Timing of the progress granite, Larsemann hills: Additional evidence for early Palaeozoic orogenesis within the east Antarctic Shield and implications for Gondwana assembly

The Progress Granite is one of numerous S‐type granitoid plutons exposed in the Larsemann Hills region, southwest Prydz Bay, east Antarctica. The granite was emplaced into a migmatitised pelitic to felsic paragneiss sequence during a regional high‐grade transpressional event (D₂) that pre‐dates high‐grade extension (D₃). SHRIMP (II) U‐Pb dating for two occurrences of the Progress Granite from D₂ and D₃ structural domains gives ²⁰⁶Pb/²³⁸U ages of 516.2 ± 6.8 Ma and 514.3 ± 6.7 Ma, respectively. These ages are interpreted as crystallisation ages for the Progress Granite and confirm Early Palaeozoic orogenesis in the Larsemann Hills region. This orogen appears to have evolved during continental convergence and is probably responsible for widespread radiogenic isotopic resetting and the near‐complete exhumation of the adjacent northern Prince Charles Mountains which evolved during a ca 1000 Ma event. The identification of a major Early Palaeozoic orogen in Prydz Bay allows tentative correlation of other domains of Early Palaeozoic tectonism both within the east Antarctic Shield and other, once contiguous, Gondwana fragments and illustrates the potential complexity inherent within intercratonic mobile belts. One such possibility, tentatively offered here, suggests a continuous belt of Early Palaeozoic tectonism from Prydz Bay eastward to the West Denman Glacier region and into the Leeuwin complex of Western Australia.

Key words:

• Antarctica
• Early Palaeozoic
• Gondwana
• Progress Granite
• uranium‐lead dating

Notes

Present address: Department of Geology and Geophysics, University of Sydney, NSW 2006, Australia.