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.

Spatial coverage of compiled U-Pb geochronology data for northern Australia. Data points include (brown) igneous crystallisation ages; (blue) metamorphic rock ages; (black) maximum depositional ages.

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.

Spatial coverage of Sm-Nd and Lu-Hf isotope data for northern Australia. Sm-Nd data as brown points, Lu-Hf data as black points.

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.

Spatial coverage of Pb-Pb isotope data for northern Australia.

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).

Spatial coverage of Ar-Ar isotope data for northern Australia (compilation in progress).

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.

Collaboration

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

Related Information