摘要
The Ordovician Majiagou Formation in Sulige region of the Ordos Basin was deposited in hypersaline restricted epicontinental environment. It is mainly composed of carbonate rocks with thin evaporate interbeds. The dolomites are characterized with varied Na, low Sr and Mn, and high Fe concentrations. The 18O values for dolomites range from -16.00‰ to -5.73‰, and the 13C values range from -11.46‰ to 1.90‰ (PDB). It indicates that carbonate rocks have experienced leaching and burial diagenesis.Most filled dolomites have lower 18O and 13C values than surrounding components, indicating that the former was formed later. The dolomites are characterized with low degrees of order and less stoichiometry. Microbial dolomitization is the reason for dolomite genesis.