[Objective]Lacustrine dolomites create a special oil and gas reservoir found in the Qingshankou Forma-tion of Songliao Basin.To explore its sedimentary environment and genetic mechanism,the macro and micro charac-teristics and environmental parameters of dolomites are conducted.[Methods]A comprehensively study with multi-ple sedimentary and geochemical proxies is presented here.The sedimentary environment and genetic mechanism of the dolomites in the lacustrine area of the Qingshankou Formation are analyzed.[Results]The results shows that the dolomites are primarily argillaceous dolomites,and the mineral components arey iron dolomite,clay,and calcite,with a thickness of 1-25 cm.It is distributed in thick lacustrine mudstones and shales in a layered or lenticular shape.The δ13C value is positive,the oxygen isotope δ18O value is negative,the rare earth element of δEu is an obvious nega-tive anomaly,and hydrothermal nutrients,such as Ca,Si,Fe,Mg,Al,and Na,are enriched.The formation is thought to be a primary dolomite caused by methanogenic bacteria in the early stage and transformed by hydrothermal action in the later stage,forming in a saline lake environment under relatively dry climate conditions.[Conclusions]The analysis of the sedimentary environment and genetic mechanism of dolomites in the lacustrine area is of great sig-nificance to the study of the sedimentary evolution and reservoir evaluation in Songliao Basin.
Songliao BasinCretaceousQingshankou Formationsedimentary fabricelemental and isotopic composition
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