| The east of Dongkunlun metallogenic belt is located in the middle of Qinghai province,it is an important geological unit in the northern part of theTibetan Plateau with its surrounding areas,and has become an important mineral resource base.The area has been largely covered by 1:500000,1:200000 or 1:2500000 stream sediment geochemical survey,many scholars have processed these data to delineate the target areas,and achieved good effect,but there are some problems.The paper bases on the geochemical data processing,applies the compositional data transformation and robust statistical method to deal with the geochemical data.The content information,spatial variation information and internal structure information of geochemical data are fully excavated.By synthesizing the geochemical information,using the idea of analytic hierarchy process(AHP),the metallogenic information of each grid is counted,so as to delineate the prospecting target area,the following results have been obtained:1)According to the geological background of deposit,combined with the classification of deposit type,the deposit in the study area are divided into:the association related to basic rock(SEDEX type,VHMS type and sedimentary metamorphic type);the association related to intermediate-acid rock(porphyry type,skarn type and hydrothermal vein type)and the association of hydrothermal gold deposit(alterated rock type and quartz vein type).2)Propsed utilization of the difference between median and geometric mean,and the coefficient of variation to analysis the metallogenic favorable elements in four sub-regions of Kunbei,Kunzhong,Kunnan and Beiba.Point out the favorable elements are W,Mo,Bi,Pb,Cr,As,Ag in Kunbei;Hg,Au,Sb,Mo,Bi,Ag,Sn,W,As in Kunzhong;Hg,Sb,Bi,Ni,Au,Cr,Mo,As,Cu,Ag in Kunnan;Hg,Au,Sb,As,W in Beiba.3)Using two methods to delineate element anomalies,CDusing robust factor analysis of ILR transformed data of rock-forming elements,to identy the geochemical unit,and standardize element content.So as to delineate anomalies.?An improved Aitchison distance method is proposed and used to delineate anomalies.Compar the effects with two methods of Au,Cu,the anomalies of delineation correspond well with the deposits,but as the Aitchison distance considers relationship with other elements,and eliminates the closing effect of compositional data,so improved Aitchison distance method is better.4)The principal component anomalies related to basic rock,intermediate-acid rock and hydrothermal gold by using principal component analysis of metallogenic(indicted)elements.Based on the principal component analysis,and combined the characteristic elements of three type deposists.I select Cu,Co,Cr,Ni,V,Zn;Ag,Cd,Pb,Sn,Mo;Au,As,Sb and Au,Bi,W four element associations to calculate the robust Mahalanobis distances and delineate the multivariate anomalies.5)The spatital variation of content of Au,Cu,Co,Pb in E,SE,S,SW four directions is analyzed,in general,the rate of spatial variation in the N-S direction is greater than that in the E-W direction,consisting with the main tectonic line and deposit trend in the region.The contour map of element content's spatial variation is better than that of element content in prospecting through comparing the content's spatial variation and content of Au,Cu.6)Based on the above research and analysis,We synthesis all kinds of geochemical information,use the idea of AHP to calculate the ore-finding beneficial degree of every grid.based on the degree,I delineat 32 prospecting target areas of three types.including ?10 prospecting target areas related to basic rock,?10 prospecting target areas related to intermediate-acid rock;?12 hydrothermal gold prospectiong target areas.So according the prospecting target area,10 metallogenic prospecting areas are divided into the study area.According to the analysis of key metallogenic areas,selected two target areas for validation,we found antimony(gold)vein in hydrothermal gold target area,and A new clue for Tungsten in target area related to intermediate-acid.So the method of geochemical data processing is proved effective. |
PDF Full Text Request