1,000 Space Marines VS The Olympians

1,000 of the Adeptus Astartes are sent to conquer Mount Olympus and kill the false Gods living there. No specific chapter in mind, but it’s up to you to choose. Each Marine is equipped with their standard weapons and armor. Some have Chainswords and Bolters, others have Plasma weapons, Melters, Shields, Grenades and a few Power Weapons spread throughout.

They don’t have access to Tanks but they do have several Thunder Hawks available. The Battle Barge is either destroyed or out of range so assume they can’t just hit the win button and Exterminatus the shit out of everyone. This also means they have no reinforcements and limited ammunition besides strategic drops from their gunships.

All Olympian Gods are present, as well as their servants and children. They all have access to their own standard weapons, armor & equipment, along with their various powers and abilities. Assume the Astartes have a few librarians fielded just in case, one of whom is Alpha Level.

What would the outcome be?