关键词: 松辽盆地, 孤店二氧化碳气田, 片钠铝石, 成因

Abstract: The sandstone with abundant dawsonite can be used to study the genetic relationship between the authigenic minerals caused by injected CO₂ gas and original CO₂ in Gudian carbonate dioxide gas field of Songliao Basin.The morphology,occurrence and components of dawsonite were described,and the paragenetic sequence of sandstone and origin of CO₂ forming dawsonite were investigated by polarization microscope,scanning electron microscope,X-ray diffraction and MAT251 stable isotope mass spectrometer.The authigenic minerals include secondary overgrowth quartz,kaolinite and illite before CO₂ influx.After CO₂ influx,the main cements include dawsonite and ankerite.Dawsonite in the shapes of foliated columnar,cluster,radial,chrysanthemum or random hair mainly filled in the intergranular pores as cements and a few replaced grains such as feldspar and quartz.The dawsonite determined by INCA energy spectrometer is mainly composed of oxygen,sodium,aluminum and carbon.The δ¹³C values of dawsonite ranged from -1.9‰ to +0.3‰.The calculated δ¹³C values of CO₂ gas being in equilibrium with dawsonite ranged from -8.7‰ to -6.9‰ and was in coincidence with the δ¹³C values ranging from -9.76‰ to -5.74‰ of CO₂ gas in Gudian carbonate dioxide gas field.According to the fact that both sandstone within dawsonite and CO₂ in CO₂ gas reservoir lie in the vicinity of deep fracture and basalt,two kinds of CO₂ both from gas reservoir and forming dawsonite almost belong to mantle origin-magma type.

Key words: Songliao Basin, Gudian carbon dioxide gas field, dawsonite, origin mechanism