Tape devices are not suited for random access (they don't provide random-access), i.e. they are not block devices. And LUKS is designed for block devices, like e.g. XFS is a filesystem for block devices. You can't
mkfs.xfs on a tape device, can you?
Thus, go with the OpenSSL streaming cipher encryption via pipe approach, like suggested by Ignacio.
Similar to the design of LUKS, you could generate a large random key for the streaming encryption which you then encrypt as file e.g. with
gpg. That means you are flexible to change this 'envelope-key' and you could encrypt the 1st key with multiple public keys, such that multiple persons have access to it (without the need of a perhaps insecure key-exchange).