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13th SAGA Biennial Conference & Exhibition
- Conference date: 06 Oct 2013 - 09 Oct 2013
- Location: Kruger National Park, South Africa
- Published: 06 October 2013
1 - 20 of 108 results
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Interpretation Of Borehole Gravity Data For Vms Deposits In The Context Of Complex Geology
Authors C. Nackers, M. Chouteau, P. Shamsipour, M. Cheman and P. BérubéA forward modeling and inversion code has been developed to study the use of the borehole gravity method for exploration of VMS deposits. Different problems are associated with the gravity method and to analyse them, synthetic data has been modeled and then inverted. The first problem encountered is the data acquisition settings including the number of boreholes, their location and data collection sampling in the boreholes. They highly influence the results of the inversion. A minimum of three boreholes within appropriate distance from the target is required to locate any structure. In the case where the geology is complex, the boreholes have to be well positioned around the deposit to be able to properly locate it. In the scenario where the borehole gravity method is used to calculate the excess mass of a deposit and to define its structure, at least one borehole should intercept the deposit. Also, fixed density constraints are highly recommended to be able to calculate precisely the excess mass of a deposit. The regional-residual anomaly separation is a very important aspect of the data interpretation. Up to now no technique is effective in performing an optimal separation. In this paper we apply four different methods and compare the inverted density model to the initial model. These methods are the graphical method, the vertical gradient, a non-linear filter and a wavelet filter. Then these methods were applied to GraviLog data that was acquired over and in the vicinity of the Virginia Gold’s Coulon deposit (Quebec, Canada). All methods were able to help locate the deposit, but densities are all underestimated.
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Multiphysics Model Of Borehole Environment And Joint Inversion Of Well Logs
Authors I. Eltsov, V. Kuvshinov, L. Nazarova, G. Nesterova, Yu. Stefanov and V. ShelukhinMultiphysics model of borehole environment was proposed. It describes main factors of generation and evolution of near well zone: mechanical impact on reservoir by well, flow of multiphasic fluids, salt transfer, lithologic characteristics of reservoir, mud cake growth and destruction. Software system for joint computer simulation of electromagnetic, hydrodynamic and geomechanical processes in the borehole environment has been constructed. Theoretical logs of VIKIZ (high frequency induction isoparametric wireline logging tool) and BKZ (Russian lateral log) are simulated for calculated electrical resistivity distribution. In consequence of deformation processes during and after drilling porosity and permeability near borehole are decreased, therefore mud filtrate invasion and salt transfer acquire another character. VIKIZ and BKZ logs are strongly depended on geomechanical parameters, such as break point stress or internal friction point and properties of pore fluid. Authors have suggested interpretation technique taking into account deformation processes and there consequences, this make it possible to improve formation evaluation. Proposed integrated interpretation methodology was verified for West Siberia well logs. Input parameters of joint model were determined from data of geophysical study of borehole and core analysis. For this purpose technique of evaluation of parameters, which are responsible for filtration-volumetric and strain characteristics of rocks were devised. Joint multidisciplinary mathematical and computer model of borehole environment make the opportunity to perfect interpretation of well data and reservoir evaluation.
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Data Driven, Objective Mapping By Clustering Satellite Imagery And Airborne Geophysical Data Suites
Authors D. Eberle, D. Hutchins and I. KahimiseConventional geological mapping using aerial photo interpretation coupled with field visits is often handicapped in areas with tropical weathering or sand cover in arid regions. High resolution airborne geophysical data acquisition over large areas covered by overburden can augment geological mapping of these areas provided information extraction is done in an adequate, automated and objective way. We suggest that the integration of airborne geophysical data with space-borne remote sensing data suites using fuzzy partitioning clustering meets these criteria. The outcome of unsupervised clustering is a classified zonal map which, in combination with some field inspections, produces a high resolution lithology map, in this case 100 m by 100 m pixel size, which is by power of spatial resolution far superior to any conventional mapping and can therefore provide new incentive for geological understanding of the area, modelling or mineral exploration. Our new approach to map hard rock geology hidden beneath overburden has been applied to a portion of largely sand and sediment covered southern Namibia by integrating airborne magnetic, radiometric and Landsat 7 data suites. The classified zonal map obtained from these data was converted to a lithology map by attributing what is known from previous geological investigations of this area. Apart from the structural control of known mineral showings, the resultant map clearly displays an area requiring further grass-root exploration.
