RE:DEEP DOWN EXTENSION question for RetiredGeoThere is a difference between the Quartz veins and the mineralized Quartz veins. The Quartz veins probably extend 25-30 kms down. Gold precipitation occurred in a narrow band perhaps a few kms thick. Time, luck and happenstance have brought the erosion level down to the gold band. How deep does the gold band still go? No one knows. We know only that it goes down at least 400 vertical meters. In my opinion it probably goes down 2000 m. If QH wants to predict kms his guess is as good as any. It does not extend down forever.
You can think of gold precipitation like a cloud deck. Water precipitation occurs within a narrow band. Above and below the band there is nothing.