岩石化学成分及复介电常数与光谱特征的关系探究

Relationship Exploration of Chemical Content,Complex Dielectric Constant and Spectral Features of Rocks

实验对辽宁省兴城地区的97块岩石样本测量了350-2 500nm间光谱反射率,岩石化学成分及部分样本的复介电常数值,并用包络线去除法计算了光谱吸收深度。研究基于岩石化学成分光谱特征理论、介电常数相关理论,利用相关性分析的方法求得岩石各化学成分与光谱吸收深度间的相关系数曲线、岩石复介电常数与光谱反射率间的相关系数曲线。通过归纳总结曲线形态特征,获得以下信息：（1）岩石中SiO2,Al2O3,CaO,K2O,MgO,灼失含量与光谱吸收深度在波段（1 900-2 500nm）间相关性明显,在1 900,2 200和2 300nm等化学元素识别特征波段处,出现局部极大/极小值;火成岩中Fe2O3含量与光谱吸收深度在铁元素的特征波段（400-550nm）有着良好的相关性,相关系数达-0.406。探讨岩石光谱吸收特征与其化学成分含量间的关系在通过遥感影像进行成矿预测、识别岩性等方面都有着积极的作用。（2）岩石复介电常数总体与岩石反射率呈负相关,实部相关性优于虚部,实部相关系数在1 900nm附近达到极小值-0.753。观查曲线可知,介电常数实部与光谱反射率相关系数在1 900和2 200nm附近都有着良好的相关性,因此实验运用不同的模型拟合了在该处的响应关系函数曲线。介电常数是介质的基本物理性质之一,现有研究中多在微波波段中分析电磁波特征与介电常数间的关系,该研究在可见光和近红外波段范围内探究了二者间的关系,为进一步探讨岩石介电特性和光谱特征奠定了基础。

In this research,97 pieces of rock in Xingcheng,Liaoning Province,China were collected to measure the spectral reflectance in 350-2 500 nm,chemical content,and complex dielectric constant of some samples.The absorption depths were calculated by using continuum-removal method.With correlation analysis method,two kinds of correlation curves were obtained based on the theory of spectral characteristics of chemical contents and the principle of dielectric constant.One described the relationship between chemical content and spectral absorption depth,and the other one represented the correlation of complex dielectric constant and reflectance.By summarizing curves morphological characteristics,several conclusions were drawn as follows：（1）There was a strong correlation between the chemical content（SiO2,Al2O3,CaO,K2 O,MgO,burnt-loss）and spectral absorption depth in 1 900-2 500 nm,furthermore,at around 1 900,2 200,2 300 nm and other identifying characteristic bands,local extreme maximum/minimum values appeared.At Fe3＋characteristic band（400-550nm）,correlation coefficient reached-0.406 between Fe2O3content and absorption in igneous rock samples collection.Exploring the relationship between rock spectral absorption features and its chemical contents had a positive effect on metallogenic prediction and lithology identification with remote sensing image.（2）Reflectance and complex dielectric constant were negatively correlated totally,compared with the imaginary part;the real part had a better relation reached-0.753 at around 1 900 nm.Curves showed that there were great correlations around 1 900 and 2 200 nm,so,our study adopted different models to simulate response relationships.Dielectric constant of media is one of the basic physical properties,and now most analyses of existing research between electromagnetic characteristics and dielectric constant are studied in microwave band,however,our research is conducted in visible and near infrared range.The conclusions will be useful for further exploration on dielectric characteristics and spectral features of rocks.