The oil-bearing dolomites exposed in the Long'eni-Angdarco-Dazuoma region have been proven to be a favorable carbonate reservoir in the Qiangtang Basin.Its genetic mechanism is significant for oil and gas exploration in the Qiangtang Basin.In this study,comprehensive analysis of rock thin section identification,carbon and oxygen isotopes,trace and rare earth elements and strontium isotopes are conducted to investigate the genetic mechanisms of the palaeo-reservoir dolomites and the formation and evolution process of the dolomites reservoirs.The main findings are as follows:(1)Dolomite types are subdivided into micritic-very fine crystalline residual structure dolomite,fine crystalline subhedral-anhedral dolomite,fine crystalline euhedral dolomite,medium-coarse crystalline subhedral dolomite,cloudy core and clear rim structure crystalline dolomite and saddle dolomite with late filling holes.(2)The petrological and diagenetic fluid geochemical studies indicate that the micritic-very fine crystalline residual structure dolomite is formed by syngenetic microbial dolomitization.The fine crystalline subhedral-anhedral dolomite and medium-coarse crystalline subhedral dolomite are formed via reflux dolomitization,which occurred during the shallow burial stage.The fine crystalline euhedral dolomite is formed by the deep burial dolomitization.The cloudy core and clear rim structure crystalline dolomite is formed by the near-surface mixing-zone dolomitization during the uplift stage.The saddle dolomite is formed by the hydrothermal dolomitization.(3)The genetic mechanism of dolomites in the palaeo-reservoir reveals the evolution process of burial conditions and reservoir space of dolomites.Secondary pores are formed by dolomitization,meteoric freshwater leaching and hydrothermal dissolution,forming a good dolomite scale reservoir,which can be used as one of the target reservoirs for oil and gas exploration.These understandings provide new theoretical references for the study of hydrocarbon accumulation evolution and the prediction of high-quality carbonate reservoirs in the Qiangtang Basin.