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Tiny grains of the mineral zircon taken from granite rocks collected in Fiordland and Stewart Island have led to a potential breakthrough in ancient continental reconstructions.
These grains also show that parts of Zealandia, below the surface, are much older than Gondwana, an ancient supercontinent which included New Zealand, Australia and the Antarctic.
Dr Rose Turnbull, a geologist at the GNS Science Dunedin office, is the lead author of a research paper, just-published in the journal Geology, which showed the continent of Zealandia was much older than previously thought.
"This represents a major shift in thinking and it comes down to the [isotopic] analysis of tiny grains of the mineral zircon in specialist laboratories in Australia and Germany," she said.
This analysis showed parts of southern New Zealand were linked with Rodinia, and specifically to rocks formed between 900million and 750million years ago in South China, which was then likely to be close to Zealandia, Tasmania and Australia.
"The isotopic signature of zircon grains from Zealandia tell us that there are ancient 1billion-year-old rocks still concealed deep in the crust beneath Fiordland and Rakiura/Stewart Island, rocks that were formed as part of the Rodinia supercontinent."
Many scientists had previously cited 500million-year-old trilobite (extinct marine arthropod) fossils in limestone rock found in the Cobb Valley, Nelson, as New Zealand’s oldest known rocks on the surface.
Rodinia’s exact reconfiguration was a highly controversial subject in geology, Dr Turnbull explained.
This information could make Zealandia a "missing link", shedding new light on ancient geographical links between South China, Australia, and North America, she said.