins and ridges distribution at the eastern region of Yemen. According to the well logs, related studies and classification of the rocks, the average density of the stratigraphic cover is about 2.45 g/cc, the average density of the crust is about 2.7 g/cc and the average susceptibility is about 0.005 cgs-units, while the average density of the upper mantle is about 3.26 g/cc. The depth regimes to the basement are varied from zero near Al-Mukalla city at the southern part to more than 4000 m at its northern part of the study area. The comparative study among the 2.5-D gravity and magnetic modeling was established by constructing 20 profiles. They adapted the relation between the gravity and magnetic anomalies and the causative rock units and their properties. The results indicated that, the area can be divided into some major units of relatively thick sedimentary cover, concealed beneath it were more complicated basement features made up of a number of swells and troughs created due to intense tectonic phases. The models indicated that, the basement rocks are almost affected by high angle or nearly vertical normal faults with varying throws and dips. They provided evidence that, the basement swell and trough structures play a vital role in the distribution of the sedimentary cover, as ridges and basins. This argument is often agreed with the local studies presented by some oil companies operating in the study area. The interpreted structural features in the concerned area can be arranged, trend-wise and depth-wise as follows: The deepest are the folds and faults of the NE-SW trend, then those of the NW-SE trend. These are

We utilized the seismicity and the potential field data to study the tectonic deformation and to delineate the seismically active subsurface tectonic trends of El-Faiyum area. To accomplish these goals, we analyzed and interpreted the seismicity data, the reduced to pole total magnetic intensity, and the Bouguer anomaly maps. We also used the spatial distribution of the recent seismic events and the focal mechanism to outline the local seismic zones that control the seismicity of the study area and to determine the sense of the motion along the subsurface active faults. The focal mechanism of the recent seismic events and the interpreted subsurface tectonic faults from the potential field data reflect strike-slip movements with normal components along the subsurface active faults. The gravity and magnetic maps show a NE-SW regional trend with low gravity and magnetic values. The NE-SW regional trend extends across the whole area and could be related to the Pelusium Megashear fault. A NE-SW trend with high gravity and magnetic exists at the northern part and coincides with the Kattania Uplift and the basaltic flows in Gabal Qatrani area. The gravity and magnetic maps also reveal several local anomalies with different polarities, amplitudes, and extensions, which reflect anticlinal and synclinal structures on the basement surface. The seismotectonic map, generated by linking the basement structure map and the spatial distribution of the recent earthquake foci, reveals the dominant tectonic trends and the subsurface active faults.

Natural remanent magnetization and self-demagnetization on high-susceptibility bodies are two important factors affecting magnetic data inversion. We propose a framework for the inversion and interpretation of magnetic anomalies, in which significant remanent magnetization and self-demagnetization are present simultaneously. The framework is based on the assumptions that the external applied field and internal self-demagnetization field are uniform and the deflection of self-demagnetization in the total magnetization direction is negligible. First, the magnetization vector distributions are obtained from magnetic data by estimating the magnetization direction, then inverting for the magnetization intensity distribution, using the inferred magnetization direction as a constraint. Based on a priori information about the Koenigsberger ratio derived from petrophysical measurements, the direction and intensity of the remanent magnetization are obtained. The self-demagnetization factor is then computed using the finite volume method. Finally, the true-susceptibility distribution is achieved by correcting for the self-demagnetization effect. The method is first applied to synthetic magnetic data produced by a prism-shaped source model that has significant remanent magnetization and high susceptibility. In a case study of the Daye iron-ore deposit, Hubei province, China, the true susceptibility and remanent magnetization are reconstructed. The remanence direction information reveals that local geological activities such as synclines and faults lead to changes in the remanence directions at different local deposits.

Kuwait state lies at the upper northeastern corner of the Arabian Plate, on the Arabian Gulf, and surrounded by Iraq from the north, the Arabian Gulf from the east, and Saudi Arabia from other sides. Kuwait settled on a thick sedimentary column built from the Permian age to recent; its thickness ranges between 7 and 8 km, take the form of the underneath basement structures. Detailed information has been got about the crustal basement structure under Kuwait state from the analysis of gravity anomaly maps and its consequential depth maps. The Geosoft Oasis Montaj software is used for preparing the geologic cross-sections from the modeling of the gravity profiles. The modeled cross-section provided us with the depth and structures of crustal basement rocks within 6 to 7 km under Kuwait and its associated sedimentary basins with a detailed geometry. We got considerable information about the sedimentary basins' geometry in Kuwait, such as the locations, extension, depth, and dimensions of the basins. This information coincides with Kuwait's oil fields location map. However, this information can be confirmed accurately from an aeromagnetic survey recommended carrying out the Kuwait region.

