Sedimentary geochemistry of Sinian strata in Jixian Region, North China

Sinian strata (isotopic ages ranging from 1,900–850 m.y.) in Jixian County and its vicinity have been studied in more detail from the viewpoint of sedimentary geochemistry. Average chemical composition of various sedimentary rocks in the Sinian sequence (sandstone, siltstone, shale, dolomite and limestone) has been calculated. The periodicity and general trend as exhibited in the course of evolution of element association have been demonstrated by mathematical statistics based on numerous chemical analyses and semiquantitative spectroscopic data with the aid of electronic computer. In accordance with the above results the classification of elements is proposed on a more reasonable ground. Considerable attention has been paid to the periodicity and evolutionary characteristics of rocks, minerals and elements. The mode of occurrence of elements is examined in the light of trace-element concentrations and the relative coefficients between them in different components (clastic debris, clay, etc.) from a variety of rocks and carbonates. Finally, the relationship between background abundances of elements and mineralization, and the effect of submarine eruption on sedimentation and the enrichment of some elements, for example, K, Si, Mn, B, P, Pb and Zn, have also been dealt with.