⁴⁰Ar/³⁹Ar Geochronology Of Metamorphic Deformed Minerals From Ductile Shear Zone

⁴⁰Ar/³⁹Ar geochronology and thermochronology play an important role in tectonic thermo history study. We gave detail ⁴⁰Ar/³⁹Ar dating on metamorphic deformed k-feldspar and biotite, which came from the sunjiawan-shaohuyingzi ductile shear zone belong to yiwulüshan metamorphic core complex, and should be helpful for our understanding the shear zone deformation thermo history and constraining the mechanism of knetic.The results of these sample are significant, except for the high reminiscent of formerly published age date, we get latest and important conclusions. CR99-2 of four biotite sample shows saddle shaped spectrum, the rest are staircase spectrum. The minimum age of CR99-2 is 126 Ma, while CR99-1,CR99-3, CR99-4 are monotonically rising from minimum age 3.85±26.69 Ma, 20.06±80.13 Ma, -6.52±29.49 Ma to Maximum 183.18±11.33 Ma, 203.58±11.32 Ma, 207.45±9.32 Ma, respectively.This is the initially report about biotite which keep integral Ar diffusion internal, its rarely external.The effective Ar diffusion illustrate that the ductile shear zone activity lasting to present from 190 Ma, and underwent an large scale tectonic thermo history at 126 Ma.Three K-feldspar sample from the edge of porphyroclasts, CR99-5, CR99-9, CR99-10 give good plateau ages of 128.77±2.07 Ma, 120.57±0.80 Ma, 136.35±4.59 Ma, while their inverse isochron ages are 126±6.29 Ma, 120.31±0.94 Ma, 119.67±7.09 Ma. Three fine-grained k-feldspar samples from the center of porphyroclast show staircase age spectra, yielding lowest age about 110 Ma and biggest mean age of 126 Ma. These results indicate the Mesozoic large scale thermo history since 126 Ma and ended by about 110 Ma, experiencing a fast cooling history.