Crystal Structure and Raman Spectroscopy of Synthetic Potassium Richterite

IF 0.7 4区地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY

Doklady Earth Sciences Pub Date : 2024-09-16 DOI:10.1134/s1028334x24602906

E. V. Limanov, V. G. Butvina, O. G. Safonov, A. V. Spivak, A. V. Kuzmin, L. Ya. Aranovich

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Abstract

The structures of two K-richterite crystals with the crystal chemical formulas (K_0.44Na_0.32\(\square \)_0.24)_Σ=1(Ca_1.18Na_0.82)_Σ=2Mg₅Si₈O₂₂OH₂ and (K_0.83Na_0.02\(\square \)_0.15)_Σ=1(Ca_1.11Na_0.89)_Σ=2Mg₅Si₈O₂₂OH₂ synthesized at a pressure of 3 GPa and a temperature of 1000°С in the MgSiO₃ + CaMgSi₂O₆ + K₂CO₃ + Na₂CO₃ + CO₂ + H₂O system were studied by single-crystal X-ray analysis and Raman spectroscopy. The monoclinic cell parameters were obtained: a = 10.0256(5) and 9.9748(11) Å, b = 17.9874(7) and 17.9879(16) Å, c = 5.2687(3) and 5.2746(6) Å, V_e.c. = 916.17(18) and 918.52(8) Å³, β = 104.520(12)° and 104.821(5)°, sp. gr. С2/m (12), and Z = 2. The sites M(1), M(2), and M(3) are inhabited by Mg²⁺, while site M(4) is occupied simultaneously by Ca²⁺ and Na⁺. The Na⁺ cations not included in M(4) are located in position A, which also accommodates K⁺ cations. Raman spectroscopy made it possible to reveal vacancies in position A in both samples. The structure corresponds to the “ideal” structure of richterite group minerals. The unit cell volume of the measured crystals is directly proportional to the K content in position A. Based on the generalization of new and published data, an equation of the dependence of V_u.c. for amphiboles of the richterite Na(NaCa)Mg₅Si₈O₂₂(OH)₂–K-richterite K(NaCa)Mg₅Si₈O₂₂(OH)₂ series with a low tremolite component on the K content in position A is proposed.

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合成钾长石的晶体结构和拉曼光谱

通过单晶 X 射线分析和拉曼光谱，研究了在压力为 3 GPa、温度为 1000°С 的条件下，在 MgSiO3 + CaMgSi2O6 + K2CO3 + Na2CO3 + CO2 + H2O 体系中合成的(K0.83Na0.02(\quare \)0.15)Σ=1(Ca1.11Na0)Σ=2Mg5Si8O22OH2。得到的单斜晶胞参数为：a = 10.0256(5)和 9.9748(11)埃，b = 17.9874(7)和 17.9879(16)埃，c = 5.2687(3)和 5.2746(6)埃，Ve.c. = 916.17(18)和 918.52(8)埃3，β = 104.520(12)°和 104.821(5)°，sp. gr.С2/m (12)，Z = 2。位点 M(1)、M(2) 和 M(3) 被 Mg2+ 占据，而位点 M(4) 则同时被 Ca2+ 和 Na+ 占据。不包括在 M（4）中的 Na+ 阳离子位于位置 A，该位置也可容纳 K+ 阳离子。通过拉曼光谱，可以发现这两种样品中 A 位都存在空位。这种结构符合富钛铁矿类矿物的 "理想 "结构。在归纳新数据和已公布数据的基础上，提出了透闪石成分较低的富闪石 Na(NaCa)Mg5Si8O22(OH)2-K-richterite K(NaCa)Mg5Si8O22(OH)2 系列闪石的 Vu.c. 与 A 位 K 含量的关系式。

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来源期刊

Doklady Earth Sciences 地学-地球科学综合

CiteScore

1.40

自引率

22.20%

发文量

138

审稿时长

3-6 weeks

期刊介绍： Doklady Earth Sciences is a journal that publishes new research in Earth science of great significance. Initially the journal was a forum of the Russian Academy of Science and published only best contributions from Russia. Now the journal welcomes submissions from any country in the English or Russian language. Every manuscript must be recommended by Russian or foreign members of the Russian Academy of Sciences.