云南兰坪富锶文石的振动光谱特征

A Study of vibrational spectra and genesis of strontianiferous aragonite from Lanping,Yunnan Province

为进一步研究富锶文石的晶体结构、颜色成因和矿物成因 ,采用振动光谱、EMPA和SEM对富锶文石进行了测试和分析。红外光谱、拉曼光谱测试分析表明 ,由于富锶文石存在着锶与钙的类质同像现象 ,其红外光谱和拉曼光谱中CO2 -3 的v1、v2 、v3 、v44种振动模式波数介于文石和碳酸锶矿之间 ,与文石、碳酸锶矿等文石型碳酸盐振动光谱特征一致 ,并且文石的v4存在分裂峰。EMPA面扫描发现Ca2 + 、Sr2 + 的分布与富锶文石内部环带的分布存在一致性。由于CuO含量较少 ,分布规律不明显。SEM分析发现在环带之间存在空隙 ,各环带中富锶文石结晶程度和晶体表面特征不一 ,不同颜色和形态的环带反复生长。生长过程中 ,流体成分中各种元素的含量、温度和压力的变化造成不同颜色环带的形成 。

The recognition of this kind of strontianiferous aragonite is important in the study of isomorphism and inner structure of aragonite. Its discovery and study are of great significance in the application and exploitation of the mineral. By such means as infrared spectrometer, Raman spectrometer, visible spectrophotometer and SEM, this paper has analyzed characteristics of the spectra, texture, color-causing mechanism, distribution of Sr^(2+), Ca^(2+), Cu^(2+) and layering of the mineral. The infrared absorption and Raman frequency of v_1, v_2, v_3, v_4 of CO^(2-)_3 are found just between aragonite and strontianite, which is attributed to substitution. Meanwhile, there is a splitting peak v_4 of CO^(2-)_3 in the infrared spectra. EMPA reveals that CuO content is 0.00%～0.39% in blue strontianiferous aragonite but very rare in white strontianiferous aragonite. It is found that the color mechanism of blue strontianiferous aragonite has something to do with Cu^(2+). Surface scanning shows that Sr^(2+) and Ca^(2+) are distributed along the zonal texture while Cu^(2+) is in random distribution. In addition,SEM shows that strontianiferous aragonite displays different microstructures and morphologic features. The changes in microelement contents, temperature and pressure cause the formation of different color zonal textures.