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Regional Cartography Of Regolith Parameters Using Airborne Gamma Ray Spectrometry
Authors G. Martelet, S. Drufin, B. Tourliere, N.P.A. Saby, J. Perrin, J. Deparis, F. Prognon, C. Jolivet, C. Ratié and D. ArrouaysAmong the remote sensing techniques, the airborne gamma-ray spectrometry has been widely developed for several tens of years (e.g. IAEA, 1991), being nowadays almost systematically surveyed in regional mapping programs, for soil/regolith (e.g. Lacoste et al., 2011), solid geology reconnaissance (e.g. Metelka et al., 2011) or mineral potential assessment (e.g. Shives et al., 2000). Gamma-ray surveys provide maps of concentration in K, U and Th chemical elements at the ground level. These data are primarily sensitive to the mineralogy and geochemistry of the parent material, as well as its weathering products, including residual and transported clays, sand and gravel (e.g.Minty, 1997). In this study, instead of addressing complex concepts such as lithology, we chose to investigate these gamma spectrometric data by mapping parameters of the regolith, which are simple objective quantities. It is known that these parameters of the regolith: density, moisture, chemistry, all influence the natural gamma ray emissions (e.g. IAEA, 2003). Several papers assess correlations between gamma-spectrometric variables and one or few soil parameters including texture (e.g. Taylor et al., 2002), regolith chemical or mineral contents (e.g. ViscarraRossel et al., 2007), and other soil parameters such as soil depth, total phosphorus or total carbon (e.g. McKenzie and Ryan, 1999).
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The Bateke Plateau Structure- A New Possible 7 Km Diameter Quaternary Meteorite Impact Structure In Gabon: A Remote Sensing Study
Authors S. Master, G.R.J. Cooper and K. KlajnikA 7 km diameter circular structure, called the Bateke Plateau Structure, has been identified on Landsat imagery of eastern Gabon, in a region dominated by Palaeogene to Neogene continental sedimentary rocks of the Bateke Plateau, which unconformably overlie cratonic Archaean basement. Processing of DEMs derived from SRTM radar imagery of the structure, using various radial shading algorithms, has demonstrated that the structure consists of two nested toroidal rings, with a ring-shaped depression between them. The outer toroid has a peak-to-peak diameter of 5.8 km, and a thickness of 1.3 km, yielding a maximum diameter of 7.1 km. It is separated by a deep moat from the inner toroid, which has a diameter of 1.4 km, and a thickness of 700 m. Such a structure is consistent with a complex impact structure containing a central peak-ring uplift, formed by meteorite or cometary impact. Other possibilities for forming such a ring structure are considered highly unlikely, given the setting of the structure in a thin continental sandstone sequence overlying an Archaean craton, and the absence of young igneous intrusions, diapiric structures, karst, or deformation features. The Bateke Plateau Structure is postulated as a post-Neogene (Quaternary) complex impact structure with a peak-ring central uplift, which, because of its degraded, eroded state, is likely to be Pleistocene rather than Holocene in age.
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3d Inversion Of Airborne Vertical Gradient Gravity Data
Authors E.B. Tchikaya, M. Chouteau, P. Keating and P. ShamsipourWe present an inversion method based on a geostatistical approach, i.e. cokriging and conditional simulation for three dimensional inversion of airborne gradient gravity data including geological constraints. Cokriging is a method of estimation that minimizes the error variance by applying cross-correlation between several variables. In this study the estimates are derived using gradient gravity data as secondary variable and the density as the primary variable. In the proposed method, the linearity between gradient gravity and density allows us to obtain a covariance matrix of densities using observed data, i.e, we adjust the density covariance matrix by fitting experimental and theoretical gradient gravity covariance matrices. To obtain various reasonable solutions in order to see the variability that can be expected from the density covariance model adopted, a geostatistical simulation algorithm is applied. The proposed method was first tested on synthetic data. The result shows the ability of the method to integrate complex a priori information. The technique was then applied to actual gravity gradient data collected by the Geological Survey of Canada in the area of Strange-Lake (Quebec) using the Falcon gravity system. Results of inversion (cokriging and co-simulation) are in good agreement with the geology of the studied regions.
