When armed, a Detonator mine emits 3 vertical laser-tripwires that acts as an area-denial indicator. Disrupting these lasers will set off the mine. When fired at organic targets, the mines will detonate instantly instead of deploying.
It is unknown exactly what role does these mines play in mining, seeing how firing a mine at (mostly) static objects would serve little purpose. They might, however, have been used to destroy incoming debris and asteroids when planted on the plating of ships, though ships does move at a relatively fast pace, and the lasers stretches indefinitely, they would most likely be tripped eventually as a ship move through space, so the debris-clearing purpose might be incorrect. It is most plausible that these were designed for military purposes, as an area-denial method.
The Detonator's alt-fire will also disarm deployed mines, so that undetonated planted mines can be recovered. It is this unique particularity of the ammunition that causes the detonator exploit, allowing to generate infinite ammo and so, credits.