摘要
在野外地质工作、显微镜下观察、电子探针分析和差热分析的基础上,运用X射线衍射分析、红外光谱分析对印章石(以著名的昌化石为例)进行了谱学分析。昌化石主要矿物成分为高岭石族矿物,主要为迪开石及高岭石-迪开石过渡矿物。通过X射线衍射图谱分析计算其结晶度指数(HI)表明,高岭石族矿物的结晶有序度存在明显的高低变化。红外光谱特征显示,其中属于外部羟基振动的3 697cm-1谱峰强度(A)与属于内部羟基振动的3 620cm-1谱峰强度(B)的比值随着结晶度指数的降低有逐渐升高的趋势,且比值A/B的大小可以大致用来区分高岭石和迪开石:一般高岭石比值大于1,而迪开石小于1。差热分析的结果也印证了高岭石族矿物有序度高低变化的现象,如:高岭石族矿物在加热到400℃～700℃时会出现一个强烈尖锐的吸热峰,吸热峰的强度及温度与其有序度的高低存在正相关性。当主要组成矿物成分为较纯净的迪开石时,其有序度相对较高,透明度也较好;当主要矿物成分为高岭石-迪开石过渡矿物时,其有序度较低,透明度也较差。X射线衍射分析和红外光谱都是研究分析印章石的有效方法,但X射线分析通常为有损分析,且仪器使用条件相对较高;而红外光谱则可以无损且具有扫描时间短等特点,可见红外光谱在鉴定印章石上是比较便捷有效的。
Based on the field and microscope observations,electron probe microanalysis （EPMA） and differential thermal analysis （DTA）, representative samples of the Changhua stone were selected for spectra analysis by using X-ray powder diffraction （XRD） and infrared spectrum （IR）. The major mineral components of the stone belong to kaolinite group, consisting of dickite and some transitional mineral along kaolinite-dickite joint. The Hinckley index indicates that the structural order of kaolinite group minerals varies significantly and the IR spectrum shows that the ratio of the intensity （A） of 3 697 cm^-1 band （corresponding to outer layer OH vibration） relative to the intensity （B） of 3 620 cm^-1 band （ corresponding to inner layer OH vibration） becomes increasingly lower as the HI is becoming higher. The DTA curve, on the other hand,reveals that the structural order of kaolinite group minerals has a great variation. When heated at 400 ℃-700 ℃ ,a strong and sharp endothermic peak appears, suggesting a positive correlation between the intensity of endothermic peak and order degree. Transparency of the Changhua stone is better as dickite component increases,and as the overall structural order is higher,whereas it is worse as transitional mineral of kaolinite and dickite becomes more,as it has lower structural order. In general,XRD and IR are the powerful tools for distinguishing kaolinite group minerals. For the use of identifying the signet stone,IR is a more rapid and effective method.
出处
《矿物岩石》
CAS
CSCD
北大核心
2011年第3期18-24,共7页
Mineralogy and Petrology
基金
教育部新世纪优秀人才支持计划(NCET-07-0771)
关键词
昌化石
X射线粉晶衍射
红外光谱
有序度
Changhua stone
X-ray powder diffraction
infrared spectra
degree of order
