| The primary mission of geochemical exploration is to seek for the Mineral body, appraises and seeks the land sector including the Mineral prospect, but its important duty is to discover the geochemical anomaly. Geochemical anomaly is an efficient path to discover the metal and the precious metal minerals, is also the premise and the basis to deploy the regional geology prospecting work. The important content of geochemical exploration anomaly processing is to determine the element anomaly and synthetic anomaly correctly and effectively, and that selecting anomaly takes geochemical exploration data processing as the premise. The core of geochemical exploration data processing is the reasonable division question relating geochemistry background and the geochemical anomaly, and the task of geochemical exploration data processing is to discover geochemical anomaly information related the mineralization from the massive primitive investigation database.The method of geochemical exploration data processing plays an important role on geochemical exploration, it takes the geochemical samples and the sampling data as the foundation, discovers and selects anomaly from the chaotic data effectively, meanwhile,the processing results and the graphical representation information serve for appraising geochemical anomaly and selecting the prospecting target area as well as other application domain. The developments of geochemical exploration data processing relate with the applied mathematics and the computer technology development. Based on the multi-variate normal distribution theory's multi objective, the method of geochemical anomaly processing is the direct promotion and application of multivariable statistical method in fact, which has two computational methods with Euclidean distance and Mahalanobis distance according to its basic mathematics principle's difference, what formerly quite universal use takes the Euclidean distance as the foundation computational method, in recent years it increases computational method's application gradually based on Mahalanobis distance, the method of Mahalanobis distance is an important application overall target in stray spot recognition and analysis for geochemistry.In order to enhance the precision of geochemical exploration data processing and excavate prospecting potential, this paper takes stream sediment geochemistry metrical data of Hebei Chengde Sangou area as the foundation, studies and discusses the rationality and the serviceability in the geochemistry background division and anomaly appraising with the method of Mahalanobis distance. Mahalanobis distance has two kinds of situations in the geochemistry practical application, one kind is that the primary data carries on the data analysis directly to all variables using Mahalanobis distance, and selects the synthesis anomaly with Mahalanobis distance; Another is to definite element combination by carrying on the preprocessing the data including the data standardization,the data point of difference rejection,then the correlation analysis,the cluster analysis or the factorial analysis, it carries on the data analysis according to the element combination using Mahalanobis distance, finally selects synthesis anomaly with Mahalanobis distance according to the processing results . The latter method, it uses the correlational dependence strong and the weak between the variable fully, carries on the analysis together combined with the relevant big variable, has guaranteed data robustness, has a better effect in the actual prospecting application. According to the element combination determined by the factorial analysis with Au, Ag, Pb, Sb factor combination and Cu, Co, Ni factor combination, this paper carries on the data analysis separately using Mahalanobis distance, finally selects combination anomaly with Mahalanobis distance, makes the combination anomaly map by accumulation element combination exceptionally, and selects many anomalies exceptionally, finally has carried on the analysis comparison and discussed the superiority and the existence question of the combination anomaly method. Interrelationship of the elements had been considered in Mahalanobis distance. Synthetic geochemical anomaly computed by Mahalanobis distance has such characters as centralized scope, clear demarcation line, prominent intensity, high anastomosis with known Mineral body. Mahalanobis distance has obvious advantage over Euclidean distance and is feasible to be applied in reality. Based on the specific applications of Mahalanobis distance adopted in the Hebei Sangou area, the corresponding relation between the combination anomaly of Mahalanobis distance and the conditions of Mineral body is more obvious than before, this relation verifies the validity and applicability of geochemical exploration data processing with Mahalanobis distance, and provides the reference data for geochemical exploration data processing in many kinds of ways.By the data processing of 1/50,000 stream sediment in the Hebei Sangou area, this paper determines the different element's background value and the anomaly minimum of it using the conventional method, selects the element's geochemical anomaly of Au, Ag, Cu, Pb, Sb, Co and Ni , it carries on the factorial analysis to the geochemical survey data and determines the element's combination relations simultaneously. Based on these relations, this paper selects the accumulation combination anomaly of Au+Ag+Pb+Sb and the accumulation combination anomaly of Cu+Co+Ni using the conventional method exceptionally. It selects nine combination anomaly of Au, Ag, Pb, Sb and four combination anomaly of Cu, Co, Ni using Mahalanobis distance method exceptionally.Based on the anomaly with the degree of the known mineralization point, the geological condition and the anomaly characteristic, gathered the other method with the anomaly nested and so on, this paper proposes the evaluation criteria of combination geochemical anomaly , divides four classes combination anomaly of Mahalanobis distance. Classâ… of Mahalanobis distance combination anomaly has six with three Au, Ag based anomaly and three Cu-based anomaly; Classâ…¡of Mahalanobis distance combination anomaly has three based on Au, Ag; Classâ…¢of Mahalanobis distance combination anomaly has three based on Au, Ag; Classâ…£of Mahalanobis distance combination anomaly has one based on Cu. Using classâ… and classâ…¡of Mahalanobis distance combination anomaly, this paper determines seven prospecting targets in the Hebei Sangou area including four prospecting targets based on Au, Ag and three prospecting targets based on Cu ,the prospecting targets based on Au, Ag are M2-2, M2-5, M2-7 and M2-6 respectively, and the prospecting targets based on Cu are M1-1, M1-2, M1-3 respectively; meanwhile, this paper gives some proposals in view of prospecting target areas for further surveying work based on the above-mentioned analysis.
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