What caused similar metals to "group together"

[EWyatt]

Once upon a time, the Earth was a molten, roiling blob of stuff. Then it cooled slowly, and I suppose gravity pooled iron toward its middle. But now we have similar metals within the planet that somehow coalesced into veins of gold, silver, areas of lithium, uranium, lead, etc. How did that happen? Why aren't ALL metallic elements equally dispersed throughout the planet, since these elements had no particular attraction to each other? (Note: all metallic elements do exist minutely everywhere, but why the pooling in many places?)

What am I missing....?

[EWyatt]

(Reposted from the Physics forum)

 

Once upon a time, the Earth was a molten, roiling blob of stuff. Then it cooled slowly, and I suppose gravity pooled iron toward its middle. But now we have similar metals within the planet that somehow coalesced into veins of gold, silver, areas of lithium, uranium, lead, etc. How did that happen? Why aren't ALL metallic elements equally dispersed throughout the planet, since these elements had no particular attraction to each other? (Note: all metallic elements do exist minutely everywhere, but why the pooling in many places?)

What am I missing....?

[studiot]

The mineral concentration occurs due to chemical reactions between the water circulating in volcanic zones and the hot rocks.

 

http://nzic.org.nz/ChemProcesses/water/13A.pdf

 

This should be in Earth Sciences.

Edited March 29, 2015 by studiot

[studiot]

The mineral concentration occurs due to chemical reactions between the water circulating in volcanic zones and the hot rocks.

 

http://nzic.org.nz/ChemProcesses/water/13A.pdf

[Moontanman]

Some of the separation is chemical with certain elements being attracted to others some of it is as you said simple gravitational separation, while it is true that Earths core consists of Iron it is not pure iron, many other heavy metals are mixed with it, I have read that the Earth's core contains enough gold to coat the land surface of the earth quite deep, many orders of magnitude more than we see on the surface.

 

Some of the separation is biological with various bacteria concentrating metals as part of their metabolism, in fact I think that in some places and elements the concentration is biological almost completely.

 

http://discovermagazine.com/2006/sep/innerfortknox

Edited March 29, 2015 by Moontanman

[Moontanman]

Actually some metals do have an affinity to each other, many metals have an affinity to iron and were pulled down by the iron as it fell.

[swansont]

these elements had no particular attraction to each other

 

…

 

What am I missing....?

 

That elements can and do have an attraction to each other.

(Reposted from the Physics forum)

 

 

!

Moderator Note

 

No, please don't do this. One topic, one thread.

 

Merging

 

[pavelcherepan]

Once upon a time, the Earth was a molten, roiling blob of stuff. Then it cooled slowly, and I suppose gravity pooled iron toward its middle. But now we have similar metals within the planet that somehow coalesced into veins of gold, silver, areas of lithium, uranium, lead, etc. How did that happen? Why aren't ALL metallic elements equally dispersed throughout the planet, since these elements had no particular attraction to each other? (Note: all metallic elements do exist minutely everywhere, but why the pooling in many places?)

What am I missing....?

 

That is an interesting question.

 

Firstly, you can talk about equal distribution throughout the planet for silicon or oxygen or any of the major elements of crust and mantle. All these other elements you have listed are generally present in such minute amounts that equal distribution would require absolutely extreme convection of all the material of the Earth which we do not observe and there's no indication that something like this was present in early Earth. That's why some less abundant elements are concentrated in some spots and all but nonexistent in the other.

 

Then chemistry plays an important role, of course. Elements close to one another in periodic table, for example elements from the same group, tend to stick together due to having similar outer electron shell configuration and being able to participate in the same reactions and that's why we have rare earth elements (REE) always stick together. Also, silver and gold in most cases go together as they tend to easily form an alloy.

 

And last, but not least geology plays its part. For any particular deposit there would generally be a geological reason for high concentrations of heavy elements. For example, for Banded iron formations - first photosynthetic bacteria producing oxygen and iron oxides precipitating from primordial ocean, for metal sulfide deposits it's metal-rich hydrothermal fluids coming through sea floor and enriching the overlaying strata. Basically, that really depends on the type of deposit and the element you're talking about.