多重分形局部奇异性分析方法在中国西藏多龙矿集区深层次地球化学异常识别中的应用

Application of multifractal and local singularity analysis method to the identification of deep-level geochemical anomalies in the Duolong mineral district, Tibet, China

勘查地球化学数据作为成矿地质体预测最重要的信息载体之一,在识别提取成矿异常以及挖掘深层次成矿信息中具有重要作用。基于地球化学元素空间分布的尺度不变性和广义自相似性,以多龙矿集区1∶5万勘查地球化学数据中的Cu、Au元素为例,运用分形/多重分形和奇异性理论开展分析研究,进行成矿元素空间分布模式的识别和异常提取。针对研究区全区、断裂缓冲区和地层分区分别运用矩方法计算多重分形谱,用于描述局部地区元素的相对富集及亏损程度,并对区内Cu、Au成矿元素进行局部奇异性分析,以识别提取成矿元素的弱、缓异常信息,圈定成矿潜力区。研究表明,多龙矿集区内Cu、Au元素均表现为成矿有利模式。其中,Cu元素存在区域的弱富集,Au元素存在局部范围的超富集,近EW向与NE向断裂的交汇区域以及侏罗系为区内最有利成矿位置。通过绘制局部奇异性指数空间分布图,表征了Cu、Au元素地球化学异常空间分布特征,进而圈定了矿集区的中部和北部为成矿潜力区。

[Objective]As one of the most crucial information carriers for predicting mineralized geological bodies,exploration geochemical data play a significant role in the identifying and extracting mineralization-associated anomalies as well as in analyzing deep-level mineralization information.[Methods]Based on the scale invariance and generalized self-similarity characteristics of the spatial distribution of geochemical elements,this paper uses Cu and Au in the 1:50000 exploratory geochemical data of the Duolong mineral district as an example and conducts a study using fractal/multifractal and singularity theories to identify the spatial distribution patterns of ore-forming elements and extract anomalies.The multifractal spectrum which is derived by the exploratory moment method for the whole study area,the fault buffer zone and the stratigraphic zone,is used to describe the relative enrichment and depletion of elements in the local area and to analyze the local singularity of Cu and Au mineralized elements,so as to identify and extract weak and low anomalies of mineralized elements and delineate potential mineralization zones.[Results]Both Cu and Au exhibit mineralization-favoured patterns in the Duolong mineral district,with the Cu showing weak enrichment in the region and Au being over-enriched on a local scale.The intersections of the east-west and northeast-trending faults,as well as the Jurassic strata,are identified as the most promising locations for mineralization in this region.[Conclusion]The spatial distribution of the local singularity index is mapped to characterize the distribution features of Cu and Au geochemical anomalies,therefore,the central and northern regions of the ore district are subsequently identified as potential areas for mineralization.