The new crust-formation research was made possible the discovery of ancient oceanic rocks in a canyon in Oman. Photo by Nick Dygert/University of Texas

May 1 (UPI) -- New research suggests water penetrates deep into the crust and upper mantle to cool rock and facilitate crust formation at mid-ocean spreading zones.

Earth's crust is formed from magma upwelling at mid-ocean spreading zones, but researchers disagree on how the cooling process actually works.


"There's a debate in the scientific community how oceanic crust forms," Nick Dygert, a postdoctoral fellow in geosciences at the University of Texas at Austin, said in a news release. "And the different models have very different requirements for cooling regimes."

To better understand crust formation, Dygert and a team of researchers analyzed ancient oceanic rocks -- rocks that are now exposed on dry land. The 100-million-year-old rocks were found in a canyon in Oman.

By analyzing the mineral compositions inside the rock samples, researchers were able to retrace the rock's cooling history and estimate the temperatures at which each rock formed. The analysis was made possible by a new type of geothermometer developed by Yan Liang of Brown University.

"Traditional geothermometers usually give you a cooling temperature rather than a formation temperature for the rock," Dygert said. "This thermometer is a neat new tool because it allows us to look at a part of the cooling history that was inaccessible for igneous rocks previously."

The new findings -- detailed in the journal Earth and Planetary Science Letters -- suggest magma cooled and formed rock almost instantly at the upper layers of the mantle.

Dygert described the process as a "hot frying pan being plopped in a sink of water."

The composition of the rock samples formed deeper in the mantle showed signs of a much slower cooling process. The variety of measured cooling temperatures suggest water cycles through the mantle, cooling different layers of magma. Rocks cooled at lower layers encourage the cooling of rocks above.

The findings support the Sheeted Sill model of crust formation, which proposes water as the main driver of crust formation. The rival model, Gabbro Glacier hypothesis, posits that magma simply cools and forms Earth's crust as it dissipates heat on its journey away from the main magma chamber.

"The Sheeted Sill model requires a very efficient mechanism for cooling because crystallization is happening at all different depths within the crust at the same time," Dygert said. "And what we were able to find strongly implies that hydrothermal circulation was very efficient throughout the crustal section."