Geochronology and Isotopic Mapping
The Geochronology and Isotopic Mapping component of the Exploring for the Future program provides key isotopic datasets in both tabulated compilations, and map form for visualisation with other geological datasets. Geochronology and Isotopic Mapping provides geologists with an understanding of the changing nature of the geology of northern Australia through time including when mineral systems were active, and helps guide prediction of the likely distribution of undiscovered mineral resources.
Key components include:
Uranium-Lead (U-Pb) geochronology and age maps of northern Australia
The U-Pb geochronology component of the program involves acquisition of new SHRIMP U-Pb ages from key samples, as well as compilation of existing U-Pb age data, both from Geoscience Australia and other sources. The U-Pb age compilation includes >4050 data points across Australia, with a particular focus on northern Australia. New data are being progressively added, and interim compilations have been published by Anderson et al. (2017) and Jones et al. (2018). The U-Pb age compilation will shortly be available for viewing and download as a webservice via the EFTF Portal.
Samarium-Neodymium (Sm-Nd) and Lutetium-Hafnium (Lu-Hf) isotopic analyses of magmatic rocks to develop a Sm-Nd/Lu-Hf model age map of northern Australia
The Sm-Nd isotopic composition of felsic magmatic rocks can be used to provide a broad indication of the bulk crustal age—a model age—of the middle and lower crustal source region of these rocks. A similar approach can be taken through Lu-Hf isotopic analysis of zircon. By combining the two isotopic systems to produce a Sm-Nd/Lu-Hf model age map over key parts of northern Australia, we can visualise the development of continental crust through time.
Lead-Lead (Pb-Pb) isotopic analyses of sulphide minerals to develop a Pb map of northern Australia
The Pb isotopic composition of Pb-rich sulphide materials (e.g. chalcopyrite, galena and sphalerite) reflects the isotopic composition of the fluids from which those sulphides were derived. This isotopic signature provides evidence of the sources of fluids that have transported metals such as copper (Cu), lead (Pb), zinc (Zn), and gold (Au).
Potassium-Argon (K-Ar) and Argon-Argon (Ar-Ar) geochronology
K-Ar and Ar-Ar geochronology methods are complementary to U-Pb geochronology, and can provide age constraints on a variety of geological processes including magmatic crystallisation, metamorphism, cooling through temperatures in the range ~500C to 300C, and mineralisation. Compilation of new and existing K-Ar and Ar-Ar constraints in northern Australia is in progress and provides indications of crustal cooling age and exhumation patterns across northern Australia.
The Exploring for the Future Geochronology and Isotopic Mapping program has involved collaboration between Geoscience Australia and the following agencies and institutions: Northern Territory Geological Survey, Geological Survey of Queensland, Geological Survey of South Australia, Geological Survey of Western Australia, the Australian National University, Curtin University, Melbourne University, and University of Alberta.
Data & Publications
- New SHRIMP U-Pb zircon ages from the South Nicolson and Carrara Range regions, Northern Territory
- New SHRIMP U-Pb zircon ages from the South Nicolson Basin, Mount Isa Province and Georgina Basin, Northern Territory and Queensland
- A shear-hosted Au-Cu-Bi metallogenic event at ~1660 Ma in the Tennant Creek goldfield (northern Australia) defined by in-situ monazite U-Pb-Th dating
- Preliminary national-scale lead isotope maps of Australia, February 2019
- A U–Pb geochronology compilation for Northern Australia: version 2, December 2018
- Identification of a new gold event at Tennant Creek expands 'search space' for more discoveries, August 2018 [PDF 756KB] [DOC 1.1MB]
- A U–Pb geochronology compilation for northern Australia: version 1, November 2017
- Joint NTGS–GA geochronology project: Aileron Province, July 2015–June 2016
- Joint NTGS–GA geochronology project: Arnhem Province, July 2014–June 2016
- New SHRIMP U–Pb zircon ages from the Birrindudu and Victoria Basins, Northern Territory: July 2016–June 2017
- Joint NTGS–GA geochronology project: greater McArthur Basin, July 2016–June 2017
- Joint NTGS–GA geochronology project: Aileron Province, July 2016–June 2017
- Neodymium depleted mantle model age map of Australia: explanatory notes and user guide
- Radiogenic isotopes, ore deposits and metallogenic terranes: Novel approaches based on regional isotopic maps and the mineral systems concept
- Metallogenesis and geodynamics of the Lachlan Orogen: New (and old) insights from spatial and temporal variations in lead isotopes
- Spatial variations in lead isotopes, Tasman Element, eastern Australia