Quantifying the Thermal Histories of Rocks Using the Helfrag Technique

This project aims at quantifying the thermal histories of rocks in the uppermost part of the crust using the newly codified Helfrag technique on single-grain apatite (U-Th)/He ages (AHe). The AHe method has been often criticized for its age dispersion, which, in some cases, may reach up to 50%. The Helfrag technique, which has been developed by our research group (e.g. [1, 2]) has, however, demonstrated that this dispersion is natural and carries information about the thermal histories of rocks. Helfrag is a Fortran code, which solves the 3D diffusion equation along with He in-growth within a grain approximated by finite cylinder geometry [1]. The inverse modelling mode exploits the Neighbourhood Algorithm [3, 4] to find the best fitting thermal histories and was successfully applied to synthetic data sets. Given the 3D complexity of the model, the assumed geometry of the crystal and the use of the inversion mode, a high performance computing facility is required to obtain data in a reasonable timeframe. This project will be the first time real data are used in Helfrag and its success will boost the use of this software to the thermochronology scientific community.

For more information about the project contact Dr Cristina Persano (Cristina.Persano [at] glasgow [dot] ac [dot] uk), Lecturer at the School of Geographical and Earth Sciences at the University of Glasgow.

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  1. Beucher, R., Brown, R., Roper, S., Stuart, F. & Persano, C. (2013), `Natural age dispersion arising from the analysis of broken crystals: Part II. Practical application to apatite (U-Th)/He thermochronometry’, Geochimica et Cosmochimica Acta 120, 395-416.
  2. Brown, R., Beucher, R., Roper, S., Persano, C., Stuart, F. & Fitzgerald, P. (2013), `Natural age dispersion arising from the analysis of broken crystals. Part I: Theoretical basis and implications for the apatite (U{Th)/He thermochronometer’, Geochimica et Cosmochimica Acta 122, 478-497.
  3. Sambridge, M. (1999a), `Geophysical inversion with a neighbourhood algorithm-I. Searching a parameter space’, Geophysical Journal International 138, 479-494.
  4. Sambridge, M. (1999b), `Geophysical inversion with a neighbourhood algorithm-II. Appraising the ensemble’, Geophysical Journal International 138, 727-746.