Detrital-zircon age-spectra for Late Archaean synorogenic basins of the Eastern Goldfields Superterrane, Western Australia

Abstract

The Kalgoorlie, Gindalbie, Kurnalpi, Duketon and Burtville terranes were amalgamated by 2658 Ma into the Eastern Goldfields Superterrane, which was later accreted Cordilleran-style onto the foreland of a pre-existing continent. Late-stage (synorogenic) basins developed within the Eastern Goldfields Superterrane during the early stage of accretion. The basins are similar to all late-stage basins of Archaean provinces, developing late in the tectonic cycle in a strike-slip regime. They developed in two stages, during the gap in granite emplacement between 2658 Ma and 2648 Ma. Basin analysis suggests that the bulk of sediments was derived from rocks readily identifiable today within the superterrane, consistent with the provenance style of all late-stage basins. Sediment derivation from the foreland occurred only during Stage II, and is recorded only from basins proximal to the suture. Detrital-zircon geochronology has corroborated those interpretations. Eleven new SHRIMP U-Pb detrital-zircon datasets and 14 previously published datasets indicate that the bulk of zircon-bearing sediment was derived from the 2715 Ma to 2658 Ma High-Ca (TTG) granites and volcanic rocks that define the terranes.Moreover, primary modes in the detrital-zircon age-spectra of 2680 ± 3 Ma, 2673 ± Ma, 2666 ± 3 Ma and 2660 ± 3 Ma coincide with the peaks of emplacement of High-Ca granites. Provenance from across the suture has also been corroborated, with detrital-zircon age-spectra of the Kurrawang Basin, a Stage II basin close to the suture, having no match to rocks of the Eastern Goldfields Superterrane. Defining modes of 2730 Ma and >3000 Ma, some as old as 3750 Ma and 3540 Ma, can be matched to an 2735 Ma calc-alkaline volcanic province and quartzites with 4350–3130 Ma detrital zircon in the foreland. The study shows that detrital-zircon age-spectra can be powerful supporters of tectonic analysis, but for the study presented here their interpretation has been greatly assisted by prior basin analysis and a considerable geochronological database of source-rock equivalents.