Geochemical Anomaly Formation Mechanism And Standardization Of Ore-seeking Technology

Crop and shallow deposits are running out because of the continuous exploration.Therefore,it's becoming more and more important to search for concealed deposits in covered area in recent years.As an effective means of mineral exploration for covered area,geoelectrochemical method(CHIM)is getting more and more attention and being widely used by people.This method has been greatly changed after decades of development.Traditional low-efficiency technology has been replaced by extremely efficient methods.However,research for the formation mechanism of CHIM anomaly still stays in the correction of traditional technology.And the new CHIM system which is mainly in the experimental and test stage,is far from achieving standardization.To solve the above problems,many field and laboratory experiments are carried out and new understanding of the formation mechanism of CHIM anomaly is achieved,as a result,the standardization of CHIM method is greatly enhanced in aspects of the establishment of effectiveness and conditions of field exploration,combination of multi-elements analytical methods and scheme of analytical quality control.The main conclusions of this thesis are as follows:1.Elements extracted by CHIM process exist in different geochemical phase states in the soil.The main phases are active phases,including water soluble,ion exchangeable and carbonate bound phases,while other micro-scale particles in relatively weak active phases,or even residue phase of particles could be migrated and adsorbed by CHIM process.And this phenomenon is more common in trace elements than in major elements.2.Anomaly in the new CHIM method is caused by nano-micron scale clay mineral particles which exist in soil.And these particles have electric activity and can be adsorbed selectively by CHIM process.While anomaly of Au in covered area of Au deposit could be caused by Au nano-micron particles,and in ore body or mineralized outcrop area(residual soil)could be caused by secondary particles of limonite.3.CHIM survey is effective in the region which is covered by semi-arid grassland aeolian sand.High density polyurethane foam(>25g/dm3)must be used when the survey is conducted.And 24 hours' extraction time can well meet the good results.4.Result of CHIM survey in 1:50,000 scale shows significant multi element combination anomaly of Pb-Zn-Ag-Cd-As-Bi,which is highly consistent with elements combination in ore and mineralization bodies.The result is much better than the one got by soil survey.And the test results show that exploration density with 9-16 sites per km2 can delineate the prospecting target area precisely.5.Foam samples of CHIM don't need to be washed by deionized water before analysis.Combination of analytical pretreatment methods with ashing,microwave digestion and multi-acid digestion can better identify the multi-elements' anomalies more comprehensively.6.The way of adding standard solution into blank foam can be used to monitor the analytical quality of Au for CHIM foam samples' analysis.However,this way does not suit other elements.We should use the repeated analysis results of field duplicated samples,laboratory duplication,digestion solution and external laboratory control to comprehensively evaluate the quality of CHIM foam analysis for these elements.