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Getting The Best Value From Gravity Gradiometry
Authors D. Fitzgerald and R. PatersonThe critically important steps to get best value from your gravity gradiometry data, assuming your contractor has done his job well in designing and acquiring the data, is the preparation of the representation of the potential field gradients. The ~200m resolving power of existing gradiometer systems approaches what is necessary for minerals applications. In particular, beyond the aircraft, the topographic surface represents the largest and most proximal density contrast encountered in an airborne survey. Hence terrain effects can have significant impact on AGG data. The critical steps are: Terrain correction and determining ‘best’ terrain density Gridding, using all the measured gradients to constrain the interpolation Smoothing/de-noising by using the 3rd order tensor constraints Anti-alias filtering of the gradient signals so that wave lengths are properly represented in all directions Transformation of the gradients by integration to estimate the gravity or magnetic field Terrain corrections are a necessary step in the processing of observed AGG data in rugged terrain, in order to highlight subsurface density variations with a minimal overprint from the terrain. We propose a simple and rapid AGG tensor-based method to estimate an optimum bulk terrain density for subsequent terrain-correction. Each of the currently deployed systems for acquiring gradiometry is evolving driven by competition and the users’ needs. Mining applications of the technology to directly detect ore-bodies that show up as anomalies can now be successful provided the dimensions are of the order of 200m or more. High resolution 3D geology models of operating mines can be used to calibrate gradiometry surveys.
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Vs Structure Of The Crust Containing The Bushveld Complex
Authors E.M. Kgaswane, A.A. Nyblade, R.J. Durrheim, J. Julià, P.H.G.M. Dirks and S.J. WebbThe crustal structure of the Bushveld Complex is investigated by jointly inverting high-frequency teleseismic receiver functions and 2–60 sec Rayleigh wave group velocities for 16 broadband seismic stations spanning the Bushveld Complex. Rayleigh wave group velocities for 2–15 sec periods were obtained from a surface wave tomography using local and regional events, while group velocities for 20–60 sec periods were taken from a published model. The 1-D Vs models obtained for each station show the presence of a thickened crust in the centre of the Bushveld Complex, and that Vs4.0 km/s over a significant portion of the lower crust (30 km depth). The 1-D Vs models also reveal that the upper crustal structure (10 km depth) across the Bushveld Complex is characterized by Vs as high as ~3.7–3.8 km/s, consistent with the presence of mafic lithologies. These results support a “continuous-sheet” as opposed to a “dipping-sheet” model for the Bushveld Complex. However, detailed modelling of receiver functions at one station within the centre of the complex suggests that the mafic layering is inhomogeneous and could have been locally disrupted by diapirism and metamorphism.
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Tectonic Evolution Of The Limpopo Belt: Constraints From Mangetotelluric Data
More LessDespite many years of work, a convincing evolutionary model for the Limpopo belt and its geometrical relation to the surrounding cratons is still elusive. This is partly due to the complex nature of the crust and upper mantle structure, the significance of anatectic events and multiple high-grade metamorphic overprints. We use deep probing magnetotelluric data acquired along three profiles crossing the Kaapvaal craton and the Limpopo belt to investigate the crust and upper mantle lithospheric structure between these two tectonic blocks. The 20-30 km wide composite Sunnyside-Palala-Tshipise-Shear zone is imaged in depth for the first time as a sub-vertical conductive structure that marks a fundamental tectonic divide interpreted here to represent a collisional suture between the Kaapvaal and Zimbabwe Cratons. The upper crust in the Kaapvaal Craton and the South Marginal Zone comprises resistive granitoids and granite-greenstone lithologies. Integrating the magnetotelluric, seismic and metamorphic data, we propose a new tectonic model that involves the collision of the Kaapvaal and Zimbabwe cratons circa 2.6 Ga, resulting in high-grade granulite Limpopo lithologies. This evolutionary path does not require a separate terrane status for each of the Limpopo zones, as has been previously suggested.
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Lebombo: Are We On The Edge Of Africa?
By C. ReevesThe history of continental dispersal is recorded in the fracture zones and magnetic anomalies of the oceans, though for various reasons it is the earliest phases of dispersal that are, at the same time, the most interesting and the least clearly defined in this record. The relative movements of Africa and Antarctica are particularly important if a reliable model for the whole of Gondwana dispersal is to be built since it affects plate circuits through both the South Atlantic and the Indian Oceans. The absence of marine magnetic anomalies through the Cretaceous Quiet Zone (125-84 Ma) leads to a lack of time control for an important part of the dispersal process, though the fracture zones created then are still clear.
