Abstract Sulfur-enriched sodalite-group feldspathoids from the Lovozero alkaline complex (Kola Peninsula, Russia) and products of their laboratory, anthropogene, and natural thermal and radiation-induced transformations have been studied by electron-probe nicroanalysis, single-crystal X-ray diffractometry, Raman, infrared, and electron spin resonance spectroscopy, and ultra-violate, visible, and near-infrared absorption spectroscopy. Sodalite Na8[Al6Si6O24]Cl2 and sapozhnikovite Na8[Al6Si6O24](HS)2 form an almost continuous, isomorphous series in highly agpaitic feldspathoid syenites and their pegmatites with the Cl : HS ratio ranging from Cl100(HS)0 to Cl12(HS)88 (mol %)]. In the Lovozero complex, the HS– hydrosulfide anion has turned out to be the major form of the sulfidic sulfur occurrence in minerals of this group, including sodalite–hackmanite. It has been found that sapozhnikovite and the HS-rich sodalite phase transition to it are important rock-forming minerals of some rocks of this complex, including a new highly alkali rock named poikilitic nepheline–sapozhnikovite syenite. Sapozhnikovite and intermediate members of the sodalite–sapozhnikovite series are the sensitive geochemical oxymeter indicator, which points out the reducing conditions of the mineral formation. Upon heating, the HS– anion in the sodalite–sapozhnikovite series minerals destroys and sulfur passes to the polysulfide with the formation of, first, the <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\text{S}}_{2}^{{ \bullet - }}\)</EquationSource>  </InlineEquation> radical anion (500–600°C) and, then, the <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\text{S}}_{3}^{{ \bullet - }}\)</EquationSource>  </InlineEquation> radical anion (700°C and higher). The <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\({\text{S}}_{3}^{{ \bullet - }}\)</EquationSource>  </InlineEquation> groups also appear at the radiation-induced transformation of these minerals. Under the natural radioactive irradiation, at the contact with Th-enriched steenstrupine, an intermediate member of the sodalite–sapozhnikovite series transformed to the <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\({\text{S}}_{3}^{{ \bullet - }}\)</EquationSource>  </InlineEquation> rich sodalite variety with the simplified formula Na8[Al6Si6O24][Cl,(S3)] earlier unknown in nature.

Rock-Forming Sodalite–Sapozhnikovite Series Feldspathoids from the Lovozero Alkaline Complex (Kola Peninsula, Russia): Isomorphism, Thermal and Radiation-Induced Transformations, and Genetic Mineralogy

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2025年12月1日

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I. V. Pekov,
N. V. Chukanov,
V. D. Shcherbakov,
M. F. Vigasina,
R. Yu. Shendrik,
F. D. Sandalov,
S. V. Vyatkin,
A. G. Turchkova

摘要

Abstract

Sulfur-enriched sodalite-group feldspathoids from the Lovozero alkaline complex (Kola Peninsula, Russia) and products of their laboratory, anthropogene, and natural thermal and radiation-induced transformations have been studied by electron-probe nicroanalysis, single-crystal X-ray diffractometry, Raman, infrared, and electron spin resonance spectroscopy, and ultra-violate, visible, and near-infrared absorption spectroscopy. Sodalite Na₈[Al₆Si₆O₂₄]Cl₂ and sapozhnikovite Na₈[Al₆Si₆O₂₄](HS)₂ form an almost continuous, isomorphous series in highly agpaitic feldspathoid syenites and their pegmatites with the Cl : HS ratio ranging from Cl₁₀₀(HS)₀ to Cl₁₂(HS)₈₈ (mol %)]. In the Lovozero complex, the HS^– hydrosulfide anion has turned out to be the major form of the sulfidic sulfur occurrence in minerals of this group, including sodalite–hackmanite. It has been found that sapozhnikovite and the HS-rich sodalite phase transition to it are important rock-forming minerals of some rocks of this complex, including a new highly alkali rock named poikilitic nepheline–sapozhnikovite syenite. Sapozhnikovite and intermediate members of the sodalite–sapozhnikovite series are the sensitive geochemical oxymeter indicator, which points out the reducing conditions of the mineral formation. Upon heating, the HS^– anion in the sodalite–sapozhnikovite series minerals destroys and sulfur passes to the polysulfide with the formation of, first, the \({\text{S}}_{2}^{{ \bullet - }}\) radical anion (500–600°C) and, then, the \({\text{S}}_{3}^{{ \bullet - }}\) radical anion (700°C and higher). The \({\text{S}}_{3}^{{ \bullet - }}\) groups also appear at the radiation-induced transformation of these minerals. Under the natural radioactive irradiation, at the contact with Th-enriched steenstrupine, an intermediate member of the sodalite–sapozhnikovite series transformed to the \({\text{S}}_{3}^{{ \bullet - }}\) rich sodalite variety with the simplified formula Na₈[Al₆Si₆O₂₄][Cl,(S₃)] earlier unknown in nature.