how to remove my gmail from facebook?

[Dean]

To add or remove a linked account,
navigate to the "Linked Accounts" section of your Account Settings page.
Click "Change" to see a list of all of the accounts that are currently linked to your Facebook account.


If you just want to quit getting the emails, try this
Account --> Account Settings --> Notifications
Than select group of notifications (Facebook, photos..) and uncheck every square that is checked!

That will stop the messages.

D