鲁东栖霞地区新元古代蓬莱群构造演化

Structural Evolution of Neoproterozoic Penglai Group in Qixia Area in Eastern Shandong Province

蓬莱群地层宏观上表现为层序正常的单斜岩层,实际却变形强烈。通过对鲁东栖霞地区蓬莱群中劈理、褶皱、韧性剪切带等构造形变的研究,总结了蓬莱群经历了三期构造演化:早期为伸展构造体制下的褶叠层构造,中期为剪切-收缩体制下中浅层次剪切变形,它们分别是苏鲁造山带俯冲折返后期的板上伸展构造不同阶段的反映;晚期则受控于太平洋板块向欧亚板块俯冲造成的NW—SE向挤压应力作用形成轴向北东的宽缓纵弯褶皱。蓬莱群与下伏结晶基底之间为角度不整合接触,并且受到早期构造作用的改造,深层次的韧性拆离断裂并不是完全沿着角度不整合界面作用。

Penglai group is a monocline with normal sequence,but it has strong deformation.Based on the study of structural deformation of cleavage,fold and ductile shear zone in Penglai group of Qixia area in eastern Shandong province,it is regarded that Penglai group has experienced three stages of structural evolution:the early stage is the fold structure under the extensional structural system,the middle stage is the shear deformation of the middle and shallow layers under the shear contraction system,which are the reflection of the different stages of the supra plate extensional structure in the later stage of subduction and exhumation of Sulu orogenic belt.In the late stage,it is controlled by compressive stress with the trend of NE—SE caused by the subduction of the Pacific plate to the Eurasian plate resulted in the formation of buckle fold with an northeast axis.Penglai group is in angular unconformity contact with the underlying crystalline basement,and later is transformed by tectonism.The deep ductile detachment faults do not affect completely along the angular unconformity interface.