Mesoarchean to Mesoproterozoic evolution of the southern Gawler Craton, South Australia

Abstract

The Gawler Craton preserves a complex and prolonged tectonic history spanning the interval c. 3200-1500 Ma. Reworking of Paleoarchean, c. 3400-3250 Ma crust led to the formation of c. 3150 Ma granites now exposed within a narrow belt in the eastern Gawler Craton. Following this, there is no known record of significant tectonic activity until the onset of bimodal magmatism during the Neoarchean to earliest Paleoproterozoic, c. 2560-2470 Ma. This magmatism was terminated by high temperature metamorphism and deformation during the 2465-2410 Ma Sleafordian Orogeny. Magmatic events associated with widespread sedimentation over the interval c. 2000-1740 Ma largely sources this older crust. The c. 1730-1690 Ma Kimban Orogeny reworked these Paleoproterozoic basins and the Neoarchean basement in a pre-dominantly transpressional orogenic system. Juvenile mantle input followed by widespread crustal melting occurred over the interval c. 1620-1570 Ma. This period of intense magmatism initiated with emplacement of the relatively juvenile c. 1620-1608 Ma St Peter Suite. This was followed by the economically significant c. 1600-1570 Ma Gawler Range Volcanics/Hiltaba Suite magmatic event, which resulted from widespread mid-crustal melting. Synchronous deformation and high temperature metamorphism accompanied the Gawler Range Volcanics/Hiltaba Suite magmatic event indicating it occurred in an orogenic environment. Far field stress was distributed around a central core zone of largely undisturbed Gawler Range Volcanics with deformation localised in the northern and southern Gawler Craton. The Gawler Range Volcanics/Hiltaba Suite magmatic event resulted in formation of a province of major economic significance that includes the giant Olympic Dam Cu-Au-U ore body.