caa a22 4500 445390069 CHVBK 20180317143043.0 cr unu---uuuuu 170323e20110301xx s 000 0 eng 10.1007/s00710-010-0143-5 doi (NATIONALLICENCE)springer-10.1007/s00710-010-0143-5 Crystal chemistry of nephelines from ijolites and nepheline-rich pegmatites: influence of composition and genesis on the crystal structure investigated by X-ray diffraction [Elektronische Daten] [Predrag Vulić, Tonči Balić-Žunić, Louise Belmonte, Volker Kahlenberg] Ten nepheline single crystals from five different localities representing rocks from nepheline-syenite pegmatites to urtite, ijolite and cancrinite-ijolite were investigated chemically and structurally. The chemical compositions were determined by electron microprobe, whereas the crystal structures were refined against X-ray diffraction data to R values of 0.022-0.031. In all cases the crystal structures conformed to space group P63, but at the same time all crystals produced some satellite reflections testifying to the modulation effects in their structure. This work confirms the presence of satellite reflections as a universal property of nepheline and resolves some controversy about this issue present in older works. The samples show a range of compositions with variable excess of Si over Al combined with vacancies in the alkaline sites. Vacancies are present exclusively in the symmetric ditrigonal channels occupied preferentially by K atoms in natural nepheline. The influence of the variable amounts of K, Na and vacancies to the increase of volume at this site is shown to be in the order □>K>Na. It has been confirmed that natural nepheline can partly depart from Loewenstein's rule and show some degree of disorder in the Si/Al distribution. Most of the samples revealed a practically full Si-Al-ordering, but the crystals from one of the nepheline-syenite pegmatites in Langesundsfjord, Norway and from the type locality of ijolite, Iivaara, Finland, showed a disorder of 10-20% suggesting a different cooling history for these rocks. Springer-Verlag, 2011 Vulić Predrag Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, 6020, Innsbruck, Austria aut Balić-Žunić Tonči Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark aut Belmonte Louise Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark aut Kahlenberg Volker Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, 6020, Innsbruck, Austria aut Mineralogy and Petrology Springer Vienna 101/3-4(2011-03-01), 185-194 0930-0708 101:3-4<185 2011 101 710 https://doi.org/10.1007/s00710-010-0143-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00710-010-0143-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Vulić Predrag Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, 6020, Innsbruck, Austria aut NATIONALLICENCE 700 1- Balić-Žunić Tonči Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark aut NATIONALLICENCE 700 1- Belmonte Louise Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, 1350, Copenhagen, Denmark aut NATIONALLICENCE 700 1- Kahlenberg Volker Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, 6020, Innsbruck, Austria aut NATIONALLICENCE 773 0- Mineralogy and Petrology Springer Vienna 101/3-4(2011-03-01), 185-194 0930-0708 101:3-4<185 2011 101 710 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer