You’ll start this quest by talking to Chief Lucan on the Operations level of the Nexus. Havarl only has one mineral deposit for you to plunder - from the Pelaav Research Station make your way east until you find a Forward Station midway between the Pelaav Research Station and a trench further east. From this Forward Station head north to find some ramps leading up to a Remnant structure, marked on your map as “To the Remnant Abyss”, southwest of which is a cave, inside of which you’ll find an Element Zero node.