通过大量的岩心和薄片观察,分析准噶尔盆地乌—夏地区风城组熔结凝灰岩岩石学特征和孔隙发育特征,探讨富孔熔结凝灰岩成因和气孔发育机制.风城组沉积期火山作用以发育熔结火山碎屑岩为典型特征,岩石组分以塑性玻屑为主,棱角圆化,脱玻化特征明显；常见塑性浆屑变形揉皱、晶屑熔蚀现象.熔结凝灰岩中发育大量石泡,使熔结凝灰岩结构特征模糊.气孔是石泡构造的空腔,为冷凝收缩成因,受脱玻化作用影响挥发分或水蒸气散溢,形成的孔隙空间后期未被充填或少量充填.一个冷凝单元中石泡体发育在垂向上具有明显的分带特征:自下而上,气孔由少增多再减少.石泡孔洞的发育提高了熔结凝灰岩的储集能力,受熔结作用影响,石泡体未被压扁破坏.深埋、高孔熔结凝灰岩是重要的油气储集层,研究区高孔熔结凝灰岩具有良好的含油气性.图8表1参18%On the basis of a large number of cores and thin-sections observations, the petrologic and pore evolution characteristics of ignimbrite in the Fengcheng Formation in the Wu-Xia area, Junggar Basin, are studied, and the genesis of vesicular ignimbrite and formation mechanism of vesicles are analyzed. Volcanic action in the Fengcheng Formation is characterized by welded pyroclastic rocks. There are predominant plastic shards with rounded edges and obvious devitrification in the rocks. Plastic debris is deformed and wrinkled, and crystal fragments are usually corroded. A lot of lithophysae occur in the ignimbrite, and welded texture is obscured. Vesicles are the cavities of lithophysae, which are formed by solidification contraction. They have little or no late filling cement because the volatile constituent and water vapour in the bubbles have escaped with the help of devitrification. Lithophysae distribution within a cooling unit obviously has the characteristic of zonation in vertical: increasing upwards and then decreasing gradually. The cavities of lithophysae greatly improve the reservoir capability of ignimbrite. Influenced by intensive welded process, lithophysae are not subject to collapse or damage. In the study area, deeply buried vesicular ignimbrite is an important hydrocarbon reservoir rock, and the vesicular ignimbrite has good petroliferous property.
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