South Georgia in a West Gondwana context: detrital zircon geochronology of a late Permian accretionary complex

Abstract

South Georgia lies in a remote position in the circumpolar South Atlantic and is one of the most isolated continental fragments on Earth. The basement geology of South Georgia is restricted to the southeast sector of the island and is termed the Drygalski Fjord Complex, which consists of metasedimentary rocks and localised paragneisses that form an accretionary complex cut by multiple dolerite dykes and gabbroic intrusive rocks. We examine the detrital zircon geochronology and geochemistry of six metasedimentary samples from the Drygalski Fjord Complex to determine their depositional and provenance history and explore correlations to elsewhere in West Gondwana. The basal Salomon Glacier Formation has a maximum depositional age of ca. 270 Ma and a secondary age peak at ca. 470 Ma that is consistent with West Gondwana accretionary complexes from the northern Antarctic Peninsula and Patagonia. This depositional age is also shared with sedimentary successions from the Karoo Basin (South Africa) and East Antarctica, but they lack the secondary age peak (ca. 470 Ma), being instead characterised by an age peak at ca. 530 Ma, associated with the recycled Cambrian sources of East Antarctica. The late Permian accretionary complex of South Georgia is closely correlated to units from the northern Antarctic Peninsula (Trinity Peninsula Group) and the southern Cordillera Darwin, and we favour a common origin on the Antarctic Plate before closure of the Rocas Verdes Basin and translation to the Scotia Plate.