Ardennite, tiragalloite and medaite: structural control of (As5+,V5+,Si4+)O4 tetrahedra in silicates
Ardennite, tiragalloite and medaite: structural control of (As5+,V5+,Si4+)O4 tetrahedra in silicates
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Ardennite、tiragalloite 和 medaite：硅酸盐中 (As5 ,V5 ,Si4 )O4 四面体的结构控制
DOI：
10.1180/minmag.2010.074.1.55
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发表时间：
2010
影响因子：
2.7
通讯作者：
T. Armbruster
中科院分区：
文献类型：
--
作者：
M. Nagashima;T. Armbruster
摘要：辉绿石- Mn42+MgAl5[Si5(As5+,V5+)O22](OH)6 （Z = 2）、钛辉石- Mn42+[Si3As5+O12(OH)] （Z = 4）和中介石- Mn62+[Si5(V5+,As5+)O18(OH)] （Z = 4）具有（V5+,As5+,P5+）O4四面体。采用电子探针分析（EMPA）和单晶x射线衍射方法，研究了产自比利时salam - ch<e:1> teau和意大利Vernetto矿的银榴石、产自意大利Gambatesa矿的铁榴石、产自意大利Molinello矿和瑞士Fianel矿的银榴石的晶体化学性质。结构精细化收敛到R1值为2.10-5.67%。化学分析表明，随着Si含量的降低，∑(As+V+P)含量增加。因此，硅取代了四面体配位中的五价阳离子。（As5+,V5+,P5+,Si4+）O4四面体根据它们与SiO4四面体的连接进行分类。辉绿石的（As5+,V5+,P5+,Si4+）O4四面体是分离的，而钛绿石和medaite的（As5+,V5+,P5+,Si4+）O4四面体则终止在一个四面体链上。分离得到的（As5+,V5+,P5+,Si4+）O4四面体的离子半径与平均离子半径呈正相关。对于单T-O-T连接的（As5+,V5+,P5+,Si4+）O4四面体，其平均离子半径也与之相关。此外，最长的桥接T-O键发生在（As，V，P,Si）O4和相邻的SiO4四面体之间。桥接O原子成过键，满足∑(As+V+Si)的电荷要求。
Abstract Several silicate-minerals, such as ardennite - Mn42+MgAl5[Si5(As5+,V5+)O22](OH)6, Z = 2, tiragalloite - Mn42+[Si3As5+O12(OH)], Z = 4 and medaite - Mn62+[Si5(V5+,As5+)O18(OH)], Z = 4 possess (V5+,As5+,P5+)O4 tetrahedra. Using electron-microprobe analysis (EMPA) and single-crystal X-ray diffraction methods, the crystal chemistry of ardennite from Salam-Château, Belgium and the Vernetto mine, Italy, tiragalloite from the Gambatesa mine, Italy, and medaite from the Molinello mine, Italy and the Fianel mine, Switzerland, were studied. Structure refinements converged to R1 values of 2.10-5.67%. According to chemical analysis, the ∑(As+V+P) content increases with decreasing Si content. Thus, Si replaces pentavalent cations in tetrahedral coordination. The (As5+,V5+,P5+,Si4+)O4 tetrahedra are categorized by their connections to SiO4 tetrahedra. The (As5+,V5+,P5+,Si4+)O4 tetrahedron of ardennite is isolated, and those of tiragalloite and medaite terminate a tetrahedral chain. The of the isolated (As5+,V5+,P5+,Si4+)O4 tetrahedron shows a positive correlation with the mean ionic radius. For (As5+,V5+,P5+,Si4+)O4 tetrahedra with one T-O-T link, and mean ionic radius are also correlated. In addition, the longest bridging T-O bond occurs between (As,V,P,Si)O4 and the adjacent SiO4 tetrahedron. The bridging O atom is over-bonded to satisfy the charge requirement of ∑(As+V+Si).
硅锰矿：硅酸盐链中具有氢键的锰辉石类化学和结构变化。
影响因子：
2.1
作者：
Yukiko Imada;本多正平;永嶌真理子
通讯作者：
永嶌真理子