Archean controls on basin development and mineralisation in the Southern Capricorn Orogen

Abstract

Basins along the northern margin of the Yilgarn Craton developed in response to extensional and compressional processes during the Paleoproterozoic. Early extension resulted in the formation of the Yerrida Basin as a large single basin over the northern Yilgarn Craton. Subsequent rifting led to voluminous volcanism in the northern part of the basin, within two depositional centres – the c. 2.03 to 1.96 Ga Bryah and Mooloogool Sub-basins. Cu-Au VMS deposits formed in the Bryah Sub-basin. Yilgarn Craton crust can be mapped using gravity and magnetic data beneath the Yerrida Basin, and Mooloogool Sub-basin. However, the Yerrida Basin can’t be mapped below much of the Bryah Basin, implying the formation of an ocean in this region. The degree of rifting of the Yilgarn Craton, and resulting architecture influenced subsequent basin development, and deformation in the region. For example, in areas where Yilgarn Craton crust can’t be mapped beneath basin sediments deformation is pronounced with the formation of disharmonic folds, refolded folds, and anastomosing shear zones. The southern part of the Yerrida Basin and the Earaheedy Basin formed shallow depositional centres over the Yilgarn Craton, and subsequent deformation in these regions is less intense. Base metal mineralisation in the region can, in part be related to the presence of deep crustal scale structures that initially developed in the Archean, and were re-activated during the Proterozoic. However, the location of c. 1800 Ma orogenic Au mineralization in the Bryah Sub-basin may not have been influenced by localisation of fluid flow around deep crustal-scale faults that formed as 200 Ma earlier, or even as early as the Archean.