I'm not sure about ASX but in the US we have t trades which are trades that are so big that the market makers can't show them/do them during the day. I forget the exact meaning but you can read here: http://www.investopedia.com/terms/f/formt.asp
MND Monadelphous inks $200M contract with Woodside to help build Pluto LNG – but will it make Scarborough cheaper?