与碳酸岩共生的霓长岩

本文归纳总结了从20世纪60年代以来国外与碳酸岩有关的霓长岩的相关研究成果,主要涉及了岩石学、矿物学和地球化学等方面。与碳酸岩有关的霓长岩是碳酸岩侵位时对围岩交代作用产生的岩石,其主要组成矿物为碱性铁镁矿物和碱性长石等。根据霓长岩与碳酸岩的空间关系、其显微结构及矿物共生组合,可将霓长岩划分为低级、中级和高级不同类型。霓长岩的矿物学研究侧重于对其矿物组成及矿物化学成分的研究,据此可了解交代流体的性质、交代作用时的物理条件并追索流体的来源。在霓长岩化过程中,初生碳酸岩浆逸出的大量碱金属和挥发分进入了围岩中形成霓长岩,因此,通过对霓长岩元素和同位素地球化学的研究,有助于理解初生碳酸岩浆的性质和其地幔来源区特征。

Fenites associated with carbonatites

This paper has reviewed the research results concerning the fenites associated with the carbonatite in abroad since 1960s of last century till more recently. The content of the paper stressed the petrology, mineralogy and geochemisty of the fenites. The fenites has been produced by the metasomatism of the country rocks in which the cabonatites intruded, and the rocks are mainly consist of the alkaline Fe-Mg minerals and alkaline feldspars. According to the microtexture and mineral assemblage of the fenites which can be divided into high-, medium- and low-grade fenites. The mineral chemistry consisting of the fenites is related to the composition of the metasomatized fluid and the physical condition in which the metasomatizm had occurred. Therefore, the research of mineralogy of fenites can be helpful for understanding the feature of the fluid and tracing back its source. During the processes of the fenitization, the original carbonatite magma lost a great deal of alkaline metals and volatile matter coming into the fenites, thus, study the elemetary and isotopic geochemistry of the fenites would help to understand the feature and the source region of the original carbonatitie magma.