冀北丰宁地区早前寒武纪构造变形与地壳演化

The Basement Tectonic Deformation and Crustal Evolution in the Fengning Area Northern Hebei

本区早前寒武纪地壳曾经历了两期区域变质作用和四期构造变形作用：２６５０Ｍａ前后单塔子岩群形成，稍后即发生第一期构造变形，形成区内最早的构造形迹一等斜平卧褶皱。第二期变形亦仅发育于单塔子岩群中，表现为闭合一直立一倾伏褶皱，其轴叠加于先期褶皱之上；２４５０Ｍａ时变质深成岩体形成．同时发生角门岩相区域变质作用，本期变质作用晚期阶段在南北向构造应力挤压下，区内产生第三期变形，形成大型复式背形构造和近东西向展布的韧性逆冲剪切带；古元古代时期，大规模的中性、中酸性及酸性岩浆相继侵位，１８００Ｍａ左右发育了绿片告相变质，晚期变质阶段伴随有北东东向脆－韧性剪切变形事件。

There are four peroids tectonic deformation in the basement of Fengning area.Dantazi rock group was formed in 2650Ma, then the first peroid tectonic deformation was happened. It formed the earliest structural features-isoclinal recumbent fold. The second peroid deformation is closed-upright-plunging fold. Only was it showed in Dantazi rock group, and coaxial superposed on the first peroid fold. The metamorphic abyssal rock were intruded in 2450 Ma, and. accompanied by amphibolite factes metamorphism. At the late stage of this metamorphism. Under the conditions of SN compressive stress. The third peroid deformation was happened in this area, it formed the large antiformorium and EW ductile thrust shear zones. The large scale of intermediate, intermediate-acid and acid magmatic emplacemented one by one inpalaeoprotero voic. Greenschist factes metamorphism was happened at 1800 Ma. At the late stage of this metamorphism. There accompanied by NEE britile-ductilt shear deformation.