High Magnetic Intensity Research Articles

Investigation of the magnetic separation performance of a low-intensity magnetic separator embedded with auxiliary permanent magnets

Low-intensity magnetic separators (LIMSs) comprise one of the most widely employed magnetic separation equipment. It is worth studying how to reduce magnetic flux leakage and significantly improve magnetic induction. Typically, auxiliary permanent magnets (APMs) are embedded in the main permanent magnets (MPMs) to increase the magnetic induction. In this study, the effect of the matching relationship between the widths of the MPM and APM and the height of the APM on the magnetic field distribution and magnetic separation performance are investigated. The wider the width of the MPM is, the wider the area of the relatively high magnetic induction intensity. Therefore, increasing the width of the MPM can effectively capture farther magnetic particles, which can effectively improve the magnetic separation performance. In addition, when the size of the MPM is constant, although the height of the APM is increased, the magnetic induction is improved less significantly. The research findings indicate that the height of the APM is approximately two-thirds of that of the MPM, so a satisfactory magnetic field distribution and magnetic separation performance can be obtained. Furthermore, to verify whether APM-LIMSs have advantages, a conventional low-intensity magnetic separator (CON-LIMS) without MPMs was designed. The magnetic field distribution and the effect of important parameters (remnant flux density, drum/tank distance, feeding speed and particle size) on the separation recovery are systematically compared and investigated through detailed computational simulations corresponding to the operating conditions. All the comparison results indicate that embedding APMs in the gaps of MPMs significantly expands the area of relatively high magnetic induction, which can ensure that there is still a strong magnetic force in the area far from the surface of the drum, thereby significantly improving the separation performance. Therefore, APM-LIMSs can capture a wider range and finer particle size. Moreover, APM-LIMSs can select low-cost, ferrite, permanent magnets and set a higher feeding speed and a wider drum/tank distance, thereby significantly increasing the processing capacity while ensuring a high separation performance.

Archaeological magnetic survey to find salt production sites, using located Euler deconvolution: An application in Onchon County, Nampho, DPRK

AbstractWe present the results of archaeological magnetic surveys in Onchon County, Nampho, DPRK. At Wonup Workers’ district in Onchon County, there are tens of heaps containing ash piles, which are seen as sites associated with salt production. The goal of the magnetic surveys was to investigate the relationships between the brine pan sites and the heaps containing ash piles within the study area. The archaeological and magnetic investigations in the study area has revealed that such areas, corresponding to the high magnetic intensity occurrence on the thick ash piles near the brine pits and ditches, could be chosen as the detailed survey areas to find salt production sites. Interpretation of the results demonstrated the reliability of located Euler deconvolution in the presence of complex magnetization effects due to various archaeological remains such as brine pan sites, kilns and potteries. The data processing and interpretation techniques presented in this article could assist in further opportunities to undertake nondestructive investigations of brine pan sites in Wonup area.

Characterizing terranes and a Neoproterozoic suture zone in Central Hoggar (Tuareg Shield, Algeria) with airborne geophysics and Landsat 8 OLI data

Integration of multisource data into a geographic information system has been a powerful tool to characterize contrasting terranes and their boundaries, such as suture zones with oceanic rocks juxtaposed to continental blocks. We present an integration study of geological, Landsat 8 OLI, and airborne geophysical data for the Wadi Takalous region (Central Hoggar, Algeria), covering the SAA (Sérouenout, Aghefsa, Aguendis) domain, rich in juvenile oceanic rocks, flanked by two continental domains, LATEA (Laouni, Aouilène, Tefedest, Egéré-Aleksod and Azrou N'Fad) to the West, and TAI (Tazat and Assodé-Issalane) to the East. The Sérouenout terrane, comprising tectonic slices of metamafic-ultramafic rocks (including eclogites) enveloped by metapelites and covered by Eopaleozoic sandstones, stands out for its low magnetic intensities and low radiometric responses. To the East, granitic rocks with abnormally high radiometric responses and high magnetic intensities highlight the TAI domain, a basement block rich in Pan-African collisional and post-collisional intrusions. To the West of Sérouenout terrane, a heterogeneous magnetic and radiometric pattern characterizes the eastern LATEA that has been interpreted as a Neoproterozoic passive margin. Our integrated data also suggests that the Afara terrane is more likely correlated with LATEA (instead of TAI). Deep magnetic lineaments outline major shear zones marking terrane boundaries, such as the crustal-scale (hundreds-km long and dozens-km thick) 7°30′E thrust zone limiting the SAA and TAI domains. Structures and kinematic indicators related to collisional deformation point to an overall NE-SW to E-W crustal shortening which induced thrusting and tight folding, followed by strike-slip shear zones related to transpressional deformation in late orogenic stage. In this scenario, the SAA domain may represent an accretionary complex associated to a Pan-African suture zone and thrust onto the LATEA passive margin.

