A revised Palaeoproterozoic chronostratigraphy for the Pine Creek Orogen, northern Australia: Evidence from SHRIMP U–Pb zircon geochronology

Abstract

New SHRIMP U–Pb zircon geochronology for volcanic and volcaniclastic sedimentary rocks from the central Pine Creek Orogen provides constraints on the Palaeoproterozoic evolution of northern Australia. An intermediate agglomerate from the Stag Creek Volcanics (Namoona Group) and two samples of volcaniclastic sedimentary rock from the Wildman Siltstone (Mount Partridge Group) were dated to constrain the age of the lower parts of the Palaeoproterozoic succession. These samples all have a youngest zircon population with an age in the range ca. 2030–2020 Ma, which is interpreted to approximate the age of volcanism and volcaniclastic deposition. Two widely separated samples of Gerowie Tuff from the overlying South Alligator Group have depositional ages of 1864 ± 3 Ma and 1862 ± 4 Ma. Zircons of the Berinka Volcanics and Warrs Volcanic Member within the overlying Finniss River Group have crystallisation ages of 1861 ± 4 Ma and 1862 ± 3 Ma, respectively. These new data suggest that the basal units of the Pine Creek Orogen were being deposited in part during a previously unrecognised episode of ca. 2030–2020 Ma felsic volcanism and sedimentation in northern Australia, which was followed by a major hiatus. The ca. 1865–1860 Ma ages for volcanic rocks within the South Alligator and Finniss River Groups provide a maximum age on the timing of deformation and metamorphism in the central Pine Creek Orogen, and allow correlation with felsic volcanic events across large areas of the Pine Creek Orogen and the North Australian Craton.