Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

The reply to a question about nucleosynthesis, that heavier than iron elements are produced in supernovae explosions, raised for me the following question which I could not answer by googling. Partially because the search for planets and stars brings out astrology answers!

Explosions are dispersive, nevertheless we find minerals in clumps, not only uniformly dispersed in the ground. Is there a coherent presentation that explains how minerals end up in veins and bands?

share|improve this question
6  
It looks like this is due to geochemical processes, not astrophysical processes: en.wikipedia.org/wiki/Ore_genesis –  Mitchell Porter Mar 18 '11 at 6:44
    
Is the question about Nucleosynthesis (the creation of heavy elements)? Or about the concentration of one or more elements via geochemical activities? –  Omega Centauri Mar 18 '11 at 14:30
    
I have found that the only suggestion for the appearance of heavy elements higher than Fe in the binding energy curve,comes from supernova explosions and scatterings of neutrons etc. So it is on the creation of heavy elements. Of course if veins and bands can come out from a uniform soup of elements by a reasonable model it would also explain the observations. –  anna v Mar 18 '11 at 16:04
    
""if veins and bands can come out from a uniform soup of elements by a reasonable model"" This model is called mineralogy and is very old and proven. –  Georg Mar 18 '11 at 16:12

3 Answers 3

up vote 5 down vote accepted

Mostly because they are heavy.

Rocks erode putting their constituents into solution, the heavy stuff settles out in river/sea beds, and metals are heavy.

For many metals hydrothermal process are more important. Super hot water deep in the earth dissolves the rock containing the minerals, it moves along cracks in the rock and cools depositing the salt and metals as lines in the rock.

In an asteroid with no geological process the metals are found in their raw state having cooled directly from the original ball of primeval gas

share|improve this answer
    
"the heavy stuff settles out in river/sea beds" - are you suggesting that veins can be essentially the "fossilized" remains of ancient stream beds? –  Michael yesterday

Almost all the various "metals" (like primitive tribes that count "1, 2 many", the astronomers describe the elements as "hydrogen, helium, metals") in the earth come from supernovae explosions. So the uranium got there pretty much the same way that the silicon, iron, oxygen, potassium, etc.

share|improve this answer
1  
In that case the uranium would be uniformally distributed every million atoms - and so rather tricky to find and mine. –  Martin Beckett Apr 19 '11 at 22:25
    
@Martin; Indeed, this is generally true. Per the wikipedia article: "Uranium is one of the more common elements in the Earth’s crust, some 40 times more common than silver and 500 times more common than gold.[1] It can be found almost everywhere in rock, soil, rivers, and oceans.[2] The challenge is to find those areas where the concentrations are adequate to form an economically viable deposit." –  Carl Brannen Apr 19 '11 at 22:53
    
Furthermore, having started college as a mining engineer, the concept that "the heavy stuff settles out in river/sea beds" is more or less true, but that "metals are heavy" has little to do with where uranium deposits appear. This is because uranium ores, while generally dense, are easily dissolved and are not sufficiently tough to appear as placer deposits. See the wikipedia article: en.wikipedia.org/wiki/Uranium_ore and look up information on placer deposits. –  Carl Brannen Apr 19 '11 at 22:55

p.s. I have found a course notes precis and it seems there are several models proposed.

Completely out of my depth, I would propose that if matter above Fe in the binding energy curve were in a concentration within a "protoplanet" with a high enough pressure, it could form a quark gluon plasma, and then all type of nuclei could precipitate/crystalize as conditions change, according to their quantum mechanical state function, so a supernova explosion might be sufficient to make uranium, but not necessary. This would explain clumping and veins.

share|improve this answer
3  
""if matter below Fe were in a concentration within a protoplanet with a high enough pressure, it could form a quark gluon plasma,"" a quark-gluon-plasma does not even exist in the core of stars, how should that develop in a protoplanet? –  Georg Mar 18 '11 at 12:44
1  
I found this interesting diagram blogs.uslhc.us/the-quark-gluon-plasma . Also found the hypothesis that neutron stars are a quark gluon plasma. Maybe during the big bang when the temperature reaches the plasma stage heavier elements than those permitted to form by the binding energy curve are crystallized out en mass, clumping together. My objective is not to have a supernova as the only mechanism of creating the heavy elements, because explosions are dispersive. –  anna v Mar 18 '11 at 15:58
    
""My objective is not to have a supernova as the only mechanism of creating the heavy elements, because explosions are dispersive. "" But how will You get the transirons out of the neutron stars? Only after some dispersion there is a chance for the material to be incorporated in a planet. –  Georg Mar 18 '11 at 16:09
1  
you beat me to asking it, but roughly this question came to mind as i was lying in bed with my wife, and intuitively i reached this same conclusion. at that point, in bed, relaxed, it seemed extremely unlikely to me somehow that astro-snowballed uranium would just end up just so in planetary crust, due to the large number of collisions that would be required over time to 'snowball' large amounts of helium and hydrogen together into uranium and all the way into planetary crust in the backwaters of the universe, the local group, no less, just in time for it to keep decaying radioactively... –  ixtmixilix Feb 24 '12 at 0:36

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.