Consider a redox cell of geological proportions. These have existed in the past and some still exist today. Probably not much to do with most concretions in my opinion, but they were/are able to move hundreds of millions of tonnes of various elements over a long period. Low voltage, locally low current, but of a truly incredible scale. Unoptimized, they run by themselves for millions of years. With a little to considerable help, a nearly unlimited electricity source. The trick is finding the special places where the geocell components are robust, and where a helping hand makes the most improvement, while making the least mess.
Yes, certainly some evidence planetary redox is around.
Io's heat is attributed to tidal motions, but that might only contribute...