Nickel Deposit Depth Estimation Using Source Parameter Imaging and Euler Deconvolution of Aeromagnetic Data of Bakin Kogi and its Environs in Jema’a Local Government Area of Kaduna state

This study aimed to estimate the depth of Nickel deposit in Bakin Kogi – Dangoma region, which lies between latitude 901''and 9027'N and longitude 8000' and 8017' E. The study area is located in Jema’a local government area of Kaduna state. The data was gridded using Oasis Montaj® to produce Total magnetic Intensity Map (TMI) of the area, and further subjected to some filtration processes in order to obtain regional and residual map of the study area. Enhancement methods such as first vertical derivative and analytic signal methods were applied to the residual map to delineate the area with potential Nickel deposit. The quantitativemethod applied were source Parameter Imaging and Euler Deconvolution to determine the various depths of Nickel deposit. From the results of the TMI map and the residual map, the magnetic intensity of the study area was between 32976.5 to 33093.3 nT and 32963.6 to 33072.9 nT respectively with Bakin kogi-Dangoma region, having the highest magnetic intensity of about 33093.3nT and 33072.9 nT respectively. The study area has a high magnetic intensity due to nickel deposit because Nickel ore environment are notable with recognizable “magnetic stratigraphy”, prospective mafic-ultramafic contact, typified by strong magnetic contrast. Abrupt changes in the magnetic intensity infer position of the outer contact of a Nickel bearing zone. The results on the superimposed analytic map on the lineament map showed regional lineaments in Bakin kogi-Dangoma region trending NE -SW, ENE – WSW and NNE – SSW directions. The fractures and faults seen around the study area were strongly associated with minerals deposit. The results of Source Parameter Imaging (SPI) gave a depth of shallower magnetic sources ranges from 92.7 to 116.0 m with an average depth value of 104.35 m while the depth of deeper magnetic sources ranges from 651.2 to 976.2 m with an average depth of 813.7 m. The results obtained from 3D Euler deconvolution which was associated with dykes (SI = 1) anomaly produced at a shallower depth range of 100 - 700 m. Results obtained, shows a correspondence between the depths results obtained from the SPI and that of the Euler Deconvolution methods, indicating correlation in the magnetic depth estimation.

Petrophysical target characterization with lithogeochemical clustering: the Metsämonttu Zn–Pb–Cu deposit, southern Finland

