Transformation of an Archean craton margin during Proterozoic basin formation and magmatism : the Albany-Fraser Orogen, Western Australia

The Albany–Fraser Orogen is a well-preserved example of Proterozoic modification of an Archean craton margin. The formation of two successive basin systems accompanied by magmatism along the southern and southeastern Yilgarn Craton margin in Western Australia reflect distinct changes in tectonic regimes, resulting in significant transformations of the Archean craton crust. Provenance analysis from detrital zircons indicates that the first basin system – the c. 1815–1600 Ma Barren Basin – was dominantly filled with Neoarchean detritus derived from the Yilgarn Craton, and Paleoproterozoic detritus derived from coeval voluminous, mostly felsic magmatism. The abundance of locally derived sediment deposited onto a reworked Archean Yilgarn Craton substrate, coupled with the progressively more juvenile isotopic signature of magmas, indicates a largely extensional tectonic setting, consistent with either a continental rift basin or a long-lived backarc basin system. This extensional regime led to the formation of a passive margin and oceanic basin along the craton edge – the c. 1600–1305 Ma Arid Basin – and formation of an ocean-continent transition in the most heavily modified, outboard region of the craton margin (the eastern Nornalup Zone). A change in tectonic regime is denoted by the formation of an oceanic-arc – the c. 1410 Ma Loongana Arc, preserved in the adjoining Madura Province. Oceanic subduction led to accretion of the Loongana Arc onto the craton edge, recorded by the presence of exotic detritus derived from this arc deposited into a foreland basin (uppermost Arid Basin). This accretion event triggered crustal thickening and the earliest phase of magmatism of Stage I of the Albany–Fraser Orogeny at c. 1330 Ma. A change to west-dipping subduction beneath the accreted portion of the Loongana Arc placed the orogen into a backarc setting, into which the remainder of the Recherche Supersuite mafic and felsic magmas were intruded. Thus, the Albany–Fraser Orogen is regarded as an Archean craton margin that preserves a long history of Proterozoic transformation dominated by extensional processes that resulted in the formation of orogen-wide, basin systems, accompanied by magmatism. The recognition that the Albany–Fraser Orogen has always been part of the West Australia Craton, and the tectonic regimes that have affected it, provide important constraints on reconstructions of the Nuna and Rodinia supercontinents.27 page(s