SAM,
We don't need any great military brains on here when we have you....
I don't suppose it has occurred to you that the location and activities of the Iranian Kilos are closely monitored on a daily basis? Do you think they could mine the Straits totally unnoticed....
As for Iran closing the straits, that would fairly quickly alienate most of the world against them, which isn't exactly going to help their cause in the fight against the 'Great Satan'! Then again, maybe they don't care.....