海拉尔盆地火山碎屑岩的成岩作用

Diagenesis of volcaniclastic rocks in Hailaer Basin

对来自海拉尔盆地40口井的白垩系火山碎屑岩样品显微镜观察与分析显示,火山碎屑岩的成岩作用具有特殊性,表现在熔结作用、脱玻化与重结晶作用、粘土矿物形成与转变和交代作用等方面。熔结作用可以区分出熔浆/熔岩熔结、浆屑熔结和热灰熔结三种类型。脱玻化与重结晶作用常常是交织在一起,流纹质玻璃物质经脱玻化,并进一步重结晶,常具有特殊的结构,呈现一种复杂的硅质胶结样式。粘土矿物形成与转变在成岩作用早期就开始了,如蒙脱石化。一些特征性矿物如浊沸石、绿泥石的出现也不代表变质作用的开始,而是特定成岩环境的产物。碳酸盐的交代-胶结和溶解在火山碎屑岩中普遍发育,使得原岩面貌发生了严重的改变。成岩作用的特征揭示海拉尔盆地火山碎屑岩的成分和结构演变,这在测井岩性解释和孔隙度预测上具有意义。

The microscopic study and analysis of the Cretaceous volcaniclastic samples from 40 drilling wells in Hailaer Basin show that,the speciality of the diagenesis is presented in welding,devitrification and recrystallization,formation and transform of clay minerals and replacement etc.There are three types of welding textures identified as weldings of magma or lava,magma fragment and hot ash.Devitrification and recrystallization were combined,showing special textures,such as a complex cementation of quartzs and siliceous matter resulted from the devitrification of rhyolitic glass and recrystallization.The forming and transforming of clay minerals started early at the initial stage of diagenesis,such as occuring of smectite.Lomonite and chlorite,some diagnostic minerals,would be products of special diagenesis rather than signs of beginning of metamorphism.The replacement-cementation and dissolution developed well in the volcaniclastic rocks during diagenesis,giving some great changes to the original types of rocks.The characteristics of diagenesis reveals the evolution of components and textures of the volcaniclastics in Hailaer Basin,which is useful to the lithological interpretation of loggings and prediction of porosity.