MultiLoop III in Mining Exploration
MultiLoop III is used for modelling fixed and moving source systems for airborne, ground and borehole interpretation. Multiloop III has flexible data importing capabilities which allows plotted field data to be overlain onto modelled data. To further assist interpretation, data can be plotted at a number of scales, with the scales switched easily. This means, for example, that in a time domain system, it is possible to view high amplitude early-time data (for modelling near surface structure) and then switch to focussing in on low-amplitude late-time data (to model deep conductors). The reason this is important is that changes in the model to fit the early-time data often cause significant changes in the modelled late time response, so changing plotting scales to view each separately is important for accurate interpretation.
MultiLoop III has changed the way data can be modelled. In simpler plate based programs, it is often necessary to fudge the effect of regional conductivity with a plate that may have limited geological meaning. A key difference with MultiLoop III is that the conductors used to fit the data have greater geological meaning. The result is that a single model can often fit data on multiple lines, across the full spectrum of channels, and over several kilometers. The impact of this development on geological interpretation is important. For more detail, please refer to the papers section of this website.
A great deal of uranium exploration is carried out in the Athabaska Basin, located in Saskatchewan, Canada. Here deep conductors that may be associated with uranium deposits need to be accurately mapped. By modelling these conductors with MultiLoop III, it has been demonstrated that the inferred locations of the conductors can depend on the coupling with the overlying sandstones. Many modelling algorithms cannot correctly account for this effect, with the result being that locations of basement conductors can be misinterpreted.
Additionally, while modelling the decays measured from ground UTEM data over a conductor in the Athabaska basin, the location of a conductor well removed from the traverse line was predicted. Subsequent inspection has shown this conductor correlates with mapped airborne conductors.
In another important development, the ability to fit the full suite of EM-37 channels (1-20) has shown that EM-37 data can be sensitive to alternation in the Athabaska sandstones that overlies a basement conductor. The presence of alteration is often an indicator of mineralization. In typical modelling, the full range of data are not fit, with the emphasis being placed on the location of the basement conductors. Multiloop III has demonstrated that electromagnetic data can contain valuable information that currently lies uninterpreted.
MultiLoop III is used in nickel exploration. It was used, for example, to model data at Lindsley for Falconbridge Ltd (now XStrata) and is used to interpret data in the Sudbury Nickel Belt. Because MultiLoop III can model complicated, non-planar shapes, it is particularly useful where the geological environment is complex.
One of the difficulties modern explorationist faces is that the many areas now being explored are not amenable to representation by the simple tabular conductor in a resistive medium, Rather, the geological settings now being explored are considerably more complicated. MultiLoop III has assisted in revealing the physics of how layers of folded material affect the response of an embedded mineralized conductor in a base metal prospect.
Much of our geophysical intuition results from the pioneering scale-model work in the 1950-s and 1960-s, in which the electromagnetic response of simple geometrical shapes was studied. Subsequent to this, numerical models of the plate, the sphere, the layered-earth, and the prism were developed in the 1970-s and 1980-s. Modern interpretation theory is based on this work, and where this work is applicable to geological settings, interpretation theory works well. The demand for minerals has forced exploration into more complicated geological environments where the assumptions of the uniform background upon which these studies are based no longer apply. MultiLoop III is being used to expand the range of applicability of modern interpretation theory. So, if you are exploring in a complex geological environment in which conductive, and perhaps folded, formations are present, MultiLoop III could be of great assistance in helping you to understand your data.
MultiLoop III has found application in the numerical testing of new EM systems. MultiLoop's versatility in representing current waveforms, receiver gates and antenna geometries provides the flexibility that EM system developers require to vet their concepts.