地球化学综合异常的圈定及找矿效果

Delineation of synthetic geochemical anomaly and evaluation of its effectiveness in ore prospecting

能否正确有效地圈定地球化学综合异常是地球化学数据处理的重要内容,对找矿效果起决定作用。传统方法多在单元素异常的基础上圈定综合异常,而忽略了异常可能由地层本身高背景富集引起。笔者引用马氏距离识别地球化学离群点的方法圈定综合异常。由于马氏距离是基于多元正态分布理论,是多变量统计方法的直接推广和应用,其全面考虑了元素均值、方差及元素间协方差3个参数,是直接针对样本的计算过程,同时也是一元方法的直接推广,所以其具有独特的异常识别功能。经各种不同比例尺和不同采样介质化探数据处理应用显示,利用马氏距离方法求得的地球化学综合异常具边界唯一、界线清楚,减少了人为圈定异常的影响;异常强度突出,指标单一,可作为评价异常的一个重要参数使用;发现矿体(矿化)的概率程度高等优势。该方法可在实际中推广应用。

The correct and effective delineation of synthetic geochemical anomaly is the key part of geochemical data processing,and plays a fundamental role in ore prospecting result. Traditional methods delineate synthetic geochemical anomaly based mainly on single element anomaly; nevertheless,many anomalies are caused by stratigraphic high background enrichment. In this paper,the authors use the method of Mahalanobis distance to identify geochemical outliers,and delineates synthetic geochemical anomaly. Because Mahalano- bis distance is based on the theory of multivariate normal distribution,and hence is the direct promotion and application of multivariate statistical method. It fully considers three parameters, i. e.,element mean content,variance and covariance,its computing process is directly based on samples,and therefore it is also the direct promotion of one-dimensional method having a unique anomaly identifica-tion function. The results of geochemical data processing applications with a variety of different scales and different sampling media show that the synthetic geochemical anomaly detected by Mahalanobis distance method has advantages of unique boundary,clear boundary, and reducing the effect of man-made anomaly delineation. In addition,with prominent anomaly intensity and single index,it can be used as an important parameter of anomaly evaluation with high probability of finding orebodies （ mineralization）. This method therefore can be promoted and applied in practice.