New U-Pb zircon ages from the Denman Glacier area, East Antarctica, and their significance for Gondwana reconstruction

Abstract

Two new U-Pb zircon ages from the area immediately west of Denman Glacier in Antarctica show that its geological history differs from that of the Obruchev Hills and Bunger Hills, to the east of the glacier. A crystallization age of 516.0 ± 1.5 Ma for syenite is by far the youngest primary age reported for this region, whereas tonalitic orthogneiss from Cape Charcot, the oldest known local rock, was derived by the high-grade metamorphism and deformation at 2889 ± 9 Ma of a 3003 ± 8 Ma igneous precursor. Both major populations of zircon in this rock lost Pb at 500–600 Ma. Although the Sm-Nd characteristics of the entire region resemble those of the Albany Mobile Belt of Western Australia, the Sm-Nd systematics of the felsic gneisses and plutonics are too old to allow direct correlation with the rocks of the Naturaliste Block (Western Australia), a potential key element for Gondwana reconstruction. However, the possibility exists that there is an indirect relationship between the Naturaliste Block and the region immediately west of Denman Glacier.