sorting out initial file ownership under NTFS - maybe a little OT

hello,
It seems that when an NT user creates a file on an NTFS volume, the
user is assigned as the owner of the file, which is what I’d expect.
However, if the user is a member of the local administrators group, the
owner of the file is ‘administrators’.
This makes me wonder what, exactly, are the rules of who is assigned
as the initial owner of a file when no security descriptor is provided
through to CreateFile? Are users who are members of the local
‘administrators’ group a special case with regards to initial file
ownership? Can groups other than the local ‘administrators’ group own a
file?
If anyone could describe the rules or point me at some documentation
which descibes the rules, it would be appreciated.

Thanks,
Joel