Isotopic dating and structural relationships of granitoids and greenstones in the East Pilbara, Western Australia

A structural Rb-Sr isotopic study has been made on two small areas in the eastern Pilbara block, Western Australia. The sites were chosen because they showed good interrelationships of granitoid and greenstone units. At Warrery Gap, on the western side of the Corunna granitic dome, the acid volcanics of the Duffer Formation (at the top of the lower Talga-Talga Subgroup of the Warrawoona Group) show some updating, but a good 3506 +- 62 Ma isochron, with initial ratio (IR) of 0.7006 +- 0.0011, was recognized, consistent with the 3452 +- 16 Ma zircon measurement of Pidgeon (1978). (Auth.)