Laser Tool Reveals Earth's 'Helium Secrets' to Help Monitor Natural Disasters

Researchers from Australia's Curtin University have for the first time been able to visualize where helium atoms are trapped within individual mineral grains - providing information that can help to determine the geological history of the Earth's crust, and assist in monitoring natural hazards like earthquakes and volcanic eruptions. Their research, published in Science  , combines laser ablation microsampling and noble gas and trace element mass spectrometry to provide the first two-dimensional, grain-scale zircon helium 'maps.'

Transcript

00:00:00 For over 100 years, helium has been used to evaluate the timing of geologic processes. In fact it was the first isotopic system applied to dating rocks. The decay of uranium and thorium to lead, produces helium as a by-product. Over time, helium accumulates in uranium and thorium, baring minerals. Zircon helium dating is currently employed to understand the low temperature history of earth's crust. Despite the utility of this method, we have not, until this study, been able to actually see how helium is distributed within minerals. Recent technological advances in the geohistory laboratory at Curtin University, have facilitated the visualisation of helium distribution in single zircon crystals.

00:00:59 Laser ablation micro-sampling has allowed us to probe very small volumes of minerals, to quantitatively characterise the distribution of helium, uranium, thorium and lead. These data have allowed the production of chemical maps that track the spacial variation of helium gas. In some cases however, helium has escaped from domains suffering from significant radiation damage. In addition we have found that fluid inclusions can trap extremely high amounts of helium and impede its diffusion. Our methodology allows for the first time, direct measurement of helium diffusional profiles, from which it is possible to reconstruct the thermal history of single crystals. Finally the ability now, to visualise the distribution of helium will allow more precise

00:02:02 characterisation of geologic processes such as mountain building, orogenesis, development of petroleum resources, earthquakes, volcanic eruptions and the interaction between tectonics, erosion and climate.