Research by Olga Yakubovich, Associate Professor at St Petersburg University, has led to the development of a new, unique method of isotope geochronology. She started it in her student years under the supervision of the prominent geochemist, Professor Yuri Shukolyukov. Of the 16 existing methods it is the only one that allows the age of platinum mineralisation to be assessed.
Olga Yakubovich subsequently found that, besides the native metals, helium is also preserved in such minerals as pyrite (often called 'fool's gold' during the Gold Rush for its resemblance to the precious metal) and sperrylite, which is the basis of platinum ore. In certain cases, they can be used to determine the age of ore mineralisation.
Since there is a rather close correlation between the age of mineralisation, its scale and ore specialisation, this information is particularly relevant for mineral exploration.
Associate Professor at St Petersburg University Olga Yakubovich
The other focus of the young scientist's research – measuring the time of formation of placer deposits of native metals (gold and platinum) – is also related to their ability to preserve helium.
'There are two ways helium can be formed: as a result of radioactive decay and in interaction with cosmic rays. In the first case, it is only helium-4 that is formed. In the second case, helium-3 is also formed. Therefore, if we measure the amount of helium-3 formed in metal by cosmic rays, we get a minimum estimate of the duration of placer formation. This calculation is essential for the reconstruction of the processes that took place on the Earth's surface hundreds of millions of years ago and led to the concentration of metal,' said Olga Yakubovich, Associate Professor at St Petersburg University.
Interest in this area of research is explained by the fact that the duration of the placer forming process cannot be measured by any other method. It can only be estimated qualitatively based on indirect geological observations and only for a relatively modern history of the Earth – the last 500 million years. Using cosmogenic helium, scientists can study the speed of the processes of weathering and transportation of native metal grains on the Earth for billions of years. This was a time when there was no vegetation on the Earth's surface, and there was practically no oxygen in the air. It was a completely different planet, and we can only guess at the speed of changes taking place on its surface.
In the future, Olga Yakubovich plans to continue working in this field together with foreign colleagues. She hopes that soon Russia will also have equipment that can measure the microquantities of helium-3 isotope. 'The Soviet Union had the strongest school in the world on the isotope geochemistry of noble gases, created by such outstanding researchers as Vitaly Khlopin, Erich Gerling, Yuri Shukolyukov, Igor Tolstikhin and many others. I was really fortunate to be able to learn from the outstanding scientist and pioneer of isotope geology Professor Yuri Shukolyukov from St Petersburg University. This is an award that I owe largely to him,' said the scientist.