LenovoA806-Bootloop and wont pass manufacture logo

[Radon66]

I have a Lenovo A806 with TWRP and CM12.1 Xperia mix. I can't get past the manufacturer logo. It seems to me that the system partition is corrupted. I can only enter fast boot or recovery when using ADB to boot into them, and I was able to erase all partitions other than /system in recovery. I want to erase it so I can do a clean install of my ROM and GApps. When I try to delete /system, I get the error E:Unable to mount '/system'. My question is how do i fix it?