ABSTRACTIn mineral exploration, reliable and comprehensive petrophysical groundwork helps evaluate the success rate of applying geophysical methods to the target and thus improves the quality of decision‐making related to geophysical surveys. Petrophysical data for potential field exploration can be efficiently collected from drill cores together with portable XRF data that provide insight into rock compositions. We acquired and analysed a multi‐parameter portable‐instrument drill core data set (2036 samples) with portable XRF, magnetic susceptibility and density measurements from the Metsämonttu Zn–Pb–Cu deposit, one of the base metal deposits in the Orijärvi Belt, southern Finland, with little post‐mining exploration during the last 50 years. Our study applied a machine learning technique (Gaussian Mixture Model clustering) to the portable XRF data to provide a pseudo‐lithological reclassification of the drill cores and used this as a basis for characterization of the deposit in petrophysical terms. We also used thermomagnetic measurements to inspect the magnetic mineralogy of the drill cores. Finally, we estimated the success of using potential field methods (magnetic and gravity) for brownfield exploration of analogous deposits in the area. With the portable XRF data clustering we were able to distinguish between barren mafic and felsic volcanic rocks, altered rocks and three different ore mineral enriched rock types. The petrophysical measurement data and thermomagnetic results were combined with the clusters to define the petrophysical characteristics for future mineral exploration with potential field methods. At Metsämonttu, the highest densities are related to the ore and iron sulphide‐bearing rocks. High natural remanent magnetization intensities are related to the iron sulphide‐bearing ore, and remanent magnetization is a significant magnetic anomaly source. Based on synthetic modelling results, both magnetic and gravimetric data could be used in direct exploration in the Metsämonttu area.

Assessment of thoracic spinal cord electrophysiological activity through magnetoneurography

ObjectiveNoninvasive and detailed visualization of electrophysiological activity in the thoracic spinal cord through magnetoneurography. MethodsIn five healthy volunteers, magnetic fields around current flowing in the thoracic spinal cord after alternating unilateral and synchronized bilateral sciatic nerve stimulation were measured using a magnetoneurograph system with superconductive quantum interference device biomagnetometers. The current distribution was obtained from the magnetic data by spatial filtering and visualized by superimposing it on the X-ray image. Conduction velocity was calculated using the peak latency of the current waveforms. ResultsA sufficiently high magnetic signal intensity and signal-to-noise ratio were obtained in all participants after synchronized bilateral sciatic nerve stimulation. Leading and trailing components along the spinal canal and inward components flowing into the depolarization site ascended to the upper thoracic spine. Conduction velocity of the inward current in the whole thoracic spine was 42.4 m/s. ConclusionsVisualization of electrophysiological activity in the thoracic spinal cord was achieved through magnetoneurography and a new method for synchronized bilateral sciatic nerve stimulation. Magnetoneurography is expected to be a useful modality in functional assessment of thoracic myelopathy. SignificanceThis is the first report to use magnetoneurography to noninvasively visualize electrophysiological activity in the thoracic spinal cord in detail.

Innovative pre-concentration technology for recovering ultrafine ilmenite using superconducting high gradient magnetic separator

To achieve the utilization of the abandoned ultrafine ilmenite (−20 μm) produced in the titanium magnetite processing plant in Panzhihua, the superconducting high-gradient magnetic separation (SMS) technology was proposed in this study. After optimizing the conditions of magnetic intensity, feeding and pulsation, an SMS concentrate with TiO2 grade of 16.03% and TiO2 recovery of 66.39% was obtained through one roughing–one cleaning pre-concentration flowsheet. The specific magnetic force and magnetic force were calculated and analysed to illustrate the pre-concentration mechanism, and the results revealed that the combination of high magnetic field and strong pulsating resulted in the effective pre-concentration of the ultrafine ilmenite in the SMS process. In addition, the magnetic force analysis indicated that the high magnetic intensity and high magnetic gradient are the key factors of the SMS technology. Furthermore, the EDS-Mapping detection certified that the ultrafine ilmenite was concentrated from the gangue minerals using SMS technology.

Structural and lithological interpretation of aero-geophysical data in parts of the Lower Benue Trough and Obudu Plateau, southeast Nigeria

