shear zones like faults are where the rocks of the crust have...

shear zones like faults are where the rocks of the crust have been moved up/down or sideways. Shears differ from faults because the rocks have not broken cleanly more of a stretching and spreading.
This leaves weaknesses in the crust that fluids can flow easily through. Hot waters or brines then flow through surrounding rocks leaching minerals as they go. When they reach the shears the pressure or temperature can drop and the enriched minerals are precipitated out of the solution. Repeat several thousand times and you have an enriched zone for Kin geos to drool over and drill into.

From bio-geo-terms.blogspot.com
Shear zones involve volumes of rock deformed by shearing stress under brittle-ductile or ductile conditions, typically in subduction zones at depths down to 10-20 km. Shear zones often occur at the edges of tectonic blocks, forming discontinuities that mark distinct terranes. Shear zones can host ore bodies as a result of hydrothermal flow through orogenic belts, are commonly metasomatized, and often display some retrograde metamorphism from a peak metamorphic assemblage.

The key words are ductile (a solids ability to be deformed under stress)
and metasomatized (chemical alteration of a rock by hydrothermal fluids or other fluid.

I am not a geo, far to old to go to Uni and do that, so I read heaps and then go out and look at the rocks that the Geos talk about to try and understand what they are seeing. Fascinating stuff.
WA's mines dept makes a lot of old geo reports available freely online and the reading of areas around Cardinia talks a lot about shears. Perhaps the Cardinia area is the Southern extension of the Mertonadale Shear Zone and if so what lies to be discovered in between?