New Sm–Nd, Rb–Sr, U–Pb and Hf isotope systematics for the southern Prince Charles Mountains (East Antarctica) and its tectonic implications

Abstract

We report isotopic (Sm–Nd, Rb–Sr and zircon Hf and U–Pb SIMS SHRIMP) data on rocks collected from various localities throughout the southern Prince Charles Mountains known as the Ruker Province. The area is made up of a high-grade metamorphic basement, overlain by variably deformed and metamorphosed supracrustal associations of Proterozoic age. The area comprises two distinct tectonic terranes, experienced major tectonothermal processes in the Archaean (ca. 3400–2800 Ma: the Ruker Terrane) or in the Palaeoproterozoic (ca. 2500–2100 Ma: the Lambert Terrane). New zircon U–Pb ages of ca. 3180–3150 Ma, ca. 2800, and ca. 2500 Ma were obtained for various orthometamorphic rocks from the Ruker Terrane and ca. 2200 Ma, ca. 1740 Ma, and ca. 920 Ma for syn-tectonic granitic veins and leucosomes from the Lambert Terrane. The Sm–Nd data provide evidence for the initial separation of the continental crust of the Ruker Terrane from the mantle mainly between ca. 3.2 and 3.4 Ga, but up to 3.8 Ga, and indicate the presence of two mantle reservoirs which correspond to (1) depleted to slightly enriched, and (2) ultra-depleted mantle. Some material was also derived from the mantle at ca. 2.7–3.0 Ga; the crust of this age apparently underlies the central part of the Ruker Terrane (the Cumpston Massif–Mt Newton block), which is also distinguished by younger (ca. 2.5–2.1 Ga) zircon ages. The Lambert Terrane contains subordinate ca. 3.6–3.8 Ga protoliths, and the bulk of the crust seems to have originated between 2.6–2.9 Ga from various mantle sources and it may represent an accretional complex onto the Archaean Ruker Terrane. We also summarize published isotopic data and propose an integrated geological evolution for both terranes of the Ruker Province, discuss its relationships with the bordering Rayner Province, and compare its isotopic features with other Precambrian cratons of Gondwana. The key geological features of the Ruker Terrane suggest a similarity to the Yilgarn Craton, which would imply considerable mineral resource potential of the Prince Charles Mountains.