GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 151-6
Presentation Time: 9:20 AM

SULFIDE TEXTURAL VARIATIONS AND MULTIPHASE ORE EMPLACEMENT IN THE EAGLE'S NEST NI-CU-(PGE) DEPOSIT, MCFAULDS LAKE GREENSTONE BELT, SUPERIOR PROVINCE, NORTHERN ONTARIO, CANADA


ZUCCARELLI, Natascia, Harquail School of Earth Sciences, Mineral Exploration Research Centre, Goodman School of Mines, Laurentian University, Sudbury, ON P3E 2C6, Canada, LESHER, C. Michael, Mineral Exploration Research Centre, Harquail School of Earth Sciences, Goodman School of Mines, Laurentian University, Sudbury, ON P3E 2C6, Canada, HOULÉ, Michel G., Geological Survey of Canada, Natural Resources Canada, Québec, QC G1K 9A9, Canada and WESTON, Ryan J., Noront Resources Ltd., Thunder Bay, ON P7B 6E6, Canada

The Eagle’s Nest Ni-Cu-(PGE) deposit occurs within the 2.73 Ga Double Eagle intrusive complex of the Ring of Fire intrusive suite in northern Ontario. It is hosted by a ~200m wide x ≤50m thick x >1600m deep subvertical, structurally-rotated komatiitic dike. Sulfide mineralization is hosted by harzburgite ± lherzolite and occurs almost exclusively along the vertical northern (variably NE-NW) contact with granodiorite country rocks, consistent with mineralization being initially emplaced along the lower edge of a sub-horizontal blade-shaped dike. Massive, semi-massive, net-textured, and disseminated sulfide textures have been defined spatially and geochemically through detailed core logging, petrography, and whole-rock and mineral geochemical analyses. From surface to 300m, massive sulfide occurs in 30-50m deep embayments along the footwall and grades upward into more continuous and more abundant net-textured sulfide. From 500-900m depth net-textured sulfide contains localized zones of ‘disrupted-net texture’ containing 3-5 cm thick zones of cross-cutting barren pyroxenite. This is interpreted to represent a late phase of more evolved magma that infiltrated the peridotite-hosted mineralization. The variations in the sulfide segregation profile with depth (length) and the presence of disrupted net-textured mineralization supports the interpretation of Eagle’s Nest as a dynamic, sub-horizontal blade-shaped dike emplaced as multiple magma pulses controlled by intrusion geometry. This emphasizes the importance of narrow and highly active magmatic feeders with small footprints as hosts of Ni-Cu-(PGE) mineralization within large intrusive complexes.