Proterozoic fold belts in Australia developed by the reworking of Archaean basement. The nature of this basement and the record of Archaean-earliest Proterozoic evolution and metallogeny is best preserved in the Western Australian Shield. ln the Yilgarn Craton, a poorly-mineralized high-grade gneiss terrain records a complex, ca. 1.0 b.y. history back to ca. 3.6 b.y. This terrain is probably basement to the ca. 2.9~2.7 b.y. granitoid-greenstone terrains to the east-Cratonization was essentially complete by ca, 2.6 b.y. Evolution of the granitoid-greenstone terrains of the Pilbara Craton occurred between ca. 3.5b.y. ano 2.8 b.y. The tectonic setting of all granitoid-greenstone terrains remains equivocal. Despitc coincidcnt calc-alkalinc volcanism and granitoid emplacement, and broad polarity analogous to modem are and marginal basin systems, there is no direct evidence for plate tectonic processes. Important differences in regional continuity of volcanic sequences, lithofacies, regional tectonic patterns and metallogeny of the terrains may relate to the amount of crustal extension during basin formation. At one extreme, basins possibly representing low total extension (e.g. east Pilbara) are poorly mineralized with some porphyry-stylc Mo-Cu and small sulphute-rich volcanogenic or evaporitic deposits reflecting the resultant subaerial to shallow-water environment. ln contrast, basins interpreted to have formed during greater crustal extension (e.g. Norseman-Wiluna Belt) are richly mineralized witb Ni-Cu and Au deposits, due to widespread eruption of komatiitcs and rapid subsidence of the volcanic pile. Some greenstone basins show intermediate character. Deposition of the earliest Proterozoic volcanics and shell sediments of the Hamersley Basin predated stabilization of the Yilgarn Craton. The change in tectonic setting heralded a major change in mctallogenesis from dominantly volcanic-related Archaean deposits to major sedimentary ore associations. The earliest of which were the iron ores of the Hamersley Group.Proterozoic fold belts in Australia developed by the reworking of Archaean basement. The nature of this basement and the record of Archaean-earliest Proterozoic evolution and metallogeny is best preserved in the Western Australian Shield. ln the Yilgarn Craton, a poorly-mineralized high-grade gneiss terrain records a complex, ca. 1.0 b.y. history back to ca. 3.6 b.y. This terrain is probably basement to the ca. 2.9~2.7 b.y. granitoid-greenstone terrains to the east-Cratonization was essentially complete by ca, 2.6 b.y. Evolution of the granitoid-greenstone terrains of the Pilbara Craton occurred between ca. 3.5b.y. ano 2.8 b.y. The tectonic setting of all granitoid-greenstone terrains remains equivocal. Despitc coincidcnt calc-alkalinc volcanism and granitoid emplacement, and broad polarity analogous to modem are and marginal basin systems, there is no direct evidence for plate tectonic processes. Important differences in regional continuity of volcanic sequences, lithofacies, regional tectonic patterns and metallogeny of the terrains may relate to the amount of crustal extension during basin formation. At one extreme, basins possibly representing low total extension (e.g. east Pilbara) are poorly mineralized with some porphyry-stylc Mo-Cu and small sulphute-rich volcanogenic or evaporitic deposits reflecting the resultant subaerial to shallow-water environment. ln contrast, basins interpreted to have formed during greater crustal extension (e.g. Norseman-Wiluna Belt) are richly mineralized witb Ni-Cu and Au deposits, due to widespread eruption of komatiitcs and rapid subsidence of the volcanic pile. Some greenstone basins show intermediate character. Deposition of the earliest Proterozoic volcanics and shell sediments of the Hamersley Basin predated stabilization of the Yilgarn Craton. The change in tectonic setting heralded a major change in mctallogenesis from dominantly volcanic-related Archaean deposits to major sedimentary ore associations. The earliest of which were the iron ores of the Hamersley Group.