Fractal Analysis On Geochemical Distribution And Anomaly Separation In The Guangxi Zhuang Autonomous Region

In this paper,the 63519 groups of Au,Mn,Cu,Pb,Zn,Sn,Sb,W,Hg,Mo,Ag and As elements from 1: 200000 stream sediments geochemical survey in the Guangxi Zhuang Autonomous Region are used to analyze the geochemical distribution and anomalies separation.Based on the analysis of geological setting and the distribution of of 78 typical deposits,the region was divided into six geochemical districts,including Youjiang basin,Guizhong basin,Dayaoshan uplift area,Western section of the Jiangnan orogenic belt,Shiwandashan basin and Yunkai massif,each of which is characterized by enrichment of specialized elements.The geochemical districts are spatially in agreement with the tectonic units.The methods applied in this study include concentration-area(C-A)model,multifractal spectrum,spectrum-area(S-A)model and singularity index,combined with multivariate statistical analysis and factor analysis.The content of Au,Sn,Sb and Mn in the Youjiang basin is higher,The C-A model extracts most of the ore-induced anomalies of Au,Sb,Mn,Cu,Pb and Zn.The S-A model and singularity index identify and enhance the local weak or hidden geochemical anomalies,and depict the NW structure.The anomalous distribution of Au-As-Sb element combination is consistent with NW main fault and Permian and Triassic gold-bearing strata.The content of Mn,W,Sb and Cu in the Guizhong basin is higher,The S-A model identifies the high background and weak geochemical anomalies of Sn in the Yongfu-Lingui area,and the high background of Mn with the obvious abnormal.The contents of Au,W,Pb and Zn in the of Dayaoshan uplift area are higher,the C-A,S-A models and singularity identify the Au enrichment and geochemical anomalies in the middle area.The medium-high temperature mineralization elements combination of W-Sn-Pb-Zn is mainly in the vicinity of acidic intrusive rocks of Yanshan period.The Cu,Sn and W contents in the Northern Guangxi area are higher,the areas with Cu and Sn geochemical anomalies are consistent with the granite intrusion sites in the Motianling and Maoer Mountain areas.The geochemical anomalies strength of the skarn type W deposit is weaker than magmatic hydrothermal W deposit,The singularity index extracts the Sn element enrichment of Dachang area.The geochemical anomalies distribution of Sn and W elements in the Shiwandashan basin is consistent with the NWW main structure,closely to the Darongshan granite body.The geochemical anomalies distribution of medium-high temperature element combination of W-Sn-Pb-Zn is closely related to granite,and the low temperature element combination of As-Au-Hg-Sb is closely related to sedimentary strata.The W geochemical anomaly is near the Youmapo granite,strong singularity points are mainly distributed along the Bobai-Cenxi fault zone,and the anomalies of Pb and Zn are mainly closly to the granites of Yanshan period in the Luchuan area and the the granites of Caledonian period in Fengshan area.This paper discusses the characteristics of different geochemical anomaly extraction methods and the applicability of different geological backgrounds.C-A model has poor recognition effect on the low background with high anomaly and high background with weak anomaly.S-A model can filter out background,highlight the remaining anomalies,make up for the lack of C-A model.The singularity index can further delineate the favorable mineralization area and measure the concentration of elements.Combining with the C-A and S-A model,the singularity index can effectively extract the mineralization-related anomalies,especially the weak anomalies.The distribution of strong singularity points is generally consistent with the main structure of the area and the direction of rock intrusion and other major ore-controlling geological bodies.The area and concentration of strong singularity are positively correlated with mineralization intensity.