| In order to study the regional geochemical composition and lateral spatial variation of the geochemical elements,sediment and rock samples along a transect across the Xing'an-Mongolian Orogenic Belt-North China Craton were collected for 550 and 1309 pieces in high density of 1-4km and 76 elements concentrations were determined.Data of statistical analyses of principal components,ore-forming elements and REE for sediment samples were based on tectonic units,geographical landscape,soil types and rainfall units,and for rock samples were based on rock types and geologic age units.An average value was calculated from each 1:50 000 map sheet,and spatial distribution of selected elements concentrations is plotted in figures.The rock samples were classified,and the characteristics of selected element concentrations in different lithology and geological age were analyzed,especially the characteristics of SiO2,Au in magmatic rocks and rare earth elements in granite were discussed.Results show that:?1?The comparison of SiO2,Al2O3,illustrates sediment mineral composition is one of the important factors affecting its concentrations;The enrichment of CaO and MgO is closely related to carbonate rocks;Rainfall significantly affects on the enrichment of Na2O and K2O in sediment and there exist slight differences.The concentrations and spatial distribution of the major elements in sediment are not only affected by the succession of the bedrock,but also by the complex factors such as,weathering,climate and geochemical characteristics.The change of the SiO2 concentrations reflects the trend of acid evolution in the upper crust,which is the highest in Hercynian magmatic rocks.The concentrations of H2O+ is generally low,besides in the carbonate rock and local quaternary area.The value of pH reflects the alkaline sediments characteristic in the north China.?2?The enrichment of Au is closely related to the Archean Proterozoic crystalline basement,and the enrichment coefficient of Au in the Yanshan Orogenic Belt is obviously higher than that in the Luxi Block,which is consistent with the distribution of Au deposits.Ag and Cu enrichment coefficient curves are very similar,moreover Pb and Zn is almost completely consistent for their minerals closely related exist.The enrichment coefficient of W is a perfect interpretation of its enrichment in granite,which also shows a high concentrations in the plain sediments,indicating that the provenance may be affected by the Yanshan Orogenic Belt and the Luxi Block.Ti corresponds well with the distribution of basic-ultrabasic rocks,and the abnormal enrichment of V in sediments of northern Jiangsu may be related to the Luxi Block.?3?The spatial distribution of the concentration of REE in sediment and rocks indicates that the source region determines the overall difference of REE in different tectonic units,but the supergene conditions also play an important role in local differences.The concentration difference of REE in different granitoids or tectonic units is larger than that in the geological age;There are also differences in the same kind of granite in different geological times,indicating the granitoids formation in different magmatic geological process.?4?The strong query function between spatial data and attribute data of geographic information system,can better manage the geochemical sample data,provide the basis for further data mining and application in basic geology,mineral resources prediction and agricultural production activities.Above all,the results highlight that the influence of the surface environment on the concentration and distribution of elements is complex and important in the complex earth's surface system,such as the geographical landscape,climatic factors,etc.The biological action,human industrial or agricultural activities on soil concentration should be paid more attention,which complex mechanism is worth studying deeply,anyway,GIS can be useful. |
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