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The Shackleton Range is a truncated Pan-African Orogen situated at the Weddell Sea margin of East Antarctica. It almost exclusively consists of basement rocks exposed at an elevated, escarpment-bound palaeosurface and is covered locally by patchy remnants of Ordovician, Permian and, controversially, Jurassic terrestrial deposits. This inventory does not match the geological record of any other place in Antarctica. Here we reconstruct the Phanerozoic evolution of the Shackleton Range by means of a multi-disciplinary approach combining petrological, geochemical and geochronological data with thermal history models of zircon and apatite fission track (ZFT, AFT) and (U–Th–Sm)/He (AHe) data. Petrographic, geochemical and 40Ar/39Ar analyses of a sedimentary cover sequence identify volcaniclastic rocks related to the Ferrar/Karoo magmatic event. Thermal history modelling of ZFT ages of 160–215 Ma, AFT ages of 124–225 Ma, AHe ages of 95–169 Ma and kinematic proxies in combination with geological information indicates a complex thermal history comprising at least three cooling episodes interrupted by reheating pulses. Thermal history refers to inversion of part of the Carboniferous–Triassic Transantarctic Basin prior to the 180 Ma Ferrar/Karoo Event and formation of an up to 3.4 km deep extensional Jurassic – Early Cretaceous basin due to Weddell Sea rifting. Basin depth was diminished by regional middle Cretaceous stress field changes. Final basin inversion and surface uplift were likely triggered by far-field tectonics and climatic influence. This history represents a typical example for the transition from an active to passive margin setting along the outer rim of Gondwana.

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Structural investigations in western Sør Rondane, eastern Dronning Maud Land (DML), provide new insights into the tectonic evolution of East Antarctica. One of the main structural features is the approximately 120 km long and several hundred meters wide WSW-ENE trending Main Shear Zone (MSZ). It is characterized by dextral high-strain ductile deformation under peak amphibolite-facies conditions. Crosscutting relationships with dated magmatic rocks bracket the activity of the MSZ between late Ediacaran to Cambrian times (circa 560 to 530 Ma). The MSZ separates Pan-African greenschist-to granulite-facies metamorphic rocks with "East African" affinities in the north from a Rayner-age early Neoproterozoic gabbro-tonalite-trondhjemite-granodiorite complex with "Indo-Antarctic" affinities in the south. It is interpreted to represent an important lithotectonic strike-slip boundary at a position close to the eastern margin of the East African-Antarctic Orogen (EAAO), which is assumed to be located farther south in the ice-covered region. Together with the possibly coeval left-lateral South Orvin Shear Zone in central DML, the MSZ may be related to NE directed lateral escape of the EAAO, whereas the Heimefront Shear Zone and South Kirwanveggen Shear Zone of western DML are part of the south directed branch of this bilateral system.

40Ar/39Ar and U–Pb data from five structural domains constrain the late Neoproterozoic – early Palaeozoic tectonothermal history of the eastern part of the East African–Antarctic Orogen in Sør Rondane. A total of 27 new Ar/Ar ages span 570–474 Ma, roughly corresponding to the age range of three generations of syn- to post-tectonic granitoids. The ages are distinct for the five structural domains. The oldest cooling ages come from the weakly deformed southern part of the SW Terrane of Sør Rondane (SW Terrane S), a sliver of a Tonian island arc, which escaped much of the late Neoproterozoic accretionary deformation. This terrane was intruded by the oldest and largest granitoid complex at c. 640–620 Ma. The oldest Ar/Ar amphibole and biotite ages of 570–524 Ma are from the Main Shear Zone, along the northern margin of the SW Terrane S sliver. It hosts granites of age c. 584–570 Ma strung out along the shear zone. Two younger granitoid phases are recorded in the adjacent four terranes to the west, north and east of the SW Terrane S, and correlate with the younger group of Ar/Ar biotite ages spanning 513–474 Ma. We interpret the magmatic and cooling history of duration > 150 Ma to reflect repeated phases of accretion, magmatism and reactivation, that is, collage-style tectonism, partly pre-dating the incorporation of Sør Rondane into Gondwana. The study area first accreted to the cryptic Valkyrie Craton in Tonian times, was then ‘sandwiched’ between the Kalahari and Indo-Antarctica cratons, and experienced extensional tectonics and elevated heat flux due to lithospheric delamination, which resulted in slow cooling during the Pan-African Orogeny.