Noble gas diffusivity hindered by low energy sites in amphibole

Colin R.M. Jackson, David L. Shuster, Stephen W. Parman, Andrew James Smye

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The diffusion kinetics of He and Ne in four amphibole specimens have been experimentally determined using stepwise degassing analysis of samples previously irradiated with energetic protons, and Arrhenius relationships have been fit to these data. The primary finding is that He and Ne diffusivities are systematically lower in amphiboles that have higher concentrations of unoccupied ring sites, suggesting that unoccupied ring sites act as traps for migrating noble gases. Ring site influence of noble gas diffusivity in amphiboles has substantial implications for 40Ar/39Ar thermochronology applied to these phases and the efficiency of noble gas recycling in subduction zones. These findings are consistent with the correlation between noble gas solubility and the concentration of unoccupied ring sites in amphibole (Jackson et al., 2013a, 2015) but are inconsistent with the ionic porosity model for noble gas diffusion (Fortier and Giletti, 1989; Dahl, 1996). Rather, these findings suggest that the topology of ionic porosity and absolute volume of ionic porosity compete in determining the rate at which noble gases diffuse.

Original languageEnglish (US)
Pages (from-to)65-75
Number of pages11
JournalGeochimica et Cosmochimica Acta
Volume172
DOIs
StatePublished - Jan 1 2016

Fingerprint

Amphibole Asbestos
Noble Gases
noble gas
amphibole
diffusivity
energy
Porosity
porosity
thermochronology
Diffusion in gases
Degassing
degassing
topology
subduction zone
Protons
Recycling
solubility
energetics
recycling
Solubility

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

Cite this

Jackson, Colin R.M. ; Shuster, David L. ; Parman, Stephen W. ; Smye, Andrew James. / Noble gas diffusivity hindered by low energy sites in amphibole. In: Geochimica et Cosmochimica Acta. 2016 ; Vol. 172. pp. 65-75.
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Noble gas diffusivity hindered by low energy sites in amphibole. / Jackson, Colin R.M.; Shuster, David L.; Parman, Stephen W.; Smye, Andrew James.

In: Geochimica et Cosmochimica Acta, Vol. 172, 01.01.2016, p. 65-75.

Research output: Contribution to journalArticle

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AB - The diffusion kinetics of He and Ne in four amphibole specimens have been experimentally determined using stepwise degassing analysis of samples previously irradiated with energetic protons, and Arrhenius relationships have been fit to these data. The primary finding is that He and Ne diffusivities are systematically lower in amphiboles that have higher concentrations of unoccupied ring sites, suggesting that unoccupied ring sites act as traps for migrating noble gases. Ring site influence of noble gas diffusivity in amphiboles has substantial implications for 40Ar/39Ar thermochronology applied to these phases and the efficiency of noble gas recycling in subduction zones. These findings are consistent with the correlation between noble gas solubility and the concentration of unoccupied ring sites in amphibole (Jackson et al., 2013a, 2015) but are inconsistent with the ionic porosity model for noble gas diffusion (Fortier and Giletti, 1989; Dahl, 1996). Rather, these findings suggest that the topology of ionic porosity and absolute volume of ionic porosity compete in determining the rate at which noble gases diffuse.

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