| Title | Alteration facies linkages among iron oxide copper-gold, iron oxide-apatite, and affiliated deposits in the Great Bear Magmatic Zone, Northwest Territories, Canada |
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| Author | Corriveau, L ;
Montreuil, J F; Potter, E G |
| Source | Economic geology and the bulletin of the Society of Economic Geologists vol. 111, no. 8, 2016 p. 2045-2072, https://doi.org/10.2113/econgeo.111.8.2045 |
| Image |  |
| Year | 2016 |
| Alt Series | Earth Sciences Sector, Contribution Series 20140270 |
| Publisher | Society of Economic Geologists |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Northwest Territories |
| NTS | 86C; 86D; 86L; 86K; 86E; 86F |
| Area | Great Bear Lake |
| Lat/Long WENS | -120.0000 -116.0000 67.0000 63.0000 |
| Subjects | structural geology; tectonics; iron; gold; copper; base metals; metamorphism, prograde; albitites; skarns; magmatism |
| Illustrations | location maps; tables; bar graphs; geological sketch maps; photographs; photomicrographs; diagrams |
| Program | Targeted Geoscience Initiative (TGI-4) Uranium Ore Systems |
| Released | 2016 11 16 |
| Abstract | High-temperature metasomatism driven by ascent of voluminous, saline fluid columns in the upper crust plays a major role in the genesis of iron oxide-alkali alteration ore systems but fundamental
questions remain on genetic linkages among iron oxide copper-gold (IOCG), iron oxide-apatite (IOA), albitite-hosted uranium, and skarn deposits that they produce. Excellent surface exposures of such systems in the Great Bear magmatic zone of
northernwestern Canada record the depth to paleosurface, prograde evolution of iron oxide-alkali alteration facies, and mineralization. Across the belt, albitite corridors that are tens of kilometers in length record the earliest reactions between
highly saline fluids and host rocks along fault zones and subvolcanic intrusions. Pervasive albitization partitioned metals from the host rocks into the ascending fluid column, leaving behind structurally weakened corridors of porous albitite. These
corridors were cut, replaced, and overprinted by amphibole- and magnetite-bearing, calcic-iron alteration assemblages. In extreme cases, the discharge of calcium, iron, and specialized metals formed iron oxide-apatite deposits (±vanadium ± rare earth
elements) while recharging the outgoing fluids in sodium, potassium, and base and precious metals. As temperatures declined and fluid chemistry evolved through fluid-rock reactions, the formation of potassic-iron alteration assemblages, breccias, and
sulfides resulted in magnetite- and hematite-group IOCG mineralization. Within carbonate units, skarns formed prior to, are replaced by, and evolved to calcic-iron alteration facies. Skarns can locally host base metal mineralization. Tectonically
uplifted albitite breccias replaced by potassic-iron alteration assemblages became a preferential host for uranium mineralization. The results of this study also illustrate that permutations and cyclical build-up of alteration products can arise from
a combination of faulting, differential uplift, and renewed magmatism. Framed within an alteration-facies deposit model, alteration zones and mineral occurrences play a pivotal role in predicting the mineral potential of iron oxide and alkali-altered
systems at district to deposit scales. |
| Summary | (Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) 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. Iron oxides and alkali-altered mineral systems stand out worldwide as hosting the most diverse suites of potential
economic metals (precious, base and specialised metals, including those needed for green energy, high technology and nuclear energy). These systems include among others iron oxide copper-gold (IOCG) deposits. This paper synthesises the extreme
mineralogical and chemical transformations undergone by precursor rocks at district to deposit scale due to their interaction with mineralizing fluids. To each set of attributes corresponds a distinct alteration facies and associated deposit type.
The proposed model change exploration paradigms for IOCG and affiliated deposits. |
| GEOSCAN ID | 295474 |
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