Scientists at the Pacific Northwest National Laboratory (PNNL) have discovered a rock containing water from an inland sea dating back 390 million years, which was once located in upstate New York, USA.
The discovery of this microscopic ‘pocket of seawater’ opens a way to understand how Earth’s oceans They have been adapting to climate change for thousands of years.
During the Middle Devonian, this inland sea stretched from present-day Michigan to Ontario, Canada. It was home to a coral reef rivaling Australia’s Great Barrier Reef. Truck-sized sea scorpions patrolled the waters, early examples of now-extinct species such as trilobites and horseshoe crabs.
But eventually the climate changed, and with that change, most of the life and the ocean disappeared, leaving only fossilized remains in the sediments that eventually became the pyrite rock sample used in the current experiment.
“We found that we can actually extract information from these mineral features that can help inform geological studies, such as the chemistry of ancient seawater,” he said. A statement Sandra Taylor, first author of the study and a scientist at PNNL.
Taylor led the analyzes along with geochemists Daniel Gregory of the University of Toronto and Timothy Lyons of the University of California, Riverside. The research team reported their findings in the December 2022 issue of Earth and Planetary Science Letters.
Tiny ‘Sea Water Pockets’ Discovered
Many types of minerals and stones contain small pockets of fluid. In fact, some gemstones are prized for their light-trapping liquid bubbles. What’s different about this study is that with advanced microscopy and chemical analysis, the scientists were able to reveal what’s inside the tiny pockets of water.
Researchers used rock samples as evidence to reconstruct how climate has changed over long geological periods.
“We use mineral deposits to estimate the temperature of ancient oceans,” said Gregory, a geologist at the University of Toronto and one of the study’s leaders. But there are relatively few useful examples in the geological record.
“Entrapment of seawater salt deposits [halita] “They are relatively rare in the rock record, so these data have been missing for millions of years, and what we know now is based on the few places where halite has been found,” Gregory said.
Conversely, pyrite is ubiquitous. “Sampling with this technique will unlock millions of years of geologic record and lead to a new understanding of the changing climate.”
“mini bubbles” inside the mineral
While the research team was trying to understand another environmental problem, the leaching of toxic arsenic from rocks, they noticed small defects. Scientists describe the appearance of these particular pyrite minerals as framboids, derived from the French word for raspberry, because they look like clusters of raspberry segments under the microscope.
“At first, we looked at these samples with an electron microscope and saw these kinds of mini-bubbles or mini-features inside the framboid and wondered what they were,” Taylor said.
Using the precise and sensitive detection techniques of atomic scanning tomography and mass spectrometry, which can detect trace amounts of elements or impurities in minerals, the team discovered that the bubbles contained water and that their salt chemistry matched that of ancient oceans.
These types of studies also have the potential to provide interesting information about how to safely store hydrogen or other gases underground.
“Hydrogen is being explored as a low-carbon fuel source for a variety of energy applications. It is necessary to safely recover and store large amounts of hydrogen in underground geologic repositories. Therefore, understanding how hydrogen interacts with rocks is important,” said Taylor.
“Atomic tomography is one of the few techniques where you can not only measure hydrogen atoms, but also see where it goes in the mineral. This study suggests that small defects in minerals can be potential traps for hydrogen. So by using this technique, we can find out what’s going on at the atomic level, which is underground hydrogen. Helps evaluate and develop strategies for saving.
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