ISOTOPIC STRUCTURE AND TECTONICS OF THE CENTRAL TRANSANTARCTIC MOUNTAINS

Regional patterns of Nd, Sr and O isotopic ratios of ~500 Ma granitic rocks are used to identify the ages and areal extents of three crustal provinces in the central Transantarctic Mountains. One of the provinces is the edge of the East Antarctic Craton. The other two provinces compose the Beardmore microcontinent. Evidence for a former ocean basin between the Beardmore microcontinent and East Antarctica is provided by basalt and gabbro of mid-ocean ridge character, dated by Sm-Nd at ~760 Ma, associated with marine sediments now located at the suture. The tectonic history deduced for the Gondwana margin began with deposition of sediments on an Atlantic-type rifted margin at ~760 Ma. The Beardmore microcontinent was most likely accreted in association with folding of the clastic sedimentary rocks before middle Early Cambrian time (550 Ma). Carbonate sedimentation and volcanism along the eastern margin of the Beardmore microcontinent commenced in Cambrian time. Folding and metamorphism of all older units occurred in late Cambrian time followed by emplacement of granitic rocks at ~500 Ma. -from Authors