Three Palaeoproterozoic basins—Yerrida, Bryah and Padbury—Capricorn Orogen, Western Australia

Abstract

The Palaeoproterozoic Yerrida, Bryah and Padbury Basins record periods of sedimentation and magmatism along the northern margin of the Archaean Yilgarn Craton. Each basin is characterised by distinct stratigraphy, igneous activity, structural and metamorphic history and mineral deposit types. The oldest of these basins, the Yerrida Basin (ca 2200 Ma) is floored by rocks of the Archaean Yilgarn Craton. Important features of this basin are the presence of evaporites and continental flood basalts. The ca 2000 Ma Bryah Basin developed on the northern margin of the Yilgarn Craton during backarc sea-floor spreading and rifting, the result of which was the emplacement of voluminous mafic and ultramafic volcanic rocks. During the waning stages of the Bryah Basin this mafic to ultramafic volcanism gave way to deposition of clastic and chemical sedimentary rocks. At a later stage, the Padbury Basin developed as a retroarc foreland basin on top of the Bryah Basin in a fold-and-thrust belt. This resulted from either the collision of the Pilbara and Yilgarn Cratons (Capricorn Orogeny) or the ca 2000 Ma westward collision of the southern part of the Gascoyne Complex and the Yilgarn Craton (Glenburgh Orogeny). During the Capricorn Orogeny the Bryah Group was thrust to the southeast, over the Yerrida Group. Important mineral deposits are contained in the Yerrida, Bryah and Padbury Basins. In the Yerrida Basin a large Pb-carbonate deposit (Magellan) and black shale-hosted gossans containing anomalous abundances of Ba, Cu, Zn and Pd are present. The Pb-carbonate deposit is hosted by the upper units of the Juderina Formation, and the lower unit of the unconformably overlying Earaheedy Group. The Bryah and Padbury Basins contain orogenic gold, copper-gold volcanogenic massive sulfides, manganese and iron ore. The origin of the gold mineralisation is probably related to tectonothermal activity during the Capricorn Orogeny at ca 1800 Ma.

SHRIMP U–Pb geochronology of magmatism and thermal events in the Archaean Marymia Inlier, central Western Australia

“…All workers agree that tectonism in the Capricorn Orogen ended prior to the deposition of the Bangemall Group; this is taken as either the age of ultrabasic lamprophyre dykes (1.68 Ga; Pearson et al 1996), which intruded during rifting of the Bangemall Basin (McMillan 1996;Krapez 1999), or the age of intrusions (1.65 Ga; Nelson 1995) within the basal members of the Bangemall Group (Jones et al 2000;Pirajno and Occhipinti 2000).…”

“…Most authors proposed that the Inlier is Archaean and is part of the Yilgarn Craton that was uplifted, rotated and reworked in the Proterozoic (Muhling et al 1976;Gee 1987;Occhipinti et al 1998b;Pirajno and Occhipinti 2000). 2.…”

“…Approximate timeframe is indicated for each model. See text for discussion and further references Model 1 (Krapez 1999;Krapez and Martin 1999) Model 2 (Pirajno and Occhipinti 2000;Jones et al 2000;Pirajno 1999 Deposition of Padbury Group in retro-arc foreland Deposition of Padbury Group in retro-arc ?Glenburgh or basin in fold-thrust belt (Martin 1994) foreland basin on top of Bryah Group Capricorn Orogeny (Martin 1994) The greenstone sequence and associated intrusive rocks in the vicinity of Marymia Gold Mine have been complexly deformed and subjected to multiphase metamorphism, as well as at least two phases of hydrothermal activity (McMillan 1996;Vielreicher et al 2001). Retrograde greenschist-facies metamorphism, subeconomic sphalerite-galena mineralisation and associated structures have been correlated with regional greenschistfacies metamorphism, base metal mineralisation and deformation elsewhere in the southern Capricorn Orogen (McMillan 1996;Vielreicher et al 2001).…”

Mapping undercover: integrated geoscientific interpretation and 3D modelling of a Proterozoic basin

“…Periods of magmatism are recorded primarily by the basaltic volcanic and intrusive rocks of the Killara and Narracoota Formations (Mooloogool and Bryah Groups, respectively), though other mafic intrusive 110 and extrusive rocks are observed in other formations (Juderina and Karalundi Formations, Occhipinti et al, 2017) and as dykes (Mueller, 2011). The geodynamic evolution of the Yerrida Basin is interpreted as a pull-apart basin opening consistent with a trailing-edge marginal sag-basin (Pirajno and Occhipinti, 2000), progressing to a rift in the north (Bryah Sub-basin) (Occhipinti et al, 2017;Olierook et al, 2018). Continued extension resulted in the intrusion and extrusion of the Killara Formation tholeiitic basalts (Occhipinti et al, 1997).…”

“…The development of the Yerrida Basin began with deposition of the c. 2200 Ma Windplain Group, followed by the 2180 to 105 1996 Ma Mooloogool and Bryah Groups (Occhipinti et al, 2017;Pirajno and Occhipinti, 2000). The rocks of the Windplain Group are representative of a shallow coastal and possible epicontinental setting (Occhipinti et al, 2017), while the rocks of the Bryah and Mooloogool Groups were deposited in relatively higher-energy and possible rift environments Pirajno and Adamides, 2000).…”