松辽盆地东南隆起区营城组柱状节理流纹岩特征和成因

松辽盆地东南隆起区下白垩统营城组出露柱状节理流纹岩。柱状节理属于原生构造节理，岩相为火山通道相次火山岩亚相-侵出相，柱体排列方式为近水平式、倾斜式、近直立式，截面为不规则的四方柱、五方柱、六方柱，柱体规模属于中小型，流纹岩中常发育隐爆角砾结构。通过对柱状节理流纹岩成分及结构构造的研究，表明本区的流纹岩柱体直径与其对应的显微组构斑晶大小成正比例相关。柱状节理的成因是熔岩冷却收缩形成的，由于受到种种内外因素制约，形成的柱状节理形态各异。

Characteristics and Genesis of Rhyolite with Columnar Joints from the Yingcheng Formation in Southeastern Uplift of the Songliao Basin

Rhyolite with columnar joints has been found in the lower Cretaceous Yingcheng Formation,in an uplift area of the southeastern Songliao Basin.The columnar joints in rhyolite are primary structural joint developed in a sub-volcanic sub-facies of volcanic conduit(extrusive) facies.The joints seen include horizontal,inclined and vertical ones.Their cross sections developed are anomalous tetragonal,pentagonal or hexagonal and are of medium to small size.Crypto-explosive breccia structures were well developed.The diameter of prisms is in proportion to the size of micro-fabric phenocryst.The primary genetic mechanism for the joints is the condensing shrinkage.Controlled by different factors,the eventual shapes of columnar joints are quite varied.