Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabic orogenic belt. A muscovite 40Ar/ 39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone. Three muscovite samples separated from mylonites of 3 localities in the earlier ductile shear belts yield 40Ar/ 39Ar plateau ages of 192.5±0.7 Ma, 189.7±0.6 Ma and 188.7±0.7 Ma, respectively. They are interpreted as cooling ages of the earlier sinistral strike-slip deformation. It is suggested that left-lateral displacement of the Tan-Lu fault zone started in a late stage of the collision orogeny in the Dabie-Sulu orogenic belt between the North and South China plates. Therefore, the earlier Tan-Lu fault zone was syn-orogenic strike-slip tectonics. The fault zone was used again for sinistral displacement during tectonic activities of peri-Pacific regime in Early Cretaceous. It is proposed that the fault zone occurred as a transform fault during the orogenic process.
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Acknowledgements The authors would like to thank Tang Shupei from the Physical and Chemical Center of Hefei University of Technology for XRD analysis. We are also indebted to Sang Haiqing from Institute of Geology and Geophysics, Chinese Academy of Sciences for his help on 40Ar/39Ar plateau age and inverse isochron calculation. This work was supported by the National Natural Science Foundation of China (Grant Nos. 49872074 and 40272094).
- Dabie-Sulu orogenic belt
- Muscovite Ar/Ar age
- Syn-orogenic strike-slip movement
- Tan-Lu fault zone