GeologyofWesternAustralia.docVIP

Geology of Western Australia Western Australia is made up of several pieces of continental crust that developed independently in different parts of the world and then later joined together. As the landmass we know as Western Australia developed, parts of these continents broke away and dispersed again - but this time in different configurations. At one stage in its history, Australia was part of a super-continent called Gondwanaland, which also included Africa, South America, India and Antarctica. The history recorded in the rocks of Western Australia is longer than anywhere else on Earth and extends back nearly 4 billion years. The oldest major piece of continental crust in Western Australia is called the Pilbara Craton and it lies between Karratha, Port Hedland, Marble Bar and Nullagine. It formed more than 3 billion years ago from the amalgamation of older volcanic rocks (greenstones) and granite. A larger fragment of an ancient continent, called the Yilgarn Craton, extends from Meekatharra south to Mount Barker, and from the Darling Range at Perth to east of Kalgoorlie. This crust is largely made up of granite and greenstones that were joined together some 2.6 billion years ago. Most of the gold deposits of Western Australia are located in this Yilgarn Craton. The gold formed when hot fluids moved up through fractures created during the last stages of consolidation of this mass of continental rocks. About 1.3 billion years ago, the combined Pilbara and Yilgarn continental crusts were joined to northern and central Australia, and another continent comprising much of South Australia and eastern Antarctica. Mountain belts formed along the junctions of these three continents. Fossils and other evidence of life are scarce in all rocks formed more than 540 million years ago. The only relatively abundant fossils are stromatolites, and Western Australia contains the world’s longest record of stromatolites. Higher levels of oxygen and carbon dioxide in the atmosphere an