Effects of rubidium and cesium on the structural states of potash feldspars from rare-metal pegmatites
Effects of rubidium and cesium on the structural states of potash feldspars from rare-metal pegmatites
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铷和铯对稀有金属伟晶岩钾长石结构状态的影响
DOI：
10.1080/00206818209467098
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发表时间：
1979
影响因子：
2.6
通讯作者：
G. G. Afonina
中科院分区：
文献类型：
--
作者：
G. G. Afonina
钾长石KFS具有高水平的Rb（高达3。5%）和Cs（高达0. 5%）常见于稀有金属花岗岩伟晶岩中（Borovik-Romanova和Kalita，1958年; Sosedko，1961年; Uchakin等人，1962; Filippova，1970; Shmakin等人，1975年），并作为指示矿物的稀有金属矿化。单斜和三斜钾长石发生与高水平的这些元素，这导致了相互矛盾的看法Rb和Cs对这些长石的结构状态的影响。Gordiyenko和Kamentsev（1967）研究了苏联欧洲部分地区伟晶岩中的KFS，并确定Rb和Cs以无序单斜的形式积累，而这些元素在这些伟晶岩的微斜长石中的水平很低。他们认为，所有这些KFS的形成和随后的蚀变条件有利于形成三斜晶型，因此他们得出结论，Rb和Cs的进入有利于无序单斜晶型的结晶，并阻止固态的有序化。另一方面，亚马逊岩具有高水平的Rb（高达3.1%）和Cs（高达0.17%）（Marin等人，1974），并且它们总是微斜长石;来自西伯利亚存款中伟晶岩的KFS（Shmakin等人，1975）是三斜晶系，无论Rb和Cs的水平如何。红柱石长石的单斜无序形式已被反复合成（Barrer和McCollum，1953; Ghelis和Lagache，1972等）。在微斜长石和低钠长石的天然样品中，Rb对K和Na的离子交换置换使Borutskaya（1975）能够合成三斜晶系的红柱石长石。她认为KFS的结构状态与大的Rb和Cs阳离子的水平无关。
Potash feldspars KFS with high levels of Rb (up to 3. 5%) and Cs (up to 0. 5%) are common in rare-metal granite pegmatites (Borovik-Romanova and Kalita, 1958; Sosedko, 1961; Uchakin et al., 1962; Filippova, 1970; Shmakin et al., 1975) and act as indicator minerals for rare-metal mineralization. Monoclinic and triclinic potash feldspars occur with high levels of these elements, and this has led to conflicting views on the effects of Rb and Cs on the structural state of these feldspars. Gordiyenko and Kamentsev (1967) examined KFS from pegmatites in an area in the European part of the USSR and established that Rb and Cs accumulate in the disordered monoclinic form, whereas the levels of these elements were low in the microcline from these pegmatites. They considered that the conditions of formation and subsequent alteration for all these KFS were favorable to the formation of the triclinic form, and they therefore concluded that the entry of Rb and Cs favors crystallization in the disordered monoclinic form and prevents ordering in the solid state.On the other hand, amazonites have high levels of Rb (up to 3.1%) and Cs (up to 0.17%)(Marin et al., 1974), and they are always microcline; KFS from pegmatites in a deposit in Siberia (Shmakin et al., 1975) are triclinic no matter what the levels of Rb and Cs. The monoclinic disordered form of rubidian feldspar has been synthesized repeatedly (Barrer and McCollum, 1953; Ghelis and Lagache, 1972 etc.). Ion-exchange replacement of K and Na by Rb in natural specimens of microcline and low albite enabled Borutskaya (1975) to synthesize the triclinic form of rubidian feldspar. She considered the structural state of KFS to be independent of the levels of the large Rb and Cs cations.