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Magnetotelluric Image Of Conductivity Distribution At The Passive Continental Margin In The Kaoko Belt In Northern Namibia And The Walvis Ridge
Authors G. Kapinos, U. Weckmann, O. Ritter and M. Jegen-kulcsarUnderstanding of processes related to the deformation and evolution of the South Atlantic margins and factors controlling the continental rifting and breakup of Gondwana 200 my ago are few objectives of the interdisciplinary SAMPLE project (South Atlantic Margin Processes and Links with onshore Evolution). In frame of this project we conducted an on- offshore magnetotelluric (MT) survey in the Kaoko Belt in Northern Namibia and the Walvis Ridge to image the subsurface electrical conductivity structure of the Southern African passive continental margin. With a conductivity model we aim to study the magmatic and tectonic activity in this area since the early Cretaceous and the influence of pre-existing neoproterozoic structures on the placement of magma and subsequent continental breakup.
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Exploration Of The Xade Complex, Botswana
Authors B. Corner, J. Blaine, R.E. Fripp, M. Jones, P.R. Hildebrand and D.R. VerranThe Xade Complex occurs in the Central Kalahari semi-desert of Botswana. It was initially identified in 1976 during the first regional aeromagnetic survey of the country (Reeves, 1978). Cover sequences comprise 200-900 m of Karoo Supergroup sediments and basalts, and overlying Kalahari Group sediments. Two boreholes were drilled as part of the follow-up Kalahari Drilling Project (Meixner and Peart, 1984), the one intersecting gabbronorite at 815 m and the other weathered basalt at 419 m, passing into dolerite. The gabbronorite has yielded an U-Pb zircon age of 1109.0±1.3 Ma (Hanson et al., 2004), which is coeval with the Umkondo Igneous Province. The Anglo American Corporation (Ambot) subsequently held exploration licenses over the Complex as part of their Kalahari Gold Project (Ambot 1998). A single Ambot borehole, drilled on a seismic line traversing the southern portion of the Complex, intersected amygdaloidal lava at 621 m, passing into dolerite and shales assigned to the Waterberg Group. More recently, Manica Minerals Ltd has held licenses over the Complex, having initially drilled a further three boreholes in partnership with Mvelaphanda Resources Ltd. Exploration of the Complex is currently being advanced in a Joint Venture with Australian company Impact Minerals Limited which has earned a majority share in the project. The current phase of exploration, still in progress, has included aeromagnetic reflying of a selected target area at a high resolution, extensive geochemical surveying using MMITM technology, trial high temperature SQUID time-domain electromagnetic profiling (HTS TDEM), and the drilling to date of a further two deep boreholes. The current target area encompasses a possible feeder (or exit) dyke system and its entry zone into the complex.
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Time Domain Electromagnetic Sounding In Southern Africa: Recent Case Studies
Authors V. Hallbauer-zadorozhnaya and P.K. NyabezeThe Council for Geoscience carried out ground based time domain electromagnetic sounding (TDEM) surveys on prospects in five countries in Southern Africa namely Democratic Republic of Congo (DRC), Mozambique, Rwanda, South Africa and Zimbabwe. The surveys were undertaken on mining, mineral exploration and engineering sites. The TEMFAST-48HPC and TSIKL-5 instruments were used for data acquisition. In addition, the Geonics Protem 47 and Zonge Nano-TEM systems are being used in South Africa for geology and groundwater investigations. The Interpretation of time domain electromagnetic data was performed using different programs namely ERA, TEM-RESEARCHER (TEM-RES-WIN), IRAF and Sτ Inversion. The parameters that were obtained from modelled data for three case studies comprised of resistivity, chargeability and magnetic susceptibility. Modelling of TDEM data collected in most parts of Southern Africa should take into consideration, the super-paramagnetic effect. In South Africa TDEM surveys were used to delineate mined-out and non-mined areas in the eMalahleni coal mining areas. Building materials and aggregates were mapped using the TDEM technique in the Democratic Republic of Congo (DRC). In Rwanda aeromagnetic interpretation targets were investigated using the TDEM method for potential mineralisation. The coal bearing and mined out areas were demarcated on the basis of resistivity contrasts for the South Africa case study. The thickness of building aggregates was estimated from resistivity data for the DRC site. Areas with high chargeability and low resistivity were identified as potential targets for mineral exploration for the Rwanda prospect. The TDEM method has proved to be an important non-invasive tool for carrying out groundwater, mineral and engineering investigations.
