| Due to the long-term change of geological development,different geochemical elements are either enriched or depleted,which makes the distribution of geochemical elements random and uneven in plane and space,thereby brings great difficulty to analyses of geochemical characteristics.In order to solve this problem,some research methods,such as mean-standard deviation method,the trend surface analysis,moving average method and content area fractal method,are put forward to determine the lower limit of anomaly for processing geochemical data.The trend surface analysis method,moving average method,fractal method and other methods entail a large amount of calculation in determining the lower limit of anomaly,which requires computer technology.At the same time,with a large number of spatial data,ordinary database management technology cannot meet the needs.GIS technology can establish the relationship between geology and geochemistry in a systematic and scientific way,provides a variety of analytical functions,and is capable of producing moredirect two-dimensional even threedimensional graphics,which can reveal more valuablepotential data.The information collected provides a convenient tool for studying the law of the distribution of geochemical elements and simplifieswork-related difficulty.Based on the data of "1:50000 regional geological and mineral survey of Guanggai,Lingding station,Sandao and Xinying sheet in Heilongjiang Province",the information of geology,geography and geochemical exploration is transformed into spatial data by using GIS tools,and the immediately perceivable graphic data and associated attribute data are established.Taking the geochemical data of the studied area as the research object,the principle and operational process of the three geochemical data processing methods,namely mean standard deviation method,trend surface analysis method and content area fractal method[1-5],are introduced.According to the results of anomaly lower limit delineated by the three methods,combined with the background information of the regional geological characteristics,GIS spatial analytical method is used to locate and delineate the abnormal area,and the mapping results are compared to analyzing the effect of geochemical data processed by each method in mineral exploration.By comparing the application of three mathematical methods of geochemical data,it could be found that the calculation of mean standard deviation method is simpler than the other two methods,and the mapping effect is remarkable.Especially for the mineral exploration in the small scope of the studied area,the results are similar to the other two methods,but workload of the calculation is relatively small,which is conducive to the promotion of mineral exploration.However,for the large-scale and research-oriented area,trend surface analysis can better fit the abnormal trend in the stuied area,significantly strengthening the performance of low anomalies,however,because of too much low abnormal information,the overall abnormal information is weakened,which is not conducive to the extraction of abnormal information.The content area fractal method does not require the distribution state of the data and does not need to eliminate high outliers from the original data.Instead,the area formed by the ultra-high value is limited in a small range,which does not have too much impact on the overall data and reduces the artificial error.After comparing the three methods,the mean standard deviation method,trend surface analysis method and content area fractal method are basically similar in the distribution and structural trend of the anomalies in the strata.But the mean standard deviation method is relatively easy to operate in GIS,simple in calculation and fast in mapping.In conclusion the mean standard deviation method is more suitable for the geochemical exploration in the study area. |
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