McIlvenna Bay is a VMS deposit, of a type commonly found in Canada in Precambrian through Mesozoic volcano-sedimentary greenstone belts occupying extensional arc environments such as a rifts or calderas. They are typified by synvolcanic accumulations of sulphide minerals in geological environments characterized by submarine volcanic rocks. The associated volcanic rocks are commonly relatively primitive (tholeiitic to transitional), bimodal and submarine in origin (Galley et al., 2006). The spatial relationship of VMS deposits to synvolcanic faults, rhyolite domes or paleotopographic depressions, caldera rims or subvolcanic intrusions suggests that the deposits were closely related to particular and coincident hydrologic, topographic, and geothermal features on the ocean floor (Lydon, 1990).

The McIlvenna Bay deposit consists of structurally modified, stratiform, volcanogenic, polymetallic massive sulphide mineralization and associated stringer zone mineralization. The structural deformation and related transposition of the stratigraphy in the deposit area appears to be responsible for the current geometry of the CSZ. This zone of stringer-style mineralization occurs as a compact, continuous zone directly underlying the massive sulphide. The sulphides contain copper and zinc, with low lead and silver and gold values.

The McIlvenna Bay deposit has undergone strong deformation and upper greenschist to amphibolite facies metamorphism. The massive sulphide lenses are now attenuated down the plunge to the northwest. Typical aspect ratios of length down- plunge to width exceed 10:1. The extent of remobilization of sulphides within the deposit is uncertain.

The McIlvenna Bay deposit dips to the north at 65° to 70°, although in selected areas it dips vertically. The average strike length of the economic deposit is 600 m with an average thickness of approximately 14-17 m. In areas where mineralized zones run parallel to each other, the distance between the host rock hangingwall and footwall can exceed 50 m.

It has been identified that due to distinctly different metallurgical properties between the different mineralization zones, it is economically beneficial to mine them separately.

JDS selected sub-level long hole (LH) stoping with cemented paste backfill as the principal mining method at McIlvenna Bay due to its high productivity, low cost, appropriate level of selectivity, and successful history of application for deposits of this nature, such as the Hudbay Mineral Inc. nearby 777 operation, which produces 4,330 tpd from their underground operation (Hudbay, Oct 2012).

Drift and fill mining may also be used at McIlvenna Bay for areas of the deposit which fall below an allowable dip for LH stoping.

LH stoping is a semi-selective and productive underground mining method, and well suited for steeply dipping deposits of varying thickness with good continuity and minimal small-scale variability is thickness, dip and strike. It is typically one of the most productive and lower cost mining methods applied across many different styles of mineralization. In the planned LH for McIlvenna, a top and bottom drift delineate the upper and lower boundaries of the stope and a dedicated long hole drilling machine drills blast-holes between the upper and lower sub levels. The drill holes would be loaded with explosives and the stope blasted in vertical slices, with broken material falling to the bottom drift for extraction. Once the stope has begun the blasting phase it cannot be accessed by personnel. For this reason, a tele-remote load haul dump machine (LHD) would be required to remove the blasted material from the stope.

One of the limitations with LH stoping is that the dimensions of the stope should not exceed a long hole drilling machine’s effective range which, for top hammer drill rigs, is generally 30 m. Another limitation with LH stoping is the stopes must remain open long enough to remove the mineralized material and fill with an engineered backfill material (if pillars are not used). These limitations generally restrict level spacing to 30 m or less, and subject stope strike lengths to geotechnical constraint.

Two methods of LH stoping are considered for McIlvenna Bay. Transverse stoping is planned to be the primary method, whereby crosscuts would cut through the stope perpendicularly, and long hole fans would drill off the strike length of the stope.

This method is beneficial for production rates as multiple stopes can be in operation at once on a level. It is also beneficial for mining parallel mineralization zones, as relatively clean separation between the mineralization types is possible with careful fan drilling.

The shortfall of transverse LH mining is that a footwall drift is required outside the mineralized zone for the entire strike length, and crosscuts must be driven long enough to maintain a safe distance between the footwall drift and the zone, which depending on geotechnical constraints can exceed 25 m.

The proposed processing facility has been designed as a nominal 3,700 dmtpd concentrator plant (i.e. slightly in excess of the nominal mine production), although the initial absence of standby equipment requires that the design availability of the process plant be practically limited to 85% for early mine life and thus no more 3,300 - 3,400 dmtpd effective capacity is initially expected. As the mine production rate will ramp up slowly over the initial production period, mill capacity is expected to always exceed the mine production rate.

Installation of standby equipment in year 3 is expected to improve plant availability to over 93%, at which time the daily throughput should peak at 3700 - 3800 tpd.

In the early years of production (years 1-3), ore will be hauled to surface in 50-tonne trucks and dumped into a surface crushing facility. As the mine development continues below 0m level, a new underground crushing station will be constructed to feed -150mm ore o ........