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Ztem-vtem-aerotem Helicopter Em Comparisons Over The 501 Project Cu-zn Vms At Mcfauld’s Lake, Northern Ontario, Canada
Authors M. Orta, J.M. Legault, A. Prikhodko, G. Plastow, S. Zhao, M. Moreton and C. UlanskyHelicopter AeroTEM, VTEM and ZTEM surveys were flown over the 501 zone in the McFauld’s Lake area, northern Ontario. The 501 zone is a relatively small VMS deposit that appears to respond well to all three active and passive airborne EM systems that have surveyed the property. Comparisons between these data sets and the geology are showcased using 1D-2D-3D EM inversion modeling.
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Evaluation Of Contamination At A Feedlot In San Pedro, Argentina, By Means Of Electromagnetic Methods
Contamination at a feedlot, enclosure of animals, in San Pedro, Argentina, was investigated using geophysical methods. Results of inversion of time domain electromagnetic (TEM) data resolved three layers at each point of investigation, namely, a surface layer of clayish soil, a second layer comprising partially water saturated clastic sediments and hydrogeological basement that was very conductive, possible clay bearing. Resistivity of sediments is very low, below 10.5 Ohm m. The three layers are characterized by different resistivity range of values. The first layer is very thin, and it is not clearly seen in the profiles. In the corral it is fully contaminated by manure. The resistivity of this layer decreases in corral up to less than 3 Ohm m (the thickness of soil is less than 3 m within the corral increasing to the test site). Resistivity of the second layer is about 9.5-10.5 Ohm m. The resistivity of clay considerably decreases beneath the corral. The identified geo-electrical layers may not always be identified with geological layers. The TEM results showed full agreement with previous results of frequency domain electromagnetic (FDEM) method and electrical resistivity tomography. It was demonstrated that electrical and electromagnetic methods are a very important tools for the evaluation of contamination.
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Natural Source Audio Magneto-tellurics (nsamt): Case Studies Over Various Structural And Mineralized Targets
More LessCase histories using a Natural Source Audio Magneto-Telluric (NSAMT) method of profiling are presented in this paper. These case histories indicate how conductive, resistive and intermediate resistive/conductive targets can be detected at depth using NSAMT. The method is also shown to work in highlighting structural elements such folding and horst and graben tectonics. Success also has been achieved in detecting and providing thickness information about conductors underneath surficial conductive overburden or overlying conductors. NSAMT can also be used to locate deep steeply dipping conductors such as nickel sulphides, negating the use of the more costly Squid TEM. Additionally, NSAMT cans be used as a deeper resistivity profiling technique to add to IP/Resistivity surveys, as is done by TITAN and MIMDAS. The NSAMT method is based around the use of hardware and software from Zonge International. Data collection, processing and modelling costs are similar to Induced Polarization (IP) and Transient Electro-magnetics (TEM) making the NSAMT profiling method a very attractive option in mineral exploration. Costs are kept to a minimum by forgoing the use of a remote reference and using novel filtering and processing schemes. NSAMT is intrinsically safer than IP and TEM as there is no transmitter or high voltages involved, and also because fewer people and vehicles are needed. Smaller crews are needed to those mobilized when doing IP and TEM as there are no heavy cables necessary or big electrodes that need to be prepared. Fly in surveys are possible on short notice.
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Magnetic Induced Polarization - Using New Technology For Greater Detection Capability Of Deep And Elusive Mineralization
More LessThe Magnetic Induced Polarization (MIP) method uses the measurement of magnetic fields to directly detect internal and external current flow from IP-generating targets, rather than the resultant surface currents as with conventional Electric Induced Polarization (EIP). Magnetometric Resistivity (MMR) measures the magnetic field produced by galvanic current flow to detect horizontal variations in resistivity. MIP/MMR is insensitive to horizontal layering, and is especially suitable for regions with highly conductive cover where EIP and resistivity responses are sharply attenuated. Magnetic fields easily propagate through such conditions; therefore MIP/MMR is minimally impacted by conductive cover. The other major advantage of MIP/MMR, over traditional electrical IP and resistivity, is that it completely eliminates the need for measurement electrodes. Hence, it is effective in difficult ground contact conditions such as dry sandy soils, frozen ground, and rocky scree slopes. For inversion purposes, MIP has an additional benefit that magnetic fields can be measured in all three axes simultaneously, which provides significantly more information about target position and attitude. By using SQUID technology and remote referencing, we are able to improve the data quality and extract useful three component MIP and MMR data. We present a number of field trials using both frequency and time domain methods to analyze the MIP and MMR responses from porphyry copper, and unconformity uranium ore bodies.
