Oct 18, 2018

Meteor impact crater yields ultra-rare mineral

Meteor impact crater yields ultra-rare mineral Shocked gneiss in drill core from the central uplift of the Woodleigh impact structure in Western Australia. The rare mineral reidite and other shock-damaged minerals were found throughout the core. Image: Aaron J. Cavosie.

Core samples taken near Shark Bay in Western Australia have yielded an ultra-rare mineral from what may be the largest-known meteorite impact crater in Australia, Curtin University researchers say.

Reidite, which starts its life as the common mineral zircon, only forms in the incredible pressure of impact when rocks from space slam into the Earth’s crust.

The Curtin University research, published in the journal Geology, examined drill core from the buried Woodleigh impact crater, near Shark Bay, and found that some zircon grains in the core had partially transformed to reidite.

The chance find of reidite gave the team new insights into how the Earth responds to the dramatic changes created by meteorite impact, a process that violently lifts deep-seated rocks to the surface in seconds.

Lead author – honours student Morgan Cox, from Curtin’s School of Earth and Planetary Sciences, said given the Woodleigh impact crater was buried below younger sedimentary rocks, its size was not known and remained hotly debated.

“Previous research estimated the size of the impact crater between 60km and more than 120km in diameter,” Ms Cox said.

“However, our discovery of reidite near the base of the core suggests a larger crater. The research team is now using numerical modelling to refine the size of Woodleigh and if we establish its diameter is greater than 100km, it would be the largest-known impact crater in Australia.”

Research supervisor Dr Aaron Cavosie, also from Curtin’s School of Earth and Planetary Sciences, said the drill core sampled the middle of the impact crater, a region called the central uplift.

“Central uplifts are desirable targets for learning about impact conditions,” Dr Cavosie said.

“They bring profoundly damaged rocks closer to the surface, and in some instances, are associated with exploration targets.

“Finding reidite at Woodleigh was quite a surprise as it is much rarer than diamonds or gold, though unfortunately not as valuable.”

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