40Ar/39Ar dating of strike-slip motion on the Tan-Lu fault zone, East China

NE-trending, sinistral ductile shear belts in the southern part of the Tan-Lu fault zone, East China are exposed along the eastern edge of the northern Dabie belt and southern Zhangbaling belt. Three hornblende, three phengite and 12 biotite separates from greenschist facies mylonites in the shear belts were dated by the 40Ar/39Ar method in this study. A hornblende plateau age of 143.3 Ma is interpreted as representing the time of sinistral motion on the Zhangbaling part of the Tan-Lu fault zone. Seven biotite samples from the same part yield 40Ar/39Ar cooling ages from 137 to 125 Ma. A phengite plateau age of 138.8 Ma from the eastern edge of the Dabie belt is considered as being close to the time of deformation in the Tan-Lu strike-slip zone. Five biotite 40Ar/39Ar ages from 120 to 110 Ma and one phengite age of 121 Ma from the same area represent cooling ages after the sinistral faulting. It is concluded on the basis of these 40Ar/39Ar ages that the sinistral ductile shear belts in the southern part of the Tan-Lu fault zone were produced in earliest Early Cretaceous. This sinistral motion on the Tan-Lu fault zone is considered to be related to high-speed, highly oblique subduction of the Pacific plate at this time.