Hi Clayton.
Melton area is a lava (Basalt) plain overlaying older sandstones and slates laid down approximately 400 million years of age. These underlying rocks are of the same age as those that contain the majority of Victoria's auriferous reefs but not invariably.
In short like vast areas of Victoria, there is no reason not to expect river gold deposits (leads) under basalt flows nor is there any reason to expect so.
Most of the sub basaltic leads in Victoria were discovered by following gold bearing gullies into areas where they were covered by basaltic flows. To find a sub-basaltic lead without something like that is a task that has defeated many a prospective miner for over a century.
You need to be guided by evidence and that evidence may be by sampling gravels in modern streams that have cut through the overlying basalt into the potentially gold bearing rocks beneath. If you have access to their valleys to see the contact line between the basalt and slate, any dips in that contact line may indicate a small creek running across the old landscape and be worth taking further samples. Tunnelling into old sub basaltic leads found in that way from the sides of modern steep sided valleys has been successful in other parts of Victoria notably in Gippsland.
Major old river courses would probably have been deeply cut before the basalt flows and would not be just a few meters below the modern surface but possibly a hundred feet or more caused by the basalt infilling the old valleys before spreading out as a plain.
Good luck and look forward to hearing what you find.
fossicking-prospecting-regulations-all-australian-states.125/
