云龙锡矿锡石的振动光谱和电子顺磁共振谱研究

本文用振动光谱和电子顺磁共振谱研究了云龙锡矿锡石的谱学特征。根据红外光谱的谱形、吸收频率和吸收峰强度特征,将云龙锡矿锡石的红外光谱划分成两种类型:A型谱和B型谱。红外光谱特征的研究结合宏观地质特征的研究表明:氧化物阶段锡石的红外光谱为A型谱,硫化物阶段锡石的红外光谱为B型谱。随着锡石成分和结构的变化,锡石的拉曼光谱的谱型、振动频率也发生变化,反映了锡石的成矿条件的差异。云龙锡矿锡石的EPR谱研究表明,云龙锡石中含有呈类质同象进入锡石晶格的V~(4+),根据V~(4+)的稳定场研究,云龙锡石主要形成于相对碱性和偏还原的条件下。

Study on Vibration Spectra and EPR Spectra of Cassiterites from the Yunlong Tin Deposit

In this paper the characteristics of IR spectra, Raman spectra and EPR spectra of cassiterites from Yunlong are studied and their geological significances are discussed. According to the spectral shape, absorption strength and frequency, the IR spectra of Yunlong cassiterites might be divided into two types, i. e., type A and type B. The spectra of type A have the same characteristics as the spectra of cassiterites from Nb-, Ta-bearing pegmatite type and granite type tin deposits, whereas the spectra of type B are identical with those of cassiterites from hydrothermal tin deposits in features. Combined with macroscopic geological investigations, it is found that the IR spectra of cassiterites formed in oxidic stage belong to type A and those of cassiterites formed in sulfidic stage belong to type B. A study on IR spectra of the cassiterites indicates that these two ore-forming stages are characterized by different metallogenic mechanisms and processes. The metallogenic process of oxide stage and that of sulfide stage are similar to the ore-forming process of magmatic deposits and that of hydrothermal tin deposits respectively. The symmetries of the spectral shape and vibration frequencies of Raman spectra vary considerably with the changes of cassiterites in composition and structure, suggesting the difference in formation condition of cassiterites. In the EPR spectra of Yunlong cassiterites the g factore of V~(4+) spectrum are =1.9265, g=1.9184, and the constants of superfine structure are A=38.17 (10~(-4)cm~(-1))and A=124.88(10~(-4)cm~(-1)). The researches on stability field of V~(4+) show that the Yunlong cassiterites were mainly formed in relatively alkaline and somewhat reducing environment.