scholarly journals The inversion of time‐domain airborne electromagnetic data using the plate model

Geophysics ◽  
1990 ◽  
Vol 55 (6) ◽  
pp. 705-711 ◽  
Author(s):  
P. B. Keating ◽  
D. J. Crossley
Keyword(s):  
Time Domain ◽  
Digital Processing ◽  
Geophysical Survey ◽  
Inverse Theory ◽  
Great Success ◽  
Plate Model ◽  
Airborne Electromagnetic ◽  
Airborne Electromagnetic Data ◽  
Airborne Em ◽  
Mining Exploration

Airborne electromagnetic (EM) methods were developed in the early 1950s, mostly by Canadian mining exploration companies as a means of economically carrying out prospecting for sulfide deposits associated with volcanics in resistive shield areas. Present interpretation techniques are based on the use of nomograms but the approach is easily amenable to digital processing. For highly accurate interpretation, however, it is necessary to develop quantitative interpretation techniques that can make full use of all the data available. Inverse theory has been used for interpretation with great success in most geophysical disciplines; however, in airborne EM surveying, inversion has only been used for the interpretation of airborne EM data using half‐space and one‐layer models. By introducing some approximations to the rectangular thin‐plate model, it is now possible to apply inverse theory to the interpretation of time‐domain EM data. This approach provides estimates of the parameter errors, the correlation matrix, and a means of assessing the validity of the model. Synthetic profile data are used to demonstrate the validity of the method. The results of the inversion of real anomalies are compared with ground geophysical survey interpretation and drillhole data. The inversion results agree with the known geology of the area and the ground geophysical survey interpretation.

3D parametric hybrid inversion of time-domain airborne electromagnetic data

Geophysics ◽  
2015 ◽  
Vol 80 (6) ◽  
pp. K25-K36 ◽  
Author(s):  
Michael S. McMillan ◽  
Christoph Schwarzbach ◽  
Eldad Haber ◽  
Douglas W. Oldenburg
Keyword(s):  
Time Domain ◽  
Electromagnetic Data ◽  
Airborne Electromagnetic ◽  
Airborne Electromagnetic Data

Resistive limit modeling of airborne electromagnetic data

Geophysics ◽  
2002 ◽  
Vol 67 (2) ◽  
pp. 492-500 ◽  
Author(s):  
James E. Reid ◽  
James C. Macnae
Keyword(s):  
Current Flow ◽  
Integral Equation Method ◽  
Near Surface ◽  
Electromagnetic Data ◽  
Airborne Electromagnetic ◽  
Source Current ◽  
Numerical Model Experiments ◽  
Airborne Electromagnetic Data ◽  
Airborne Em ◽  
Direct Induction

When a confined conductive target embedded in a conductive host is energized by an electromagnetic (EM) source, current flow in the target comes from both direct induction of vortex currents and current channeling. At the resistive limit, a modified magnetometric resistivity integral equation method can be used to rapidly model the current channeling component of the response of a thin-plate target energized by an airborne EM transmitter. For towed-bird transmitter–receiver geometries, the airborne EM anomalies of near-surface, weakly conductive features of large strike extent may be almost entirely attributable to current channeling. However, many targets in contact with a conductive host respond both inductively and galvanically to an airborne EM system. In such cases, the total resistive-limit response of the target is complicated and is not the superposition of the purely inductive and purely galvanic resistive-limit profiles. Numerical model experiments demonstrate that while current channeling increases the width of the resistive-limit airborne EM anomaly of a wide horizontal plate target, it does not necessarily increase the peak anomaly amplitude.

Discovery of polymetallic porphyry at the Silver Queen, British Columbia using airborne EM and TITAN-24 DCIP and MT surveys

2013 ◽  
Vol 1 (1) ◽  
pp. T101-T112 ◽  
Author(s):  
Nasreddine Bournas ◽  
Ellen Clements ◽  
Rob Hearst
Keyword(s):  
British Columbia ◽  
3D Inversion ◽  
Ground Survey ◽  
Airborne Electromagnetic ◽  
Polymetallic Mineralization ◽  
Two Phases ◽  
Airborne Em ◽  
Mining Exploration ◽  
Base Metal Mineralization

Airborne electromagnetic, ground direct current and induced polarization (DCIP), and magnetotelluric (MT) surveys have extensively been used in mining exploration and more particularly for the exploration of base metal mineralization. The continuous development of geophysical techniques with advances in the instrumentation and signal processing and the recent development of robust 3D inversion algorithms make possible the detection and accurate delineation of deep-seated mineralization of economic interest. Recently, a deep-penetrating TITAN-24 DCIP and MT survey was conducted over the Silver Queen project area, located in British Columbia, Canada in two phases (2011 and 2012, respectively) by Quantec Geoscience Ltd. on behalf of New Nadina Explorations Ltd. for the exploration of porphyry-style polymetallic mineralization. The ground survey was carried out as a follow-up to the helicopter-borne z-axis tipper electromagnetic survey flown during the spring of 2011 by Geotech Ltd. with the aim to delineate favorable areas for the exploration of porphyry-style deposits. A deep-seated significant zone of anomalously high chargeability occurring in coincidence with a conductive zone was detected by the ground DCIP and MT survey. Drill-testing based on the 3D inversion results of the data led to the discovery of a new significant deep-seated porphyry-style mineralization. The discovery drillhole contained visible disseminated to semimassive sulphide mineralization, gold and molybdenite over 350 m for a total drillhole depth of approximately 800 m and occurs in association with a significant mineralized stockwork zone open at depth.

Automated interpretation of airborne electromagnetic data

Geophysics ◽  
1984 ◽  
Vol 49 (8) ◽  
pp. 1301-1312 ◽  
Author(s):  
G. T. DeMoully ◽  
A. Becker
Keyword(s):  
Data Interpretation ◽  
Earth Model ◽  
Computer Algorithms ◽  
Conductive Layer ◽  
Electromagnetic Data ◽  
Airborne Electromagnetic ◽  
Survey Results ◽  
Airborne Electromagnetic Data ◽  
Airborne Em ◽  
Interpretation Method

Recent improvements in equipment quality make it possible to increase the usefulness of airborne electromagnetic (EM) systems in areas of moderate electrical conductivity for the purpose of constructing simple electrical property maps which can be related to surficial geology. This application of airborne electromagnetics may be demonstrated and evaluated using Barringer/Questor Mark VI Input® survey results in places where independent verifications of the airborne data interpretation are available. For this purpose we have developed a set of computer algorithms which read digitally recorded Input data and interpret them automatically in terms of a simple electrical section that is defined by a single conductive layer whose thickness, conductivity, and subsurface depth are determined from the data. Because this technique is formally based on a one‐dimensional, three‐layer, three‐parameter, horizontally stratified earth model, it is only applicable in regions where the surficial formations are mildly dipping and the conductive layer is covered by, and rests on, highly resistive materials. The interpretation method is illustrated by three field examples. At the first field survey site, in Alberta, Canada, airborne EM survey data are used to map the depth of the interface between coarse and clayey sands. Data from a second survey site, this time in the Western USA, are interpreted to yield the section of a subsurface valley filled with conductive clay. The final example, taken from British Columbia, Canada, involves the mapping of all the three parameters for a weathered volcanic unit.

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