Sea salt has a range of different minerals in it, like Iodine. Salt mines has prehistoric salt that has had these minerals squeezed out. The oil industry loves salt domes, because there is usually oil there as well. I remember years back an oil well drilled into the salt mine underneath and the whole lake went down the hole. In fact, everything on the lake went down the hole, including the drilling well! After a while it all came spitting back up out of the well. this happened near Delcambre many years ago. The drilling company had to pay a large damage suit brought by the salt mine owners!
What might be true for one area is not the same in others. There are many major salt mine over here but with out the trace of oil.
__________________ "Ask not what your country can do for you"