北山马鬃山地区野马泉和勒巴泉韧性剪切带构造变形特征与年代学约束

Structural Characteristics and Chronological Constraints on the Yemaquan-Lebaquan Ductile Shear Zone in Mazongshan Area, Beishan

野马泉和勒巴泉韧性剪切带作为北山造山带微陆块碰撞的产物,在北山造山带早古生代碰撞—造山过程中具有重要的地质意义。前人对其研究主要集中于勒巴泉地区构造变质核杂岩以及其中产出的蛇绿岩带。为了更好确定其构造变形时代,文章通过对野马泉和勒巴泉韧性剪切带野外构造剖面和显微构造特征的研究表明:野马泉和勒巴泉韧性剪切带具有由北西西向南东东逆冲,兼具右行剪切运动特征。通过对韧性剪切带中糜棱岩带中未变形花岗岩脉的锆石U-Pb定年,确定了野马泉和勒巴泉地区韧性剪切变形年龄上限为416 Ma,结合前人所报道的年龄,将韧性剪切变形时代大致限定在423~416 Ma之间,可能与牛圈子洋壳往北北东方向朝野马泉弧俯冲有关。

The Yemaquan-Lebaquan ductile Shear Zone,as the result of microcontinent collision in the Beishan Orogen,is of great geological significance in the Early Paleozoic collision-orogenic process of the Beishan orogenic belt.Previous studies mainly focused on the tectonic metamorphic core complex and the ophiolite in Lebaquan area.In order to better constrain its active age,the structural profile and microstructural characteristics of the Lepaquan-Yemaquan ductile shear zone were studied.It shows that the shear zone thrust from NWW to SEE during the earlier period,which then transformed into nearly E-W dextral strike-slip during the late stage.The mylonite zone was intruded by the late undeformed granite veins,which have a zircon U-Pb age of 416 Ma.Integrated with the previous studies,the time ductile deformationwas constrained between 423-416 Ma.