摘要:郯庐断裂带在造山阶段之后发生了明显的左行平移活动，但到目前为止对于其发生时间仍存在较大争议。大别山东缘郯庐断裂带内存在一系列花岗质、基性岩脉，其形成与郯庐断裂带左行平移活动密切相关，因而对其形成年龄的测定可以为断裂带左行平移时间提供限定。本次工作在大别山东缘郯庐断裂带内糜棱岩及岩脉中采集了6个样品开展锆石LA-ICP-MS年龄测定。两个花岗质糜棱岩样品均得到了新元古代和印支期两组年龄结果，但并未得到早白垩世年龄结果，可能指示了强烈的构造变形抑制了锆石的生长。与断裂带左行平移活动同期的基性岩墙侵位时间为128 Ma左右；斜切糜棱岩面理的基性岩墙侵位于127 Ma 左右；发生韧性变形形成糜棱岩的二长花岗岩侵位时间为128 Ma左右；仅出现NE向劈理的钾长花岗岩侵位于126 Ma。综合以上结果，大别山东缘郯庐断裂带与下扬子地区存在类似的构造背景，其早白垩世左行平移事件的发生时间为128 Ma之前，之后断裂带在区域伸展背景下转变为正断层活动。
关键词: 郯庐断裂带/
造山后左行平移/
锆石定年/
多期活动
Abstract:The Tan-Lu fault zone moved as a sinistral strike-slip fault during post-collisional stage of the Dabie Orogen, but its movement timing is still ambiguous. A series of granitic and mafic dikes developed in the Tan-Lu fault zone on the eastern terminal of Dabie Orogen, which formation were close to strike-slip movement of the Fault zone. Therefore, development of dikes can offer timing evidences for the strike-slip movement of the Tan-Lu fault zone. In this work, six samples were collected from mylonites and dikes in the Tan-Lu fault zone for zircon LA-ICP-MS dating. Two groups of ages, Neoproterozoic and Indosinian, and no Early Cretaceous age data were obtained from two granitic mylonites, indicating that intense deformation restrained formation of zircon rim. A mafic dike, emplacing along fault plane of the fault zone, and a ductile deformed monzogranite formed at ca. 128 Ma, which suggests that strike-slip movement of the Tan-Lu fault zone was still??under??way at that time. Another mafic dike, crossing obliquely with the mylonite foliation, formed at about 127 Ma. A K-feldspar granite just with NE-striking cleavages emplaced at ca. 126 Ma. Considering these age data and previous works synthetically, the Tan-Lu fault zone should move before 128 Ma during the Early Cretaceous and then transfer to normal fault movement.
Key words:The Tan-Lu fault zone/
Post-orogenic sinistral strike-slip/
Zircon dating/
Multiple movements
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