How to deactivate the automatic emails sent to administrator?
Enable and Install the Mailcontrol module and then go to admin/config/people/accounts turn off the checkbox.


  This small module extends original Drupal 7 account settings page with
  the ability to globally turn ON/OFF all standard mails.


By default Drupal 7 provides no option to globally disable the following mails:


Welcome (new user created by administrator)
Welcome (awaiting approval)
Welcome (no approval required)
Password recovery