Abstract:

The dolomite deposited in the Dengying Formation of Upper Sinian in the Qiannan Depression.Based on the actual measurement the Yangtiaozhai section, Majiang, we used the geochemical analyses to discuss the sedimentary geochemistry characteristics and the palaeosedimentary environment significance of Dengying FormationsThe results indicated:(1)CaO and MgO remarkably positively correlated with each other；SiO₂  negatively correlated with CaO and MgO; Sr negatively correlated with MgO, and positively correlated with Al₂O₃, K₂O, Na₂O, TiO₂, P₂O₅, TFe; V, Al₂O₃, K₂O, TiO₂, TFe and P2O5 positively correlated with each other; Mn weakly positively correlated with TFe.  (2) The content of Sr and the value of 1,000×Sr/Ca increased with the depth of sedimentary water, regarded as the mark of the palaeobathymetric and succession boundary.  (3)The analytic results of the ratios of Sr/Ba, MgO/Al₂O₃, MgO/CaO and V/(V+Ni) revealed that the palaeosedimentary environments of Dengying Formation is ocean sediments which was formed in reducing environment of continental sea in hot arid climate,and with the detrital material of terrigenous origin Especially, the second member of Dengying Formation was formed in the deepest water environment and the paleosalinity of the fifth member of Dengying Formation is the highest；The geochemical characteristics and the sedimentary environment are closely correlated, and the geochemical characteristics can be regarded as an important mark in the sedimentary phase analyses

Key words:  Qiannan Depression, Upper Sinian, Dengying Formation, geochemical characteristic;sedimentary environment