Geology and SHRIMP U-Pb Zircon Chronology of the Clemence Massif, Central Prince Charles Mountains, East Antarctica
A.F. Corvino1*, S.D. Boger1, C.J.L. Wilson1 & I.C.W. Fitzsimons2
1School of Earth Sciences, University of Melbourne, 3052 Parkville, Victoria – Australia
2Tectonics Special Research Centre, Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth, WA 6845 – Australia
Received 22 April 2005; accepted in revised form 28 September 2005
Abstract - New single zircon SHRIMP U-Pb analyses from Clemence Massif reveal that both Proterozoic and Cambrian ages are ubiquitous in rocks of pre-, syn- and post-tectonic origin. Igneous zircon cores from a pre-tectonic felsic orthogneiss yielded a mean 207Pb/206Pb age of 1062 ±9 Ma, whereas metamorphic rims all gave Cambrian-Ordovician ages of c. 535-464 Ma. Zircons from a syn-tectonic leucogneiss gave scattered 207Pb/206Pb ages of c. 1079-782 Ma with a high density at c. 910 Ma, along with a single 238U/206Pb age of 527 ±10 Ma. An undeformed pegmatite dyke yielded zircons with core ages of c. 1116-828 Ma about a mean age of 905 ±6 Ma, along with discrete rim ages of c. 552-494 Ma. The available evidence suggests that Clemence Massif witnessed a high-grade tectono-metamorphic event during the Cambrian Period similar to nearby domains of the Mawson Escarpment, Prydz Bay and the Grove Mountains. Although there is some overlap of Early Neoproterozoic zircon ages (c. 990-900 Ma) with those from the northern Prince Charles Mountains (PCM) of the Rayner Complex, the data do not show clear affinities with this region. Consequently, the tectonic setting of Clemence Massif, and possibly that of the central PCM, appears to have been different from the Rayner Complex during Neoproterozoic-Cambrian times. A model that considers deposition of paragneiss protoliths at Clemence Massif during the Neoproterozoic is consistent with the field and isotopic data.
*Corresponding author (a.corvino@pgrad.unimelb.edu.au)