A geological event known as the Oenpelli Dolerite intrusive event occurred about 1,720 million years ago in western Arnhem Land, in the Northern Territory, creating curved ridges of Oenpelli Dolerite stretching over 30,000 square kilometres (12,000 sq mi).

Where is diabase formed?

Where does diabase form? Diabase is an intrusive igneous rock with the same mineral composition as basalt. It cools under basaltic volcanoes, like those at mid-ocean ridges. Diabase cools moderately quickly when magma moves up into fractures and weak zones below a volcano.

How was diabase formed?

Diabase is a fine-grained igneous rock that would have formed when molten rock material cooled rapidly on or near the surface of the Earth.