{"title":"Hydrogen defects in feldspars: alkali-supported dehydrogenation of sanidine","authors":"Harald Behrens","doi":"10.1007/s00269-023-01242-9","DOIUrl":null,"url":null,"abstract":"<div><p>In the first two papers of this series [Behrens, Phys Chem Minerals 48:8, 2021a; Behrens, Phys Chem Minerals 48:27, 2021b], incorporation of hydrogen in the feldspar structure, partitioning of hydrogen between feldspars and gases/fluids and self-diffusion of hydrogen in feldspars have 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 are 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. in Defect Diffus Forum 363: 79–84, 2015; Hergemöller et al. in Phys Chem Minerals 44:345–351, 2017) supports a mechanism of proton diffusion charge-compensated by Na<sup>+</sup> diffusion for hydrogen removal in the sanidines under dry conditions.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2023-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-023-01242-9.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-023-01242-9","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
In the first two papers of this series [Behrens, Phys Chem Minerals 48:8, 2021a; Behrens, Phys Chem Minerals 48:27, 2021b], incorporation of hydrogen in the feldspar structure, partitioning of hydrogen between feldspars and gases/fluids and self-diffusion of hydrogen in feldspars have 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 are 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. in Defect Diffus Forum 363: 79–84, 2015; Hergemöller et al. in Phys Chem Minerals 44:345–351, 2017) supports a mechanism of proton diffusion charge-compensated by Na+ diffusion for hydrogen removal in the sanidines under dry conditions.
期刊介绍:
Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are:
-Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.)
-General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.)
-Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.)
-Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.)
-Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems
-Electron microscopy in support of physical and chemical studies
-Computational methods in the study of the structure and properties of minerals
-Mineral surfaces (experimental methods, structure and properties)