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.
https://pdfs.semanticscholar.o…b0e96922a7055ab3634b8.pdf
Io's heat is attributed to tidal motions, but that might only contribute...