关键词: 基性岩墙群, 圆柱状节理, 冷却收缩, 黏滞性剪切作用

Abstract: A rare kind of primary round columnar joints is developed in the basic dyke swarms in the western Shandong，which is made of the radial joints and the round columnar joints with same axis vertical to the strike of the dyke, arranged one by one along the strike of the dyke. The round columnar joints are one of the flow structures showing the horozontal emplacement of basic dyke swarms. The round columnar joints show that the basic dyke has rheological behaviour of the viscous shearing in magma emplacement. Usually the dip of the axis of round columnar joints vertical to the dyke boundary shows the dip of the dyke and the tilting of the block with the dyke. The round columnar joints show that the dyke swarms are in upper crust brittle tectonic setting, and the western Shandong block is brittle extensional in the Mesoproterozoic time.

Key words: basic dyke swarms, round columnar joints, cool shrink, viscous shearing