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本文以几个典型实例,综合评述了与碱性岩和碳酸岩有关的碱质交代蚀变岩——霓长岩的岩石学特征。按照在霓长岩化作用过程中形成的新生矿物组合、结构构造、化学成分、空间分布及物质来源等特征,霓长岩可以分为低级、中级、高级、接触和脉状等5种类型。控制霓长岩化作用的主要因素包括:①碳酸岩或者碱性岩的岩石学特征和侵位条件;②流体的来源、性质和成分;③围岩的矿物组合、结构构造和化学成分;④霓长岩化作用过程中的温度—压力条件。由于碳酸岩容易遭受后期地质作用的影响而改变其固有的地质—地球化学特征,以致难以与沉积变质大理岩相区别;而霓长岩却能够保持相对稳定,因此,对霓长岩的研究有助于识别与之相关的碳酸岩。本文对白云鄂博矿床的碱质蚀变围岩和与碳酸岩相关的霓长岩进行了对比,考察它们是否具有相似性,这是解决该矿床成因问题的关键。
In this paper, a few typical examples are summarized in this paper. The petrologic characteristics of alkaline metamorphic alteration rocks associated with alkaline rocks and carbonate rocks are reviewed. According to the characteristics of the new mineral assemblages, structural structures, chemical compositions, spatial distribution and source of the materials formed during the process of nioblastic petrofacies, the aerodigesites can be divided into five types: low grade, intermediate grade, high grade, contact and vein. The main factors controlling the lithofacies of niobium include: (1) the petrological characteristics and emplacement conditions of carbonate rocks or alkaline rocks; (2) the source, nature and composition of fluids; (3) the mineral assemblages, structural structures and chemical compositions of the surrounding rocks; Temperature and pressure conditions in the process of niobate lithification. Because carbonate rocks are susceptible to late geologic processes and change their inherent geo-geochemical characteristics, they are difficult to distinguish from sedimentary metamorphic rocks. However, they are relatively stable, so the study on them Help identify carbonates associated with them. In this paper, we compared the alkali alteration surrounding rocks and the carbonate-related aematites in the Bayan Obo deposit to investigate whether they are similar or not, which is the key to solve the genesis problem of this deposit.