T151 Geology and Fluid Dynamics of Cr, Ni-Cu-PGE, and PGE Mineralized Magmatic Plumbing Systems

Tuesday, 6 November 2018
8:00 AM - 12:00 PM
Room 233

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

Paper number: T151-6
Program: Technical Sessions
Time: 9:20 AM – 9:35 AM

Authors

Abstract

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.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-317024

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