High resolution airborne magnetic and radiometric data were used to map probable sites for polymetallic-magmatic hydrothermal deposits in the study area. The first and second vertical derivatives, horizontal gradient, analytic signal and tilt angle derivative were used to enhance magnetic data in order to determine the location of short wavelength anomalies, magnetic sources and geologic boundaries. Also, to understand and detect radiometric anomalies controlling mineralization in host rocks, enhancement operations involving potassium (K), equivalent thorium (Th), equivalent uranium (U) concentrations and ternary imageries were carried out. All these operations enabled the delineation of responses associated with mineralization, lithology and geologic structures. Generally, lineaments trend in the NE-SW, NNE-SSW, NW-SE and E-W directions, and serve as potential pathway for hydrothermal fluid migration and mineralization. Radiometric anomalies from spectrometric imageries are caused by felsic minerals, hydrothermal rock alterations, widespread shales, residual clay, oxides and accessory minerals that constitute regolith of the area. The coincident high magnetic and potassium intensities sites in Anambra Bain (AB), Abakaliki Anticlinorium (AA), Ikom-Mamfe Rift (IMR) and Obudu Plateau (OP) are probable sites for polymetallic-magmatic hydrothermal deposits. Generally, the joint magnetic and radiometric results were able to establish link between lithology, geologic structures and hydrothermal alteration patterns.

Influence of Early Low‐Temperature and Later High‐Temperature Diagenesis on Magnetic Mineral Assemblages in Marine Sediments From the Nankai Trough

AbstractDiagenesis can have a major impact on sedimentary mineralogy. Primary magnetic mineral assemblages can be modified significantly by dissolution or by formation of new magnetic minerals during early or late diagenesis. At International Ocean Discovery Program Site C0023, which was drilled in the protothrust zone of the Nankai Trough during Expedition 370, offshore of Shikoku Island, Japan, non‐steady state conditions have produced a complex sequence of magnetic overprints. Detailed rock magnetic measurements, which characterize magnetic mineral assemblages in terms of abundance, grain size, and composition, were conducted to assess magnetic mineral alteration and diagenetic overprinting. Four magnetic zones (MZs) are identified down‐core from ∼200 to 1,100 m below sea floor based on rock magnetic variations. MZ 1 is a high magnetic intensity zone that contains ferrimagnetic greigite, which formed at shallow depths and is preserved because of rapid sedimentation. MZs 2 and 4 are low magnetic intensity zones with fewer magnetic minerals, mainly coarse‐grained (titano‐)magnetite and hematite. This magnetic mineral assemblage is a remnant of a more complex assemblage that was altered diagenetically a few million years after deposition when the site entered the Nankai Trough. MZ 3 is a high magnetic intensity zone between MZs 2 and 4. It contains authigenic single‐domain magnetic particles that probably formed from fluids that circulated through faults in the accretionary prism. Varying sediment supply and organic matter input through time, burial temperature, and tectonic fluid circulation are the primary drivers of magnetic mineral assemblage variations.

Numerical and experimental study on the flow characteristics and the erosive ability of magnetorheological jet

Fluid jet machining has been widely used in machining of hard-brittle materials. However, the diffusion of a jet flow significantly affects the erosion capacity. Magnetorheological (MR) fluid has been considered to take the role of pure water for carrying abrasive particles, due to its better concentration when the external magnetic field is applied. The present investigation focuses on the flow characteristics of a magnetorheological jet, which are involved in the basic aspects of erosion mechanism. 3D numerical models of excitation coil and jet flow field were established to investigate the fluid pressure distribution on the target surface and the trajectories of laden particles. Experiments were also conducted to verify the simulation results and evaluate the feasibility of a MR jet on surface finishing. The results indicated that the utilization of high magnetic intensity can effectively improve the concentration of a jet flow and the processing quality of workpiece surface.

Mixed crystalline basement of Junggar basin revealed by wide-angle seismic evidence

A wide-angle seismic reflection / refraction survey along a ~ 600 km long transect through the Junggar basin from Emin to Qitai allows to receive several images near N-S trending blind faults, which are located at the lower part of the upper crust, the middle crust and the lower crust within the basin and cut up the Moho. These faults, with high seismic velocity and without obvious dislocation, are considered as “extensional faults” formed by north-south compression and east-west extension. These deeply rooted faults provide channels via which basic to ultra-basic materials from upper mantle migrate into the crust and mix up with the crustal material causing thin thickness, high seismic velocity, high density and high magnetic intensity after cooling in the crust of the basin.

