Sulphide textural variations and multiphase ore emplacement in the Eagle's Nest Ni-Cu-(PGE) deposit, McFaulds Lake Greenstone Belt, Ontario

Abstract

The McFaulds Lake greenstone belt, in addition to its world-class chromite endowment, also hosts significant magmatic Ni-Cu-(PGE) mineralization at the Eagle's Nest deposit. Mineralization at Eagle's Nest occurs in a dynamic system that contains multiple generations of sulphide textures, consistent with its interpretation as a magmatic feeder among a network of ultramafic intrusions. Massive sulphides and abundant leopard net-textured, oikocrystic net-textured, and inclusion net-textured sulphide mineralization formed first and were consolidated enough to be cross-cut by late-stage pyroxenite, creating disrupted net-textured sulphide and minor late-segregating massive/semi-massive sulphide melts. Resolving the fundamental characteristics and genesis of mineralization at Eagle's Nest will provide critical information about the evolution of large chromium and Ni-Cu-PGE ore systems associated with Archean komatiitic magmatism within the Superior Province.

3D Geological Modeling of the Double Eagle – Black Thor Intrusive Complexes, McFaulds Lake Greenstone Belt, Ontario, Canada

“…The resulting model is expressed in three-dimensions as a flattened tube measuring up to 120 m wide by at least 300 m long and constrained by exploration drilling to a depth of 1300 m (Fig. 4.7b), more-or-less corroborating previous descriptions of the Eagle's Nest conduit (see the discussion section of this Chapter; Mungall et al, 2010;Zuccarelli et al, 2017;Barnes and Mungall., 2018).…”

“…Similar to most economic grade Ni-Cu-(PGE) deposits around the world (e.g., Voisey's Bay, Noril'sk, Jinchuan, Shurugwi;Naldrett 1997;Li et al, 2001;Maier et al, 2001;Pendergast, 2008), the majority of the sulphide mineralization in the DEIC and BTIC is primarily hosted in what appear to be magma conduits of the plumbing system, within the Eagle's Nest conduit (Mungall et al, 2010;Zuccarelli et al, 2017) and the Blue Jay occurrence of the AT-12 keel (Houlé et al, 2015) respectively, as opposed to the overlying layered intrusions. Sulphide segregation and therefore mineralization within magmatic plumbing systems (as well as at the base of komatiite flows) is attributed to the contamination of the S-undersaturated komatiitic magma achieved through the assimilation of sulfur-rich country rock (Lesher and Groves, 1986;Naldrett, 1999;Spandler et al, 2005;Song et al, 2011).…”

“…Near the surface, mineralization is confined to the northwestern margin of the peridotite host dike but tends to be more concentrated near the western and northern extremities extending to the east ( Fig. 4.13a; Mungall et al, 2010;Zuccarelli et al, 2017;Zuccarelli et al, 2018). The peridotite dike is closed at its northern and southern ends and, despite some local deformation, the body is not significantly deformed.…”

“…• Studies on Ni-Cu-(PGE) mineralization at Eagle's Nest (Mungall et al, 2010, Zuccarelli et al, 2018 and Black Thor -Black Label (Farhangi et al, 2013).…”

“…pyrite, chalcopyrite, pyrrhotite) and magnetite that form sheets extending approximately 200 m in strike length and up to 50 m in thickness to a depth of more than 1600 m (e.g., Zuccarelli et al, 2017). Having accumulated in a sub-horizontal keel structure at the base of a chonolith, the body has been subsequently tilted to a subvertical dip, striking north-south over a distance of approximately 500 m (Mungall et al, 2010;Zuccarelli et al, 2017;Zuccarelli et al, 2018). Near the surface, mineralization is confined to the northwestern margin of the peridotite host dike but tends to be more concentrated near the western and northern extremities extending to the east ( Fig.…”