徐家围子断陷兴城地区营城组火山岩旋回和期次的划分与对比

Division and Correlation of Volcanic Cycles and Stages of Yingcheng Formation of Xingcheng Area in Xujiaweizi Depression

徐家围子断陷位于松辽盆地北部的东南断陷区,断陷形成于晚侏罗世到早白垩世早期,中生代火成岩较为发育,主要目的层段为营城组一段。在钻井取心研究基础上,根据火山岩的岩性、电性及地震反射特征,对研究区火山岩旋回和期次进行了划分与对比,建立了营城组火山岩旋回、期次模式,总结了旋回、期次的岩心标志、测井响应标志及地震反射标志。通过对研究区火山岩旋回、期次的对比发现,研究区营城组一段发育4个喷发旋回,旋回Ⅰ为中基性岩浆喷发,规模小,旋回Ⅱ为流纹质酸性熔浆喷发,局部可见少量安山岩,火山岩发育厚度和范围比旋回Ⅰ都有明显的增大,旋回Ⅲ为流纹质的酸性岩浆喷发,是本区火山喷发活动的高潮期,旋回Ⅳ以沉火山碎屑岩为主。通过对研究区火山岩地层的划分与对比,为下一步的火山岩勘探开发工作奠定了基础。

Xujiaweizi depression locates at southeast depression region in the north of Songliao basin,formed at late Jurassic to early Cretaceous.Mesozoic eruptive rocks developed well and major interval of interest is the first member of Yingcheng formation.Based on drilling core,volcanic cycles and stages are divided and compared by lithology,electrical property and seismic reflection characteristics of the volcanic.Pattern of the volcanic cycles and stages is set up and the core symbols,logging response marks and seismic reflection in the study area are summarized.It is found that the first member of Yingcheng formation develops four eruption cycles by comparison of volcanic cycles and stages.The lithology of cycleⅠis intermediate and basic igneous rock,which has a small scale;the mainly lithology of cycleⅡis acidic magma,and few andesites locally,but the thickness and the range of the volcanics are obviously bigger than cycleⅠ;the lithology of cycle Ⅲ is acidic magma,and it is in the height of volcanic eruption;the lithology of cycle Ⅳ is sedimentary pyroclastic rocks.The research on division and correlation of the volcanic rock formations in the study area provides foundation for the next exploration and production of the volcanic rocks.