The Mesoproterozoic Rayner Province in the Lambert Glacier area: its age, origin, isotopic structure and implications for Australia–Antarctica correlations

Abstract

Abstract Within the Rayner Province in the Lambert Glacier area, two Proterozoic lithotectonic zones are distinguished, which differ in age and lithology. In the Fisher Zone, a significant juvenile component (ε Nd ( t )=+2 to +4) is represented by mafic, intermediate and felsic plutonic and volcanic rocks; the tectonomagmatic processes were concentrated at c. 1400–1200 Ma. In the Beaver Zone, orthogneisses record multiple emplacement, metamorphism and ductile deformation at c. 1150–930 Ma. New U–Pb SHRIMP-II zircon ages ( c. 1140 Ma and 1095 Ma – protolith emplacement; c. 950–850 and c. 540 Ma – metamorphism), chemical and Sm–Nd isotopic data indicate that both zones have their continuations in the eastern Amery Ice shelf coast. The Rayner Province has some geological features in common with the Albany-Fraser Orogen in Western Australia, suggesting that these regions evolved in similar tectonic environments at c. 1400–1300 Ma, followed by steady closure, from east to west, of the ocean that separated the Mawson Continent from Western Australia. Supplementary material: Chemical compositions of rocks, a summary of trace element ratios, a summary of published U–Pb dates, field photo views, new U–Pb analyses by SIMS SHRIMP-II and new Sm–Nd data are available at www.geolsoc.org.uk/SUP18621