To Stop Block or Ignore FacebooK Group Chat Messages and & Email Notifications in facebook
Go to the facebook group page and then click Edit Settings on the top right corner of the facebook group page .
Once you click the facebook group edit settings button, you will see small popup window which will show the option to unsubscribe email notifications and group chat messages just by unchecking two check boxes as shown in the image below.
Once you have unchecked both of these options shown in the image above, click Save Settings button to save these preferences.
You can also ignore Group messages and Email Notifications by ignoring messages from non friends in this way you can receive Notifications only from your friends.