Pb isotopic domains from the Indian Ocean sector of Antarctica: implications for past Antarctica-India connections

New feldspar lead isotope compositions of crystalline rocks from the Indian Ocean sector of East Antarctica, in conjunction with the review of data from elsewhere within the continent and from continents formerly adjacent within Gondwana, refine boundaries and evolutionary histories of terranes previously inferred from geological mapping and complementary isotope studies. Coastal Archaean Vestfold and Napier complexes have overlapping compositions and had Pb isotopes homogenized at 2.5 Ga sourced from or within already fractionated protoliths with high and variable U–Pb. Identical compositions from the Dharwar Craton of India support a correlation with these Antarctic terranes. The Proterozoic–Palaeozoic Rayner Complex and Prydz Belt yield more radiogenic compositions and are broadly similar and strongly suggest these units correlate with parts of the Eastern Ghats Belt of India. A strikingly different signature is evident from the inboard Ruker Complex, which yielded unradiogenic compositions. This complex is unlike any unit within India or Australia, suggesting that these rocks represent exposures of an Antarctic (Crohn) Craton. Compositions from the enigmatic Rauer Terrane are consistent with a shared early history with the Ruker Complex but with a different post-Archaean evolution

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

<p>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(<em>t</em>)=+2 to +4) is represented by mafic, intermediate and felsic plutonic and volcanic rocks; the tectonomagmatic processes were concentrated at <em>c.</em> 1400–1200 Ma. In the Beaver Zone, orthogneisses record multiple emplacement, metamorphism and ductile deformation at <em>c.</em> 1150–930 Ma. New U–Pb SHRIMP-II zircon ages (<em>c.</em> 1140 Ma and 1095 Ma – protolith emplacement; <em>c.</em> 950–850 and <em>c.</em> 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 <em>c.</em> 1400–1300 Ma, followed by steady closure, from east to west, of the ocean that separated the Mawson Continent from Western Australia. </p

Pb isotopic domains from the Indian Ocean sector of Antarctica: implications for past Antarctica–India connections

<p>New feldspar lead isotope compositions of crystalline rocks from the Indian Ocean sector of East Antarctica, in conjunction with the review of data from elsewhere within the continent and from continents formerly adjacent within Gondwana, refine boundaries and evolutionary histories of terranes previously inferred from geological mapping and complementary isotope studies. Coastal Archaean Vestfold and Napier complexes have overlapping compositions and had Pb isotopes homogenized at 2.5 Ga sourced from or within already fractionated protoliths with high and variable U–Pb. Identical compositions from the Dharwar Craton of India support a correlation with these Antarctic terranes. The Proterozoic–Palaeozoic Rayner Complex and Prydz Belt yield more radiogenic compositions and are broadly similar and strongly suggest these units correlate with parts of the Eastern Ghats Belt of India. A strikingly different signature is evident from the inboard Ruker Complex, which yielded unradiogenic compositions. This complex is unlike any unit within India or Australia, suggesting that these rocks represent exposures of an Antarctic (Crohn) Craton. Compositions from the enigmatic Rauer Terrane are consistent with a shared early history with the Ruker Complex but with a different post-Archaean evolution. </p