郯庐断裂带肥东韧性剪切带的变形规律、同位素年龄及其构造意义

Deformation Features and Isotopic Ages of the Feidong Ductile Shear Belt in the Tan-Lu Fault Zone and Its Tectonic Implications

郯庐断裂带肥东韧性剪切带的几何学形态为一正花状左行平移断裂带,目前出露的为该韧性剪切带的根部,具有典型的深层次左行走滑变形特征。肥东韧性剪切带中糜棱岩、超糜棱岩测得的^(40)Ar/^(39)Ar全岩年龄分别为120.48Ma和118.75Ma,说明郯庐断裂带的大规模左行平移时代为早白垩世。对该带构造变形和构造叠加的研究表明,肥东浮槎山一带是被郯庐断裂带截切、牵引、叠加、改造的印支期大别—胶南造山带的残块。郯庐断裂带与大别—胶南造山带是不同时期、不同构造系统的产物,前者属于滨太平洋构造系统,后者属于特提斯构造系统。

The Feidong ductile shear belt in the Tan-Lu fault zone is geometrically a sinistral stike-slip fault of a flower pattern. The mylonite and ultramylonite in the ductile shear zones yield whole-rock 40Ar/39Ar ages of 120. 48 Ma and 118. 75 Ma respectively, which suggest that large-scale sinistral displacement in the Tan-Lu fault zone took place in the Early Cretaceous. Studies on deformation and overprinting structures in the belt demonstrate that the Fuchashan area of Feidong is a relict block of the Indosinian Dabie-Jiaonan orogenic belt, which has been transected, dragged, overprinted and reworked by the Tan-Lu fault zone. The Tan-Lu fault zone and the Dabie-Jiaonan orogenic belt were developed in different times and belong to different tectonic systems. The former belongs to the circum-Pacific system while the latter is part of the Tethys system.