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TitleMetasomatic alteration control of petrophysical properties in the Great Bear magmatic zone (Northwest Territories, Canada).
AuthorEnkin, R JORCID logo; Corriveau, LORCID logo; Hayward, NORCID logo
SourceEconomic geology and the bulletin of the Society of Economic Geologists vol. 111, no. 8, 2016 p. 2073-2085,
Alt SeriesEarth Sciences Sector, Contribution Series 20150284
PublisherSociety of Economic Geologists
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS86C; 86D; 86E; 86F; 86L; 86K
AreaGreat Bear magmatic zone
Lat/Long WENS-119.0000 -116.0000 67.0000 63.0000
Subjectsgeneral geology; mineralogy; economic geology; iron oxides; alteration; ore mineral genesis; mineral deposits; metamorphism, prograde; magnetic properties
Illustrationslocation maps; geological sketch maps; plots
ProgramTargeted Geoscience Initiative (TGI-4) Methodological Development
Released2016 11 16
AbstractThe Great Bear magmatic zone in the Northwest Territories of Canada contains large iron-oxide alkali alteration systems noted for having high potential for iron oxide-apatite, iron oxide-copper-gold, and affiliated ore deposits. Physical properties (density, magnetic, and electrical) were measured on 824 rocks samples selected to represent the range of metasomatic alteration types in the region. Mineralogical and geochemical classification of the prograde iron oxide and alkali alteration facies reveals large variations in physical properties through the evolution of the metasomatic systems. In particular, deep and early sodic alteration produced rocks having low densities and low magnetic susceptibilities. During calcium and iron precipitation, rocks gain extremely high density and susceptibility, due to crystallization of amphibole and especially magnetite. Subsequent hightemperature, potassic- and iron-altered rocks are marked by cocrystallization of magnetite with K-feldspar or biotite, and as the transition from magnetite to hematite takes place, K-feldspar crystallizes instead of iron oxides leading ultimately to potassic felsites having low densities and susceptibilities. Subsequent cooler, shallower, and more oxidized potassic-iron alteration produced high densities but moderate susceptibilities owing to crystallization of hematite. Understanding these major variations in physical properties of rocks enables detailed geophysical mapping of alteration zones, which builds and improves the regional context for integrated mineral exploration vectors to potential ore deposits.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. The Great Bear Magmatic Zone in the Northwest Territories of Canada is a region which hosts several mines, but is under-explored for minerals. Recent work has developed a new model for mineralization in the region, and demonstrates that regional mapping of zones of particular minerals help focus mineral exploration. In this study, the physical properties of 824 rock samples collected from across the zone have been measured. They reveal major variations in density, magnetic and electric properties which can be exploited to interpret regional geophysical studies in terms of these zones, thus assisting mineral exploration.

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