辽东铀成矿带连山关地区韧性剪切带与铀成矿作用

Ductile shear zone and uranium mineralization in the Lianshanguan area of eastern Liaoning uranium metallogenic belt

连山关地区位于华北克拉通北缘铀成矿省辽东铀成矿带,已知铀矿床(点)均发育在韧性剪切带附近。为了解韧性剪切带运动学、几何学构造变形机制及与铀矿的关系,本文以连山关岩体周缘韧性剪切带为研究对象,通过野外宏观调查和室内微观研究相结合的研究方法,探讨构造变形期次、韧性剪切带形成机理及其对铀成矿的控制作用。研究表明:连山关岩体周缘发育的韧性剪切带与近南北向挤压构造变形有关,其右行韧性剪切带应变类型为压扁应变,属于一般压缩-平面应变范围,Flinn指数K值在0.19~0.69之间,岩石类型属于S/SL型构造岩。研究区内铀矿体均为隐伏盲矿体,主要赋存于沿着连山关岩体和辽河群接触带右行剪切作用形成的背斜褶皱核部,和北东东向断裂关系密切。综合分析认为,连山关岩体南缘北西向韧性剪切带为一级控矿构造,是区内铀矿热液运移的通道,而剪切带边部的晚期北东东向断裂则是铀矿储存空间;铀源可能来自于太古宙古风化壳,并在大型韧性剪切活动(提供热液运移通道)和基性脉岩侵入(提供热源和还原剂)等综合因素作用下运移、富集成矿。

The Lianshanguan area is located in the eastern Liaoning uranium metallogenic belt which belongs to the uranium metallogenetic province of the North China Craton.The previously discovered uranium deposits(or points)are all developed near the Lianshanguan ductile shear zone.Taking the ductile shear zone around the Lianshanguan granitic pluton as the research object,we carried out a combination study of macroscopic field investigation and microscopic indoor study to discuss the kinematic and geometric structural deformation mechanism of the ductile shear zone and its relationship with uranium deposits.The results show that the ductile shear zone developed around the Lianshanguan granitic pluton is related to the near SN compressional structural deformation,resulting in the dextral ductile shear zone in the south margin of the Lianshanguan granitic pluton.The strain is characterized by flattened strain,which belongs to the general compression plane strain range.The K value of Flinn index is between 0.19 and 0.69,indicating that the rock is S/SL type tectonite.The uranium ore bodies in the study area are all concealed blind ore bodies,which mainly occurs in the core of anticline fold formed by dextral ductile shear along the contact zone between the Lianshanguan granitic pluton and the Liaohe Group,and are closely related to NEE trending faults.The comprehensive analysis shows that the NWW trending ductile shear zone in the southern margin of the Lianshanguan granitic pluton is a first-order ore controlling structure,which is the channel of hydrothermal migration of uranium deposits in the area,while the late NEE trending faults at the edge of the shear zone are the storage space for the uranium deposits.Meanwhile,the uranium may be derived from Archean weathering crust and migrated and enriched under the comprehensive factors of large-scale ductile shear(providing hydrothermal migration pathway)and basic rocks intrusion(providing heat source and reducing agent)migration and enrichment mineralization.