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

摘要： 松辽盆地孤店二氧化碳气田储集砂岩中含有大量片钠铝石,根据其特征可以查明注入CO₂气形成的自生矿物与CO₂成因之间的联系。利用偏光显微镜、扫描电镜、X-射线衍射分析仪和MAT251稳定同位素质谱仪,详细描述了片钠铝石的形貌、产状和成分,确定了含片钠铝石砂岩的成岩共生序列和形成片钠铝石的CO₂的成因。注入CO₂气前形成的自生矿物组合主要为次生加大石英、高岭石和伊利石,注入CO₂气后形成的自生矿物组合主要为片钠铝石和铁白云石。其中,片钠铝石呈板柱状、束状、放射状、菊花状、杂乱毛发状集合体,主要作为胶结物产于碎屑岩碎屑颗粒间的孔隙中,少量交代长石、石英等碎屑。INCA能谱测试表明组成片钠铝石的主要元素为氧、钠、铝、碳。片钠铝石的δ¹³C值为-1.9‰~+0.3‰,与片钠铝石平衡的δ¹³C_CO2为-8.7‰~-6.9‰,与孤店CO₂气田中CO₂气的δ¹³C_CO2值(-9.76‰~-5.74‰)接近。由于含片钠铝石砂岩与CO₂气的分布都受控于深大断裂和玄武岩,CO₂气和形成片钠铝石的CO₂绝大部分属于幔源-岩浆型。

关键词: 松辽盆地, 孤店二氧化碳气田, 片钠铝石, 成因