| Title | Magmatic architecture of the Esker intrusive complex in the Ring of Fire Intrusive Suite, McFaulds Lake greenstone belt, Superior Province, Ontario: Implications for the genesis of Cr and Ni-Cu-(PGE)
mineralization in an inflationary dyke-chonolith-sill complex |
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| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Houlé, M G; Lesher, C M; Metsaranta, R T; Sappin, A -A ; Carson, H J E; Schetselaar, E M; McNicoll, V; Laudadio, A |
| Source | Targeted Geoscience Initiative 5: Advances in the understanding of Canadian Ni-Cu-PGE and Cr ore systems - Examples from the Midcontinent Rift, the Circum-Superior Belt, the Archean Superior Province, and
Cordilleran Alaskan-type intrusions; by Bleeker, W (ed.);
Houlé, M G (ed.); Geological Survey of Canada, Open File 8722, 2020 p. 141-163, https://doi.org/10.4095/326892  Open Access |
| Image |  |
| Year | 2020 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| Related | This publication is contained in Targeted Geoscience
Initiative 5: Advances in the understanding of Canadian Ni-Cu-PGE and Cr ore systems - Examples from the Midcontinent Rift, the Circum-Superior Belt, the Archean Superior Province, and Cordilleran Alaskan-type intrusions |
| File format | pdf |
| Province | Ontario |
| NTS | 43C/05; 43C/12; 43C/13; 43D/07; 43D/08; 43D/09; 43D/10; 43D/15; 43D/16; 43E/01; 43E/02; 43F/04 |
| Lat/Long WENS | -87.0000 -85.5319 53.2492 52.3411 |
| Subjects | economic geology; Science and Technology; Nature and Environment; mineral deposits; nickel; copper; chromium; iron; titanium; vanadium; phosphorus; magmatic deposits; sulphide deposits; stratiform
deposits; ore mineral genesis; mineralization; ore controls; modelling; bedrock geology; lithology; igneous rocks; mafic rocks; ultramafic rocks; tholeiites; volcanic rocks; intrusive rocks; komatiites; sedimentary rocks; iron formations; tectonic
setting; tectonic history; magmatism; intrusions; dykes; sills; chonoliths; partial melting; sulphur; oxides; Archean; Superior Province; Esker Intrusive Complex; Ring of Fire Intrusive Suite; McFaulds Lake Greenstone Belt; Koper Lake Subsuite; Ekwan
River Subsuite; platinum group elements; Precambrian; Proterozoic |
| Illustrations | location maps; plots; tables; magnetic maps; stratigraphic columns; photographs |
| Program | Targeted Geoscience Initiative (TGI-5) Nickel-copper-PGE-chromium systems |
| Released | 2020 09 08; 2023 03 17 |
| Abstract | One of the dominant geological features in the arcuate, >175 km long, Mesoarchean to Neoarchean McFaulds Lake greenstone belt in northern Ontario is the semi-continuous trend of mafic to ultramafic
intrusions belonging to the Ring of Fire intrusive suite, which hosts world-class Cr mineralization, major Ni-Cu-(PGE) mineralization, and potentially significant Fe-Ti-V-(P) mineralization. It appears to have been emplaced over a relatively short
time interval of approximately 4 to 4.5 million years. The intrusive suite contains two subsuites: the less widely distributed Koper Lake subsuite, which consists of komatiitic ultramafic- dominated intrusions and typically hosts Cr and Ni-Cu-(PGE)
mineralization (e.g. Esker intrusive complex), and the more widely distributed Ekwan River subsuite, which consists of tholeiitic high-Fe-Ti mafic-dominated intrusions and typically hosts Fe-Ti-V-(P) mineralization (e.g. Thunderbird intrusion). The
Esker intrusive complex contains the majority of the known Cr and Ni-Cu-(PGE) mineralization in the Ring of Fire intrusive suite. It is a semi-continuous, structurally rotated, subvertical ultramafic-mafic sill-like body that is composed of multiple
intrusions with morphologies that vary from bladed dyke morphologies (e.g. Eagle's Nest), transitional dyke/chonolith morphologies (e.g. Double Eagle, AT-3, and AT- 8), to some with transitional chonolith/sill morphologies (e.g. Black Thor). It
extends over more than 16 km, youngs to the south-southeast, and is bordered to the north-northwest by several keel-like ultramafic intrusive bodies (e.g. AT-12, C-6, AT-5, AT-1). Clear connections between AT-12 and AT-1 and the overlying Black Thor
and Double Eagle intrusions, respectively, and the continuous spectrum of intrusion morphologies suggest that the keels were originally subhorizontal blade-shaped dykes (e.g. Eagle's Nest), the upper parts of which expanded laterally to form
transitional dykes/chonoliths (e.g. Double Eagle intrusion) and chonoliths/sills (e.g. Black Thor intrusion), which inflated laterally and coalesced over time to form the silllike Esker intrusive complex. Most of the Ni-Cu-(PGE) mineralization in the
Esker intrusive complex appears to have formed by incorporation of sulphur from footwall oxide-silicate-sulphide iron formations, a process that is similar to most other komatiite-associated Ni-Cu-(PGE) deposits worldwide. A fundamental issue in the
genesis of all stratiform chromite deposits is how to form thick layers of massive to semi-massive chromite, an issue exacerbated by the vast amounts of chromite in the Esker intrusive complex. A genetic model that resolves the mass balance problem
involves partial melting of Fe+/-Ti oxide-rich rocks (oxide-facies iron formation or ferrogabbro) and conversion of fine-grained oxide xenocrysts to chromite by reaction with Cr-rich komatiitic magma in a dynamic magma conduit. This model has been
recently challenged based on the capacity of komatiitic magma to dissolve large amounts of magnetite, which would prevent upgrading. However, alternative models cannot explain the presence of composite chromite-silicate-sulphide grains with textures
like those in footwall magnetite-silicate-sulphide facies iron formations. More research is required to reconcile the discrepancies. Regardless of their origin, the wide diversity of mineral deposit types in the McFaulds Lake greenstone belt,
including world-class Cr, significant Ni-Cu-(PGE), and potential Fe-Ti-V-(P) mineralization related to mafic and ultramafic rocks, make the Ring of Fire region an excellent exploration target to increase the world's supply of critical minerals.
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| Summary | (Plain Language Summary, not published)
Key objectives of Phase 5 (2015-2020) of the Targeted Geoscientific Initiative (TGI) program of Natural Resources Canada and the Geological Survey of
Canada were to generate new knowledge, methodologies, and models to enhance the exploration industry's ability to detect buried ore deposits and extensions of existing ore systems, and to provide models for targeting new deposit areas. This synthesis
volume contains nine individual papers that discuss deposit scale to magmatic system fundamentals from various Canadian examples pertaining to the TGI-5 Ni-Cu-PGE-Cr project. |
| GEOSCAN ID | 326892 |
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