Early Palaeozoic intracratonic shears and post-tectonic cooling in the Rauer Group, Prydz Bay, East Antarctica constrained by 40 Ar/ 39 Ar thermochronology

• Published in: Antarctic Science
• Main Authors: Wilson, Christopher J.L., Quinn, Cameron, Tong, Laixi, Phillips, David
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2007
• Subjects: Geology; Ecology, Evolution, Behavior and Systematics; Oceanography; East Antarctica; Prydz Bay; Prince Charles Mountains; Rauer Group; Antarc*; Antarctic Science; Antarctica
• Online Access: http://dx.doi.org/10.1017/s0954102007000478; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102007000478

Abstract The Rauer Group, in Prydz Bay, contains reworked Archaean-Proterozoic crust in high-strain zones that formed during a pervasive high-temperature ductile deformation event related to intracratonic mechanisms. The effects of this event extend southwards from Prydz Bay into the southern Prince Charles Mountains. The associated structural evolution involved development of ductile and brittle structures that formed during an approximately north–south directed transpressional deformation event that is confined to high-grade (>800°C) shear zones in the Rauer Group. Minerals from the Rauer Group, yield 40 Ar/ 39 Ar cooling ages ranging from 560 to 460 Ma. Thermal histories derived from hornblende, biotite and feldspar suggest that the onset of rapid cooling began sometime prior to 510 Ma with cooling rates of c . 42 to 33°C myr -1 from c . 510 Ma to c . 500 Ma. Whereas, 40 Ar/ 39 Ar data obtained from plagioclase and K–feldspar suggest a slower cooling from c . 500 Ma to c . 460 Ma with cooling rates from 5 to 2°C myr -1 . These results demonstrate that the early Palaeozoic cooling history and comparable palaeostress regimes are regionally extensive, which has important implications for the tectonothermal and stress-field variability across Gondwana. The elevated thermal conditions would induce lithospheric weakening and promote the early Palaeozoic intraplate orogeny observed in eastern Antarctica with the development of a large intracratonic shear system.