Australian Diamond Exploration 2006: Where are the Greenfields?

Summary

The paper gives an overview of current diamond exploration and discovery in Australia and reviews the state of knowledge of the geological setting and controls on known diamondiferous intrusions in Australia as an important indicator of Australia’s diamond potential. Reduced levels of spending in recent years has been associated with a contraction of exploration largely to brownfields regions. Exceptions are the discovery of the diamondiferous Blacktop kimberlite in the West Pilbara region and, to a lesser extent, new kimberlites discovered in the eastern Gawler Craton.

Most Australian kimberlites and lamproites, like those elsewhere, show evidence of strong structural controls. These features are commonly evident in continental scale geophysical datasets. Many of the diamondiferous intrusions lie at major boundaries/discontinuities evident in seismic S-wave tomographic models and at discontinuities evident in multi-scale analysis of horizontal gradients of continental magnetic anomaly and gravity datasets (Jaques and Milligan, 2004: Lithos 77, 783-802). These relationships are predicted by modelling with numerical mantle convection code which indicates that abrupt changes in lithospheric thickness focus lithospheric stress gradients affecting melt migration and accumulation thereby making the mantle beneath the margins of stable cratons favourable sites for kimberlite generation (O’Neill, Moresi and Jaques, Tectonophysics 404, 217-236).

Diamond potential is intimately linked to craton evolution. Eclogitic diamond suites appear to be linked to subduction events at craton margins. Continental-scale geophysics can help define fertile source regions (mantle roots) and identify favourable tectonic zones/corridors. Improved targeting is required to better identify greenfields provinces which have the potential to host new diamond pipes. Such targeting would be enhanced by improved seismic tomographic models of the Australian lithosphere and through a better understanding of geodynamic evolution of the Australian continent.

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Further information

For more information, please email Lynton Jaques.