Cracking diamonds reveals continental origins

An analysis of the mineral inclusions in diamonds dredged up by eruptions from deep within the Earth has allowed scientists to get a handle on when the process of plate tectonics began. Trapped within the diamonds are tiny inclusions, the mineral clues as to how the Earth’s continental crusts formed.

I asked Shiring to offer me a little more background for this my first Chemistry World news story in many years.

This research was based on some 20 or so published studies from the literature, he told me. What is perhaps unique about his team’s relationship to the published body of work is that between the two of them, they are the authors or co-authors of every one of the studies. In other words, the entire worldwide data set is all their own work (with coinvestigators). Richardson, first at MIT in 1984, then Paris, and finally in his lab in Cape Town is the only one to have done the Sm-Nd and Rb-Sr work on silicate inclusions. No one else in the world does this, Shiring told me

With a postdoc in our Geochemistry Group at the Carnegie Institution of Washington, Graham Pearson, he first applied the method for Re-Os to the sulfide inclusions in 1997. It was originally Graham’s suggestion but we co-developed it. There are currently only three labs in the world capable of this work: Shiring’s at the Carnegie Institution of Washington, the University of Alberta (wherre he transferred the technique by teaching a postdoc, Sonja Aulbach how to do it), and Durham University (which has stopped doing the work because Pearson who was there went to Alberta). Richardson and many others went to Washington to do the sulfide work and Shiring worked with them all directly in the lab.

Shiring also pointed out that the Carnegie Institution of Washington has a more than 60 year history (which actively continues) in the research development of isotopic systems to be used as tracers and as tools for dating minerals and rocks. “We are tiny compared to the National Labs -just equivalent to the size of a medium academic department at a university,” he told me. “But we have played a seminal role in the development and pioneering application of the Rb-Sr, U-Pb, K-Ar, and Re-Os radiogenic isotopic systems in the Earth Sciences which continues today with other radiogenic isotopic systems such as Re-Os, Sm-Nd, Pd-Ag and stable isotopes such as C, D-H, O, B, Li, S and Si.”

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