By Geoff Heggie, Senior Geologist
Noront’s recently completed exploration program was carried out in the McFaulds Lake area and it targeted Volcanogenic Massive Sulfide deposits otherwise known as VMS. Their discovery sparked curiosity among Noront staff and launched a discussion around how VMS deposits are formed.
While they can host a diverse range of metals; VMS deposits are usually made of copper (Cu), zinc (Zn), lead (Pb), silver (Ag), and sometimes gold (Au). This collection of metals differs from the Eagle’s Nest deposit (copper, nickel, platinum group elements) and the Ring of Fire chromite deposits (chromium) because
each of these deposits is the result of different conditions
The McFaulds deposits were formed 2.7 billion years ago when the earth’s core was much hotter and the oceanic and continental plates were constantly breaking apart and coming together. Fractures were formed as a result, and sea water seeped into them. When the sea water got close to the molten core, it would heat up and shoot back to the surface as hot springs. Along the way, these hot fluids would leach minerals out of the surrounding rocks. When the mineral rich hot-springs reached the cold water of the sea floor, metals in the solution would crystalize in large mounds.
In some cases, the process of leaching and deposition happened efficiently over an extended period of time (maybe millions of years) and resulted in an accumulation of metal enriched massive sulfide mounds. In the eons that followed, the mounds would get covered over by sand and volcanic lava and preserved for us to one day discover as we are now through our current exploration program.