A study on 1∶50 000 stream sediments survey in Beishi area,Guangdong Province

A study on mesh experiment of stream sediments survey at a scale of 1∶50 000 was conducted in a selected area about 310 square kilometers of Guangdong Beishi area. The -10~+80 mesh and -60 mesh of stream sediments was collected at the same sam-pling site for the content analysis of various elements. The effect of mesh was evaluated comprehensively from the distribution character-istics of elements content,the enrichment tendency and the characteristic of geochemical. The result shows that:1)The weight of the-10~+80 mesh assumes absolute? superiority? in stream sediments. 2)Elements in the two grade with similar content distribution characteristics in the mass and enriched in high background or mineralization zone with varying degrees,in low background or non-min-eralization zone by contrary,except W、Sn、Pb. 3)The regional geochemical distribution of most elements in -10~+80 mesh shows a higher degree of agreement with the regional geological and more close to the geological boundary. 4)Elements in -10~+80 mesh shows a larger scale and intensity geochemical high background and positive anomaly than -60 mesh, particularly in Mo, Sb. There-fore,the optimal sampling fraction of the Beishi area in Guang Dong is -10~+80 mesh.