2 Geological Evolution of the Earth System: Precambrian to Early Paleozoic
Monday, 25 June 2001
10:00 AM - 3:00 PM
TECTONIC EVOLUTION OF THE BROKEN HILL REGION, SOUTH-CENTRAL AUSTRALIA AS A KEY TO IMPROVED RECONSTRUCTIONS OF RODINIA
Paper number: 2-12
Program: GENERAL SESSIONS
Time: 2:10 PM – 2:30 PM
Authors
Abstract
Greater credence can be placed in reconstructions that combine the late Neoproterozoic tectonic histories with older basement events. In the case of Broken Hill, basement events include episodic crustal extension and clastic sedimentation between 1710 and 1640 Ma, bimodal magmatism at 1670-1690 Ma and accompanying early low pressure-high temperature amphibolite-granulite facies metamorphism. These events were followed by crustal thickening, higher pressure granulite facies metamorphism (anticlockwise P-T-time path) and northeast-directed nappe formation, heralding the onset of the Olarian Orogeny which culminated around 1600 Ma in an orogenic belt 50-60 km thick. Further crustal shortening occurred between 1595 and 1590 Ma when the Willyama was subjected to northwest-directed thrust faulting. Validation of existing reconstructions for Rodinia requires a greater range of equivalent events be present in western Laurentia than is presently recognised.