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A Multipurpose Squid Receiver For Electromagnetic Measurements
Authors A. Chwala, J. Kingman, R. Stolz, M. Meyer and H.-g. MeyerGeophysical exploration is getting more and more difficult – many of the easy explorable ore-bodies are exploited or under production. Finding new mines requires new technologies and tools. Transient Electromagnetics (TEM) is widely used in mineral exploration, but conventional sensors (especially induction coils) cannot fulfil the needs anymore: deep targets, very conductive targets or targets under conductive overburden are much better (or sometimes only) detectable using SQUIDs. IPHT and Supracon AG are developing low temperature SQUID magnetometer systems for ground based TEM for Anglo American (AOL). As AOL is applying these systems worldwide it is necessary to harden the systems for all conceivable application scenarios. The new multipurpose SQUID system features two orthogonal sets of SQUIDs of different sensitivities: the “low” sensitivity SQUIDs (about 20fT/√Hz) are meant for active methods like TEM that require high slew rates, while the sensitivity channels (below 2fT/√Hz) shall be used for passive methods (MT) or methods with low signals like TEM in slingram configuration. Here, we report on the latest development of these systems which are now routinely used in South Africa, Australia, Finland and Canada. This paper highlights the main features of the system, gives an estimate of the intrinsic sensor noise in shielded environment as well as in the typical exploration setup and will show some results from a first MIP test.
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Magnetic Induced Polarization Survey Using Low Temperature Squids
Authors D. Khoza, L. Polome, W. Pettit and A. RobertsonFrom 20th November – 21st December 2012, Anglo American conducted a geophysical test surveys over porphyry copper systems. The purpose of the Magnetic Induced Polarization (MIP) survey was to test the viability of the MIP method in known porphyry copper prospect. There is broad correlation between the known chargeability anomaly and the MIP results, in terms of percentage frequency effect. There is a need to further test the viability of collecting MIP data using inductive sources instead of galvanic sources. Preliminary indications are that SQUID sensors are most suitable for MIP data acquisition and can be applied and used for exploration of buried porphyry copper deposits. Success in measuring inductive MIP effects using SQUID sensors will constitute a major breakthrough in terms of finding and defining new buried porphyry copper resources.
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New Processing Methods For Data Of A Full Tensor Magnetic Gradiometer System
Authors R. Stolz, M. Schiffler, A. Chwala, M. Queitsch, M. Meyer, N. Kukowski and H.-g. MeyerAdvanced system calibration and data processing methods have to be developed for high sensitive magnetic measurements using the Full Tensor Magnetic Gradiometer (FTMG) system developed at the Institute of Photonic Technology (IPHT) Jena. The instrument consists of an array of six extremely sensitive gradiometers and a triple of orthogonal magnetometers based on low-temperature Superconducting Quantum Interference Devices (SQUIDs). First we implemented in the semi-automatic processing scheme the calculation of the magnetic field component from the IGRF and developed the extension towards the gradient tensor components. The next step is to do a fast calibration of the magnetometer signals which compensates for scaling errors, misalignment, and also for arbitrary offsets introduced by the SQUID the read-out electronics using the IGRF. In a subsequent step we have to compensate for the parasitic magnetometer areas of the gradiometers called balancing. They lead to a strong influence of motion noise in the tensor components. The calculated tensor components have to be transformed from the local system frame into an Earth-Centered, Earth-Fixed coordinate system. Additional processing steps have are introduced which allow to convert between the magnetic signals. Hilbert and Hilbert-like transforms are used to transform between gradient tensor components, magnetic field vector components and total magnetic intensity (TMI). The processes are performed either in wavenumber or Fourier domain or in space domain by integral presentation. First results are shown and a comparison of the two transformation schemes discussed. The transformations allow calculating low noise TMI and the magnetic field components from the gradient tensor components. Besides the improvement of magnetic resolution the mentioned transforms are used for calibration of the system components to and for comparison with data from other surveys. Example data are shown.
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