Contrasting Detrital Feldspar Pb Isotope Ratios and Zircon Geochronology to Distinguish Proximal versus Distal Transport

Abstract

Sediment routing systems are commonly investigated by applying the well-established U-Pb isotopic system to date the crystallization of detrital zircon grains in order to reveal the ultimate source of the dated component in a sediment. However, detrital zircon U-Pb geochronology provenance analysis cannot distinguish between sediment supplied from first-cycle erosion of crystalline basement and multicycle reworking of older basin components. Instead, analysis of Pb isotopes in detrital K-feldspar tends to track first-cycle sediment, as this mineral is more labile than zircon. Here we present new in situ Pb isotope ratios of detrital K-feldspar from the Mungaroo and Brigadier Formations (Northern Carnarvon Basin, North West Shelf, Australia) and K-feldspar crystals of potential (meta)igneous crystalline source rocks. These new K-feldspar Pb isotope ratios, in combination with detrital zircon U-Pb geochronology, allow for more holistic investigation of sediment provenance and refinement of sediment recycling histories. The Albany Fraser Orogen/Wilkes Land, the Musgrave Province, the Pilbara Craton, and other northern terranes (Lhasa Block, southwest Borneo) across a broad region of former northeast Gondwana are identified as the main source regions of the sampled intervals of the Mungaroo and Brigadier Formations. Additionally, differences between the relative volumetric significance of source regions interpreted from K-feldspar and zircon datasets reveal the extent of sediment reworking along a major sediment pathway. We propose a model of relatively more recycled material from the distal Albany Fraser Orogen/Wilkes Land, entraining additional recycled material from the central Australian Musgrave Province and finally mixing with directly sourced sediment from the proximal Pilbara Craton.