Distribution of transition elements in tetrahedral sites of silicates and its effect on change of the crystal structures

过渡元素在硅酸盐四面体位点的分布及其对晶体结构变化的影响

• 批准号: 08454158
• 负责人: AKASAKA Masahide
• 金额: $ 4.86万
• 依托单位: SHIMANE UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454158/
• 关键词: transition elements; silicates; synthesis; Mossbauer; X-ray powder diffraction; Rietveld method; tetrahedral sites; site occupancy; 結晶構造; メスバウアー; リートヴエルト法; 4配位席; 準長石; ネフェリン

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.

本文用光谱和X射线粉末衍射方法研究了Fe、Mn、Cu、Ti在天然硅酸盐矿物和合成硅酸盐矿物中的分布。合成的钠黄长石在NaCaFe^&lt;3+&gt; Si_2O_Ca2MgSi_2O_7中的穆斯堡尔谱<7->由一双峰组成，而含有Ca_2Fe^3+ AlSiO_2成分的钙黄长石和Sr黄长石<7->则由两双峰组成。这一结果与赤坂等（1985，1986）的结果一致，支持了他们关于黄长石中Fe分布的理论，即Fe在黄长石四面体位置的分布受T-O键共价性的影响。虽然成功地合成了NaAlSiO_<4->NaFe^&lt;3+&gt;SiO^4晶体中的霞石，但X射线粉末衍射分析表明，晶体结构在冷却过程中发生了变形，偏离了理想结构。它们的穆斯堡尔谱都是由黄长石和双峰组成的，说明铁在两种四面体位置上的选择性不同。然而，由于在室温下的晶体结构是变形的，在霞石中的Fe的占位是可变的样品。因此，有必要通过原位观察进行进一步的研究。本文确定了Ca-tschermak型单斜辉石中Fe、Cr、V在八面体位和四面体位之间的占位位置，提出了控制这些元素分布的规律。通过Rietveld方法的结构分析，发现在含CaTiAl_2O_6组分的单斜辉石中，Ti主要分布在四面体位置，表明辉石中存在避Al规则。

项目成果

Akasaka M., Ohashi H., Shinno I: "Distribution of Trivalent Al,Fe and Ga Ions in Synthetic Calcium Tschermak-type Clinopyrorenes" Geochemical Studies on Synthetic and Natural Roch Systems. 166-181 (1997)

Akasaka M.、Ohashi H.、Shinno I：“合成钙 Tschermak 型单斜吡咯烯中三价 Al、Fe 和 Ga 离子的分布”合成和天然 Roch 系统的地球化学研究。

Masahide Akasaka, Haruo Ohashi and Isamu Shinno: "Distribution of trivalent Al, Fe and Ga ions in synthetic calcium Tschermak-type clinopyroxenes" Geochemical Studies on Synthetic and Natural Rock Systems (Gupta, A., Onuma, K.and Arima, M., eds). New Delh

Masahide Akasaka、Haruo Ohashi 和 Isamu Shinno：“合成钙 Tschermak 型单斜辉石中三价 Al、Fe 和 Ga 离子的分布”合成和天然岩石系统的地球化学研究（Gupta, A.、Onuma, K. 和 Arima, M.

Shibata G., Akasaka M., Kimura N.: "Area analysis of chondrules in the Allende meteoriteby electron microprobe" Earth Science (Chikyu Kagaku). 51・3. 173-176 (1997)

Shibata G.，Akasaka M.，Kimura N.：“通过电子探针对阿连德陨石中的球粒进行面积分析”地球科学（地球科学）51・3（1997）。

Akasaka M., Kimura Y., Omori Y., Sakakibara M., Shinno I., Togari K.: "57Fe Mossbauer study of pumpellyite-okhotskite-zulgoldite series minerals" Mineralogy and Petrology. 61. 181-198 (1997)

Akasaka M.、Kimura Y.、Omori Y.、Sakakibara M.、Shinno I.、Togari K.：“57Fe Mossbauer 对 Pumpellyite-okhotskite-zulgoldite 系列矿物的研究”矿物学和岩石学。

Takasu A., Sakamoto S.: "End-member kosmochlor and nyboite discovered from the Itoigawa area in the Omi-Renge belt, southwest Japan" Earth Science (Chikyu Kagaku). 52. 341-344 (1998)

Takasu A.、Sakamoto S.：“在日本西南部 Omi-Renge 地带的糸鱼川地区发现的端元 kosmoluc 和 nyboite”地球科学（Chikyu Kagaku）。