Millennial-Scale Environmental Variability in Late Quaternary Deep-Sea Sediments from the Demerara Rise, NE Coast of South America

We carried out a rock magnetic study of two deep-sea gravity cores from the Demerara Rise, NE South America. Our previous studies provided radiocarbon and paleomagnetic chronologies for these cores. This study presents detailed rock magnetic measurements on these cores in order to characterize the rock magnetic mineralogy and grain size as indicators of the overall clastic fraction. We measured the magnetic susceptibility, anhysteretic remanence, and isothermal remanence and demagnetized the remanences at several alternating field demagnetization levels. The magnetic intensities estimate the magnetic material concentration (and indirectly the overall clastic fraction) in the cores. Ratios of rock magnetic parameters indicate the relative grain size of the magnetic material (and indirectly the overall clastic grain size). Rock magnetic intensity parameters and rock magnetic ratios both vary systematically and synchronously over the last 30,000 years in both cores. There is a multi-millennial-scale cyclicity, with intervals of high magnetic intensity (high magnetic and clastic content) with low magnetic ratios (coarser magnetic and clastic grain size), alternating in sequence with intervals of low magnetic intensity with high magnetic ratios (finer grain size). There is also a higher-frequency millennial-scale variability in intensity superposed on the multi-millennial-scale variability. There are nine (A–I) multi-millennial-scale intervals in the cores. Intervals A, C, E, G, and I have high magnetic and clastic content with coarser overall magnetic and clastic grain size and are likely intervals of enhanced rainfall and runoff from the NE South American margin to the coastal ocean. In contrast, intervals B, D, F, and H have lower clastic flux with finer overall grain size, probably indicating lower continental rainfall and runoff. During the Holocene, high rainfall and runoff intervals can be related to cooler times and low rainfall and runoff to warmer times. The opposite pattern existed during the Pleistocene, with higher rainfall and runoff during interstadial conditions and lower rainfall and runoff during stadial conditions. We noted a similar pattern of Pleistocene multi-millennial-scale variability in a transect of deep-sea sediment cores along the NE Brazilian margin, from the Cariaco Basin (~10 N) to the NE Brazilian margin (~1° N–4° S). However the NW part of this transect (Cariaco Basin, Demerara Rise, Amazon Fan) has an out-of-phase relationship with the SE part of the transect (NE Brazilian margin) between warm–cold and wet–dry conditions. One possible cause of the high–low rainfall and runoff patterns might be oscillation of the Intertropical Convergence Zone (ITCZ), with higher rainfall and runoff associated with a more southerly average position of the ITCZ and lower rainfall and runoff associated with a more northerly average position of the ITCZ.

Rock magnetic evidence for a middle Holocene transition in marine sediments from La Paz basin, southern Gulf of California

Results of a rock magnetic study of a marine sediment core from La Paz Basin are used to investigate the Holocene paleoclimate in the Gulf of California. Chronological control based on AMS radiocarbon dating shows that the sequence covers the past ~7650 cal yr BP. The coercivity, magnetization intensity, susceptibility and magnetic hysteresis loops point to dominant fine-grained magnetite and titanomagnetites as main magnetic carriers. In the magnetic hysteresis ratio plot, magnetization and coercivity ratios fall in the pseudo-single domain field. High magnetic susceptibilities and magnetization intensities characterize the upper core section, with lower values downcore on a low amplitude oscillation trend. The late Holocene is marked by low susceptibilities, frequency-dependent, paramagnetic slope factors and variable hysteresis parameters with low Mr/Ms magnetization ratios, low Bc and Bcr coercivities and high Bcr/Bc ratios. The lower core section in the ~7650-5000 cal yr BP interval shows increased susceptibilities as compared to the upper sections with lower values. The magnetic hysteresis logs for the interval around 5000-4000 cal yr BP show some samples with distinct lower magnetization (Mr/Ms) and higher coercivity (Bcr/Bc) ratios, which characterize the interval from the downcore variation trend. The pattern in the magnetic properties is interpreted in terms of a change in precipitation from high to low humidity from the middle to the late Holocene. The sediment section records a middle Holocene climate transition in the southern Gulf ~5000-4000 cal yr BP, supporting a northward migration of climate patterns along the western North America margin, from the southern Gulf of California to Alaska.

