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TitleGreat Bear magmatic zone rock property database: Linking geology and geophysics within IOCG systems
AuthorEnkin, R J; Hayward, N; Lee, M D; Corriveau, L; Montreuil, J -F; Acosta, P
SourceGAC-MAC joint annual meeting, St. John's 2012, abstracts/AGC-AMC congrès annuel conjoint, St. John's 2012, résumés; by GAC-MAC organizing Committee; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 35, 2012 p. 41
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20120260
MeetingGeological Association of Canada, Mineralogical Association of Canada, Joint Annual Meeting; St. John's; CA; May 27-29, 2012
ProvinceNorthwest Territories
NTS85N; 86C; 86D; 86E; 86F; 86K; 86L
AreaGreat Bear Lake; Lac la Martre; Hottah Lake
Lat/Long WENS-119.0000 -116.0000 67.0000 63.0000
Subjectseconomic geology; geophysics; sediment properties; magnetic properties; densities; magnetic susceptibility; electrical properties; iron oxides; copper; gold; mineralization; Great Bear magmatic zone
ProgramGEM: Geo-mapping for Energy and Minerals, Iron-oxide Copper-gold (IOCG) / Multiple Metals - Great Bear Lake (NWT)
AbstractThe two primary poles of mineral exploration are geological mapping and geophysical surveying. In order to link these two great exploration investments, labs such as the Geological Survey of Canada Paleomagnetism and Petrology Laboratory and the McMaster Applied Geophysics and Geological Imaging Centre have undertaken extensive measurements of physical properties to strategically chosen rock collections: density (bulk and skeletal), magnetic susceptibility and remanence, and electrical impedance spectra for resistivity and chargeability. The Great Bear magmatic zone (GBmz) Rock Property Database provides a useful example of this approach. The current exploration model for the GBmz is iron oxide copper gold (IOCG) mineralization (and affiliated deposits) featuring a six-zone alteration classification of mineral assemblages. From the high temperature-deeper-earlier-core to the cooler-shallower-later-distal alteration indices, the zones are identified as 1:Na(Ca); 2:Ca-Fe(Na); 3:High Temp K-Fe; 4:Skarn (if carbonates are present); 5:Low Temp K-Fe; 6:Low Temp silicification. Analysis of the distributions of physical properties as a function of the lithologies and alteration zones of the range of rocks collected in the GBmz reveals useful patterns to provide new exploration vectors. The geometric mean magnetic susceptibilities [E-3 SI units ± standard error] are: 1: 3.2±40%; 2: 17.7±16%; 3: 12.6±18%; 4: 1.5±83%; 5: 3.9±3.3%; 6: 2.1±15%. Note that the magnetite produced in the higher temperature zones 2 and 3 lead to magnetic susceptibilities 6 to 8 times higher on average than that of zone 6 samples. The iron oxide mineralization leads to high magnetic remanence values which must be taken into account in magnetic survey interpretation. One quarter of rocks identified to be in zone 2 or 3 alteration have Koenigsberger ratios above 1, compared to 10 to 15% of the samples in the other zones. The correlation of high magnetic and density values leads to hybrid density-magnetic potential field models. Current work on resistivity-chargeability properties is motivated by strong unexpected anomalies observed in electromagnetic surveys in the Port Radium region. As of January 2012, rock properties from over 700 samples from the GBmz have been measured and compiled, and several hundred are currently under examination. Through the petrophysical link coupled with clear understanding of the relevant mineralization model, new effective strategies are being developed to target and locate new mineral deposits.