I would think it more chemical than via electrolysis. It’s not like the rocks formed and all of a sudden were cast into saltwater. The deposition of metals and oxygen creation would have to be part of the same reaction.
That was my first thought - that the rocks trapped oxygen when they formed. Or that they are catalyst splitting ocean H2O.
:: I would think it more chemical than via electrolysis. ::
Agreed.
Did they also test for twice as much Hydrogen?