Sinian strata(isotopic ages ranging from 1,900—850m.y.)in Jixian County and itsvicinity have been studied in more detail from the viewpoint of sedimentary geochemistry.Average chemical composition of various sedimentary rocks in the Sinian sequence(sand-stone,siltstone,shale,dolomite and limestone)has been calculated.The periodicity and generaltrend as exhibited in the course of evolution of element association have been demonstratedby mathematical statistics based on numerous chemical analyses and semiquantitativespectroscopic data with the aid of electronic computer.In accordance with the above resultsthe classification of elements is proposed on a more reasonable ground.Considerable attentionhas been paid to the periodicity and evolutionary characterictics of rocks,minerals and ele-ments.The mode of occurrence of elements is examined in the light of trace-element concen-trations and the relative coefficients between them in different components(clastic debris,clay,etc.)from a variety of rocks and carbonates.Finally,the relationship between back-ground abundances of elements and mineralization,and the effect of submarine eruption onsedimentation and the enrichment of some elements,for example,K,Si,Mn,B,P,Pb andZn,have also been dealt with. Sinian strata (isotopic ages ranging from 1,900-850m.y.) In Jixian County and itsvicinity have been studied in more detail from the viewpoint of sedimentary geochemistry. Average chemical composition of various sedimentary rocks in the Sinian sequence (sand-stone, siltstone, shale, dolomite and limestone) has been calculated. periodicity and generaltrend as show in the course of evolution of element association have been demonstrated by mathematical statistics based on numerous chemical analyzes and semiquantitativespectroscopic data with the aid of electronic computer. According to the above result result classification of elements is proposed on a more reasonable ground. Canonsiderable attentionhas been paid to the periodicity and evolutionary characterictics of rocks, minerals and ele-ments. The mode of occurrence of elements is examined in the light of trace-element concen- trations and the relative coefficients between them in different components (clastic debris, clay, etc.) from a vari ety of rocks and carbonates. Finally, the relationship between back-ground abundances of elements and mineralization, and the effect of submarine eruption on segmentation and the enrichment of some elements, for example, K, Si, Mn, B, P, Pb and Zn, have also been dealt with