Geospeedometry

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Geospeedometry is a rapidly developing field. The technique can be used to constrain the duration of thermal pulses during metamorphism by diffusion modelling of element profiles in garnet, for example. Garnet geospeedometry involves measurement of diffusive loss of an element during the entire heating and cooling history, giving information as to the time-integrated thermal response to the heating and cooling history.

Currently, garnet geospeedometry is plagued by the difficulty of differentiating between growth zoning, as a result of Rayleigh-Taylor fractionation, and diffusion profiles. Development of a new geospeedometer that utilises the exchange of Fe-Mn between garnet and ilmenite inclusions will aid in solving this problem.

Argon geospeedometry is similarly difficult, being hindered by lack of certain knowledge as to the magnitude of the diffusion parameters, such as the activation energy, activation volume, or frequency factor. Other factors that need to be taken into account include fractal (or multi-scale) and multi-path diffusion.

Both the 40Ar/39Ar system and the garnet-ilmenite system, if properly calibrated, will allow determination of the duration of heating events.

Updated:  20 October 2017/Responsible Officer:  RSES Webmaster/Page Contact:  RSES Webmaster