http://gsc.nrcan.gc.ca/mindep/synth_dep/ni_cu_pge/index_e.php

The Voisey's Bay discovery has emphasized, as is also the case at Noril'sk-Talnakh, the importance of relatively small intrusions as parts of large magmatic systems. Their role as conduits for large volumes of magma provides sites for accumulations of settled sulphide out of the passing magma.

Consequently, within a large mafic magmatic province, the target reduces to identifying smaller differentiated cognate intrusions that could represent magma conduits.

Sulphide-rich Ni-Cu deposits achieve their concentrations mostly through the settling effects of gravity. Consequently in virtually all magmatic bodies (sills, flows and dykes), the sulphide-rich ores are most likely to be found at the base of those bodies. Determination of the base of a given body is thus an important part of exploration targeting.

My point being that the deposit was going to depth.I believe the data for hole 18 showed the massive sulphides were encountered at a vertical depth greater than that of any previous hole.Every aspect of the exploration program to date is closely related to this genesis model described on the above website.One more important cut and paste below.

However if it is clear that faulting is a possibility, the distribution pattern of sulphide-rich zones may be more complex. For instance in the Thompson Nickel Belt, some of the sulphide ores are extended far beyond the parent ultramafic bodies.

Electromagnetic surveys designed to detect conductors should be effective on the sulphide-rich (i.e., massive, breccia and matrix-textured sulphides) deposits. IP methods may identify disseminated sulphides, but presence of serpentinization in the same body may render the technique ineffective.

In the credits for this site I did not see Dr.Mungall's name but a very large contribution by Dr. A.J. Naldrett was acknowledged.Aldrett was one of the first professionals to view cores from Voisey's bay in Mort Virbisky's garage.