Geologists have discovered a new type of rock. While drilling deep into the seafloor, a team of scientists found a new form of basalt that’s vastly different from any other on Earth, and the planet hasn’t produced any more of it for millions of years.
It’s easy to assume that there aren’t that many types of rocks left to discover, but it turns out that the Earth is still hiding some up its sleeves – or, as the case may be, deep below the ocean.
The team, made up of scientists from all over the world, discovered the new rock in the Amami Sankaku Basin (ASB), in the ocean south of Japan. There, the researchers lowered their equipment 6 km (3.7 miles) below the surface to the seafloor, then drilled down another 1.5 km (0.9 miles).
At that depth, the team found a new type of basalt with a completely unique chemical and mineral makeup. It’s a tholeiite that’s low in titanium and potassium, and bears aluminum-rich gemstones called spinels.
"The rocks that we recovered are distinctly different to rocks of this type that we already know about,” says Dr. Ivan Savov, co-author of the study. “In fact, they may be as different to Earth's known ocean floor basalts as Earth's basalts are to the Moon's basalts.”
The geologists say that these rocks were produced during large and very hot volcanic eruptions, back when the Ring of Fire was first forming some 50 million years ago. The magma that formed them was transported to the surface very quickly, from its source in the upper mantle where it was exposed to pressures between 0.7 and 2 GigaPascals.
The depth at which they were found, in terms of both the ocean and the crust, explains why these rocks haven’t been discovered before. The Earth stopped making these particular rocks millions of years ago – so you could consider them kind of a Limited Edition, long out of print.
"Now that we know where and how this rock type is formed, we anticipate that many other rocks that we know were originally formed by ocean floor eruptions will be re-examined and potentially alter our wider understanding of the basalt formation,” says Savov.
The research was published in the journal Nature Communications.
Source: University of Leeds via Eurekalert