I looked over my last post to you. Wow. That was pretty harsh! Sorry. it sounded much much worse than I intended. Yikes.
You are correct in that a well tempered evaporation or slow boil would have very little in the way of disolved solids. This is, after all, how one distills water or liquor.
But this is anything but a gentle boil, it was a wall of sea water trying to flood into a hundred mile wide white hot crater. This instantly flashed the water that touched the molten rock to live steam, so much steam that the edge of the ocean was held back from filling the hole for days. This was a days long steam explosion with the live steam shredding sea water off of the encroaching walls and blasting it and any mud it carried up into the stratosphere and near space to be distributed around the globe.
It is a recipe for pasteurized planet. That local heat gets carried world wide by the steam, as does the dirt and dissolved salts.
Compare this to the relatively gentle boiling a moonshiner does. Even with the slow, even heating a moonshiner needs a 'thump keg' to catch any chunks blown out of the mash by the heating process:
A large white hot crater? Well...