辽南庄河地区栗子房变质核杂岩的发现及意义

Discovery and significance of Lizifang metamorphic core complex in Zhuanghe area of southern Liaoning

在区域地质调查资料基础上,根据宏观与微观构造测量,通过分析区域岩浆活动性及其测年资料等,揭示了在辽南庄河栗子房地区存在另一个变质核杂岩构造,即栗子房变质核杂岩。该核杂岩具有3层结构和5个部分,即由新太古代变质深成岩及中生代花岗岩侵入体构成的下盘、由不同层次的构造岩组成的中部拆离断层带以及由前寒武纪沉积盖层和白垩纪伸展盆地构成的上盘。栗子房变质核杂岩形成于早白垩世,运动方向为上盘相对下盘由NWW向SEE方向运动,与辽南金州变质核杂岩和万福变质核杂岩在几何学、运动学极性和形成时间等方面具有很多相似性,形成于同一动力学背景。该变质核杂岩的厘定可为阐明华北克拉通东部晚中生代岩石圈减薄过程及岩石圈的力学和流变学属性提供依据。同时,变质核杂岩与金矿床成矿关系密切,栗子房变质核杂岩的拆离断层带附近可作为下一步金矿勘查的重点工作区,成矿潜力较大。

On the basis of the previous regional geological survey,based on the macroscopic and microscopic structural survey,combined with the comprehensive analysis of the regional magmatic activity and dating data,the authors in this paper revealed that there is another metamorphic core complex structure in Lizifang area of Southern Liaoning,namely Lizifang metamorphic core complex.A typical three-layer structure and five parts exist in the core complex,which are the footwall composed of Neo-archean metamorphic plutonic rocks and mesozoic granite intrusive rocks,the detachment fault zone composed of different levels of tectonic rocks,and the upper plate composed of Precambrian sedimentary cap and Cretaceous extensional basin.Lizifang metamorphic core complex formed in the Early Cretaceous Epoch,and the upper plate moved from NWW to SEE relaive to the footwall,which was similar with Jinzhou metamorphic core complex and Wanfu metamorphic core complex in geometry,kinematics polarity and formation time,indicating the same dynamic background.The determination of the metamorphic core complex may provide a basis for the late Mesozoic lithospheric thinning process and the mechanical and rheological properties of the lithosphere in the east of North China Craton.At the same time,the metamorphic core complex is closely related to the mineralization of gold deposits.So the detachment fault zone of Lizifang metamorphic core complex can serve as the key work area for further gold exploration,which may possess large mineralization potential.