It is my understanding that surface gold has disassociated through weathering effects from veins of solidified liquid which has gold in it (amongst other minerals) and typically SiO2 (Quartz). Millions and millions of years ago the gold was dissolved in fluids deep in the earths crust and under the intense pressure of the earth above it was forced up through weak points i.e cracks in the earth. If you can imagine a tree being inverted and the canopy of all the branches being the cracks in the ground where the liquid was forced up. As the liquid rose and cooled it solidified and gold solidified in the Quartz. In the Vic GT there was an East West compression of the ground which caused North South running cracks and folds which were the least path of resistance for pressurised liquids to rise up. In some cases the North South running veins of solidified Quartz/gold ended up on top of hills, known as a saddle reefs. These main veins also had off shoots called Spurs which branched out in different directions subject to inherent weakness in the earth. As these hills eroded over the years the Quartz eroded and gold broke free from the Quartz. So the gold sheds down from those main veins but also the Spurs. So I would expect gold all around a hill subject to where the main reef and Spurs are and relative to main sources of erosion. For example if further movement of the earths crust caused two hills with a reef running through them both and a river/creek formed cutting the vein the river/creek would be an extra source of erosion which could create a source of free gold. I'm no geologist but have tried to understand this phenomenon so that I look for the best place to detect. To me you should be looking for signs of exposed reef, any where around a hill, and detect down hill from it. It is the opposite to what the old timers use to do after exhausting alluvial gold. They use to loam up hill from the alluvial diggings to find the Quartz vein source. I'm more than happy for anyone to correct me, as I am still learning and trying to get my head around it.
Cheers