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TitleVariations in the textural facies of sulphide minerals in the Eagle's Nest Ni-Cu-(PGE) deposit, McFaulds Lake greenstone belt, Superior Province, Ontario: insights from microbeam scanning energy-dispersive X-ray fluorescence spectrometry
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorZuccarelli, N; Lesher, C M; Houlé, M G; Barnes, S J
SourceTargeted 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, WORCID logo (ed.); Houlé, M G (ed.); Geological Survey of Canada, Open File 8722, 2020 p. 165-179, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis 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 formatpdf
NTS43C/11; 43C/12; 43C/13; 43C/14; 43D/09; 43D/10; 43D/15; 43D/16; 43E/01; 43E/02; 43E/07; 43E/08; 43F/03; 43F/04; 43F/05; 43F/06
Lat/Long WENS -87.0000 -85.0000 53.5000 52.5000
Subjectseconomic geology; mineralogy; geochemistry; Science and Technology; Nature and Environment; mineral deposits; nickel; copper; magmatic deposits; sulphide deposits; ore mineral genesis; mineralization; ore controls; greenstone belts; bedrock geology; lithology; mafic rocks; ultramafic rocks; igneous rocks; volcanic rocks; komatiites; intrusive rocks; pyroxenites; websterites; gabbros; metamorphic rocks; metavolcanic rocks; tectonic setting; tectonic history; rifts; magmatism; intrusions; dykes; emplacement; shear zones; textural analyses; x-ray fluorescence analyses; mineral assemblages; inclusions; fractional crystallization; fluid dynamics; fluid migration; mineral occurrences; host rocks; facies; Archean; Eagle's Nest Deposit; Esker Intrusive Complex; Ring of Fire Intrusive Suite; McFaulds Lake Greenstone Belt; Superior Province; Black Thor Intrusion; Double Eagle Intrusion; Eagle's Nest Dyke; Koper Lake Subsuite; McFaulds Shear Zone; Frank Shear Zone; Black Thor-Black Creek-Big Daddy Shear Zone; platinum group elements; Precambrian; Proterozoic
Illustrationslocation maps; geoscientific sketch maps; schematic sections; tables; photomicrographs
ProgramTargeted Geoscience Initiative (TGI-5) Nickel-copper-PGE-chromium systems
Released2020 09 08; 2023 03 17
AbstractThe Eagle's Nest Ni-Cu-(PGE) deposit occurs within the 2.73 Ga Esker intrusive complex of the Ring of Fire intrusive suite, in the McFaulds Lake greenstone belt of northern Ontario. Sulphide mineralization occurs along the northwestern margin of a subvertical ~500 m wide (north-south) x 1500 m deep komatiitic ultramafic body composed of harzburgite+/-lherzolite+/-wehrlite that is interpreted to represent a structurally rotated, originally subhorizontal blade-shaped dyke. Disseminated (<15 wt% sulphide), net (15-35 wt% sulphide), and lesser semi-massive (50-80 wt% sulphide) and massive (>80 wt% sulphide) -textured sulphides have been characterized using microbeam scanning energy-dispersive X-ray fluorescence spectrometry (uXRF). The images produced by this process have identified the abundances and locations of Fe, Ni, Cu, Ca, Si, and Cr within different minerals in 11 samples with representative sulphide textures: disseminated, leopard net-textured (containing bimodal coarse- and fine-grained olivine), pinto net-textured (containing bimodal coarse orthopyroxene and fine olivine), inclusion net-textured (containing coarse inclusions of peridotite), disrupted net-textured (containing pyroxenite invading leopard and pinto net-textured sulphides), semi-massive (containing inclusions of peridotite, pyroxenite, gabbro, and net-textured sulphides), and massive. All sulphide textures typically contain magmatic assemblages of pyrrhotite-pentlandite-chalcopyrite-magnetite+/-chromite. Notable differences include small ellipsoidal chromite inclusions only in facies with disseminated textures, little to no clinopyroxene in leopard net-textures, abundant clinopyroxene in invasive pyroxenite in disrupted net-textures, high-Cr orthopyroxene oikocrysts in pinto net-textures, and variable degrees of segregation of Cu-rich residual sulphide liquid from fractionally crystallizing Fe-Ni-rich monosulphide solid solution, more in disrupted and inclusion net-textures than in disseminated textures or leopard or pinto net-textures. The wide variety of net textures, the abundance of inclusions, and the invasive pyroxenite indicate a complex history for the magmatic plumbing system. Inclusions and late-stage pyroxenitic melt may have physically facilitated migration of residual sulphide liquid from monosulphide solid solution, and the emplacement of the late pyroxenite may have slowed cooling and/or reheated the mineralization. Many of these details are less evident visually in slabbed cores or polished thin sections, highlighting the usefulness of uXRF in interpreting the genesis and beneficiation of texturally complex magmatic Ni-Cu-PGE ores.
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.

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