[johndiver (OP)]

John Berger  asked the Naked Scientists:

If the Earth's core is made of heavy and dense metals, mostly iron, are the most dense metals at the centre of the core.

That is, if we could drill down 6,000 km, would we find large quantities of gold, uranium and osmium?

John Berger
Vancouver Island.


What do you think?

[JimBob]

no - it is too hot - anything you manage to get that deep will melt first.

[johndiver (OP)]

Yeah, heat would be one problem. I think movement of layers would break any drill bit before we reached the core.
Therefore, the question is hypothetical.

[RD]

Knowing that the concentrations of precious heavy metals increase with depth is not an academic point ...

Magma released from the earth's interior has many components, Dr. Noble said, including gold...
Most of the world's biggest gold deposits, like those found in South Africa, were formed when ancient gold-bearing rocks -- ultimately volcanic in origin -- were eroded by streams, causing the gold to be concentrated in alluvial deposits called placers, said Dr. Don Noble, an economic geologist at the Mackay School of Mines at the University of Nevada in Reno. But now that these deposits are being depleted by mining, he said, prospectors are paying more attention to lesser amounts of gold found in extinct volcanoes.

http://query.nytimes.com/gst/fullpage.html?res=990CE5DA133FF93BA15753C1A962958260

Thar's gold in them thar volcanies.

[johndiver (OP)]

In college, I spent time trying to figure out an economical way of extracting gold from sea water.
I considered using electrical current, centrifuge, boiling off the water, and even certain plants which take up metals through their root system, but none were worth pursuing due to the small size of gold particles, the volume of water needed to process, and the vegetation that would clog any filter.
One other gold resource that many geologists don't talk about is that found on sunken vessels. With advances in underwater cameras, robots, submersibles and salvaging, more "out of reach" ships are being salvaged for their gold and silver cargo.

[Bass]

Knowing that the concentrations of precious heavy metals increase with depth is not an academic point ...

Thar's gold in them thar volcanies.

It's not quite that simple.

While average concentrations of gold (and some other metals) increase with depth in mantle rocks (but only by a few ppb), digging deeper will not a gold deposit make.

Gold, and other metals must be concentrated to form viable mineral deposits.  This requires a source area (rocks with slightly higher concentrations), transport and deposition of the metals in a concentrated area.  Deposition may be controlled by fracturing (faults), chemical reactions, mixing, or by temperature-depth-pressure parameters.  Not every volcano has gold- and not all gold deposits are created by volcanoes.

[Alan McDougall]

The core it mainly iron

[Bored chemist]

Glad that hasn't changed since the first post.