A new laboratory at Colorado State University is using cutting-edge techniques to determine the age of sulfide minerals, allowing mining companies to better pinpoint ore deposits. The technique also can be used to help environmental agencies trace contaminants from mining and other operations back to the source.
The Applied Isotope Research for Industry and the Environment laboratory employs a new method to measure the radioactive decay of the parent isotope rhenium against its daughter isotope, osmium. Until recently, chemical processes did not exist that could extract rhenium and osmium–which occur in minute amounts–efficiently enough to measure the isotopes and date the minerals.
The AIRIE lab includes a 4,000-pound mass spectrometer used in the dating process, located in the university’s department of Earth resources in the College of Natural Resources. Colorado State spent $110,000 to renovate two large rooms to house a new chemical laboratory and the mass spectrometer.
Renovations were recently completed and the first mineral samples are in the initial stages of being processed, said Judith Hannah, head of the department of Earth resources and an associate professor.
Hannah said the lab will be completely self-sufficient, generating funds from research agencies, clients in the mining industry and from geological survey agencies worldwide that want to more accurately define the location of sulfide minerals or trace contaminants. Hannah is coordinating the project with Holly Stein, an affiliate faculty member at Colorado State and the principal force behind the lab.
"There are only a few labs in the world that can analyze sulfide minerals with enough precision to provide useful ages and tackle the full range of ore deposit types," Stein said. "With ore deposits growing increasingly hard to find, this lab will provide a clearer picture of where to look. It will also give us another tool in tracing environmental contamination back to its source." Radiometric dating determines the age of rocks or minerals by measuring concentrations of naturally-occurring radioactive isotopes, which decay at constant rates and produce daughter isotopes. The amount of parent and daughter isotopes enables researchers to determine the age of a rock in millions or billions of years.
Hannah explained that for years, researchers knew rhenium and osmium existed in sulfide minerals, but could only measure them in minerals with unusually high concentrations. Even minerals with large amounts of rhenium presented analytical problems that prevented accurate dating.
One example of a rhenium-rich sulfide mineral the AIRIE lab is now able to analyze is molybdenite, an important ore mineral produced in Colorado. Molybdenite is the ore for the metal molybdenum, a major component of high-strength steel. Stein points out that working with molybdenite provides a means of dating both some of the youngest and oldest rocks on Earth.
Recently, new chemical methods were developed to extract rhenium and osmium from a wide variety of rocks and minerals, Stein said. Equally important, improved analytical techniques allow more precise measurement of isotope ratios in minerals with very low concentrations of these elements.
John Morgan, the chemist who pioneered the chemical processes now used to extract rhenium and osmium, will join the AIRIE group this summer. Another addition is Richard Markey, a research technician who has helped to oversee the laboratory’s construction since last fall.
While the laboratory offers cutting-edge methods in radiometric dating of sulfide minerals, the equipment and technology also have other important applications for research under way at Colorado State.
Jerry Magloughlin, isotope chemist and assistant professor of Earth resources, uses similar techniques to date the movement on ancient faults to better understand Earth history and the behavior of modern faults.
William Sanford, assistant professor of Earth resources who specializes in hydrology, uses radioactive isotopes and their daughter elements to trace the movement of contaminants in water. Sanford’s research could lead to new ways of identifying sources of contamination and tracking water pollution.
"This is the kind of collaborative research that benefits Colorado State’s efforts in studying all aspects of the Earth in a way that benefits both industry and the environment," Hannah said.