Island arc volcanoes, such as those in Japan or the Caribbean, form when water-rich fluids are released from the down-going plate and melt is generated in the overlying mantle. This paper presents the first detailed study to use relatively short-lived isotopes to constrain the time period from the release of those fluids from the down-going plate to eruption in a volcano. On average these fluids would appear to travel 20-40 metres per year, which is 100 times faster than the movements of mantle material in response to plate tectonics. One implication is that they move in fractures.

The potential of these short-lived isotopes has been known for several decades, but the development of improved mass spectrometric analytical techniques has made it possible routinely to obtain more precise data on much smaller samples. This has made it possible now to use these isotopes in a number of different fields.

The time scales of natural processes are often diagnostic, and physically realistic models require an understanding of the rates at which natural processes occur. However, it is often very difficult to obtain estimates of the rates of natural processes from rocks and minerals, and it is only relatively recently that this has become possible from these relatively short- lived isotopes. The significance of these results is that they highlight that the fluids move faster than the movement of the mantle in response to plate tectonics, and so some other mechanism, such as movement along fractures, is required. The time scale constrains the mechanism.

This was a natural progression from a long-term interest in both isotope and trace element geochemistry, and in the rates of natural processes.