| Co-Investigator(Kenkyū-buntansha) |
SHINNO Isamu Kyushu Univ., Graduate School of Social and Cultural Studies, Professor, 比較社会文化研究科, 教授 (00038465)
TAKASU Akira Shimane Univ., Department of Geosciences, Professor, 総合理工学部, 教授 (00183848)
SAWADA Yoshihiro Shimane Univ., Department of Geosciences, Professor, 総合理工学部, 教授 (80196328)
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| Research Abstract |
Distribution of Fe, Mn, Cu and Ti in the natural and synthetic silicate minerals has been investigated by using spectroscopic and X-ray powder diffraction methods. The Mossbauer spectrum of synthetic Na-melilite in the join NaCaFe^<3+>Si_2O_<7->Ca2MgSi_2O_7 is composed of one-doublet, whereas Ca-melilites and Sr-melilites containing Ca_2Fe^3+AlSiO_<7-> component composed of two-doublets. This result is consistent with Akasaka et al. (1985, 1986), and supports their theory on the distribution of Fe in melilites that distribution of Fe in the tetrahedral sites of melilites is influenced by the covalency of T-O bonding. Although nephelines in the join NaAlSiO_<4->NaFe^<3+>SiO^4 were synthesized successfully, their csytal structures were deformed during the cooling process and deviated from the ideal structure, which were observed by the X-ray powder diffraction patterns. Their Mossbauer spectra were composed of two-doublets as well as melilite, which suggests the different preferency of Fe in the two kinds of tetrahedral sites. However, as the crystal structure at room temperature is deformed, the site occupancy of Fe in the nephelines were variable sample by sample. Thus, further study by in situ observation is necessary. The site occupancies of Fe, Cr and V between octahedral sites and tetrahedral sites in Ca-tschermak type clinopyroxenes has been determined by the present study, and the rule controlling the distribution of these elements has been proposed. By the structural analyses using Rietveld method, present study revealed that Ti distributes dominantly in the tetrahedral sites in the clinopyroxenes containing CaTiAl_2O_6-component, which suggests the Al-avoidance rule holds for in the pyroxene.
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