The reduction potential of the earth

[sunspot]

Somethings has always confused me. It is currently assumed that the earth has a metallic iron/nickel core. The question I have is where did the reduction potential come from to make an elemental iron core when there was so much oxygen present? In other words, if one took the average composition of the earth, i.e., mostly oxygen, and heated and pressurized it, it would form a solution of sorts with the iron becoming iron oxide. To make metallic iron phase separate, one would need to add hydrogen or carbon to reduce the iron. With the earth's core 1000 times larger than the oceans, where did all the hydrogen and carbon go? Venus can support a dense atmosphere. Shouldn't the surface, crust and mantle of the earth have way more hydrogen and carbon?

[akcapr]

the iron formed long before the oxygen appeared, it formed wen some stars died. ANd also, the oxide layer/crust protects it from further oxidztion.

[sunspot]

That would account for the iron core but that raises another set of questions. First, if the iron came from spent stars where were these stars located and where did the rest of the iron go, seeing that spent stars should produce way more iron than needed for just the earth's iron core? With all this iron present near our solar system, why did only the earth get so much iron? Shouldn't the larger perimeter planets get first picks?

[insane_alien]

i believe mercury and venus have a higher percentage of iron than the earth. iron isn't the most abundant element on earth anyway. the iron/nickel core is solid because of the extreme pressures and not oxidised because

1. its too hot for the oxides to form in appreaciable amounts(we can use temperature only to smelt iron. the carbon is so we can extract the iron at a reasonable temperature where some things are solid.)

2. an iron/nickel alloy is resistant to rusting. i believe that there is a stainless steel that is an iron/nickel alloy.

3. there isn't a lot of free oxygen that deep in the earth. as it is a light element most of it has worked its way to the surface/ near surface.

[sunspot]

This sort of makes sense but something seems wrong. If I was to make a molten bath of magma and throw a piece of iron/nickel into it, it would dissolve into the bath. Chunks of iron hitting the earth might takes days or even years to reach the core, slowly moving within the dense mantle. In the mean time, they are flowing through something far more severe than subcrustal magma with a temp higher than the melting point of iron/nickel. The core is assumed at 10,000 K so the mid mantle may be 3000K. Iron/nickel is also a good conductor and should heat quickly. How does the iron survive and stays as iron without dissolving. It would appear to me once the iron/nickel dissolved high in the mantle, they are part of a hot high pressure mantle solution. Solutions stay uniform unless there is a potential created. If the iron precipated below the crust, that would make sense because of the thermal gradient. Most materials that dissolve at lower temp do not precipate at higher temp. Is there any example of this besides the iron core in nature?

[Tetrahedrite]

You've missed the point slightly, the matter that the earth was originally formed from contained a very high content of pure iron an nickel, much the same as many of the stoney meteorites that fall to earth these days do.

[insane_alien]

why would iron and nickel dissolve in magma? as far as i know molten rock(magma) is neither acidic or alkaline. i assume you mean that they melt and then mix in with the magma. this can happen on a small scale but when you then take it to VERY large scales things get a bit more complicated and funny stuff starts to happen. like the metals sinking to the core (yes it probably would take years and years, probably centuries to millenia) and forming a nice big lump.