Extensive field and site investigations were conducted to assess and evaluate the situation in quarries presently exploited for the production of cement raw materials in Yemen. These quarries have several geological complications represented mainly by high elevations, steep slopes, rugged topography, heterogeneity in bed thickness, lithologic composition and quality, presence of igneous sills and dykes, intensive fracturing and jointing, and abundance of karstification features. Moreover, the processes of quarrying and related activities have several negative environmental impacts, the most important of which are soil failure, overburden and land sliding, toppling and rock falls (which result in considerable mass wasting) as well as dust and noise emissions. Generally, quarrying operations are more hazardous in quarries of gypsum and basement rocks than in those of carbonates and volcanics. Furthermore, the quarries have problems related to the conservation of natural resources. These are represented primarily by the excavation of the valuable agricultural and reclaimed lands and improper exploitation of the cement raw materials, as well as the depletion of fresh and underground water reserves. To deal with the above-mentioned problems, a number of recommendations are outlined. They comprise mitigation measures which must be strictly implemented. Also, it is of utmost importance to conduct prospecting for new occurrences of cement raw materials and their possible substitutes as well as additional groundwater resources.

The eastern Alboran basin and its transition to the Algerian basin is a key area in the Mediterranean realm where controversial kinematic and geodynamical models are proposed. Models imply striking differences regarding the nature of the crust, the prevalence of brittle faulting and ductile shear, the origin of magmatism, the style of Miocene deformation and the driving mechanisms of the Alboran plate kinematics. Combining a new chronostratigraphic chart of the Alboran and Algerian basins based on the Habibas (HBB-1) core drill, deep seismic sections striking WSW-ENE and SSE-NNW, and potential field data, we reassess the tectonic evolution that controlled the sedimentation and basement deformation of the westernmost limit of the Algerian basin and its transition with the Alboran domain. A WSWdirected extensional tectonic phase has shaped a stretched continental crust with typical tilted blocks along ∼100 km from Burdigalian to Tortonian times, which is assumed to result from the WSW-directed migration of the Alboran block driven by a narrow slab rollback. In the Algerian basin, this event was followed by the emplacement of an oceanic-type crust. Potential field signatures of the deep basin as well as geometrical correlations with onland outcrops of inner zones suggest a minimum WSW-directed displacement of the Alboran terrane of ∼200 km. At the southern foot of the Algerian basin, the continentocean transition is sharp and may result from the westward propagation of a slab tear at depth, forming two segments of STEP (Subduction-Transform Edge Propagator) margins. Our results support models of intense shear tractions at the base of an overriding plate governed by slab rollback-induced mantle flow. Finally, Messinian salt tectonics affected overlying deposits until today. A late Tortonian to Quaternary dominantly transpressive tectonic episode linked to the Africa-Iberia convergence postdates previous events, deforming the whole margin.

Mining activities in Lavrion began during the first millennium B.C. after the decline of ancient Athens and then restarted more deliberately during the nineteenth century. Aeromagnetic data from a 1967 survey of the mining area was recompiled, processed, and interpreted for the present study. The original flight lines were digitized and leveled, and the international geomagnetic reference field (IGRF) was removed. The data were inverted by means of a terracing technique that defines separate domains of uniform distribution of physical properties that cause the magnetic anomalies. The log power spectrum was computed; along with the results of terracing, it suggested the existence of two sources of the magnetic anomaly. The long-wavelength anomaly reflects a large, concealed body that is most probably a granitic intrusion, consistent with local geological evidence. The source of the short-wavelength anomaly is a strongly magnetized body attributed to the net effect of various thin, magnetite-bearing sulfide zones. The anomalies were then separated in the wavenumber domain. Magnetic susceptibility measurements were made in situ on the exposed parts of the local formations. Three-dimensional models whose effect simulates the observed anomalies were calculated. Results of the modeling show that the large magnetic body is buried at 0.68 km depth. The small, relatively shallow body is about 0.035 km thick and buried at 0.6 km depth. The bodies do not show any corresponding gravity anomaly on the regional Bouguer gravity anomaly map.

