It is not possible to prohibit the editing of specific fields in a record that was created using the Duplicate icon. When a record is created using the Duplicate icon, the values of all of the fields into which values can be entered are copied, and the copied values become editable.

For your reference, the following workarounds are possible using either the App Action feature or access permissions.

• Workaround using the App Action feature
  By specifying the same app (the app you are currently using) for Target in the settings of the App Action feature, you can create a button to transcribe (copy) a value of a specific field. This button can be used separately from the Duplicate icon.
  Creating an action to duplicate a record in the same app
  
  

• Workaround using access permissions
  In the Permissions for fields settings, specify a user for a target field and deselect the Edit checkbox for one or more users. This prohibits the users from editing the field. When a specified user duplicates a record, they will not be able to edit the field and the field will be saved as a blank field.
  Configuring permissions for fields