摘要
近年来，在我国山东蒙阴及南非、西北澳大利亚的金伯利岩、钾镁煌斑岩等地幔岩中陆续发现了一系列新的钛酸盐矿物，包括蒙山矿系列、沂蒙矿系列、柱红石系列、钾钡石及易解石类矿物新种。它们分别具ＡＭ２１Ｏ３８，ＡＭ１２Ｏ１９，Ａ０～２Ｂ８Ｏ１６，Ａ２Ｂ６Ｏ１３，ＡＢ２Ｏ６等化合物的结构，其共同特征是含亲石大阳离子（ＬＩＬ：Ｋ，Ｂａ，Ｓｒ，ＲＥＥ等）及硅酸盐不相容元素（ＳＩＥ：Ｔｉ，Ｚｒ，Ｎｂ，Ｔａ…）。笔者通过对其中一些矿物的晶体结构测定，综合国内外的有关资料，指出大阳离子在这些复杂钛酸盐中以三种基本形式存在：＂三明治＂型、通道型及替代氧进入最紧密堆积型，其中，以后两种最为重要。在通道型中，分数量大阳离子的存在可能引起不相称调制结构；大阳离子替代型中，含大阳离子层与纯氧层的不同组合将引起结构类型的变化，而层间阳离子的有序化有可能产生超结构。ＡＭ１２Ｏ１９，ＡＭ２１Ｏ３８结构型皆以尖晶石结构段为基本部件，其中的大阳离子具可交换性，从而为其交代成因提供了晶体结构方面的依据。
Several new titanate minerals have been found in recent years in kimberlites,lamproltes and the other mantle rocks of Shandong Province of China,South Africa and Northwest of Australia. These minerals include LIMA,YIHA,Periodites series,jeppeite and some new phases of aeschynite.They are of different compositions and structures:AM21O28,AM12O19,A0-2B8O16,A2B6O13,and AB2O6,and contain large ion lithophile elements (LIL:K,Ba,Sr,REE…) and sillicate incompatible element(SIE:Ti,Zr,Nb,Ta…). By crystal structure determination and study of concerned literatures, the auther found the large ions in these complex titanates existing in three forms:'sandwich'type,'tunnel'type and'close-packed'insteading for oxgen type.In'tunnel'type,the fractional large ion may give an incommensurate modulating structure ; in'close packed' type, the different associations between layers containing large ions and pure oxygen make some variable structures,and the order of the ions in one layer may form superstructures. AM12O19 and AM21O38 are all spinelbased structures;the large ions between blocks have exchangeability,which provides evidence for their metasomatic cause of formation.
出处
《地质科技情报》
CAS
CSCD
北大核心
1994年第1期37-44,共8页
Geological Science and Technology Information
基金
&国家自然科学基金
关键词
钛酸盐
阳离子
金伯利岩
晶体
complex titanates,large ion,structure type,spinel-like structure,superstructure