There is still much that needs to be understood about the physical properties of rocks in mineralised geological environments. This knowledge gap becomes more important as the transition to deeper exploration targets under cover occurs, with an associated greater reliance on geophysical exploration methods. The major challenge associated with understanding petrophysical data is not making the measurement, but rather understanding the results. The interpretation of the data is a cross disciplinary problem. Fundamentally it is necessary to understand the rock mineralogy and geochemistry to put the petrophysics in context with the geophysical results. Several case studies are presented where the petrophysics have determined not only which geophysical techniques to apply but whether a geophysical target has indeed been tested. Drill testing EM plate approximations for nickel sulphide and volcanogenic massive suphide (VHMS) ore deposits can benefit from inductive conductivity measurements on core as it can determine whether an EM conductor has been intersected. Chargeability highs associated with porphyry copper mineralisation is indicative of disseminated pyrite in the propylitic and pyrite +/-chalcopyrite +/bornite in the potassic alteration zones and higher chargeability does not necessarily mean more copper. In most porphyry systems magnetite is coarse-grained, therefore a world class porphyry deposit should not have dominant remanent effects and the only likely source of remanence features in younger terrains are oxidised mafic intrusions and skarns. Furthermore, porosity and specific types of alteration (argillization) display the strongest correlations with resistivity and can be tied to gold distribution in Carlin Type Deposits.

Abstract: In the present work, we present a reconnaissance study to elucidate and delineate the subsurface structures and tectonics of the area between Dahshour and El Fayoum province using available magnetic data; including land magnetic survey and ...

The Geologic and Tectonic Setting The Western Desert of Egypt covers an area more than 600,000 km 2 and comprises almost two thirds of the whole area of Egypt. The North Western Desert represents an important part of the unstable shelf of Northern Africa. It has been subjected to different tectonic regimes since the Paleozoic time, which were able to form the construction of many basins, sub-basins, ridges, troughs and platforms. The West Qarun concession is located to in the north part of the Western Desert (Figure 1). It is close to the Nile Delta region and the convergence boundary of three plates (Euroasian, Africa and Arabian). Also, it is affected by the opening of the Red Sea and its branches (Gulf of Suez and Gulf of Aqaba). Thus the seismic activity there is due to the interaction between the three plates. These structural features encourage foreign companies to establish condensed exploration works in this region. The Western

Western Desert region between Cairo and Fayoum in Egypt is a geologically interesting area due to its active seismicity status and the continuous bidirectional urban expansions ongoing northward and southward growth. This work aims to develop a geological model of the region by combining magnetic intensity data (aeromagnetic) and potential field data (airborne gravity) with magnetotelluric (MT) data to offer decision-makers an additional evaluation tool for long-term future planning. Applying a number of filters to aerial gravity and magnetic data allowed us to calculate the subsurface density distribution and structure of the area between Cairo and Fayoum. In addition, the surface of the crust was imaged down to a depth of 6 km using a 3-D inversion of gravity data. Magnetotelluric data were gathered at eight locations over the NS-extended Cairo-Fayoum Road profile. MT data were inverted in 2-D to generate a resistivity model that defines the subsurface structure of the researched ...

The characterization of the sources of gravity anomaly in the Vindhyan basin is important to constrain the basement structure for hydrocarbon exploration. In this method, scaling function which is a function of altitude is used to characterize the scaling behavior of homogeneous field. It determines the depth to sources of bodies like sphere, cylinder, dike, sill etc. using extreme points of the scaled potential field. The method is tested on synthetic cases of gravity anomaly of isolated and extended sources such as sphere, elongated prism and applied on the gravity data of Jabera-Damoh region of Vindhyan basin, central India. The results show that the shallow features represent high density material which is underlain by the combination of high and low density material of crystalline basement along both sides in Vindhyan basin.

HE PRESENT study intends to elicit subsurface shear (wrench) zones that affected the northeastern part of Sirt Basin area, which is considered as one of the most important hydrocarbons-producing regions, and its impact on similar areas around the world. Several techniques have been carried on gravityand magnetic data to achieve this goal, such as least squares, tilt angle derivative, horizontal gradient, and sourceedge detection. In addition, power spectrum and Euler deconvolution methods have been carried out with a view to depict clearly faulting pictures along successive depths of deep-seated structures. 2D modelling has been constructed along two profiles and with the aid of data available from four drilled wells in the study area. New eleven sets of wrench zones that have not been extracted before could be revealed from the interpreted tectonic map and faulting pictures of the study area, mostly of sinistral and dextral strike-slip movements. Also, these zones were traced on six successive levels to know whether they are superficial or deep. Seven sets were revealed from gravity data and six from RTP data. Two sets of shears traced from gravity coincide with two shears from the RTP map. Some of these zones intersect with each other. These intersection points weakened the Earth's crust which in turn becomes tectonically unstable in this area. These wrench zones are predicted to be due to tectonic movements of the Arabian and African plates and additionally the ensuing East African Rift which led the Megashear System of North Africa to reactivate in a dextral strike-slip pattern. Sinistral transtensional reactivationsalong the northwest faults resulted due dextral reactivation of the Megashear System of North Africa.

