Geochemical characteristics and genesis of Middle Proterozoic Jixian System dolomite in the Southwest margin of Ordos Basin

Shallow marine dolomite of Jixian System in Qishan area of Ordos Basin is of great significance for deep exploration of the basin, but its genetic mechanism is still unclear. On the basis of field sampling, by means of analysis and testing of major and trace elements, C, O isotopes, Sr isotopes, combined with the evolutionary background of Middle Proterozoic, this paper has analyzed the geochemical characteristics of Jixian dolomite in Qishan area, and further discussed the origin of dolomite. This study shows that the Jixian dolomite in Qishan area is mainly composed of dolomite, siliceous dolomite and chert bearing banded dolomite, and stromatolites are relatively developed; Geochemical characteristics show that the diagenetic fluid of dolomite in the study area mainly comes from marine sediments, and fresh water may be added later; The genesis of crystalline dolomite is mainly burial genetic model, while the residual texture dolomite and calcareous dolomite are mixed water genetic model; Dissolution dolomite is the cause of seepage reflux mode.