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TitleOverview of geophysical signatures associated with Canadian ore deposits
AuthorFord, K; Keating, P; Thomas, M D
SourceMineral deposits of Canada: a synthesis of major deposit-types, district metallogeny, the evolution of geological provinces, and exploration methods; by Goodfellow, W D (ed.); Geological Association of Canada, Mineral Deposits Division, Special Publication no. 5, 2007 p. 939-970
Alt SeriesEarth Sciences Sector, Contribution Series 20070219
PublisherGeological Association of Canada, Mineral Deposits Division (St. John's, NL, Canada)
Mediapaper; DVD; digital
RelatedThis publication is contained in Mineral deposits of Canada: a synthesis of major deposit-types, district metallogeny, the evolution of geological provinces, and exploration methods
File formatpdf
ProvinceBritish Columbia; Alberta; Saskatchewan; Manitoba; Ontario; Quebec; New Brunswick; Nova Scotia; Prince Edward Island; Newfoundland and Labrador; Northwest Territories; Yukon; Nunavut; Canada
NTS1; 2; 3; 10; 11; 12; 13; 14; 15; 16; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 52; 53; 54; 55; 56; 57; 58; 59; 62; 63; 64; 65; 66; 67; 68; 69; 72; 73; 74; 75; 76; 77; 78; 79; 82; 83; 84; 85; 86; 87; 88; 89; 92; 93; 94; 95; 96; 97; 98; 99; 102; 103; 104; 105; 106; 107; 114O; 114P; 115; 116; 117; 120; 340; 560
Lat/Long WENS-141.0000 -50.0000 90.0000 41.7500
Subjectseconomic geology; geophysics; mineral deposits; mineral occurrences; diamond; gold; nickel; copper; platinum; volcanogenic deposits; sulphides; base metals; Mississippi Valley deposits; porphyry deposits; porphyry copper; uranium deposits; host rocks; densities; magnetic susceptibility; conductivity; radioactivity; magnetic field; electromagnetic fields; geophysical surveys; resistivity surveys; i p surveys, airborne; e m surveys; gamma-ray surveys; gravity surveys; platinum group elements
Illustrationstables; graphs; geophysical maps
ProgramConsolidating Canada's Geoscience Knowledge
ProgramTargeted Geoscience Initiative (TGI-3), 2005-2010
Released2007 01 01
AbstractCanadian ore deposits have typical geophysical signatures, either at regional or detailed scales. The particular geophysical response of an ore deposit depends on the contrast between its physical properties and those of its host rock. The most important physical properties are density, magnetic susceptibility, electrical conductivity and chargeability, and radioactivity. Density and susceptibility contrasts have a local influence on the measurement of the Earth's gravity and magnetic fields. Electrical properties contrasts can be detected using natural fields, as in magnetotelluric methods, or by artificial electromagnetic fields. Radioactivity is a natural phenomenon and is related to the chemico-physical nature of the rocks and minerals. Some types of deposits do not have any direct geophysical response; the best example is gold mineralization. In that case, geophysics is used in an indirect fashion to map favourable structures that have a good geophysical response. Other types of deposits are directly detectable by geophysical techniques. For example, massive sulphide deposits generally produce significant electromagnetic, gravimetric, and magnetic responses. Here, we first present the principal geophysical techniques currently in use in Canada. Only a brief and simplified description of each method is given since extensive descriptions are available in the geophysical literature. Some typical survey specifications are provided. This is followed by a description of the geophysical responses of the major mineral deposit types found in Canada. In each case, we discuss the physical properties that can give rise to a geophysical response and we present typical examples. Applicability and effectiveness of the techniques are also discussed. Geophysics was instrumental in the discovery of many Canadian ore deposits. Although there are likely many shallow
ore deposits still to be discovered, the next major discoveries are expected to be at greater depth. Hopefully, some current geophysical techniques can detect deposits at depths in excess of one kilometre.

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