EM聚类方法在岩性复杂区水系沉积物地球化学异常圈定中的应用  

The application of EM clustering method to the determination of stream sediment geochemical anomalies in areas with variable lithologies

作　　者：孙尧尧 郝立波[1] 赵新运[1] 陆继龙[1] 马成有[1] 魏俏巧[1] SUN Yao-Yao;HAO Li-Bo;ZHAO Xin-Yun;LU Ji-Long;MA Cheng-You;WEI Qiao-Qiao(College of Geo-Exploration Science and Technology,Jilin University,Changchun 130026,China)

机构地区：[1]吉林大学地球探测科学与技术学院,吉林长春130026

出　　处：《物探与化探》2020年第6期1306-1312,1321,共8页Geophysical and Geochemical Exploration

基　　金：中央级公益性科研院所基本科研业务费专项(AS2016P02);国家重点研发计划项目(2016YFC0600606)。

摘　　要：地球化学背景与异常的划分是化探找矿工作的关键环节,然而,岩性复杂区水系沉积物地球化学异常的圈定常受到岩性背景的影响,若不消除这个影响而直接进行异常圈定,可能会造成一些严重的错误。研究表明,岩性背景问题的本质是多重母体问题,而Expectation-Maximization(EM)聚类方法能有效地分解多重母体,可在一定程度上消除岩性背景的影响。本文以湖南省某地1∶20万水系沉积物地球化学数据为例,采用EM聚类方法进行多重母体分解,然后进行地球化学异常圈定,并讨论了多重母体分解对异常圈定的影响。结果表明,EM聚类方法的应用可使异常圈定更加合理,主要体现在虚假异常的削弱和低弱异常的强化方面。The separation of anomalies from backgrounds is a critical step in geochemical prospecting.However,the determination of stream sediment geochemical anomalies is always affected by lithologic backgrounds in areas with variable lithologies.If this influence is not eliminated prior to anomaly determination,some serious errors may occur.In fact,a problem of lithologic background is essentially a problem of multiple population,which can be effectively solved by the clustering method based on the Expectation-Maximization(EM)algorithm.In this study,the authors applied the EM clustering method to a geochemical data set from a 1∶200,000 scale stream sediment survey,and then discussed the influence of separating multiple populations on anomaly determination.A practical example demonstrates that geochemical anomalies of stream sediments in lithologically complex regions can be determined in a more reasonable way by using the EM clustering method.This is mainly reflected in two aspects:on the one hand,strong but false anomalies can be eliminated,and on the other hand,weak but important anomalies can be uncovered.

关 键 词：地球化学异常 岩性背景 多重母体 EM算法 水系沉积物 

分 类 号：P632[天文地球—地质矿产勘探]