Recently, a number of large molybdenum (-copper) deposits have been discovered successively in the Laba area, Shangri-La county, northwestern Yunnan province. The investigation confirmed that there is a superlarge porphyry-skarn hydrothermal vein type molybdenum-polymetallicmetallogenic system with the total prediction reservoir of more than 150 mt molybdenum. The porphyry intrusions contributed to the mineralization closely, the superficial little vein molybdenum (-copper, lead, silver) ore-bodies are usually located in faults and fractures, and the deep porphyry type ore-bodies occurred in the granodiorite porphyries, the skarn type ore-bodies occurred in the contact zone intrused into Triassic limestone or Permian basalts. Laba ore block is a new exploration area with great prospecting potential. In order to reduce the target area and guide the further exploration work, the magnetic method measurement about 3.3 square kilometres was carried out in the ore field. This paper presents an application of analyzing the horizontal and vertical derivative, using Fast Fourier Transform (FFT) filter (FFT high-pass, low-pass, cosine roll-off, suscepbility), calculated spectra frequency energy to predict the depth and intensity of the apparent remanence magnetization of source (Hilbert). The calculated results and magnetic anomalous show that the remanence anomaly is caused by the intrusions into the Triassic limestone and Permian basalts with small anomalies, and the depth of located source is not great. We have identified a number of positions to the three drilled well, the drilled result specify interpretation with very high accuracy. The magnetic method is helpful to identify porphyry mineralization, and judge the shape and depth of the concealed ore-bearing intrusive bodies under the similar geological condition.

Extensive field and site investigations were conducted to assess and evaluate the situation in the presently exploited quarries of cement raw materials in Yemen. These quarries have several geological complications represented mainly by high elevations, steep slopes, rugged topography, heterogeneity in bed thickness, lithologic composition and quality, presence of igneous sills and dykes, intensive fracturing and jointing and abundance of karstification features. Moreover, the processes of quarrying and related operations have several negative environmental impacts the most important of which are soil failure, overburden and land sliding, toppling and rock falls (which result in considerable mass wasting) and emission of dust and noise. Generally, quarrying operations are more hazardous in quarries of gypsum and basement rocks than in those of carbonates and volcanics. Furthermore, the quarries have problems related to the conservation of natural resources. These are represented pri...

Extensive field and site investigations were conducted to assess and evaluate the situation in the presently exploited quarries of cement raw materials in Yemen. These quarries have several geological complications represented mainly by high elevations, steep slopes, rugged topography, heterogeneity in bed thickness, lithologic composition and quality, presence of igneous sills and dykes, intensive fracturing and jointing and abundance of karstification features. Moreover, the processes of quarrying and related operations have several negative environmental impacts the most important of which are soil failure, overburden and land sliding, toppling and rock falls (which result in considerable mass wasting) and emission of dust and noise. Generally, quarrying operations are more hazardous in quarries of gypsum and basement rocks than in those of carbonates and volcanics. Furthermore, the quarries have problems related to the conservation of natural resources. These are represented pri...

This study is focused on the recognition of the geological structure of the southern part of the province of Sankuru in the D.R. Congo which covers the oil blocks 18 and 18b. Gravity and magnetic data were processed using the horizontal derivative and upward continuation methods. Note also that the Reduction yo Pole (RTP) was previously applied to the magnetic data in order to eliminate the distortions of the anomalies. Thus, we found that the region was affected by several tectonic phenomena, the most important of which was the rifting phenomenon that shaped this region by establishing a large collapsed central zone forming an NW-SE direction graben and raised peripheral reliefs forming horsts to the northeast and southwest. This study also revealed several faults, some of which, which are of the normal type, are parallel to the central graben and others are perpendicular to it. It should also be noted that the large negative gravity anomalies result from the salt domes located for...

