I don't have much time now.But will dash this off.Depth to...

I don't have much time now.
But will dash this off.
Depth to economic mineralisation varies.
Super Pit = 1890s surface prospecting. which is basically stubbing your toe on something and recognizing Broken Hill Telfer Mt Isa. etc

Nowadays these are rare and geophysics, magnetics for one, are ways to see through the "crud" that covers potentially economic deposits.  The crud is various recent sands, weathered and commonly leached bedrock that in WA is often 50-100m or more thick.  In the Paterson province the margins of the Canning Basin and its sediments onlap and cover the "crud" with 0 to 1000s of meters.

Cover is one aspect of depth to economic mineralisation.  
Another is where it actually starts.  
Currently Yappsu and OTH are bedrock discoveries under ? less than 100m of crud but starting 2-300m below ground in fresh rock.  Nova-Bolll and Eagle fit this starting at depth category

Nebo Babel are only slightly covered in crud to the extent they can't be toe stubbers like Wingellina to the east.

Havieron and Olympic Dam and Carra have >300m of crud on top but are all very strong geophysical sore thumbs that beg to be drilled by well heeled companies


Magnetics are inverse square related.  The more cover the weaker the response I believe.  The image in my post and for the Paterson area show some areas with lots of detail while others look like blurred images.  IMO this is a function of cover to a certain extent.  The image below IMO suggests shallow cover in the NE half and deeper to the SW.  Out of time hope this helps.  Sorry for any confusion.