Diffusion of helium in olivine at 1 atm and 2.7 GPa

Helium diffusion in olivine based on first principles calculations

“…As olivine consists of over 50% of earth's upper mantle, there have been several studies in the last three decades on the diffusion of He in olivine (Hart, 1984;Trull et al, 1991;Futagami et al, 1993;Trull and Kurz, 1993;Burnard, 2004;Shuster et al, 2004;Tolstikhin et al, 2010 andWatson, 2012). However, the different experimental methods (e.g.…”

“…However, the different experimental methods (e.g. direct profiling method employed in a recent study of (Cherniak and Watson, 2012) and the step-heating bulk release method that had been adopted previously) provided very different results, with diffusion rates ranging from 10 -16 m 2 /s to 10 -11 m 2 /s at 1300 K under ambient pressure (Hart, 1984;Shuster et al, 2004;Tolstikhin et al, 2010 andWatson, 2012).…”

Diffusion of helium in carbonates: Effects of mineral structure and composition

“…We utilize a technique which involves implantation of 3 He atoms followed by isothermal heating, and then measurement of the relaxed 3 He profile using nuclear reaction analysis (NRA) with the reaction 3 He(d,p) 4 He (Cherniak et al, 2009). Similar experimental and analytical procedures have been used previously to characterize diffusion in a variety of minerals, including zircon and apatite (Cherniak et al, 2009), titanite and rutile (Cherniak and Watson, 2011) olivine (Cherniak and Watson (2012), and monazite .…”

“…Analyses were performed at the 4 MeV Dynamitron accelerator at the University at Albany. This nuclear reaction has been used to measure 3 He in a variety of minerals and ceramic materials (e.g., Gosset et al, 2002;Costantini et al, 2003;Trocellier et al, 2003;Miro et al, 2006;Cherniak et al, 2009;Cherniak and Watson, 2011, 2012. The protons produced in the reaction, along with backscattered deuterons and products of various (d,p) and (d,a) reactions induced with light elements contained in the samples, were detected with a solid state surface barrier detector with 1500 lm depletion depth and 100 mm 2 area positioned at 167.5°with respect to the incident beam.…”

“…The cross-section of the reaction has a maximum around 430 keV, but the peak is relatively broad (several hundred keV in width) so it is not possible to obtain high depth resolution for 3 He profiling using typical approaches for resonant or non-resonant NRA. For these analyses, we take the approach used in earlier studies (Cherniak et al, 2009;Cherniak and Watson, 2011, 2012, performing analyses over a range of energies (0.5-0.9 MeV for the samples implanted with 100 keV 3 He, 1.2-1.6 MeV for samples implanted with 3 MeV 3 He) to better define the spreading of the helium profile due to diffusion, with the proton yield from an annealed sample (i.e., a sample from a diffusion experiment) compared to an implanted, unannealed sample at each energy step. It should be emphasized that the sampling depth in the carbonates in these 3 He analyses extends to greater than ten microns, considering the ranges in carbonates of deuterons with the incident energies used in the NRA measurements (e.g., Ziegler and Biersack, 2006).…”