Magmatic Ore Deposits - Metals and Society: An Introduction to Economic Geology - page 64

Fig. 3.17 The Sudbury irruptive complex (a) map, (b) section (from Eckstrand and Hulbert
( 2007 ) http://gsc.nrcan.gc.ca/mindep/synth_dep/ni_cu_pge/index_e.php
interacted with its wall rocks, perhaps picking up sulfur from sulfide-rich
metasediments, a process that led to the deposition of Ni-bearing sulfides higher
in the magma conduit. The intrusion that hosts the largest ore body is relatively
small and it is clear that the sulfides could not have been derived from the small
amount of magma represented by the intrusion. Evidently the sulfides were
transported from elsewhere, probably from a deeper magma chamber, and were
subsequently trapped in the narrow conduit where they are now found.