Detrital zircon geochronology of Mesoproterozoic rocks at Strathgordon, Tyennan Domain, Tasmania

The Tyennan Domain of western Tasmania consists of structurally complex Proterozoic metasedimentary rocks, whose stratigraphy is poorly constrained. A new detrital zircon geochronology dataset for nine samples along a transect in the Strathgordon area (eastern Tyennan subdomain) was used to constrain maximum depositional ages, stratigraphic correlations and provenance affinities. Detrital zircons in one sample have a distinctive age peak in the Kernel Density Estimate (KDE) at ca 1350 Ma and age spectra that most closely match the Irby Siltstone, upper Rocky Cape Group. The other eight samples have zircon KDE patterns typical of the lower Rocky Cape Group. These samples can be classified into three provenance groups based on detrital zircon age distributions. Comparison with the previous detrital zircon data show these groups cover most of the variation across the Mesoproterozoic samples from Tasmania. Group A has <8% of zircon grains with a ca 1450 Ma (1500–1400 Ma) age and the largest peak in the KDE is at 1800 Ma. Group B has a large proportion of ca 1450 Ma zircon grains (20% of grains) and the dominant peak in the KDE is at 1700 Ma. Group C has a wide range in detrital zircon age from 1900 to 1450 Ma with no dominant peak and >10% of zircon grains in the Laurentian Magmatic Gap (1610–1490 Ma). These three detrital zircon age distributions match the provenance groups recognised in the Belt–Purcell Supergroup in the USA and Canada supporting previous tectonic reconstructions placing western Tasmania close to the Belt–Purcell Basin in Nuna at 1300 Ma. The group C provenance is restricted to the oldest units in the Rocky Cape Group and is also limited to the older formations in the Belt–Purcell Supergroup (below the Missoula Group) along the western side of the Belt–Purcell Basin.