Ā鶹ֱ²„ researchers have for the first time been able to visualise where helium atoms are trapped within individual mineral grains, providing information that can help to determine the geological history of the Earthās crust and assist in monitoring natural hazards like earthquakes and volcanic eruptions.
The researchers, led by Professor Brent McInnes of Curtinās John de Laeter Centre, teamed up with Canberra-based high-technology instrument manufacturer ASI Pty Ltd to create a new laser microanalysis instrument, the RESOchronā¢, capable of measuring helium at high resolution ā to one-tenth the width of a human hair.
Dr Martin DaniÅ”Ćk, lead author of a paper on the research published in Science Advances, said helium ā generated over long periods of time in uranium and thorium-bearing mineral crystals ā was a highly sought-after commodity used in medical and industrial applications. It has also been used by geoscientists to date rocks.
āScientists have been using the helium dating technique to determine the age of minerals for over 100 years, but until now, nobody has been able to observe the actual distribution of helium within the crystal structure,ā Dr DaniÅ”Ćk said.
Dr DaniÅ”Ćk said that by using the RESOchron to repeatedly raster a laser across a zircon crystalās surface, the team was able to create the first helium abundance map.
āWe then used numerical simulations to determine how thermal events in the Earthās crust influenced helium abundance patterns in the crystal over geological time,ā Dr DaniÅ”Ćk said.
āBy matching measured and simulated helium distributions, we were able to decipher the mineralās geological history.ā
[youtube]http://www.youtube.com/watch?v=O1kMei_JLCE[/youtube]
Professor McInnes, who conceived the instrument concept and assembled the project team, said the ability to measure radiogenic helium distributions in individual grains could help scientists understand more about the timing of fault movement, volcanic eruptions and mountain building processes, as well as assist in the exploration for mineral and petroleum deposits.
āWe were surprised to discover extremely high concentrations of helium in cavities within crystals, and speculate that this could be useful in earthquake monitoring, because the crushing of minerals during fault motion should break open these cavities and release a flux of helium gas that can be detected at surface,ā Professor McInnes said.
āOur team has previously demonstrated that minerals in diamond-bearing kimberlite pipes have uniquely low abundances of helium, and this technology can be used to rapidly scan exploration samples to both detect kimberlitic zircon and identify the age of the kimberlite pipe.ā
Dr Bruce Godfrey, CEO of ASI Pty Ltd, said the company was pleased to collaborate with Curtin in the development of this innovative geochemical technique.
āWe look forward to developing the instrument platform for the international market,ā Dr Godfrey said.
A paper detailing the findings, Seeing is believing: Visualization of He distribution in zircon and implications for thermal history reconstruction on single crystals, was published recently in .
