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331 results on '"Spivak, A. V."'

25. High-Pressure Monosulfide Solid Solution Fe x Ni 1−x S Phases: X-Ray Diffraction Analysis and Raman Spectroscopy.

Author

Spivak, Anna V., Sharapova, Ninel Yu., Setkova, Tatiana V., Bobrov, Andrey V., Korepanov, Vitaliy I., Iskrina, Anastasia V., Zakharchenko, Egor S., Voronin, Mikhail V., and Drozhzhina, Natalia A.

Subjects
SOLID solutions, RAMAN spectroscopy, CRYSTALS, RIETVELD refinement, MATRIX decomposition
Abstract

High-pressure high-temperature (HPHT) crystalline monosulfide solid solution (Mss) phases (FexNi1−xS, x = 0.90, 0.75, 0.50, 0.25), troilite (FeS I), and α-NiS of the Fe-Ni-S system were synthesized at 7 GPa and 900–1550 °C. The structural parameters of the obtained phases were refined by XRD using the Rietveld method. Factor group analysis revealed the number of active Raman modes for FeS I and α-NiS. Raman spectra of troilite, α-NiS, and Mss phases were obtained. It was shown that the Raman spectra of Mss phases and α-NiS have a similar topology. The Raman spectra of the experimental phases in the Fe-Ni-S system were analyzed with non-negative matrix factorization, which provided a meaningful concentration dependence of the spectral patterns. The spectral components were assigned to the FeS I and α-NiS structures. The structural and spectroscopic studies show linear dependencies of unit cell parameters and spectral components on composition and confirm the existence of a series of monosulfide solid solution FexNi1−xS. [ABSTRACT FROM AUTHOR]

Published
2024
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39. Formation of Richterite in the Enstatite–Diopside System in the Presence of K2CO3–Na2CO3–CO2–H2O Fluid: Implications for the Processes of Mantle Metasomatism.

Author

Limanov, E. V., Butvina, V. G., Safonov, O. G., Spivak, A. V., Van, K. V., and Vorobey, S. S.

Subjects
METASOMATISM, BANKING industry, RAMAN spectroscopy, FLUIDS, AMPHIBOLES, PERIDOTITE
Abstract

The paper presents data on the formation of K–Na richterite in the enstatite + diopside association with K2CO3–Na2CO3–CO2–H2O fluid at 3 GPa and 1000°C as a model for the formation of this mineral in peridotites of the upper mantle. Richterite formation depends on the (H2O + CO2)/(K2CO3 + Na2CO3) and K2CO3/Na2CO3 ratios in the starting material. A high concentration of alkaline components in the fluid leads to the decomposition of clinopyroxene, the formation of olivine, and a change in the component composition of the pyroxene and amphibole. Fluids with a high potassium concentration are favorable for the formation of K-richterite similar in composition to that formed in metasomatized peridotites of the upper mantle. In some cases, such a fluid leads to the decomposition of amphibole and stabilization of alkaline melt. An increase in the activity of the sodium component results in richterite similar in composition to richterite from lamproites. The clarified relations can be used to assess the activities of fluid components and conditions for the formation of K-richterite. To update the data bank of the Raman spectra of minerals, the largest and most homogeneous amphibole crystals of different compositions were studied. [ABSTRACT FROM AUTHOR]

Published
2024
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