The Geologic and Tectonic Setting The Western Desert of Egypt covers an area more than 600,000 km 2 and comprises almost two thirds of the whole area of Egypt. The North Western Desert represents an important part of the unstable shelf of Northern Africa. It has been subjected to different tectonic regimes since the Paleozoic time, which were able to form the construction of many basins, sub-basins, ridges, troughs and platforms. The West Qarun concession is located to in the north part of the Western Desert (Figure 1). It is close to the Nile Delta region and the convergence boundary of three plates (Euroasian, Africa and Arabian). Also, it is affected by the opening of the Red Sea and its branches (Gulf of Suez and Gulf of Aqaba). Thus the seismic activity there is due to the interaction between the three plates. These structural features encourage foreign companies to establish condensed exploration works in this region. The Western

In this paper, a geophysical strategy based on the recently proposed Manta-Ray Foraging (MRF) Optimization algorithm is adapted and presented for the blind computation of depth/shape defining parameters from magnetic anomalies due to buried geo-bodies. The model parameters deciphered are the coefficient of amplitude (K), buried structure’s origin (x0), the depth (z), magnetization angle (α), and a shape factor (q). After detailed and piecewise design, the new inversion tool is originally trial-tested on anomaly data generated synthetically. The uncorrupted version of the test data is first analyzed, then - it is corrupted with noise varied at 5, 10, 15, and 20% corruption levels. Thereafter, it is experimented with magnetic profiles taken from exploration fields in the United States, Peru, and Egypt. From the evaluation of results obtained, the new procedure is observed as exhibiting outstanding stability and flexibility especially with noisy dataset and notable efficiency in the qu...

The Manta-Ray Foraging Optimization has been adapted and implemented in computing model parameters from potential field anomalies originating from two-dimensional dipping faults. The inversion technique was originally demonstrated on magnetic anomalies from uncorrupted–then, corrupted synthetic datasets. Thereafter, it was experimented on profiles taken from mining fields in the United States, and Australia. The results obtained showed that the design procedure is admirably stable and flexible, especially when dealing with noisy data. It is also notably efficient in the quantitative resolution of geophysical inverse problems. The consistency in results obtained from analysis of deep-seated and shallow field examples, even when compared against background results, is also impressive. The new technique has also exhibited notable superiorities over other well-known and conventional techniques, especially on the grounds of convergence rate, cost, and quality of resolved anomaly paramete...

Magnetic methods of exploration have proved to be efficient and have potential in the gold mineralization industry. New magnetic processing technologies aid in improving the process of interpretation and gold opportunity identification. In this work, we show the possible application of combined digital magnetic filters to explore new gold mineralization localities with application to a well-known Au mineralization zone. Um Garayat (UG) region, southeastern desert, Egypt, is an ancient example of a potential area for gold mining. Modern analysis showed that other types of mineral concentrations are present. So, exploiting the magnetic signature of the area for future investment is of great interest. The old UG gold mine is characterized by volcanic and tectonic features such as faulting and folding that affect the arc sedimentary rock sequence of repeated deformation stages. A thorough geophysical effort has been carried out around the old gold mine in the UG area to explore the exte...

Geophysical techniques such as gravity, magnetic and seismology are perfect tools for detecting subsurface structures of local, regional as well as of global scales. The study of the earthquake records can be used for differentiating the active and non-active fault elements. In the current study, more than 2,200 land magnetic stations have been measured using two proton magnetometers. The data are corrected for diurnal variations and then reduced by the International Geomagnetic Reference Field. The corrected data have been interpreted by different techniques after filtering the data to separate shallow sources (basaltic sheet) from the deep sources (basement complex). Both Euler deconvolution and 3-D magnetic modeling were carried out. The results of interpretation indicate that the depth to the upper surface of basaltic sheet ranges from \10 to 600 m, depth to the lower surface ranges from 60 to 750 m, while the thickness of the basaltic sheet varies from \10 to 450 m. Moreover, gravity measurements are conducted at 2,250 stations using a CG-3 gravimeter. The measured values are corrected to construct a Bouger anomaly map. The least squares technique is then applied for regional-residual separation. The third order of least squares is found to be the most suitable to separate the residual anomalies from the regional one. The resultant third-order residual gravity map is used to delineate the structural fault systems of different characteristic trends. The trends show an NW-SE trend parallel to that of Gulf of Suez, an NE-SW trend parallel to the Gulf of Aqaba and an E-W trend parallel to that of the Mediterranean Sea. Taking seismological records into consideration, it is found that most of the 24 earthquake events recorded in the study area are located on fault elements. This gives an indication that the delineated fault elements are active.

