Hi, BR.

I thought of tectonics, but it's interesting how these mountains left the old crater that 'they are on' intact. So it seems from these images.

"Does it seem possible that the mountain chain, if that's actually what it is, formed at a crack in the surface, and that fluid/semi-fluid material from the interior was pushed upwards, freezing of course at the surface? A process analogous to what is thought to go on at Europa even as we speak. Only of course at the distance of Iapetus/Saturn, temperatures are colder, surfaces more rigid, etc. Ergo, a crack might offer an outlet for interior material -- ices of some sort -- but cold conditions might preclude any substantial resurfacing."

It would also depend on just how old these 'mountains' are.

I have to admit that at first glance, I thought of the pearls left over from comet Shoemaker-Levy as it broke up over Jupiter. :}