Global oil prices plunged and Australian shares have enjoyed a sharp jump after US President Donald Trump abandoned his threat of annihilation at the 11th hour and struck a deal with Iran.Both countries have agreed to a two-week ceasefire to allow ships to pass through the Strait of Hormuz, brokered by Pakistan.Following the announcement, futures for US crude oil fell 14.7 per cent to $US96.27 a barrel while futures for Brent crude oil (the global benchmark for oil prices) sank