Once an USB storage device with several partitions gets connected to the system, something automatically mounts each filesystem on a partition in read-write mode. Filesystems on LVM volumes are recognized, but not automatically mounted. LUKS partitions are entirely ignored.
To avoid datacorruption during a crash, one can unmount these partitions easily in the Nautilus UI. But once the screen is locked, and later unlocked, something mounts the filesystems again.
To me it is not clear at all what the benefit of that action would be.
The question is: what must be done to avoid these automounts during screen unlock?