Precambrian Iron-Formations of Australia

The Precambrian iron-formations of the Australian continent can be classified naturally into six divisions which are definable with about equal validity by geographical separation, lithologic type, stratigraphic geometry, and age. The divisions, in order of decreasing age, are: (1) Iron-formations of the Yilgarn Block and Pilbara Block of Western Australia: these blocks lie, respectively, between the approximate limits 116-123 ø east and 26-34 ø south, and 118-121 ø east and 20-22 ø south. (2) Iron-formations of the Hamersley Group of Western Australia: these lie in a basin developed over older Precambrian rocks between approximate limits 116-122 ø east and 21-23 ø south, between the two blocks referred to in (1). (3) Those of the Cleve Metamorphics of South Australia, whose main linear outcrop is in the Middleback Range at about 137 ø east between 33 ø and 34 ø south.