Self-Potential data have been widely used in numerous applications. The interpretation of SP data from subsurface bodies is quite challenging. The advantages of geophysical inversion for interpreting non-linear geophysical problems have gained a great deal of attention over conventional interpretation. The efficiency of the present inversion approach in interpreting SP anomalies from a thin dipping layer/bed is presented in the study. The inversion approach was applied to interpret synthetic model parameters such as the self-potential of the layer (k), depth to the body top (h), location of the body (x0), dip angle (θ), and the upper and lower end of the sheet (δ1 and δ2). The interpretation of the results showed that the parameters Δh, δ1, and δ2 exhibited a wide range of results. The estimated parameter values lay within the limit of uncertainty. The inversion approach was also applied to two field datasets obtained from polymetallic deposits in Russia and Azerbaijan for mineral e...

Inverse potential field problems have ambiguous solutions, and a unique solution can only be computed if additional a priori information is incorporated into the solution process. We discuss several kinds of ambiguity, and show how each type of ambiguity occurs and is handled differently. We demonstrate that potential-field data provide depth information when used in connection with certain discretizations of the problem, and that the role of the regularization term in the Tikhonov formulation is primarily to filter out noise. In addition we show how the inspection of two graphical tools, based on the singular value decomposition, can guide the regularization and also reveal how much depth information can be achieved for a given noisy problem.

Three-dimensional (3D) interactive modeling with the IGMAS+ software provides means for integrated processing and interpretation of geoid, gravity and magnetic fields and their gradients (full tensor), yielding improved geological interpretation. IGMAS+ fully three-dimensional models are constructed using triangulated polyhedra and/or triangulated grids, to which constant density and/or induced and remanent susceptibility are assigned. Interactive modifications of model parameters (geometry, density, susceptibility, magnetization), access to the numerical modeling process, and direct visualization of both calculated and measured fields of gravity and magnetics, enable the interpreter to design the model as realistically as possible. IGMAS allows easy integration of constraining data into interactive modeling processes, visualization and combination of geodata with density/susceptibility models. These visual overlays of different 2D and 3D datasets enables quantitative comparison and adjustment and results in models that are constrained by as much independently derived information as possible. 1. Compilation of an initial model that fits concepts and data.

The difficulties in unravelling the tectonic structures, in some cases, prevent the understanding of the ore bodies' geometry, leading to mistakes in mineral exploration, mine planning, evaluation of ore deposits, and even mineral exploitation. For that reason, many geophysical techniques are introduced to reveal the type, dimension, and geometry of these structures. Among them, electric methods, self-potential, electromagnetic, magnetic and gravity methods. Global meta-heuristic technique using Whale Optimization Algorithm (WOA) has been utilized for assessing model parameters from magnetic anomalies due to a thin dike, a dipping dike, and a vertical fault like/shear zone geological structure. These structures are commonly associated with mineralization. This modern algorithm was firstly applied on a free-noise synthetic data and to a noisy data with three different levels of random noise to simulate natural and artificial anomaly disturbances. Good results obtained through the...

The present report on the state of the art on cobalt mineral resources in Chile was prepared as part of the study “Exploration and mining potential for cobalt mineral resources in Chile” requested by the Non Metallic Mining Committee of Corfo. The following topics are described in this document: Cobalt mining in Chile, past and present; Metallogenic evolution and metallic mineral deposits in Chile; Historic cobalt mining districts in Chile; Mineral resources for cobalt in Chilean deposits, and Mining exploration and mining potential of the historic cobalt mining districts.

The Flinders Ranges in Australia are located within the well defined South Australian Heat Flow Anomaly. Anomalously high heat flow is recorded in this area, offering world-class opportunities for the development of significant and economically viable Enhanced ...

The Teisseyre-Tornquist Zone (TTZ) is the longest European tectonic and geophysical lineament extending from the Baltic Sea in the NW to the Black Sea in the SE. This tectonic feature defines a transition zone between the thick crust of the East European Craton (EEC) and the thinner crust of the Palaeozoic Platform to the SW. The TTZ is evident from the seismic data as a perturbation of the Moho depth as well as from magnetic and gravity anomaly maps and heat flow distribution. For over a century, the TTZ has been considered a fossil plate boundary of the EEC corresponding to the limit of early Palaeozoic palaeocontinent Baltica. The results of quantitative interpretation of gravity and magnetic data, integrated with data from the new reflection seismic profiles crossing the TTZ, indicate the continuation of the Precambrian basement of the EEC and its lower Palaeozoic cover toward the SW underneath the Palaeozoic Platform. Potential field modelling also suggests the occurrence of a crustal keel underneath the TTZ. These results imply the location of a Caledonian tectonic suture, marking the site of the collision between Avalonia and Baltica, not along the TTZ, but farther SW, in NE Germany and SW Poland. Consequently, the extensive Permo-Mesozoic sedimentary basin of western Poland is established above the attenuated margin of the Baltica palaeocontinent.

