| Title | The diversity of net-textured sulfides in magmatic sulfide deposits: insights from the Eagle's Nest Ni-Cu-(Platinum Group Element) deposit, McFaulds Lake Greenstone belt, Superior Province,
Canada |
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| Author | Zuccarelli, N; Lesher, C M; Houlé, M G; Weston, R; Barnes, S J |
| Source | Economic geology and the bulletin of the Society of Economic Geologists vol. 117, no. 8, 2022 p. 1731-1759, https://doi.org/10.5382/econgeo.4924  Open Access |
| Image |  |
| Year | 2022 |
| Alt Series | Natural Resources Canada, Contribution Series 20210462 |
| Publisher | Society of Economic Geologists |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Ontario |
| Area | McFaulds Lake |
| Lat/Long WENS | -86.8400 -84.9925 53.2783 52.2647 |
| Subjects | Science and Technology; mineralogy; Nature and Environment; mineral deposits |
| Illustrations | location maps; diagrams; tables; photomicrographs; cross-plots; charts |
| Program | Targeted Geoscience Initiative (TGI-6) Ore systems |
| Released | 2022 12 01 |
| Abstract | The Eagle's Nest Ni-Cu-(platinum group element; 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. Mineralization occurs along the northern margin of a formerly ~500-m-high, ~85-m-thick, >1,500-m-long subvertical structurally rotated blade-shaped dike composed of harzburgite, lherzolite, and wehrlite. Three sulfide textural facies are
present (percentage as proportion of total mineralization): (1) disseminated (~5%), (2) net texture (~80%), and (3) semimassive to massive (~15%). Five subfacies of net texture have been identified: (1) bimodal olivine-bearing leopard net texture
(~50%), (2) inclusion net texture (~5%), (3) orthopyroxene-bearing pinto net texture (<1%), (4) localized zones of disrupted net texture (~30%) containing 3- to 5-cm-thick zones of barren amoeboid crosscutting pyroxenite, and (5) fine-grained patchy
net texture (~15%). All textural facies are characterized by typical magmatic pyrrhotite-pentlandite-chalcopyrite-(platinum group mineral) assemblages. Massive sulfides are localized in two embayments along the basal contact separated by a
topographic high, grading upward to rare semimassive, laterally more continuous net-textured, and disseminated sulfides, with gradational contacts between all textures except massive. Similar mean ore tenors of different sulfide textural facies
(Ni100 ~7.5, Cu100 ~4.8), suggest that the majority of the mineralization formed from similar magma compositions at similar magma/sulfide ratios, but the presence of different inclusion populations (peridotite, gabbro, chromitite) and the presence of
disrupted net texture indicates that the olivine, inclusions, and sulfide melts accumulated from multiple pulses in a dynamic system. The smaller, blade-shaped, sulfide-rich, chromite-poor Eagle's Nest body does not appear to be the feeder to the
overlying larger, oblate, sulfide-poor, chromite-rich Double Eagle body. This highlights the need to understand the fluid dynamics of entire plumbing systems when exploring for these deposit types and the significance of smaller, more dynamic
magmatic conduits as environments favorable for Ni-Cu-(PGE) mineralization. |
| Summary | (Plain Language Summary, not published)
Under the Targeted Geoscience Initiative (TGI) Program of the Geological Survey of Canada (GSC), this study aims to better understand how nickel (Ni),
copper (Cu) and platinum-group elements (PGE) mineralization form in the Canadian Shield. This work describes a wide range of sulfide textures of Ni-Cu-PGE mineralization in the Eagle's Nest deposit in the James Bay Lowlands, the largest deposit yet
discovered in the "Ring of Fire" area of northern Ontario. Furthermore, it is one of the most significant greenfields discoveries in Canada in the past two decades. A wide range of methods were used to characterize the ore types and show that they
formed in a dynamic magmatic system. Our results and interpretations provide constraints on the mechanism of formation of other deposits containing complex ranges of sulfide textures. |
| GEOSCAN ID | 329314 |
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