Funding for the collaborative project has also been provided by Cameca Inc., a developer of analytical instrumentation, and the University.
Electron microprobes have been workhorses in scientific labs for some time, Williams noted, but until recently they could not have been used for precise geologic dating.
Reading the record of materials the Earth provides, and particularly the record of plate tectonics, is critical, explains UMass geologist Michael Williams, because the phenomenon governs much of our understanding of issues such as the development of Earth’s crust, the evolution of climate throughout Earth’s history, and how human beings and different species of animals spread across the planet.
"If we can read the past, we have a better chance to understand the future," he said.
Being able to date specific parts of rocks, and pinpoint their constituent elements, offers a new perspective to scientists as they consider the movement of the Earth’s tectonic plates, a crucial issue in Earth science.
"This will better enable us to read records of how the continents (actually tectonic plates) have grown and collided with one another," Williams explained.
Detrital grains from a metaquartzite of the Highland Group preserve premetamorphic U-Pb ages of between 3.17 and 2.4 Ga and indicate derivation of the sediment from an unidentified Archean source terrain.
Uncertainties in rock ages produced using the current technique are on the order of 5-10 million years, but the UMass researchers hope to chip that number down to 1-2 million years using the new microprobe.The new techniques, dubbed "high-resolution age mapping and microprobe dating," involve the analysis of monazite, a mineral that is present in many rocks but typically in such small quantities that it is rarely noticed in geologic studies.It is widely used in radiometric dating because it contains significant amounts of the elements thorium and uranium, which decay to the element lead at a known rate."It’s the difference between having a single snapshot, or a lengthy, detailed videotape of a series of events.
We don’t want to know just where and when a rock was formed, but also when and where it was buried, deformed, heated, melted, and eventually exhumed to the Earth’s surface.
The high-grade gneisses of Sri Lanka display spectacular in-situ granulitization phenomena similar to those observed in southern India and of current interest for evolutionary models of the lower continental crust.