Isomorphism and Mutual Transformations of S-Bearing Components in Feldspathoids with Microporous Structures

Abstract

The isomorphism of S-bearing feldspathoids belonging to the cancrinite, sodalite, tugtupite, vladimirivanovite, bystrite, marinellite and scapolite structure types has been investigated using a multimethodical approach based on infrared, Raman and electron spin resonance (ESR), as well as ultraviolet, visible and near infrared (UV–Vis–near IR) absorption spectroscopy methods and involving chemical and X-ray diffraction data. Sapozhnikovite Na8(Al6Si6O24)(HS)2 and sulfite and thiosulfate analogues of cancrinite are synthesized hydrothermally and characterized by means of electron microprobe analyses, powder X-ray diffraction and Raman spectroscopy. The possibility of the incorporation of significant amounts of SO42−, S4 and SO32− in the crystal structures of cancrisilite, sulfhydrylbystrite and marinellite, respectively, has been established for the first time. Thermal conversions of S-bearing groups in the synthetic sulfite cancrinite and sapozhnikovite analogues as well as natural vladinirivanovite and S4-bearing haüyne under oxidizing and reducing conditions have been studied using the multimethodical approach. The SO42− and S2− anions and the S3·– radical anion are the most stable S-bearing species under high-temperature conditions (in the range of 700–800 °C); their ratio in the heated samples is determined by the redox conditions and charge-balance requirement. The HS− and S52− anions are stable only under highly reducing conditions.

Structure Modulations and Symmetry of Lazurite-Related Sodalite-Group Minerals

“…Apparently, for some time, domains characterized by different periods of incommensurate structural modulation coexisted in the sample. Similar processes were observed for other samples of LRMs and were explained using complex mutual transformations of sulfate and sulfide groups [25,27].…”

“…Positions of bands and their assignments are given in Tables 1 and 2. The assignment of the bands was made based on data from [5,6,9,10,[21][22][23][24][25][26][27]. The IR spectra are dominated by strong bands of the aluminosilicate framework, and the Raman spectra are dominated by strong bands of the S 3…”

Bystrite, Na7Ca(Al6Si6O24)S52–Cl–: formula redefinition and relationships with other four-layer cancrinite-group minerals

“…Raman spectroscopy is a sensitive tool used to detect polysulfide species (Eckert and Steudel, 2003;Chukanov et al, 2020aChukanov et al, , 2020bSapozhnikov et al, 2021;Chukanov et al, 2022aChukanov et al, , 2022bChukanov et al, , 2022cChukanov et al, , 2022d. Both bystrite and sulfhydrylbystrite show strong Raman bands corresponding to the S 5 2anion which is a yellow chromophore.…”

“…Sample 3 is sulfhydrylbystrite previously described by Kaneva et al (2017). Its empirical formula is H x Na 4.37 K 2.22 Ca 1.17 (Si 6.12 Al 5.87 Fe 0.01 O 24 )S 5.86 Cl 0.09 , where S is total sulfur (Chukanov et al , 2022d). Sample 3 forms red–orange anhedral grains up to 0.4 mm across in a metasomatic rock mainly composed of calcite, diopside, nepheline, lazurite, afghanite, phlogopite and plagioclase, with Ca- and Ba-bearing stronalsite, Na 2 (Sr,Ca,Ba)(Si 4 Al 4 O 16 )⋅ n H 2 O, occurring in the rock in different proportions (Figs 2b and 3).…”

“…The assignment of Raman bands was carried out in accordance with data from Eckert and Steudel (2003), Steudel and Chivers (2019), Rejmak (2020) and Chukanov et al (2020aChukanov et al ( , 2020b2022a, 2022b, 2022d.…”