| Abstract: | The present paper shows the practical use of a combined electromagnetic and magnetic helicopter transported system in the search for steeply dipping high-grade magnetic taconite bodies (magnetic ribbons). The principles of operation of the heliported system and the essential parts of the instrumentation are described. The quantitative interpretation of the data allows the geophysicist to calculate the tonnage of magnetite within the iron ores and to obtain an approximate idea of their grade. According to the tonnage and grade calculations obtained from the surveys, three regions in the west-central sector of the Labrador trough (Wishart Creek, Knob Lake Ridge, and Swampy Bay areas) appear to be the most interesting locations for the site of a magnetic taconite deposit (the Howells River area, which has been evaluated previously, is excluded from the discussion). The tonnages calculated by this geophysical method are not to be compared with probable or possible mineable ore reserves, but are only rough estimates in terms of mining engineering standard. The physical parameters determined with such a system are also used as a tool for indirect geological mapping of the areas flown when interpreted carefully. Practical examples related to results obtained on the magnetic iron formations of the Schefferville mining district are presented. |
