Les B., if you go to The authoritative mines site you will see a lot of apparent histories of treacle mines. Of my own personal knowledge, I know some of them cannot be real. I don't know why I used "cod" to define an invented humorous history, full of detail to add verisimilitude to an otherwise bald and unconvincing narrative. I don't know why, if that is correct usage, it is so. Related to red herring, maybe!
If you google the terms "treacle mine" and "treacle mines" you will find a good number of other sites which play the same trick, some with geological diagrams. There seems to be something about the term that encourages it. One of my ICT Club at school, who had not hitherto heard of treacle mines, and had not seen any of the sites, when told of them to search at home, immediately produced the concept of the Great Treacle Sea, which is obviously the source of at least some of the deposits of molassinite.