Dolerite

Gondwanaland and Australia

The vast areas of mafic volcanism/plutonism associated with the Jurassic breakup of the Gondwana supercontinent in the Southern Hemisphere include many large diabase/dolerite sills and dike swarms. These include the Karoo dolerites of South Africa, the Ferrar Dolerites of Antarctica, and the largest of these, the most extensive of all dolerite formations worldwide, are found in Tasmania. Here, the volume of magma which intruded into a thin veneer of Permian and Triassic rocks from multiple feeder sites, over a period of perhaps a million years, may have exceeded 40,000 cubic kilometres. In Tasmania, dolerite dominates much of the landscape, particularly alpine areas, with many examples of columnar jointing.