geo question for neil wa, page-5

I'm not a geo by profession though have spent several years reading company reports in gold/nickel/iron ore/oil/gas/zinc mining industries and reading up on these to understand the geology and significance.

Thanks for that link - that site was a nice find and I've spent a few hours reading the documents.

The structures are very old, though as long as they remain intact, gold sulpide bearing water is moving through the formation, and adequate chemical conditions are met then gold will continue to be deposited. Much gold was probably deposited during periods of high volcanic activity millions of years ago when there was plenty of sulphur in the atmosphere producing acid rain (sulphuric acid), with the gold carried in this and depositted at sites where water seaped through slowly and pooled where slow chemical reactions removed the sulphur from the gold, which then became much less soluble and when it hit a particle of gold (nidus) it is deposited, forming nuggets over millions of years.