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The structural evolution of the Rauer Group, East Antarctica: mafic dykes as passive markers in a composite Proterozoic terrain

Published online by Cambridge University Press:  12 May 2004

John P. Sims
Affiliation:
School of Earth Sciences, University of Melbourne, Parkville, Victoria 3052, Australia
Paul H. G. M. Dirks
Affiliation:
Department of Earth Sciences, University of Utrecht, P.O. Box 80.021, 3508TA, Utrecht, Netherlands
Chris J. Carson
Affiliation:
School of Earth Sciences, University of Melbourne, Parkville, Victoria 3052, Australia
Chris J. L. Wilson
Affiliation:
School of Earth Sciences, University of Melbourne, Parkville, Victoria 3052, Australia

Abstract

Archaean gneisses in the Rauer Group of islands, East Antarctica, record a prolonged history of high-grade deformational episodes, many of which predate that identified in mid-Proterozoic gneisses. Eleven generations of mafic dykes, belonging to discrete chemical suites, have been used as relative time markers to constrain this deformational history. Based on the timing of intrusion with respect to structures, dykes in the Rauer Group have been correlated with largely undeformed and dated dyke suites in the adjacent Vestfold Hills. This has allowed absolute ages to be inferred for the early- to mid-Proterozoic mafic dyke suites in the Rauer Group, and a correlation of the interspersed structural events. Most structures in the Rauer Group, however, developed in response to high-grade progressive deformation at approximately 1000 Ma. During this deformational episode, strains were repeatedly partitioned into sub-vertical, noncoaxial, high-strain zones recording NW-directed sinistral transpression, that separated zones of lower strain dominated by coaxial folding with axes parallel to the shear direction. Three additional mafic dyke suites intruded during this deformation which was followed by three stages of brittle-ductile deformation and a final suite of lamprophyre dykes. Due to the numerous intrusive time markers, the Rauer Group serves as an excellent illustration of how complicated gneiss terrains may be.

Type
Papers—Earth Sciences and Glaciology
Copyright
© Antarctic Science Ltd 1994

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