Brief history of isotope geology at the Australian National University

Abstract

Isotope geology began in the Department of Geophysics, the Australian National University, Canberra, in the late 1950s. A K–Ar dating laboratory was set up in 1960, with development of Rb–Sr dating facilities taking place soon after. These laid the foundations for extensive programs of isotopic dating with emphasis on providing quantitative age information related to the geological evolution of the Australian continent. Demonstration of progressive younging of granite emplacement to the northeast in the Tasman Fold Belt of eastern Australia was a notable initial achievement. Early successes on broader questions included the demonstration of the ability to measure K–Ar ages on young volcanic rocks, leading on to a significant role in the establishment of the geomagnetic polarity time-scale. In the early 1970s, dating of returned lunar samples by the Rb–Sr method was another most notable success. The development of the SHRIMP ion microprobe, commencing in the mid-1970s, resulted in U–Pb dating of zircon (and other minerals) becoming possible on very small areas of single crystals, revolutionising the approach to dating, with wide application not only to rocks in Australia, but indeed worldwide. Isotope geochemical study of the Earth's mantle and crust was also an important activity, especially in the 1980s. Subsequently, emphasis has been redirected toward studies of the Quaternary, including U-series isotopic dating as well as high-resolution isotopic and element ratio measurements, especially on corals, to track climate change. Many other developments in isotopic dating and isotope geochemistry have taken place over the last 45 years with installation and, in some cases, development of appropriate instrumentation, facilitating the updating of capabilities and expanding the range of techniques, continuing to the present time.

Key Words:

• Australia
• geochronology
• isotope geology
• SHRIMP

Acknowledgements

Thanks are due to Bill Compston, Malcolm McCulloch and Ian Williams for providing helpful comments on a much earlier version of this manuscript. Bill Compston and Ian Williams kindly provided additional comment that helped improve the present version.