基于数字高程模型因子分析的地球化学异常提取

利用R型因子分析方法,对西北某地区1∶5万图幅岩屑样测试数据进行了分析,提取了5个代表性因子,绘制地球化学分区图。结合区域成矿地质背景、研究区地质条件及野外地质调查发现的41个矿化点,确定具有成矿意义的因子F3(Cu-Zn-Ag组合)。利用基于GIS数字高程模型对F3因子进行异常信息提取,结果显示76%的铜矿化点与异常吻合,较铜单元素圈定的异常提高了10%。异常主体位于志留系公婆泉组变质安山岩与石炭纪侵入岩的接触带(岩性偏安山岩),野外异常查证发现这些异常部位多见矿化现象。研究区北部钾长花岗岩区出现的少量弱小异常,为岩浆热液有关的黄铁矿化及黄铜矿化引起。槽探工程进一步验证了该方法在中大比例尺异常提取方面的良好效果。

GEOCHEMICAL ANOMALY EXTRACTION USING FACTOR ANALYSIS METHOD BASED ON MAPGIS DIGITAL ELEVATION MODEL

This paper analyzed the 1∶50000 rock-scrap data obtained from northwestern China,using the R-mode factor analysis method.Geochemical subdivisions were carried out with the extracted five representative factors from the data.Then the authors decided factor F3(Cu-Zn-Ag) which was related to mineralization,in comparison with regional mineralization characteristics,geological conditions and mineralization in the study area.Geochemical anomalies were extracted with the factor analysis method based on MAPGIS digital elevation model.The result suggests that the anomalies are well consistent with 76% Cu mineralizations,raising the efficiency by 10% in comparison with the single element copper geochemical anomalies.The main anomalies are located in Gongpoquan Group,particularly in the contact zone with parts of magmatic rocks.Mineralizations were found in most of the anomalies.In addition,some small anomalies were found in the K-feldspar granite,and field anomalies inspection has proved that these anomalies are caused by limonitization and malachite of quartz veins and K-feldspar granite.The project of trench has also proved the superiority of the method in the medium-large scale anomaly extraction.