Who made the frame? Your first job is to contact them and get their opinion on whether it can be fixed. If you can't get hold of them, take it to your local bike shop and get an opinion from someone with a clue. As I understand it, Alu frames can be repaired, but it's difficult and expensive compared to steel, especially when a part of the bike that comes under a lot of stress is involved.
Who made the frame? Your first job is to contact them and get their opinion on whether it can be fixed. If you can't get hold of them, take it to your local bike shop and get an opinion from someone with a clue. As I understand it, Alu frames can be repaired, but it's difficult and expensive compared to steel, especially when a part of the bike that comes under a lot of stress is involved.