The Wellgreen deposit is hosted in the Quill Creek Complex, one of a number of mafic-ultramafic sills that are enriched in nickel-copper-PGE mineralization that outcrop within the Kluane Ultramafic Belt of the Wrangellia Terrane in southwestern Yukon. The sills which form the Kluane maficultramafic complex are thought to be part of a sub-volcanic system that fed the Nikolai Formation flood basalts and have been compared to the Noril’sk in Russia.

Many sill-hosted Ni-Cu-PGE deposits are generally considered to be part of a large, interconnected magmatic system that fed voluminous flood basalts and resulted from the impingement of a mantle plume upon the base of the crust. At Noril’sk, the main sulphide bodies formed from segregated sulphide at the base of magmatic conduits through which multiple pulses of magma travelled, and this mechanism is believed to have been also applied to the Wellgreen deposit. The Quill Creek complex intruded a Pennsylvanian-Permian island arc, whereas many of the other deposits are Precambrian and all intruded into cratons. Greene et al. (2010) offer compelling evidence that the mafic-ultramafic intrusions and flood basalts of Wrangellia were formed in an oceanic plateau, which itself was formed by a mantle plume (Richards, 1991), and the terrane was subsequently accreted to the margin of North America in the Jurassic. These circumstances make Wellgreen unique among other sill-hosted Ni-Cu-PGM deposits.

Mineralization on the Property occurs within the Quill Creek Complex. This variably serpentinized, ultramafic-gabbroic body intrudes Pennsylvanian-Permian sedimentary and volcanic rocks. Historic exploration and development programs defined two main zones of gabbro-hosted massive and disseminated sulphide mineralization known as the East Zone and West Zone. These zones have since been subdivided into the contiguous Far East, East, West, and Far West Zones with the connecting Central Zone. The historic North Arm Zone has only limited drilling to date.

The main sulphide minerals associated with potentially economic mineralization at the Wellgreen project include pentlandite (nickel), chalcopyrite (copper), and cobaltite (cobalt). The PGMs platinum, palladium, rhodium, iridium, ruthenium, and osmium, along with gold, are included in sperrylite, merenskyite, sudburyite, and other lesser known minerals that are often associated with magnetite, pyrrhotite, chalcopyrite, and pentlandite.

The Wellgreen deposit is amenable to large scale open pit mining with portions of high grade zones at depth having potential for extraction by underground mining methods.

SNC-Lavalin Inc. (SNC) evaluated the open pit potential of the Property at a mill feed rate of 25,000 t/day increasing to 50,000 t/day in Year 6. The ultimate pit for the 2015 PEA base case is scheduled to be phased into four preliminary pushbacks. Mining cut-offs and stockpiling grades would be established for each pushback to target higher-grade mill feed.

Mill feed is planned to be hauled directly to the crusher and low grade material would be hauled to the long term stockpile and processed at the end of the mine life. Waste rock is planned to be hauled to the 1540 dump and the tailings management facility (TMF).

The pre-stripping period is scheduled to be one year in duration and provides the necessary construction materials for the tailings dam and other surface infrastructure facilities.

The objective of the underground mine planning was to provide high grade mill feed early in the life of mine plan. The underground mining is planned to come from zones that would otherwise not be mined until late in the 2015 PEA base case mine plan or with the Stage 5 pit that is considered to be an opportunity in the 2015 PEA and is not part of the base case.

The underground mine design takes advantage of existing level development, ventilation and vertical development. The underground mine is scheduled to provide feed to the mill starting in year three of production with a relatively low capital requirement.

The current study reviewed the following four underground mining methods:
• Shrinkage mining: eliminated due to geotechnical concerns. These openings would affect open pit mining, which was scheduled to operate oncurrently with the underground activities;
• Block caving: considered as an alternative to a Stage 5 open pit scenario;
• Open stoping with backfill: chosen for those blocks amenable to bulk mining; and
• Post pillar cut and fill: chosen for shallow dipping, high grade mineralization zones.

This study assumes that the lateral development and the post pillar cut and fill production mining would be completed by one contractor who would provide his own mobile equipment. This contractor would also be responsible for the remote mucking of the open stope. A second contractor is planned to be used for drilling and blasting the open stopes and installing the ground support cable bolting. The second contractor would be required to provide his own mobile equipment and grouting pumps.

The current project plan begins with a 25,000 t/d nominal mill utilizing conventional crushing. Crushing is planned to be in three stages with a primary gyratory crusher, a secondary cone crusher and a tertiary cone crusher in closed circuit with a screen. The circuit would produce a feed for two single stage ball mills operating in parallel.

Metal recovery is designed to be by bulk flotation followed by concentrate regrind and cleaning. In addition, a magnetic separation circuit on the rougher flotation tailings, followed by regrind and flotation cleaning would be used. A final bulk concentrate for sale planned to be produced. Regrind is proposed to be done by small ball mills or alternately stirred media mills. Concentrate for sale would be thickened, filtered and trucked off site. Tailings would be thickened and pumped to the tailings management facility.

In the sixth year, mill capacity is scheduled to be doubled to 50,000 t/d. The recovery process would remain the same. Increased capacity would be accomplished by twinning most of the circuit.