Gary Coffman says in
:
On Sat, 03 Jul 2004 00:38:46 GMT, Martyn Harrison
wrote:
I'm fascinated by the "meteoric copper" idea.
I'm ok with the notion that elements up to Iron are formed
by gradual fusion processes inside stars.
But as far as I know, that's where these fusion processes
stop.
Copper isn't formed in that way.
So I can't see how a lump of space debris could reasonably
be copper. It could reasonably include a *bit* of copper,
but not easily *be* a copper lump. Iron yes, you certainly
get lumps of iron when, e.g. a supernova goes whomp, but
copper, no I don't see how that's going to happen.
So I find it enormously unlikely that a lump made
predominantly of copper might end up as a meteor. Does
anyone know if there is any credibility in this claim in
practice?
You're being confused by Eric's use of an obscure term of
art for geochemically processed copper originating in a
water saturated subsurface environment. All that "meteoric
copper" means in this context is that it was deposited
geochemically from a mildly acidic aqueous fluid whose
watery origin was surface precipitation
(rain-meteorology-meteoric), rather than liberation of
water of hydration in the deep rock.
A more complete explanation is that rainwater percolated
down through faults in volcanic rock and reacted with
volcanic sulphur to form a mild sulfuric acid solution.
This acid solution, raised to temperatures on the order of
350C in the basement rock (and still liquid due to the high
pressure there), then dissolved copper being held in more
complex oxide or sulphide form in the deep rock, producing
a solution of CuSO4. Over time, geologic processes forced
this copper laden solution back up towards the cooler
surface regions. When iron bearing rock was encountered,
the reaction
CuSO4 + Fe = FeSO4 + Cu
resulted. Since copper and iron sulphates are soluble in
water, they are free to move about in the rock following
fissures and faults. But metallic copper isn't soluble in
water, so after the reaction it is left behind to form
"veins" of native copper in the rock matrix.
Metallic copper is readily oxidized by Oxygen with dissolve
clorine under acidic conditions. Forms copper chloride which is
soluble in relative high concentrations. Nitrates and other
acids that are also present can do similarly. The problem with
Sulferic acid, the product of hydration of S03 produced by
volcanism is that it is incredibly unstable, and tends to
deprotonate protonating anything. This will result in the
protonation of NaCl forming NaHSO4 and HCl which is capable of
catalyzing the oxidation of metalic copper to copper I chloride.
When this is neutralized the copper with precipitate, forming
copper carbonates usually.
It is a certain Irony of chemistry that sulfate is an oxidant,
but because its so stable it generally doesn't act as an
oxidant, but HCL which is technically a reductant can catalyze
the oxidation of metals. The reason it can do this is that
metals generally form a coat of oxide on the surface that
prevent the underlying layers from oxidizing, the chloride ion,
In the case of copper, although sulfate can solubilize copper I
and II salts, the most common metal that coats copper is calcium
or other common divalent cations. This is the reason its not
good to have absolutely pure water running through copper, a
small amount of calcium coats the copper and protects it.
However calcium carbonates and calcium/copper complexes with
carbonate are completely stable in acidic chloride solutions,
and once the divalent cations are stripped from the surface of
the copper it is free to oxidize with oxygen free radicals that
are dissolved in water. Thus if the metalic copper is exposed to
s acid sulphate solution, with contaminating salts of chlorine,
floride or bromine, the consequence will be the oxidation of the
metal.
--
Philip
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