Summary:
Both the Eagle River and Mishi deposits are mesothermal lode gold deposits hosted by Archean Greenstone Belts.
The Eagle River deposit has been described as a vein type deposit along a regional deformation zone with discrete brittle-ductile shears localized along lithological contacts (Heather 1986 and 1991).
Gold bearing quartz veins at Eagle River are hosted primarily by subvertical to steeply north dipping east-west striking shear zones within an elliptical quartz diorite stock with dimensions of 2.0 kilometres east-west and 0.5 kilometres north- south.
The quartz diorite stock intrudes a steeply dipping north-facing sequence of thin mafic to intermediate volcanic flows, flow breccias and interflow volcaniclastic rocks.
A number of different ore zones have been distinguished that constitute different segments of the overall shear zone corridor and each has its own gold grade characteristic. Mineable portions of the individual zones form ore shoots that plunge steeply to the east. The bulk of the historic production has come from Zone 8 and Zone 6, which are entirely within the intrusive quartz diorite, while Zone 2 mineralization is hosted in sheared mafic volcanic rocks just east of the stock.
In general, the ore shoots mined to date occur at a spacing of 400 metres along a 2.4 kilometre strikelength. They appear to be spatially related to an array of oblique 110º striking mafic dykes, which pre-date mineralization and deflect into and out of the shear zones.
Gold mineralization is structurally concentrated within highly strained portions of the various quartz veins. Ore microscopy (Clemson, 1989; Johnston, 1990) indicates that 60% of the gold occurs along quartz-sericite grain contacts, 32% along sulphide-gangue contacts and 1.4% within sulphide grains. The grains are generally less than 500 microns, free milling and 40 to 60% recoverable by gravity methods. Gold grains less than 5 microns account for a negligible percent of the total gold. Free gold generally occurs as a multitude of fine grains which result in a relatively low sub sampling variance generating very good assay precision for a vein type gold deposit.
The Mishi deposit is somewhat different. Gold occurs primarily with subordinate, discontinuous quartz veins and lenses. In the Mishi Mine area mineralization is hosted by a series of at least 8 tabular parallel zones consisting of ankerite-sericite ± chlorite alteration zones containing 2-8% fine disseminated and a system of sub conformable, dislocated, smoky grey quartz veinlets and lenses. Veins generally vary from 5-20% of the bulk volume of the zones with individual quartz lenses commonly 5-15 centimetres wide.
The 8 zones recognized to date are labelled from south (footwall) to north (hangingwall) M2, M4, M6, M8, M10, M12, M14 and M16. Zones M2 and M4 are close together and are merged when modelling into a Main Zone. The zones strike 100º, dip north 40º and plunge northeast. In general the zones become more felsic, discrete and vein dominated towards the north. Additionally, they appear to be converging eastward and possibly diverging westward.
Historically, mineralization of the Eagle River Mine has been hosted in the mine diorite; however, the Falcon 7 Zone is hosted in volcanic rocks west of the intrusion. Hence, the discovery and subsequent development of the Falcon 7 Zone is important to the Company as it highlights the prospectivity of the volcanic rocks both to the east and west to host additional gold mineralization beyond the currently existing footprint of the Eagle River Mine. Consequently, near-mine exploration is continuing and is focusing on the adjacent Falcon 300 Zone.
The Falcon 7 Zone was discovered in 2019 and now initial sill development has been completed on the 622 and 635 levels in preparation for mining in Q4 2021.