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TitleA magnetotelluric survey and preliminary geophysical inversion and visualization of the NICO IOCG deposit, Northwest Territories
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorCraven, J A; Roberts, B J; Hayward, NORCID logo; Stefanescu, M; Corriveau, LORCID logo
SourceGeological Survey of Canada, Open File 7465, 2013, 26 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaLou Lake
Lat/Long WENS-116.7667 -116.7167 63.5583 63.5250
Subjectseconomic geology; geophysics; mineral deposits; mineral occurrences; mineral potential; mineralization; iron; iron oxides; copper; gold; magnetotelluric surveys; magnetotelluric data; magnetotelluric interpretations; geophysical interpretations; magnetic field; magnetic interpretations; Great Bear magmatic zone; NICO deposit; Lou Lake deposit
Illustrationslocation maps; tables; flow charts; profiles; plots
ProgramGEM: Geo-mapping for Energy and Minerals Iron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT)
Released2013 10 02
AbstractTo improve our understanding of the NICO deposit and Iron Oxide-Copper-Gold (IOCG) deposits in general we conducted both a regional-scale (10's km) and mine-scale (a few km) magnetotelluric (MT) study at the NICO deposit in the summer of 2010. An MT study involves the measurement, along a profile or on a grid, of variations in the natural magnetic field and correlated changes in voltages in the ground due to so-called "telluric" currents. The data collected enable a view of the electrical resistivity structure from the surface to the depth of the mantle. The survey itself is relatively easy to conduct, requiring a crew of only 2 or 3 persons due to the simplicity of installing the receiver equipment and the fact that no artificial or man-made energy source needs to be installed. The purpose of the MT survey is twofold. The first is to test the IOCG exploration model proposed by Corriveau et al (2010). The Corriveau et al alteration vector-to-mineralisation model enables effective exploration in a geologically complex region by providing a framework to understand the spatial and temporal relationships amongst the alteration products associated with the mineralization event (Corriveau et al., 2010). The model can be treated as a scientific hypothesis and tested. For example, Potter et al. (2013) have successfully tested the validity of the model to vector towards ore at the Fab lake showing. A fundamental result of Potter et al. (2012) is their demonstration that the model provides sufficient detail and tools that can be used by others to explore for ore. In this paper we test the spatial associations predicted by the model using geophysical methods due to the unique geophysical signatures alteration products in the model suggests. For example, sulphides should be conductive, but not magnetic. Magnetite should be magnetic, but not conductive. The second purpose of the MT work is more regional in nature. Regional MT studies (Heinson et al, 2006) and isotope studies at the Olympic Dam deposit (Johnson and McCulloch, 1995) have suggested a mantle source for mineralizing fluids. Seismic surveys (Drummond et al., 2006) support this notion by suggesting that deep faults or conduits beneath Olympic Dam permit mantle fluids access to the uppermost portions of the lithosphere. In addition, at Olympic Dam, the lithospheric architecture includes tapering out of an Archean lithospheric root, the extremity of which is directly under Olympic Dam (cf. Drummond et al., 2006; Cook et al., 1998; Snyder, 2008; Spratt et al., 2009). Whether similar roots and deep-seated conduits exist beneath the NICO deposit, and if there is evidence for large-scale fluid movement along them are key questions a regional MT survey can address.
Summary(Plain Language Summary, not published)
Results of a successful geophysical test of a hypothesis based on a exploration vector model for iron oxide deposits.

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