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Regional Geochemical Mapping Project of China has been carried out by China Geological Survey since the end of 1970sĄŻ. The data of 39 elements and oxides were collected and put into China Regional Geochemical Database which is consists of around 1,400,000 items of sampling records and 55,400,000 of analysis data covering an area of about 6,500,000km2. The National Geochemical Atlas scaled 1:5,000,000 and 1:12,000,000 were compiled based on GIS technology and have been provided to the public service recently.
Multiple Geo-Spatial Data Management and Analysis System (GeoExpl) which was developed by Development and Research Center of China Geological Survey was adopted to manage, process and analysis the geochemical data, and to generate the national geochemical series maps. The following methods or steps were involved in the maps compilation.
First, the original data collected from provincial geological survey need to check and adjust the integrity and the correctness, integrate into national geochemical database.
Second, the data were standardized to eliminate the system error between different analysis samples, quadrangles, provinces, and different geographical units by using data error correction system of GeoExpl.
Third, data gridding is a key process. The optimal geometric parameters, like the grid distances and the search radius of data points, of the grid and mathematical method were applied for data grid processing by comparing and analyzing with several processing methods.
Fourth, the contours and the equivalent areas of geochemical elements could be created automatically with grid data by using the contour generation function of GeoExpl. The classification of data for contours were based on cumulative frequency calculation and the relative statistical eigenvalues of the element dataset were computed simultaneity and marked on the map by distribution graph. The national geochemical series maps clearly describe the geochemical characteristics of different geological units and reflect the main element distribution features of important metallogenic betls, ore fields and large deposits in China. In addition, the maps and database also provide the preliminary data for the research of geology, ecological environment, mineral exploration, land planning and decision-making.
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