Where is Phazon Elite in Metroid Prime Origins?

Phazon Elite is fought in Elite Research (Phazon Mines). Beating it gets you: Artifact of Warrior.

How to get there

Starting a new game from Landing Site, get these first, in this order, then go to Elite Research (143 rooms in all):

1. Missile Expansion in Landing Site (0 rooms; needed for Elite Research (Missile))
2. Space Jump in Alcove (1 room; needed for Elite Research (Space Jump Boots))
3. Morph Ball in Ruined Shrine (10 rooms; needed for Elite Research (Morph Ball))
4. Power Bomb Expansion in Magma Pool (6 rooms; needed for Elite Research (Power Bomb))
5. Morph Ball Bomb in Burn Dome (11 rooms; needed for Elite Research (Morph Ball Bomb))
6. Charge Beam in Watery Hall (7 rooms; needed for Wave Beam (Charge Beam))
7. Varia Suit in Sunchamber (7 rooms; needed for Wave Beam (Varia Suit))
8. Wave Beam in Chapel of the Elders (20 rooms; needed for Ice Beam (Wave Beam))
9. Boost Ball in Phendrana Canyon (8 rooms; needed for Ice Beam (Boost Ball))
10. Super Missile in Observatory (10 rooms; needed for Spider Ball (Super Missile))
11. Spider Ball in Quarantine Cave (9 rooms; needed for Ice Beam (Spider Ball))
12. Ice Beam in Antechamber (39 rooms; needed for Elite Research (Ice Beam))