JCU geology team finds a piece of Australia under Vanuatu

Researchers from James Cook University have found a fragment of Australia beneath Vanuatu—and it may cause a rethink on how continents are built.

JCU environmental sciences
JCU geologists rethink how we calculate the rates and processes of generating new continents
Geologists thought the volcanic Vanuatu islands, about 2200 km east of Townsville, were isolated from continental influences. But now research by a JCU team suggests the ‘geological basement’ of Vanuatu contains ancient material from northern Australia.

The team discovered volcanic rocks from Vanuatu contained tiny crystals of a mineral called zircon, carried up in magma from the depths by the volcanic plumbing systems. Using the state-of-the-art radiometric dating techniques in the JCU labs, the crystals were dated at up to 3 billion years old.

Dr Carl Spandler, one of the co-authors of the paper, said the zircon “shouldn’t be there,” and its presence has major implications for how scientists understand continents are made.

“The range of ages of the zircon crystals from Vanuatu closely matches the age of rocks that make up northern Australia. There is nothing else like it in the south west Pacific,” he said.

The fragment of Australian crust now under Vanuatu is thought to have separated from the mainland prior to the Cenozoic Era, around 100 million years ago.

“Just because island chains or landmasses may be far removed from each other today, doesn’t mean that they always were. This calls for a rethink of how we calculate the rates and processes of generating new crust on Earth,” he said.

Dr Spandler said it was particularly satisfying that the findings were made by one of James Cook University’s honours students, Janrich Buys, who completed his Geology degree in 2013.
“It goes to show that you don’t have to be a long-established researcher to make a significant scientific breakthrough,” he said.

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