On the Hunt to Understand Really Old Rocks

Using radioactive dating, researchers found that the mantle underneath New Guinea melted sometime in the past 540 million years.

IMAGE: Scientists analyzed peridotites like this, from ophiolite in Papua New Guinea, to better understand the complex geology of the region. CREDIT: Natasha Barrett

Understanding the origin and timing of life and world-building materials is important science. All of this work is tied together in the larger quest for understanding how life came about and can we find it elsewhere. A rock can tell you something new about the world and how it changed over time.

Now, using mantle rocks found in the jungles of New Guinea, researchers may have timed just when the mantle under that region melted.

These lowermost rocks are different from ones found elsewhere on Earth. They’re full of elements that generally don’t like to be in melted rock. They lack elements that do prefer to be in melted rock. So scientists thought that meant they were extremely old and formed during the Archean epoch — about 2.5 to 4 billion years ago — when the mantle was much hotter and therefore more liquid melt was available. However, that turned out to not be the case.

Using radioactive dating, the team discovered that the mantle in this region melted during the Phanerozoic, which, unfortunately, covers everything from about 540 million years ago until now. More dating is going to be needed to get a more precise timeline of events. And more research is needed to understand just how the mantle melted in this manner at that time.

Science takes time, everyone.

More Information

Million or Billion? Narrowing Down the Age of Mantle Processes in New Guinea (Eos)

Ultra-Refractory Peridotites of Phanerozoic Mantle Origin: the Papua New Guinea Ophiolite Mantle Tectonites,” Natasha Barrett et al., 2022 February 23, Journal of Petrology

This story was written for the Daily Space podcast/YouTube series. Want more news from myself, Dr. Pamela Gay, and Erik Madaus? Check out DailySpace.org.

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