湘西南元古宙高涧群微量元素主成分分析

Principal component analysis of trace elements in Proterozoic Gaojian Group of southwestern Hunan

主成分分析法 (PCA)是多元样本数据的数理统计方法。本文结合湘西南元古宙高涧群地层剖面等离子光谱分析所得Au、Ag、As、Sb、Cu、Pb、Zn、Sr、Ba、Mn、Co、Ti、Cr共 13个微量元素的主成分计算结果和图解 ,解释了主成分参数和图解的地质含义。在C剖面和L剖面上 ,主成分F1具有相似的信息量 ,反映高涧群“原始”沉积物以铁镁矿物为主要特征。F2的信息量不同 ,在L剖面上 ,F1-F2图解可以将 13个“原”变量分为 5组“原”变量的组合 :Co -Zn -Cu(Mn、Ba)、Ti-Cr、As -Sb、Au -Pb -Sr和Ag ,Ag主要来自碎屑沉积物 ;在C剖面上 ,“原”变量的组合特征不明显 ,As、Cr、Sb、Ti与F2呈正相关 ,Sr与F2呈负相关。在L剖面上 ,Au主要受氧化条件制约 ;在C剖面上 ,海水较深 ,还原条件有利于Au、Ag的沉积。由于沉积环境不同 ,研究区的南部和北部一些微量元素存在明显的差异。根据 (dki) 2 计算值 ,Ag。

Principal component analysis (PCA) is aimed at explaining the covariance structure of multivariate data by way of reducing the whole data set to a smaller number of independent variables. By means of iso_ion spectrometry, the authors have analyzed 56 groups of trace elements data (Au, Ag, Sb, Cu, Pb, Zn, Sr, Ba, Mn, Co, Ti, Cr) along two sections of Gaojian Group in southwestern Hunan, and explained the geological implications of the calculated results and PCA figures. Components F1 in Section C and Section L have similar information, reflecting the main characteristics of original sediments in the two sections. As for the data of section L, 13 kinds of trace elements data are divided into 5 groups: Co-Zn-Cu(Mn, Ba), Ti-Cr, As-Sb, Au-Pb-Sr and Ag, as indicated in F1-F2 diagram. With regard to the data of Section C, the groups of variables are not identified very well. As, Cr, Sb and Ti are correlated closely with component F2, whereas Sr is in negative correction with component F2. The processes controlling the distribution of such noble metals as Au and Ag were complex. The oxidization environment controlled distribution of Au in Section L, and the reduction environment was beneficial to the precipitation of Au and Ag in Section C. As sedimentary environments are different, some trace elements in the northern part of the district are obviously different from those in the southern part. According to the squared distance (d k i) 2 of the 'noise', the distribution of Ag and Pb was partly affected by the late tectonic movement.