A University of Arkansas researcher and his colleagues have used magnesium isotopes to determine the temperature at which rocks form, which will allow scientists to better study the formation of the earth’s crust and mantle as well as the formation of meteorites.
Fang-Zhen Teng, professor of geosciences, and Wang-Ye Li, Yilin Xiao and Jian Huang of the University of Science and Technology of China report their findings in Earth and Planetary Science Letters.
“Knowing the temperature of rock formations is important to understanding the earth’s evolution,” Teng said. “We also can study extraterrestrial samples to know more about how meteorites formed and evolved.”
Of course, most rocks on earth have been rocks for millions and millions of years, making it difficult to determine their thermal history.
“We have to study the formation temperature of rocks indirectly,” Teng said. Several methods for doing so exist, but most do not give accurate readings at the high temperatures where rocks form. “How the temperature varies at depth within the earth’s crust and mantle is still uncertain,” Teng said.
The researchers studied magnesium isotope fractionation in eclogite, a metamorphic rock that contains the minerals omphacite and garnet, found in a mountain range in China. Eclogites form at high temperatures and pressures and often form from subducted ocean floor basalts that are drawn below the earth’s crust, and are brought to the surface during mountain-building processes.
Isotopes have the same chemical properties, but different weights, so some processes cause what looks like the same material to behave differently. In this case, the researchers looked at isotope fractionation, or the separation of isotopes into different areas within the rock. The magnesium isotope fractionation within a rock depends upon the temperature at which the atoms stopped moving within it, which is the time that the rock has formed.
The scientists found that the fractionation of magnesium isotopes is big at high temperatures, which allows researchers to then study it accurately. The researchers looked at other isotopes, but found the fractionation to be too small to measure precisely. The light magnesium isotopes move quickly to a low energy state (i.e., garnet), whereas the heavy isotopes prefer a high-energy state (i.e., omphacite). The proportion of light and heavy isotopes in each state in a given rock determines the temperature at which the rock formed. Using this magnesium isotope fractionation, the researchers can determine the temperature of rock formation to a higher precision. For example, if previous isotope “thermometers” only determined the temperature to a precision of within 50 degrees Celsius, then the magnesium thermometer can reach a precision of within 20 degrees Celsius.By knowing the temperature of the rock formation, scientists will be able to determine the cooling rate of rocks at different depths within the earth’s crust and mantle. This will help them learn more about how the rocks cool down.
“This will help us determine how mountains were built. If we know the ‘cooking’ history, we can determine how fast the mountains were built and how the plates collide and evolve,” Teng said.
The researchers plan to collect samples from mountain building areas to further use this new tool.CONTACTS:
Fang-Zhen Teng | Newswise Science News
Diving robots find Antarctic seas exhale surprising amounts of carbon dioxide in winter
16.08.2018 | National Science Foundation
Diving robots find Antarctic winter seas exhale surprising amounts of carbon dioxide
15.08.2018 | University of Washington
There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
20.08.2018 | Life Sciences
20.08.2018 | Information Technology
20.08.2018 | Power and Electrical Engineering