Video available on request from Steam.
When Fragment of the Enigma is equipped, it doesn’t apply any spark charges. I have tried with my melee weapon, teleporting to the creatures, various spells (lightning blast, disintegrate, runic invocation with 3 gon symbols, etc). Notably, I have not tried mana strike with the sparke charge node activated – I’m hoping you don’t need that.
I’m also assuming that you will see an icon over the creature when a spark charge is present.
I asked in chat, to see if it was PEBCAK but no one had any ideas.