Инд. авторы:	Golovin A.V., Korsakov A.V., Gavryushkin P.N., Zaitsev A.N., Thomas V.G., Moine B.N.
Заглавие:	Raman spectra of nyerereite, gregoryite, and synthetic pure Na2Ca(CO3)(2): diversity and application for the study micro inclusions
Библ. ссылка:	Golovin A.V., Korsakov A.V., Gavryushkin P.N., Zaitsev A.N., Thomas V.G., Moine B.N. Raman spectra of nyerereite, gregoryite, and synthetic pure Na2Ca(CO3)(2): diversity and application for the study micro inclusions // Journal of Raman Spectroscopy. - 2017. - Vol.48. - Iss. 11. - P.1559-1565. - ISSN 0377-0486. - EISSN 1097-4555.
Внешние системы:	DOI: 10.1002/jrs.5143; РИНЦ: 31067000; WoS: 000416235800025;
Реферат:	eng: In this study, we present Raman spectra of pure synthetic hydrothermal orthorhombic Na2Ca(CO3)(2) carbonate together with naturally occurring orthorhombic nyerereite (Na,K)(2)Ca(CO3)(2) and hexagonal gregoryite (Na,K,Ca-x)(2-x)(CO3) from Oldoinyo Lengai natrocarbonatites (Tanzania) to show the diversity of spectra and permit the use of Raman spectroscopy to identify these minerals in small inclusions. Synthetic orthorhombic Na2Ca(CO3)(2) carbonate has only one type of Raman spectrum, which is independent of the crystallographic orientation. The Raman spectra of nyerereite can be divided into three types, depending on intensity of symmetric stretching (1)(CO3)(2-) vibrations in region 1070-1090cm(-1). All these nyerereite types have identical chemical compositions; thus, the differences in Raman spectra are likely to be related to crystallographic orientations. Some nyerereite Raman spectra can be erroneously interpreted as gregoryite because of similarity in peak position of strong (1)(CO3)(2-) band. However, the diagnostic features of the gregoryite Raman spectrum can be summarized as follows: (1) presence of a symmetric peak attributed to (1)(CO3)(2-) vibrations at 1078cm(-1); (2) presence of one broad band (4)(CO3)(2-) with a peak position at 702-707cm(-1); (3) a stronger band (1)(SO4)(2-) that occurs at 1003-1006cm(-1) and the presence of additional weaker bands (2)(SO4)(2-) and (4)(SO4)(2-) at 460-462 and 630-635cm(-1); and (4) a (1)(PO4)(3-) band that appears at 952-954cm(-1). Incorporation of significant amounts of additional cations (up to 0.5apfu) and particularly K (up to 0.4apfu) in natural nyerereites leads to a change in the commensurately modulated structure of pure Na2Ca(CO3)(2) (P2(1)ca), which becomes an incommensurately modulated structure (less ordered) with space group Cmcm; and these changes are reflected in a reduction of the number of Raman bands in symmetric stretching (1)(CO3)(2-) and inplane bending (4)(CO3)(2-) vibration regions or even the complete absence of the Raman bands in antisymmetric stretching (3)(CO3)(2-) and 2*(2)(CO3)(2-) vibration regions compared with pure Na2Ca(CO3)(2). Copyright (c) 2017 John Wiley & Sons, Ltd.
Ключевые слова:	raman spectroscopy; gregoryite; nyerereite; alkaline carbonates; carbonatite and kimberlite;
Издано:	2017
Физ. характеристика:	с.1559-1565