Palaeoenvironmental reconstruction and oolitic ironstone mapping of the Agbaja Ironstone Formation in the Nupe Basin, North-central Nigeria: Insights from sedimentological and aeromagnetic analyses

This study focusses on the sedimentological and aeromagnetic characteristics within the Agbaja Ironstone Formation to establish the sedimentary depositional history and map oolitic ironstone zones in the Lokoja district of the Nupe Basin. Forty sandstone samples were collected for granulometric, sedimentary facies and petrographic analyses to reconstruct depositional processes of the Agbaja Ironstone Formation. Aeromagnetic data analysis was engaged to map the oolitic ironstone rich zones. The iron-rich sandstones in the Agbaja Ironstone Formation occur as oolitic ironstone, ironstone concretion and laterites. The bivariate grain size plots and multivariate discriminant analyses suggest that 92% of the sandstone in the formation were deposited in beach and coastal dunes under fluvial-river actions, while 8% are of the marine environment deposited under wave actions. The quartz-feldspar lithic (QFL) ternary diagram and palaeocurrent analyses of the samples revealed that the matured, sub-arkosic sandstones originated from the cratonic interior (Abakaliki uplifts). The bioturbation and reactivation by Ophiomorpha burrows and herringbone on the fine-medium grained sandstones in the formation contributed to the observed high magnetic intensity values. High magnetic signatures (−94.784 to 1.191 nT), analytic signal peaks and depth levels from the 2-D source parameter images are the basis for the produced oolitic ironstones prospectivity map in this study.

Mathematical Modeling of Unsteady Flow with Uniform/Non-Uniform Thermal and Magnetic Fields in a Half-Moon Shaped Domain

The mathematical modeling of two-dimensional unsteady free convective flow and thermal transport inside a half-moon shaped domain charged in the presence of uniform/non-uniform temperature and magnetic effects with Brownian motion of the nanoparticles has been conducted. Thirty-two types of nanofluids in a combination of various nanoparticles and base fluids having different sizes, shapes, and solid concentrations of nanoparticles are chosen to examine the better performance of heat transfer. The circular boundary is cooled while the diameter boundary is heated with uniform/non-uniform temperature. An external uniform/non-uniform/periodic magnetic field is imposed along diameter. The powerful partial differential equations solver, finite element method of Galerkin type, has been engaged in numerical simulation. The numerical solution's heat transfer mechanism reaches a steady-state from the unsteady situation within a very short dimensionless time of about 0.65. The thermal transport rate enhances for increasing buoyancy force whereas decreases with higher magnetic intensity. The uniform thermal condition along the diameter of half-moon gives a higher thermal transport rate compared to non-uniform heating conditions. The non-uniform magnetic field provides greater values of the mean Nusselt number than the uniform field. In addition, the outcomes also predict that a better rate of temperature transport for kerosene-based nanofluid than water-based, ethylene glycol-based, and engine oil-based nanofluid. The heat transfer rate is observed at about 67.86 and 23.78% using Co-Kerosene and Co-water nanofluids, respectively, with an additional 1% nanoparticles volume fraction. The blade shape nanoparticles provide a better heat transfer rate than spherical, cylindrical, brick, and platelet shapes. Small size nanoparticles confirm a higher value of average Nusselt number than big size. Mean Nusselt number increases 22.1 and 5.4% using 1% concentrated Cu-water and Cu-engine oil nanofluid, respectively, than base fluid.

