勘查地球化学异常多尺度分析方法——以赣东北德兴矿集区为例

以赣东北德兴矿集区铜元素地球化学数据为例,提出了一种勘查地球化学异常多尺度分析的方法,内容包括:(1)采用具有平移不变性的平稳小波变换进行勘查地球化学异常的多尺度分解;(2)随着小波分解阶数的增大,在多尺度逼近累积频率—含量曲线图上,如果数据分布较均匀,没有出现明显的拐点,则该尺度逼近可以作为最大尺度的背景,该分解阶数为最大分解阶数;(3)各尺度的逼近不能直接代表该尺度的背景,各尺度的背景都是起伏的带而不是曲面,在多尺度细节累积频率—含量曲线图上,以拐点作为各尺度的异常下限;(4)大尺度的细节主要反映区域性的控岩控矿信息,而异常的形态和规模对研究控矿地质因素很重要,直接将各细节的正值作为异常;(5)小尺度的细节的正值分布过于复杂,分布规律不明显,因此一定要进行异常的提取,异常主要反映由矿和蚀变引起的局部变化,具有重要的找矿价值;(6)在各个尺度均表现为异常的区域具有找矿远景,特别是小尺度的局部异常,其不同尺度重叠区域是重要的找矿远景区。勘查地球化学异常的多尺度分析可获得多尺度的曲面背景和对应的异常,并可得到异常的精细结构,突出异常的局部变化特征,从而更有效地识别与矿有关的异常。

Multiscale Analysis of Exploration Geochemical Anomalies:A Case Study of Dexing Ore Concentration Area,Northeast Jiangxi Province

The paper puts forward a method of multiscale analysis of exploration geochemical anomalies,with a case study of Cu element anomalies of Dexing ore concentration area,northeast Jiangxi Province.Shift-invariant stationary wavelet transform was used to do multiscale decomposition of the anomalies.With the increase of decomposition level,statistical distribution of the approximations changed to uniformity,and the level was maximal.The approximation was not the background at each scale,and the background was a wave belt.The upper inflexions at the accumulative frequency-content graphs of multiscale details anomalies indicated the threshold of the anomalies,and which should be used to the details at lower levels.The threshold of the anomalies of the details at higher level was zero in view of the geological implication.The areas with existence of multiscale Cu anomalies were propitious to prospecting,especially at lower levels.Fine structure and local variation of exploration geochemical anomalies could be acquired with the method of multiscale analysis,which are helpful to identify the anomalies relating to mineralization.