Geochronology and Isotopic Mapping
The goal of the Geochronology and Isotopic Mapping component of the Exploring for the Future program is to provide key isotopic datasets in map form for visualisation with other geological datasets. Geochronology and Isotopic Mapping will provide geologists with an understanding of the changing nature of the geology of northern Australia through time including when mineral systems were active, and help guide prediction of the likely distribution of undiscovered mineral resources.
Key components will include:
Uranium-Lead (U-Pb) geochronology and age maps of northern Australia
The U-Pb geochronology component of the program involves compilation of existing U-Pb age data, both from Geoscience Australia and other sources. The U-Pb compilation as of June 2018 includes >3600 data points building upon the >2200 data points in version 1 of the compilation (Anderson et al. 2017). Ongoing compilation work includes additional data from Western Australia and Northern Territory.
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 effectively ‘see’ into the deep crust and gain understanding of the nature of the rocks we are interested in.
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
Compilation of new and existing K-Ar and Ar-Ar constraints in northern Australia will guide acquisition of new data and provide indications of crustal cooling age and exhumation patterns across northern Australia.
The Exploring for the Future Geochronology and Isotopic Mapping program involves 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.
- Upcoming release of A U—Pb geochronology compilation for northern Australia: version 2 (version 1 released November 2017)
- Ongoing compilation and acquisition of key isotopic datasets
- Data visualisation and map view testing
- U-Pb, Sm-Nd/Lu-Hf, Pb-Pb, K-Ar/Ar-Ar isotopic data compilations and viewable isotopic map layers
- An Isotopic Atlas of northern Australia outlining all the input data compilations
Data & Publications
- 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 [756kb PDF ] [ 1.1mb DOC]
- 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