Sm-Nd, Rb-Sr and U-Th-Pb systematics of granulite facies rocks from Fyfe Hills, Enderby Land, Antarctica

New Sm-Nd isotopic measurements made on granulite-facies metamorphic rocks from East Antarctica provide firm evidence that crust of ~3,500-Myr age exists in the Fyfe Hills. Zircon U-Pb data provide further documentation for a granulite-facies event 2,500 Myr ago, during which Rb, U, Sm and Nd were highly mobile. The U-Pb and Rb-Sr isotopic systems were seriously disrupted and in most samples give meaningless model ages. In contrast, Sm-Nd model ages were offset only slightly. A large time interval of 1,000 Myr between the times of crust formation and granulite-facies metamorphism has not previously been reported for Archaean rocks, and suggests that 2,500 Myr ago the Fyfe Hills may have been located in an Andean- or Himalayan-type continental margin where crust already 1,000-Myr old was involved in an orogenic event.