Affiliation:
1. Leibniz University Hannover
Abstract
Abstract
In the first two papers of this series (Behrens 2022a,b), incorporation of hydrogen in the feldspar structure, partitioning of hydrogen between feldspars and gases/fluids and self diffusion of hydrogen in feldspars has been discussed, with particular focus on sanidine. Here, the results of reactions between sanidine containing strongly bonded hydrogen defects and (Na,K)Cl are presented. Experiments were performed at ambient pressure at temperatures of 605–1000°C and hydrogen profiles were measured by IR microspectroscopy. Profiles can be interpreted by an incomplete dehydrogenation at the crystal surface or a strong concentration dependence of hydrogen diffusivity. Both is consistent with hydrogen located on interstitial sites and difficult to substitute by the larger alkali ions. Chemical diffusivities of hydrogen derived from fitting of the profiles or Boltzmann-Matano analysis are similar to self diffusivities determined by D/H exchange experiments. Activation energies are also comparable. Comparison to sodium and potassium diffusion data for sanidine (Wilangowski et al 2015, Hergemöller et al. 2017) support a mechanism of proton diffusion charge-compensated by Na+ diffusion for hydrogen removal in the sanidines under dry conditions.
Publisher
Research Square Platform LLC