BHP may have elected not to continue with negotiations, or may have just waited to see what the actual Wyloo off would be as there was talk of a new company etc. Its clear its a straight cash offer and if you wish to remain a shareholder, uou would elect to hold your shares and Noront still exists as it is.

In my opinion BHP has the right to amend its agreement to a matching or superior offer. If so, it will remain in tact. 

BHP may also let its offer expire, and resubmit something else as well. 

I do feel BHP will respond, it petty cash for them at this point still.

good luck!

Navi