Suppose that it is a result of a natural process. How would you create the conditions necessary for supercriticality given only plate tectonics, an atmosphere,

Suppose that it is a result of a natural process. How would you create the conditions necessary for supercriticality given only plate tectonics, an atmosphere, multiple asteroid impacts, and liquid water? One necessary prerequisite is enrichment of the Uranium. We currently use industrial processes to do this. How else might uranium become enriched, absent an industrial process? Are there other elements or isotopes that are also capable of supercriticality? Could those become enriched through a natural process? I'm not arguing against Occam's Razor. I actually think, given those broad questions, that we haven't even begun to scratch the surface of the simplest explanation(A).