The age and tectonic setting of basaltic intrusions of the south coast of NSW

Crystals of olivine, the main mineral of the mantle, can be grown in the lab to study igneous processes

The rocks of the Sydney Basin and Lachlan Fold Belt exposed along the south coast of NSW contain numerous basaltic (basalt and dolerite) intrusions (e.g. Bingie Bingie Point, Dolphin Point, Snake Bay, Long Reef, North Bondi).  The ages of these dykes and sills are unknown, however, they are assumed to be Tertiary and associated with rifting of Australia from New Zealand.  The problem with this model is that most of the dykes are oriented E-W whereas extension associated with rifting would have produced fractures oriented N-S.  The reason why the intrusions have not been dated previously is that they do not contain zircon (the mineral most commonly used for U-Pb dating) due to their low silica activity.

In this project samples of the intrusions will be collected and dated using the new 40Ar/30Ar facility that has recently been commissioned at RSES.  The bulk composition and mineralogy of each rock will also be determined to identify any trends or correlations with age.  The results will be interpreted in terms of the tectonic events that have shaped the geology of south-eastern Australia.  The project will provide training in geochronology, sample preparation and polishing, scanning electron microscopy, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry.

For more information about this potential research topic or activity, or to discuss any related research area, please contact the supervisor.

Andrew Berry and Marnie Forster