Comparative Study On Extraction On Geochemical Anomalies And Effectiveness Of Methods In Lanping-Simao Region

Lanping-Simao area is an important lead-zinc,copper and silver source in China which have great metallogenic potential.There are many large deposits such as Jinding,Baiyangping and Baiyangchang,In the previous studies,the extraction of geochemical anomalies in this area is insufficient,and the comparative study of the effectiveness of different research methods is still unclear.Therefore,the Lanping-Simao area is chosen as the study area,and 22165 stream sediment geochemical data are taken as the research object.Based on the study scales of the whole area,tectonic units(Lanping-Simao region,Yunxian-Jinggu volcanic arc and Lincang-Menghai magmatic arc)and 162 large-scale catchment basins in the Lanping-Simao area,the principal component analysis is used to discern the element groups in the study area,and the traditional method is used.Methods(85%cumulative frequency method and average+2 times standard deviation)and fractal method(number-size fractal dimension model and concentration-area fractal dimension model)were used to determine the lower limit of geochemical anomaly,and the effectiveness of different anomaly extraction methods was compared.Through principal component analysis,four principal components are identified in Lanping-Simao area.The first and second principal components represent the spatial distribution of femic rocks and felsic rocks in the area,and the third and fourth principal components represent the spatial distribution of Cu and Pb-Zn-Ag metallogenic elements,respectively.By comparing the lower limit of metallogenic element anomalies determined by different research scales and methods,it is found that the Pb,Zn and Ag anomalies extracted by 85% cumulative frequency method at the scales of Lanping-Simao area,tectonic units and catchment basins are in good agreement with the known Pb-Zn deposits and Ag deposits;the Ag anomalies extracted by average+2 times standard deviation method are in good agreement with the known Ag deposits,and in structural single.The Pb and Zn anomalies extracted at the scale of Yuanhe catchment basin are in good agreement with the known Pb-Zn deposits,the Ag anomalies extracted by thenumber-size fractal dimension model are effective,the Pb and Zn anomalies extracted at the scale of tectonic units and catchment basins are in good agreement with the known Pb-Zn deposits,and the Cu anomalies extracted at the scale of catchment basins are in good agreement with the known Cu deposits.The Ag anomalies extracted by type I coincide well with known Ag deposits.The Pb and Zn anomalies extracted at the scale of tectonic units and catchment basins coincide well with known Pb-Zn deposits.The Cu anomalies extracted at the scale of catchment basins coincide well with known Cu deposits.Various methods to determine the lower limits of anomalies based on the whole region scale can better highlight the high concentration anomalies;various methods to determine the lower limits of anomalies based on the scale of tectonic units can better avoid the interference caused by structural and lithological factors;and various methods to determine the lower limits of anomalies based on catchment basin scale can effectively highlight the local low concentration anomalies.It is difficult for a single method to accurately and effectively determine the lower limit of ore-forming element anomalies.It is necessary to combine different research scales and methods to better delineate prospecting targets.