辽南中生代造山期缩短滑脱与晚造山伸展拆离构造  

Mesozoic orogeniccontractional extensional detachment in the decollement and late-orogenic southern Liaoning Peninsula

作　　者：郑亚东[1] 曾令森[2] 李健波[2] 欧阳志侠[2] 

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]中国地质科学院地质研究所,北京100037

出　　处：《地质科学》2009年第3期811-824,共14页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金委项目(编号:90714006)资助

摘　　要：该区的构造格局主要由早期近东西向紧闭的褶皱带和晚期北北东向构造组成。早期的南北向缩短构造以龙王庙平卧褶皱和大小长山岛的直立紧闭褶皱为代表,分别具有扇状间隔性压溶劈理和透入性轴面片理,褶面倒向以北为主。北北东向构造切割近东西向构造,表层表现为北西西向薄皮逆冲推覆构造,浅层构造具有扇状压溶劈理的紧闭褶皱,深层表现为基底与盖层间的拆离断层及其下的韧性剪切带。早期的研究者将该断层作为辽南推覆构造底部的滑脱面,现今则压倒性地采用变质核杂岩的构造理念。根据相关剪切带早期面内褶皱发育,晚期伸展褶劈理发育,通过运动学涡度和应力状态分析,论证早期滑脱—推覆到晚期伸展拆离的演化过程。野外观测证明,辽南基底变质岩西侧的金州断层为一伸展拆离断层,它切割东侧的董家沟断层,前者平行于下伏糜棱岩中的同向伸展褶劈理,后者平行下伏糜棱岩的糜棱面理。金州拆离断层的形成及其东侧的隆起标志着辽南构造体制从缩短到伸展的转折。根据相关的年代学研究,这一构造体制转化发生在早白垩世(约120～107 Ma)。该区最新的构造事件是北东—南西向的缩短,相关的北北东向的右行走滑断层与晚白垩世以来的郯庐断层活动方式一致。The structural framework in the area is composed of an older sub-E-W-trending fold zone and younger NNE-NE-trending structures. The Dragon-King Temple recumbent folds with fanlike spaced cleavages caused by pressure-solution and the Vertical and closed folds with penetrative axial foliation in the Changshan Islands are major features of the earlier sub-N-S contractional event. The axial surfaces of the folds commonly verge N-wards. The NNE-NE- trending structures that cut across the sub-E-W features are thin-skin WNW thrusts near the earth surface, tight folds with fan-like spaced cleavages caused by pressure-solution at shallow levels, and at depth, the decollement between cover strata and basement rocks and the underlying ductile shear zone. The decollement is regarded as the floor of the southern Liaoning Peninsula thrust belt by earlier researchersand nowadays, however, the concept of metamorphic core complex is overwhelmingly used researchers. An evolution process from contractional decollement to extensional detachment is argued by analyzing earlier formed intrafoliation folds and crosscutting extension crenulation cleavages in terms of kinematic vorticity and stress state. Observations in field show that the Jinzhou fault on the western flank of the Archean metamorphic basement terrane in the area is an extensional detachment fault that is parallel to the C＇-foliation in the underlying mylonitic rocks and truncates the Dongjiagou ductile fault that is normally parallel to the mylonitic foliation underneath. The formation of the Jinzhou detachment fault and the uplift on its eastern side are the major indicator of switch in tectonic regime from contraction to extension. The switch occurred at earlier Cretaceous（ -120 -107 Ma） based on chronologic data available. The youngest event in the area is NE-SW contraction and the major features are NNE-trend and dextral strike-slip faults that are compatible with the behavior of the Tanlu Fault since late Cretaceous.

关 键 词：滑脱-推覆作用 伸展拆离作用 运动学涡度 伸展褶劈理 

分 类 号：P542[天文地球—构造地质学] P313[天文地球—地质学]