The Mantoverde area of the III Región of northern Chile hosts numerous copper(-gold) deposits and prospects assigned to the iron oxide-coppergold (IOCG) clan. These range from sulphide-poor magnetite-apatite-actinolite bodies (e.g. Carmen) to chalcopyrite-rich, hematite-cemented breccias and veins (e.g. Mantoverde, Cerro Negro and Palmira). The most important Cu-rich deposits are associated with the main or, more commonly, subsidiary structures of the plateboundary-parallel Atacama Fault System, and are hosted by Middle to Upper Jurassic andesites and Lower Cretaceous dioritic to quartz dioritic plutons. The rocks in the wider Mantoverde area exhibit a complex evolution involving early sub-seafloor albitization (stage R1), subsequent, very low-grade diastathermal metamorphism (R2), and more local stage I K and Fe metasomatism and stage II hydrolysis, all preceding the emplacement of sulphide-bearing hematitic breccias and veins (i.e. ore-stage III). We develop a lithogeochemical exploration protocol specifically for Cu-rich IOCG-type deposits hosted by calc-alkaline volcano-plutonic terrains, based on the integration of whole-rock molar element ratios and oxygen isotope chemistry. Zirconium, the most conserved (least mobile) element in the volcanic and plutonic rocks of the area, was used as a common denominator for molar element ratios. The molar ratios Na/Zr, K/Zr and Al/Zr indicate that the host rocks proximal to the major deposits were affected by sodium depletion and potassium enrichment. The molar ratio (14Ca+19Na 14CO 2)/(6Si+Al+2Fe+2Mg), recalculated to a percentage scale, constitutes a modified alteration index which can be used to quantify the degree of hydrothermal alteration in the host rocks. However, although this index differentiates barren from potentially prospective sectors (i.e. strongly altered host rocks), it does not identify the hydrolytically altered rocks that are closely associated with economic copper mineralization. The 18 O values of igneous rocks in the Mantoverde area vary widely from +4.2 to +14.1‰. Integrating the modified lithogeochemical alteration index with wholerock 18 O values differentiates the least altered volcanic and plutonic rocks (i.e. alteration index <30%), with 18 O values close to +7‰, from moderately altered volcanic rocks (alteration index of 30 to 65%) having higher 18 O values of +10 to +13.2‰ due to enrichment in 18 O during regional metasomatism hydrothermal alteration sub-seafloor related to albitization and metamorphism. A third group comprises strongly K-feldspathized, Fe-metasomatized and chloritized rocks localized in Cu-mineralized centres which have alteration indexes exceeding 65% and 18 O values of +4.2 to +14.1‰. The 18 O values of paragenetically related minerals indicate that barren, K-and Fe-metasomatized host rocks equilibrated with magmatically derived fluids at temperatures exceeding 420 C. Although no recognizable alteration haloes are associated with the ensuing lower-temperature Cu-(Au) ore stage (III), the genetically related hydrolytic alteration (II) which preceded it generated distinctive alteration indices and Na/Al and K/Al ratios, as well as 18 O values averaging +10‰, with chlorite O and H isotope compositions indicating

The eastern Alboran basin and its transition to the Algerian basin is a key area in the Mediterranean realm where controversial kinematic and geodynamical models are proposed. Models imply striking differences regarding the nature of the crust, the prevalence of brittle faulting and ductile shear, the origin of magmatism, the style of Miocene deformation and the driving mechanisms of the Alboran plate kinematics. Combining a new chronostratigraphic chart of the Alboran and Algerian basins based on the Habibas (HBB-1) core drill, deep seismic sections striking WSW-ENE and SSE-NNW, and potential field data, we reassess the tectonic evolution that controlled the sedimentation and basement deformation of the westernmost limit of the Algerian basin and its transition with the Alboran domain. A WSWdirected extensional tectonic phase has shaped a stretched continental crust with typical tilted blocks along ∼100 km from Burdigalian to Tortonian times, which is assumed to result from the WSW-directed migration of the Alboran block driven by a narrow slab rollback. In the Algerian basin, this event was followed by the emplacement of an oceanic-type crust. Potential field signatures of the deep basin as well as geometrical correlations with onland outcrops of inner zones suggest a minimum WSW-directed displacement of the Alboran terrane of ∼200 km. At the southern foot of the Algerian basin, the continentocean transition is sharp and may result from the westward propagation of a slab tear at depth, forming two segments of STEP (Subduction-Transform Edge Propagator) margins. Our results support models of intense shear tractions at the base of an overriding plate governed by slab rollback-induced mantle flow. Finally, Messinian salt tectonics affected overlying deposits until today. A late Tortonian to Quaternary dominantly transpressive tectonic episode linked to the Africa-Iberia convergence postdates previous events, deforming the whole margin.

