Researcher confirms the hottest rock ever

Zircon with baddeleyit edge that preserves cubic zirconia orientations. Credit: University of Western Ontario

If there was ever any doubt that the discovery of a post-doc student in 2011 was actually the hottest rock on Earth, new findings from a Western-led research team put this uncertainty to rest.

Eleven years after Western scientists revealed what was then considered the hottest rock on Earth, a recent study found four additional zircon grains – a hard mineral commonly known as a substitute for diamonds – which confirmed the previous rock’s record high temperature of 2,370 C …

The study, published in the journal Earth and Planetary Science Letters, was led by geoscience post-doc student Gavin Tolometti and co-authors: Timmons Erickson of the NASA Johnson Space Center, Gordon Osinski and Catherine Neish of the Department of Geosciences; and Cayron Cyril from the Laboratory of Thermomechanical Metallurgy.

In 2011, Ph.D. student Michael Zanetti was working with Osinski at the Mistastin Lake crater in Labrador when he found a glass stone containing small zircon grains frozen inside it. This rock was later analyzed and found to have formed at 2,370 ° C as a result of an asteroid impact. These results were shared in a study published in 2017.

In their own study using samples collected between 2009 and 2011, Tolometti and his colleagues were able to find four additional zircon grains that confirmed that the 2011 discovery was true. The researchers located and also found evidence elsewhere within the same impact structure that the melting stone – rocks created after rocks and soil melted into liquid after a meteor impact – was differently overheated in more than one place, to a greater extent than previously theorized.

“The biggest implication is that we get a much better idea of ​​how hot these impact melt tests are, which were originally formed when the meteorite hit the surface, and that gives us a much better idea of ​​the history of the melt and how it cooled in this particular crater, “Tolometti said.

“It can also give us insight into studying the temperature and melting of other impact craters.”

Tolometti also noted that most of the preserved evidence, such as glass samples and smelting samples, was found near the crater floor. By applying this knowledge to other impact craters, researchers may be able to find more evidence of temperature conditions in other craters, but in less extensive studies.

“We are beginning to realize that if we want to find evidence of temperatures so high, we need to look at specific regions instead of randomly choosing across an entire crater,” he said.

Second discovery

The newspaper also noted that this is the first time that reidites – a mineral formed when zircon undergoes high pressures and temperatures – have been discovered at this site. The team found three reidites still preserved in the zircon grains, and evidence that two more were once present but had crystallized when the temperature had exceeded 1,200 C, at which point the reidite was no longer stable.

This mineral allows researchers to better limit the pressure conditions, indicating that there may have been a peak pressure state around 30 to potentially over 40 gigapascals. These are the pressure conditions that were created when the meteorite hit the surface at that time. The closer something is to the shock event, the higher the pressure will be. Certain minerals that have been compressed much by this event – referred to as ‘shocked’ – leave structures that can be studied.

“Given how large the reidite was in our samples, we knew that the minimum pressure it probably detected was about 30 gigapascals. But since there are still many reidites present in some of these grains, we know that even could be over 40 gigapascals., “Tolometti explained.

This gives a better idea of ​​the amount of pressure produced outside the melting zone when the meteorite hit the surface. The melting zone will by default have pressures usually above 100 gigapascals, at which point a rock will completely melt or evaporate outside these conditions.

Research expansion

The research team plans to extend this work to other impact craters on Earth. Some Ph.D. students will work with Osinski to look at other craters such as Lac Wiyâshâkimî (Clearwater West Crater) in Quebec. Tolometti is also seeking to expand this work and look at Apollo lunar samples brought back to Earth, which have plenty of evidence to form from impact craters.

“If we were to find evidence of microstructures in zircon grains or other grains under pressure conditions, we could get a much better idea of ​​how impact cratering processes are on the moon,” he said.

“It can be a step forward in trying to understand how rocks have been modified by impact craters across the entire solar system. This data can then be used in impact models to improve the results we get.”


Transformations into Granular Zircon Revealed: Meteor Crater, Arizona


More information:
DG Tolometti et al., Hot rocks: Limiting the thermal conditions in the Mistastin Lake impact melt deposits using zirconium microstructures, Earth and Planetary Science Letters (2022). DOI: 10.1016 / j.epsl.2022.117523

Nicholas E. Timms et al., Cubic zirconia in> 2370 ° C melting records the Earth’s warmest crust, Earth and Planetary Science Letters (2017). DOI: 10.1016 / j.epsl.2017.08.012

Provided by the University of Western Ontario

Citation: Researcher confirms the hottest rock ever (2022, April 14) retrieved April 15, 2022 from https://phys.org/news/2022-04-hottest.html

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