i have a comment on your modified placer model: considering how conglomerates originate, and how they end up being a multitude of various rock types from very different sources cemented together "somehow", some are highly lithified, some are degraded, some have not been heated, or compressed, and too young to have gone through further metamorphoses a much older rock type exhibits, it makes sense, especially considering the age of witwatersrand ores, that conglomerates in general can most certainly go through one or more precious metal enrichment events, and high temperature compression events that mechanically concentrate precious metals as well as chemically concentrate/enrich precious metals over a very long period of time, i was studying some of the pictures of witwatersrand high grade ores on wikipedia, and in one picture of carbon leader gold ore, it appears to exhibit stratification, and may have been compressed into bands, i'm no expert, but the modified placer theory seems possible to me, for instance, one claim i own is placer gold, silver and electrum in conglomerate that is concentrated in layers of stratification in a type of caliche cemented gravel, it's visible gold attached to small fragments and small pebbles of it's original host rock that's cemented to various other rock types from roughly the same period, tertiary 7.5 ma, i believe that if this or similar ore type was to endure another 2 billion+ years or more of heating, steaming, litification and compression, it may very well resemble/morph into witwatersrand ore, i enjoy your video series, and only wish to learn more about geology, and correct anything i may have misinterpreted or possibly outdated , regards.
Fantastic video. I am no geologist and I am open to the hydrothermal theory. But if true, should there be significant gold deposits outside and/or below the thin conglomerate deposits? I understand people are skeptical of the placer theory because there are no comparisons on earth in that richness but this reminds me of my own locale in Michigan. We have unique pure copper deposits that almost defy logic. And they are of a similar age to the witwatersrand. Perhaps there was a massive surficial deposit to the northwest that was entirely eroded. They say there is no evidence, but it seems to me that it is possible that an entire deposit (richest deposit ever) was completely eroded away into alluvial plains.
Thanks for the comment. We can always speculate on an eroded gold source to explain the Wits gold, but it would have been a complete anomaly, many orders of magnitude greater than any other Archaean greenstone deposit discovered anywhere else in the world, which seems unlikely. To me, the 'path of least astonishment' is the one I suggested, but I believe it is unproven and should be regarded as just a theory.