Anomalous Magnetic Field Cancer Cause And Therapeutic Possibilities By Natural Earth Magnetic Field

Cancer cause are three factors, stated by official medical science: cancerogenous substances, viruses and physical agencies from external environment. Earth magnetic fields (EMF) measurements have started in cancer diseased patients' rooms. The measured high magnetic fields intensities found much higher than EMF, are named anomalous magnetic fields (AMF). Work Aim: Prove that AMF enabled body viscous magnetization (BVM) formation. Explain that BVM in breast creates breast cancer. Prove that locating breast cancer patients away from AMF to natural EMF leads to recovery. Explain that today's medical science risk factors are misinterpreted. Show that mammography and scintigraphy are evidence that AMF created breast cancer. Work Method: AMF measurements were performed with a protonic magnetometer. Three patients groups were included in AMF measurements. Physiology and etiopathological literature were studied. Results: AMF measurements in breast cancer patients' beds if found BVM was formed, enabling paraoncogen into oncogene mutation, and then clonal breast cancer developed. Thousands examples were measured and there were no breast cancer disease created in natural EMF. Based on a 6 patients group with metastases, it can be said that time limits for starting the disease treatment are not taken into account, but everything should be treated, including palliative patients, but in natural EMF. Conclusion: It was found that environmental AMF created BVM producing breast cancer. It is proven that locating patients away from AMF to a natural EMF leads to recovery. It is proven that the official risk factors are AMF consequences and not breast cancer causes. In advanced diseases with metastases where surgery cannot remove everything, it is necessary to introduce hyperthermia - only in natural EMF.

Research on Magnetism and Magnetization Intensity of Magnetic Fluid

Magnetic fluid is a liquid magnetic material with high magnetization, fluidity and superparamagnetism. The composition and the performance of magnetic fluid in magnetic field were introduced. Magnetic model of magnetic fluid for application was established. Magnetic particles could be seen as magnetic needles with certain N-S directions whose direction could be controlled by external magnetic field. Magnetization mechanism of magnetic fluid was researched. Measurement principle of magnetization intensity was studied and the formulas were deduced. The working principle of vibrating sample magnetometer was introduced and the magnetization curve of magnetic fluid was measured and plotted. It was concluded that magnetic fluid has superparamagnetism which means that the remanence and coercivity of aggregation of magnetic fluid are both zero. Magnetism is an important characteristic of magnetic fluid for engineering applications that magnetic fluid with high magnetization intensity will be explored and researched.

Interpretation of Airborne Magnetic and Geo-electric Data: Resource Potential and Basement Morphology of the Ikom–Mamfe Embayment and Environs, Southeastern Nigeria

The Ikom–Mamfe Embayment, which cuts across southeastern Nigeria and southwestern Cameroon, is a bifurcation of the Benue Trough and the NW–SE splay component of the NE–SW trending trough. The Nigerian sector of the embayment, a sedimentary province bounded to the north and south by basement terrains, is considered a relatively frontier basin with little information about its resource potential. Here, airborne magnetic, resistivity and self-potential (SP) data were integrated in studying the Nigerian sector of the embayment and its surrounding localities. This study aimed to delineate (possible) mineral-bearing lineament structures and their corresponding trend orientations, to evaluate their relationship to tectonic fabric, to estimate depth of perturbing causative sources, to map ore bodies, and to identify probable locations for detailed petroleum system analysis. For the first time, 2D electrical resistivity and SP methods were deployed in the sub-surface characterization of the embayment. Results of aero-magnetic data analysis revealed the presence of high magnetic intensities predominantly in the western and northeastern parts of the study area. The high intensities observed at the western part are due to mineral ore bodies present within a sedimentary host. In addition to the presence of mineral ores, the noticeable high magnetic signatures at the northeastern part are associated with the presence of outcropping units of basement complex rocks that comprise mainly of migmatitic metasediments. The large variation in magnetic intensities within the embayment is attributed to the combined effect of igneous intrusives and mineral-bearing lineaments emplaced within the overlying sediments. Analysis of structural lineaments depicts E–W and ENE–WSW as the dominant orientations with minor NW–SE, NE–SW and NNE–SSW trends. The NE–SW and ENE–WSW structures are aligned parallel to the Benue Trough and the Cameroon Volcanic Ranges, and are genetically related. These lineaments occur in the form of faults, fractures and veins, and they are densely distributed within some areas of moderate to high intensities and analytical amplitudes. This suggests a possible relationship between structural lineaments and metalliferous deposits. These lineaments were marked for ground geophysical surveys. The geophysical traces derived from these areas reveal numerous underlying mineral bodies of contrasting resistivity and potential with their host formation. These bodies are shallow magnetic sources exposed in the first and second vertical derivative images. These show remarkable agreement between the geo-electric data and the aero-magnetic data. The results of quantitative assessment show shallow basement depth and, hence, thin sedimentary layer (0.2–2.4 km) within and around the embayment, which is insufficient for the concealment of hydrocarbon resource. In addition, the presence of numerous intrusive rocks implies a high temperature environment favorable for “cooking” of potential source rocks beyond the hydrocarbon generating window. This renders the area disadvantageous for hydrocarbon exploration. However, we discover that the sedimentary thickness (ranging between 3 and 4 km) mapped at the southwestern part of the area could favor the formation and accumulation of hydrocarbon fluids. This area, characterized by moderate igneous intrusion, lies approximately northeast of the prolific Niger Delta oil province and shows fair to good sub-surface structural conditions required for hydrocarbon entrapment. The basement morphology, sedimentary thickness and structural disposition call for a detailed petroleum system analysis within this area.

