Oldie-Goldie said:
I'm curious to see how you look for new and unsearched areas..
Here in the UK we use a numbers of ways to discover new area's mainly through books, Internet and mapping methods like satellite images to discover historical sites for coins and relics.
Do you use the same type of method or is it all down to pure luck?
Cheers!
OG
For "new" gold areas in Oz you can start from old gold areas and extend or start totally from scratch.
Extending is much easier.
1) State Gov geological data ( kml files for old mine locations)
2) Trove to get historical newspaper info about life in the workings in the area - a lot start with alluvial and then go shallow shaft then deep reef/ deep leads
3) State Govt Geological Reports ( for geology ie local gold host rock types eg quartz intrusion in Tertiary shale )
4) State Govt Geological Maps to see the distribution of the host rock type
5) geopdf Topo Maps 1:25k or 1:50k to see the lie of the land ie gullys & ridges, land use (private , State Forest etc) & access tracks
6) Google Maps satellite for same reasons as 5)
By the time you overlay the old mines on the geo map & topo maps with your understanding of the type of gold ( alluvial, elluvial, reef) that you are looking for then you can figure out where you would want to explore. Then you reduce the area to that you can legally access and hopefully it is bigger than a postage stamp.
Trilobite Solutions do a great app for Oz geology mapping including gold info like mine locations, GPA boundaries, current exploration & mining leases .
Starting from scratch to find surface gold is much harder as attested by the tens of thousands of diggers combing Australia during the rushes of the 1800s, then after returning from WW1 & during the Depression. These days we have a lot more tools but less enthusiasm & more restrictions.
If you are using geo maps from scratch the first step is to find an area with a likely rock type. Detectable gold is deposited mainly from hydrothermal processes (with or without bacterial assistance) where hot fluids have percolated up through cracks in the host rocks and deposited quartz and minerals (inc gold) as the pressure & temperature has dropped and the fluid reacts with the host rock. The host rocks can be nearly any type ( Ig, Met, Sed) eg (shale, sandstone,serpentine, schist ...) but they will have to have been buried quite deep at some stage and then faulted to provide the conditions needed. Then we want the host rock lifted to the surface and enough erosion to have occured to expose the harder quartz reef & liberate the gold. We only want enough erosion to expose the gold, leaving it in place, or moving it a short way by gravity & water. If it is moved the gold will sink down through any loose material until it reaches a more solid layer. If it sinks too far or is transported too far then we wont find it.
So there are ground types that have near zero chance of having detectable gold eg deep soft fine river mud plains or deep sand. Beds of limestone or fine sandstone that have no evidence of quartz intrusions are also given a miss.
Then at some point, assuming you dont have access to GPR, mag survey aircraft etc then its time to get out with that fine instrument - Mark 1 Eyeball and tromp around the countryside.
There are millions of barren white quartz veins, there are hundreds of thousands of "dirty" quartz veins where other minerals have come out of solution, then there are the precious few veins where gold has come out. So finding quartz is good, dirty quartz is a lot better. Ironstone is a good sign as well as it is often another hydrothermallly deposited rock associated with gold.
Then we need conditions so that the gold is still in the top 1m of ground so we can detect it. Shallow ground where the host rock only has a foot or so dirt on top, rock bars across waterways (ancient or modern), the bottom contact zone between a layer of rounded boulders or pebbles on top of a layer of rock or clay (visible on surface or buried) are also very worth a look, especially if dirty quartz or ironstone present.
Simple !
