Abstract: There are two types of diabaseprophyrite dikes in the third member of the Cretaceous Yingcheng Formation at the Shanghewan area in the southeastern uplift of the Songliao Basin. One type of diabaseprophyrite was emplaced in the NE30°-35° trending trackingexpansion joints, and contained dikes of 1-5 m in width, 75°-88° in dip angle and showed indented contact between the dikes and the county rocks. Another type of dikes was emplaced in the 40°-45° direction shear joints, with the dikes being 2-10 m in width, 75°-88° in dip angle and showing lowangle lineation or striation in the slippery boundary between the dikes and the county rocks. There are strong to weak schistosity from rim to centre in all the dikes. The chemical compositions of the dikes are similar to that of the basalts. However, the dikes show secondary changes, including hypo-calcspar and crystallite biotite, indicating fluid-rock metasomatism. The diabaseprophyrite dikes recorded some important events happened in the area when the terminal deposition of the Cretaceous Yingcheng Formation took place in this area-NE-SW compressive tectonic stress and basic magmation. The research for the incursion and deformation of the dikes indicates that they were controlled by the Jiamusi-Yitong faulting and was under compression after intrusion of dikes. The study on the geological characteristics of the diabaseprophyrite provides some important information to the relations between the original fracture-cracks in dikes and their reservoir significance.

Key words: Songliao Basin, Yingcheng Formation, diabaseprophyrite, NE-SW compression-tectonic stress