It’s been almost 10 years since I pointed out that hydrocarbons in the Earth’s crust can’t be coming from decaying plant matter (and here). That’s a good explanation for coal, but for hydrocarbons, it doesn’t provide enough hydrogen unless the soil is pouring out oxygen. Which it isn’t.
Except now they’ve found a rare type of diamond. They’ve concluded that it came straight from the mantle, erupting through the Earth’s crust without spending significant time there.
And it’s full of an olivine mineral called ringwoodite. Ringwoodite can lock up hydroxide ions within its structure.
Hydroxide ions are 2/3 of a water molecule. The other part is a hydrogen ion.
It's actually the confirmation that there is a very, very large amount of water that's trapped in a really distinct layer in the deep Earth
But that would mean that there’s excess hydrogen ions down there too. Where’d all the hydrogen ions go?
One possible explanation is that the highly chemically reactive hydrogen ions percolated upwards, and reacted with carbon sinking from the surface to form hydrocarbons.
If that’s the case, you can stop worrying about running out of oil, gas, or natural gas any time in the next few millenia.