Examining the Nuna-Rodinia supercontinent cycle in East Antarctica and testing correlations to the southwest United States: evidence from the Read Group (Shackleton Range) and the Nimrod Complex

The Read Group of the southern Shackleton Range and the Nimrod Complex of the central Transantarctic Mountains (cTAMs) form two cratonic blocks with unknown spatial extent and ambiguous crustal affinities. They may form an extension of the Mawson Continent, which is generally thought to adjoin the Gawler Craton of South Australia with the Adélie Craton of East Antarctica. Additionally, variations of the original SWEAT (SouthWest United States – East AnTarctica) hypothesis for the Nuna-Rodinia supercontinent cycle envisages that the Mojave and Yavapai orogenic provinces of the American Southwest continue into East Antarctica, either via the Shackleton Range or beneath the Ross-Delamerian orogen in the cTAMs.

New U-Pb zircon geochronology and whole-rock geochemical analyses of meta-igneous suites from the Read Group indicate arc-related magmatic pulses at c. 1850–1825, 1810–1790, and 1780–1770 Ma. The extensive metasedimentary and metavolcanic paragneiss sequences of the Read Group are defined by detrital zircons with primary age peaks at c. 1830 Ma and secondary age peaks between 2700–1900 Ma. The paragneisses are cut by 1810–1770 Ma granitoid intrusions, demonstrating that their formation was prior to c. 1810 Ma. K-feldspar Pb isotope compositions from the Read Group (μ = 10.0–10.1) are different to the Nimrod Complex (μ = 8.1–9.8), suggesting that the Read Group and the Nimrod Complex are not contiguous and are therefore unlikely to form a coherent cratonic block with the Gawler-Adélie cratons. By contrast, K-feldspar Pb and zircon Lu-Hf isotope compositions from the Read Group are an excellent match for the Mojave and Yavapai provinces. The Mojave-Yavapai provinces also have coeval magmatic pulses and matching detrital zircon age spectra to the Read Group. A tectonic piercing point between the Shackleton Range and Mojave province is supported by the new data and is consistent with the Laurentian affinity of the Mesoproterozoic Coats Land block to the north, raising the possibility that both Coats Land and the Shackleton Range are remnants of the Great Proterozoic Accretionary Orogen, which remained attached to Laurentia throughout the Nuna-Rodinia supercontinent cycle until the break-up of Rodinia at c. 750 Ma.