Study On The Method For Evaluating Geochemical Anomalies In Shallow Overburden Areas

In the in shallow overburden areas in Great Xing'an mountain, the special cold humid weather condition and the geographical character with flouring plant coverage, made the sample gathered there to be or part to be the reminder of its original soil and rock, which is different from the traditional stream sediment. As the result, the conventional method for evaluation anomalies didn't achieve the anticipative effect when being used in processing the data of the shallow overburden areas'sample. Based on the data of Inner Mongolia Xinbarag youqi area (grass-covered region) and Tahe area in Great Xing'an mountain, the author try to research and discuss the rationality and the applicability of many kinds of traditional methods for evaluating anomalies ,in order to dig up the potential of forest—marsh,grass covered regions, and discuss how the feeble anomalies means for finding deposit. First, to ensure the stability of the data, step by step tail-delete method is often used in data pre-processing to eliminate the outliers , but the outliers have its special meanings in shallow overburden areas because of the effect of the territorial rock background .We should not eliminate the outliers directly but record the location of those outliers first, eliminate them temporarily when finding out the background, and endow it with great power when it met the character of the mineral resources in the region. Second, In the process of regional geochemical prospecting, since the data of various maps are measured in the different laboratories or in the different period in the same laboratory, systemic error inevitably exits among various maps and the phenomenon that the content contour circles the subregion is often appeared in the plotting course of geochemical contours. Although a special meeting to solve such question was convoked by national geochemical group, no definite problem-solving scheme was presented. A method of systemic error rectification among maps is advanced against the map merging problem in regional geochemistry and its computing project is also given in this paper which is proved to be effective by the example of the map merging problem in the article. Meanwhile, by the relativity analysis between the petrogenetic elements and the metallogenetic elements, it is validated that there is influence by the territorial rock background. And because the influence, the widespread regions with higher value in the single element contour maps is different form the traditional mine anomalies. To diminish the effect, we adopt the method of moving standardized and decompose the anomalies by alter the size of the window, finding lots of small and low anomalies which are...