• Nadezhda V. Shchipalkina
  • Igor V. Pekov
  • Sergey N. Britvin
  • Natalia N. Koshlyakova
  • Evgeny G. Sidorov

The influence of pentavalent arsenic and phosphorus on crystal chemical features of the feldspar framework was studied on the minerals belonging to the sanidine–filatovite solid-solution series from fumarolic exhalations of the Tolbachik volcano (Kamchatka, Russia). The reported feldspars demonstrate the first example of natural continuous solid solution between silicate and arsenate. The content of As2O5 varies from 0.0 to 45 wt% along with the highest phosphorus content found in natural feldspars: up to 5 wt% P2O5. The major substitution schemes in the studied feldspars are Al3+ + M5+ → 2Si4+ and M2+ + M5+ → Al3+ + Si4+, where M2+ = Zn and Cu and M5+ = As and P. The crystal structures of four samples with empirical formulae K0.95[(Si2.98Al0.93Fe0.08As0.02)Ʃ4.01O8] (space group C2/m), (K0.91Na0.06Ca0.03)Ʃ1.00[(Si2.81Al1.14As0.03P0.03Fe0.01)Ʃ4.02O8] (C2/m), K0.82[(Al1.92As1.11Si0.89Zn0.05Fe0.03Cu0.02P0.01)Ʃ4.03O8] (I2/c), K0.99[(Si1.87Al1.51As0.53P0.05Fe0.02Cu0.01)Ʃ3.99O8] (I2/c) were studied. The phase transition in the sanidine–filatovite solid-solution series is C2/m → I2/c. This is caused by the change of the Al:(Si + As) ratio from 1:3 in sanidine to 1:1 in filatovite along with significant ordering of Al, Si and As in the framework.

Original languageEnglish
Article number1
Number of pages15
JournalPhysics and Chemistry of Minerals
Volume47
Issue number1
Early online date9 Dec 2019
DOIs
StatePublished - 1 Jan 2020

    Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

    Research areas

  • Arsenic, Filatovite, Fumarole sublimate, Isomorphism in tectosilicate, Phosphorus, Potassic feldspar, Sanidine, Tolbachik volcano

ID: 50635346