New SHRIMP U-Pb zircon geochronology for the central Pine Creek Orogen, Northern Territory: implications for Top End orogenesis

Abstract

The Palaeoproterozoic Pine Creek Orogen, northern Australia, forms part of the North Australia Craton, and is a highly prospective terrain, with abundant mineral occurrences including gold and uranium. Geologically, it comprises sedimentary sequences deposited on rifted Archaean basement that were deformed, metamorphosed, and intruded by granitoids and mafic bodies during the ca. 1880-1850 Ma Nimbuwah Event, one of the constituent events of the Barramundi Orogeny. The stratigraphy of the central Pine Creek Orogen is well-characterised due to its extensive exposure, preservation, and low grade greenschist facies metamorphism. It contains units suitable for isotopic dating, permitting determination of absolute ages within a well-controlled stratigraphic framework. We present new zircon U-Pb SHRIMP results for volcanics and volcanogenic strata from various intervals within the pre-orogenic stratigraphy. These data: (a) indicate the presence of volcanic activity in the Pine Creek Orogen at ca. 2025 Ma; (b) provide revised constraints on the tectono-thermal evolution of the Pine Creek Orogen, specifically a revision of the Nimbuwah Event by some 20 Ma; (c) suggest that volcanism was widespread across the Pine Creek Orogen at ca. 1860 Ma; and (d) permit assessment of relative deposition rates of and time intervals between deposition of the Palaeoproterozoic stratigraphic sequences.