The new findings are in line with recent findings in other high-mass isotope systems – such as thallium or mercury – that had been assumed to be invariant. Additionally, the new measurements “could represent the first evidence of the nuclear field shift found in nature,” said U. of I. graduate student Charles J. Bopp, who led the study.
What, exactly, causes the variance is not yet clear, though, Bopp said.
There are two basic types of uranium ore deposits: magmatic, which develop due to hydrothermal effects; and sedimentary, which develop by chemical reduction of uranium in groundwater in subsurface aquifers.
In 1976, scientists George Cowan and Hans Adler analyzed gas mass spectrometry results of uranium hexafluoride (before artificial isotopic enrichment processes took place) derived from uranium ores around the world. This assessment revealed a slight offset in the distribution of the ratio of U-235 to U-238, with magmatic-type deposits having on average higher U-235 percentage weight and sandstone-type deposits having lower.
However, the precision of individual analyses remained approximately 3 per mil (3 parts per thousand) while the average offset between deposit types was less than this.
With the higher precision now obtainable in the UI geochemistry laboratory, Bopp and UI geology professor Craig Lundstrom have observed the same offset between uranium ores from different geologic settings.
The researchers used a technique called multiple-collector inductively coupled plasma-mass spectrometry to measure the ratio of U-235 to U-238 in three sandstone-type and three magmatic-type uranium ores provided by the Smithsonian Institution.
“Repeated analysis of the ore samples shows the sandstone-type ores to be consistently depleted in U-235 relative to magmatic-type ores by approximately 1 per mil, which is a significant amount of variation,” said Bopp, who will present the findings at next week’s annual meeting of the Geologic Society of America.
The observed depletion of U-235 is most likely the result of a nuclear field shift effect as isotopes partition between the water and the reduced uranium ore mineral, Bopp said. But what uranium reduction process – biotic or abiotic – is responsible is not yet clear.
“We can’t parse that apart at this stage,” Bopp said. “We observe a depletion, and we know there are microbes present in these types of deposits, but we can’t say for sure who’s doing what without a much more in-depth study of a single locality.”
James E. Kloeppel | EurekAlert!
Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland
15.11.2018 | Faculty of Science - University of Copenhagen
The unintended consequences of dams and reservoirs
14.11.2018 | Uppsala University
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences