Extraction Of Geochemical Anomaly And Delineation Of Prospecting Target For Sn-W And Pb-Zn-Ag Polymetallic Mineralization In Bozhushan-Laojunshan Area,Southeastern Yunnan

Bozhushan-Laojunshan ore concentration area is located in the middle zone of the GejiuDachang Sn-W polymetallic mineralization area,which develops a series of world-class tintungsten and silver-lead-zinc polymetallic deposits,including Bainiuchang silver polymetallic deposit,Guanfang tungsten polymetallic deposit and Dulong zinc polymetallic deposit.In order to extract the geological anomaly ore-forming information of W-Sn and Pb-Zn-Ag in the southeast of Yunnan Province,Principal Component Analysis(PCA)and Bi-dimensional empirical mode decomposition(BEMD)methods were applied to the stream sediment geochemical data at the scale of 1:200,000 in this paper.The studied results show as follows.1.Element associations that related to diagenesis and mineralization can be intrinsically identified by the Principal component analysis method.The factor score images meticulously depict the spatial distribution relationship between various element association anomalies and the different geological units included strata,rock mass and ore body in the study area.The results of principal component analysis illustrate that there are four element associations existing in southeastern Yunnan area: a)[Fe2O3-Ti-Cr-V-Ni-Co-Al2O3-Cu-Nb-Y-Zn-Mn]—-[SiO2]: This groups reflected a negative correlation that with the gradual growth of acid components,the mafic components gradually reduced in the process of the evolution of granitic magma crystallization.b)Bi-W-Sn-As-Pb: This group reflected a typical middle-high temperature hydrothermal W-Sn polymetallic mineralization.c)[Sb-Hg-As]—-[Na2O-Sr]: This group is a common indicated accompanying element association of low temperature hydrothermal Au,Ag,Pb,Zn polymetallic deposit.d)Ag-Cd-Zn-(Pb): This group represented the middle-high temperature hydrothermal Ag-Pb-Zn polymetallic mineralization.2.Two tungsten-tin ore-finding targets were delineated in this study.Both two high anomaly areas are located in the inner contact zone of granite and surrounding rock.Because of the arching action of magmatic intrusion,a lot of tensional fracture appeared around the magmatic rocks.Magmatic hydrothermal in transit along the fracture and rock formation then occurred metasomatism with surrounding rock,which is corresponding to the high temperature hydrothermal W-Sn mineralization.3.The Ag-Pb-Zn anomalies distribute in the contact zone of the Yanshanian granite and surrounding rock.The distribution is controlled by the north-east,north-west and north-south of three-level fractures.This phenomenon shows that the local structures not only control the occurence form and distribution direction of the ore body,but also control the enrichment of mineralization.The three-level fractures and interlayer fracture zones can be used as an important path for ore to migrate and store.4.The combination of the PCA and BEMD not only effectively attained the ore-forming element associations,but also revealed the regional metallogenic geological background and the geochemical characteristics of the local ore-forming anomalies.The anomalies distribute be identical with the known mines,geological structures and rock mass,which proves these two methods are of benefit to the concealed ore-forming anomaly information extraction.