The majority of the damage clearly doesn't have raised edges on the pits. The root of the problem is detonation.

Did detonation cause a spark plug insulator to fail and bounce around a little? Maybe. Did a chunk of the HG end up in the cylinder after detonation stretched the head studs? Maybe.

Root cause though is 100% detonation or possibly pre-ignition, although it doesn't show a hot spot but maybe it was something in the head causing pre-ignition?

 

The damage that I can clearly make out has raised edges, its hard to make out most of the smaller marks on my phone. So if you're seeing what I'm not, it very well could be detonation.

 

I'll check when I get home but I think it's more pitted out than raised. The second enlarged picture at the top center shows one raised spot and that's about the only one that looks raised and not pitted out.