Wadi al-Dawasir area is very important province in Saudi Arabia. It contains the main water aquifer that stores a proven groundwater reserve (Wajid aquifer). This study aims to investigate the subsurface features of this aquifer (thickness, depth to basement and the structural elements) using an integrated gravity (2D profiles) and aeromagnetic data interpretation (RTP, low-pass and high-pass maps). Gravity data are measured in the field using CG-5 AutoGrav, while magnetic data are taken from a survey made by Saudi Geological Survey. The interpretation of aeromagnetic data revealed presence of interesting structural elements trending toward N-S, NNE-SSW, WNW and NNW-SSE directions. Positive magnetic anomalies are found indicating the presence of anticlinal blocks and strike-slip fault patterns. These structural elements are associated with the prevailing Najd fault and the transform fault systems. Gravity data showed that the depth to basement vary from 600 to 1150 m, giving rise to local basins with a considerable range of aquifer thicknesses (250-700 m). Finally, a basement relief map is conducted based on an integrated interpretation of the magnetic, gravity and seismic outputs. It shows an increase in depth (aquifer thickness) from south to north. The petrophysical analysis of the Wajid Formation assigns good aquifer properties in the upper section. In terms of subsurface features determinations, the concluded results (top of basement, thickness of aquifer and the prevailing structural elements) are matched with the interpreted seismic section, indicating a good compatibility of data. Keywords Gravity and magnetic data Á Subsurface structures Á Wajid aquifer Á Wadi al-Dawasir area Á Saudi Arabia This article is part of a Topical Collection in Environmental Earth Sciences on ''NovCare 2015-Novel Methods for Subsurface Characterization and Monitoring:

In the present work, we present a reconnaissance study to elucidate and delineate the subsurface structures and tectonics of the area between Dahshour and El Fayoum province using available magnetic data; including land magnetic survey and aeromagnetic data. The study area has been selected due to its active tectonic situation. The magnetic data have been analyzed to provide new information about the tectonic setting and subsurface structures of the study area. A detailed land magnetic survey has been carried out for the total component of geomagnetic field using two Proton magnetometers, one of them as a local reading base station placed in the middle part of the area, while the second was used for measuring the total intensity of the different points in a mesh-like configuration. The necessary corrections for the measured magnetic data have been carried out. The total land intensity and aeromagnetic maps have been reduced to the north magnetic pole. Moreover, wave number filtering technique has been carried out on the magnetic data utilizing three types of filters with varying wavelengths. The application of these tools on magnetic data discriminated the variable sources of specific depth ranges for the residual and regional anomalies, as well as those limited to a certain depth interval. It was found that the main tectonic trends taken the directions NE-SW, NW-SE and E-W. Three basement cross-sections have been generated using the 2-D modeling to support the interpreted structures and give idea about the configuration of subsurface basement shape. Depth estimations have been conducted by application of the Power spectrum, analytical signal and 2-D modeling techniques. The results indicate that the average calculated depth ranges between 1.8 km to 3.5 km, while the depth to volcanic intrusions ranges between 0.20 km and 0.30 km.

Mining activities in Lavrion began during the first millennium B.C. after the decline of ancient Athens and then restarted more deliberately during the nineteenth century. Aeromagnetic data from a 1967 survey of the mining area was recompiled, processed, and interpreted for the present study. The original flight lines were digitized and leveled, and the international geomagnetic reference field (IGRF) was removed. The data were inverted by means of a terracing technique that defines separate domains of uniform distribution of physical properties that cause the magnetic anomalies. The log power spectrum was computed; along with the results of terracing, it suggested the existence of two sources of the magnetic anomaly. The long‐wavelength anomaly reflects a large, concealed body that is most probably a granitic intrusion, consistent with local geological evidence. The source of the short‐wavelength anomaly is a strongly magnetized body attributed to the net effect of various thin, ma...