Did Silicates Form on Early Earth Without Basic Aqueous Solutions?

[Ferrus]

How did the silicates form during the period in which a gas of silica coalesced into a ball of molten silicon? I thought silicate typically only forms in basic aqueous solutions, which clearly did not exist at this period.

 

[Borek]

One of the ways of synthesizing salts is - metal oxide plus acidic anhydride -> salt. In the presence of metal oxides silica will react creating silicates - slowly, but there was plenty of geological time. Plus, once the mixture got hot, reaction speed up.

 

[Ferrus]

Excellent thank you.

What is mechanism of their reaction? I have seen the mechanisms for oxides on water with both acidic and basic characters, electrostatics, etc... how without the polar molecules of water are they able to mediate a reaction? Is it just a matter of gibbs free energy reduction, along with a large activation energy (hence slow speed under normal conditions) reflecting the very awkward transition molecules?

 

[Borek]

No idea about the detailed mechanism, for sure silicates are thermodynamically much more stable than silica/metal oxides mixture. Oxides - especially of first two groups metals - are mostly ionic, which probably plays a role.

 

[Studiot]

There is quite a lot of useful information in Navrotsky p300ff (The Physics and Chemistry of Earth Materials - Cambridge) in the chapter on high temperatures and high pressures and plenty of references at the end of that chapter.

Go well