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Fellows Directory

Keith O'Nions

Keith O'Nions

Sir Keith O'Nions HonFREng FRS


Elected: 1983


Keith O’Nions is a geochemist whose research has significantly added to our understanding of the composition and evolution of the Earth. He pioneered a type of radioactive dating involving the rare earth elements, samarium and neodymium. From this he calculated an average age for the upper crust of the Earth’s mantle of slightly less than two billion years.

Keith’s work has extended to analysing the chemical composition of meteorites. Interpreting the results gives clues about the make-up of the young solar system. In addition, he has studied the outgassing from the Earth’s mantle of the primordial helium created in the Big Bang.

Keith has also made his mark on science and public policy through positions such as Chief Scientific Adviser to the Ministry of Defence and Director General of the Research Councils. His other leadership positions include serving as Rector of Imperial College and as trustee and chairman of the Natural History Museum. He was knighted for services to earth sciences in 1999.

Interest and expertise

Subject groups

  • Earth and environmental sciences
    • Geochemistry


  • UK-Canada Rutherford Lecture

    On 'The retention and loss of volatiles by the Earth'.

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