Aeromagnetic mapping of fault architecture along Lagos–Ore axis, southwestern Nigeria

AbstractA seismic wave is released when there is sudden displacement on a fault plane. The passage of this wave along the fault plane or within the lithosphere could result in ground shaking or vibration at the surface of the Earth. To provide a geophysical explanation to this phenomenon, the high-resolution aeromagnetic data of the sedimentary terrain and part of the Basement Complex of Southwestern Nigeria were processed and interpreted to provide fault architecture of the area, which could serve as conduit for the passage of seismic energy in the study area. High-resolution aeromagnetic data along the Lagos–Ore axis are processed for fault mapping in the study area. The reduced-to-equator (RTE) residual aeromagnetic data used were enhanced using the total horizontal derivative (THD) and upward continuation (UC) filtering techniques on Oasis Montaj 6.4.2 (HJ) software. The resultant maps were overlaid and compared with the plotted RTE residual maps for relevant interpretations. Varying signatures of magnetic anomalies are grouped into high (57.9–89.1 nT), intermediate (38.2–57.9 nT), and low (4.0–38.2 nT) magnetic intensities, which are associated with contracting basement rocks features. The obtained lineaments from the THD reveal areas of various deformations such as brittle, which is associated with faults/fractures, and ductile deformation, which is associated with folds of geological features. The faults, as depict by the UC map, reveal different depth ranges of 500–2250 m at the western side and 1,500–1,250 m at the northwestern area of the study. Since it has been on record that September 11, 2009, earth tremor of magnitude 4.4, with the epicenter at Allada, Bennin Republic, 128 km west of Lagos, Nigeria occurred within the study area, it can be inferred that the established geologic fault architecture could be responsible for the hazard and be part or synthetic to the Ifewara-Zungeru fault in Nigeria.

Manufacture and Performance Test of 3.5 T High Temperature Superconducting Coils for the Magnetic Separation

With the development of the high temperature superconducting (HTS) materials technology, the manufacturing process of the HTS tape has been further improved and hundreds of meters of HTS tapes have been applied in industry. In beneficiation field, the magnetic separation facility of using HTS technology can not only improve the work efficiency of the material purification and separation, but solve the problem that some weak magnetic materials are difficult to separate due to the high magnetic intensity and gradient. Today, a 3.5 T HTS magnetic separation facility cooled by a cryocooler was manufactured in China. This paper focuses on the manufacturing process and performance test of the HTS magnet. Some new structure was adopted in the design and manufacture of the magnet and verified in the magnet performance test. Test results indicated that the magnet could be cooled below 20 K by the direct heat conduction, the center magnetic field could reach 3.57 T and the center axis uniformity of the magnetic field was better than 95% in the range of ±100 mm from the mid-plane. In short, the magnet design is reasonable and it is likely to be applied on other similar magnet in future.