Thermochronologic constraints on deformation and cooling history of high- and ultrahigh-pressure rocks in the Qinling-Dabie orogen, eastern China

摘要: The Hong'an block is the best place to study exhumation of high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks in Qinling-Dabie orogen eastern China because it lacks extensive Cretaceous tectonic thermal overprint observed Dabie Shan. We measured timing deformation rate cooling HP-UHP by 40Ar/39Ar analyses synkinematic minerals from tectonites key structural zones Tongbai Normal-sense shear along north dipping Huwan detachment at northern edge occurred between 237 231 Ma; this facilitated bulk rocks. Our new ages, combined with U/Pb zircon Sm/Nd ages 245–240 Ma, suggest that UHP mantle depths rates 5–25 mm/yr ∼245 230 Ma. mountain range a warped extensional footwall, within which white mica cooled 225 205 Locally, younger extension recorded recrystallization 198–194 after entire had below 300°C. Early zone indicate dextral southwest boundary was contemporaneous normal sinistral-oblique slip Xiaotian-Mozitan fault boundary. Coeval sinistral southwestern margins Shan would have caused eastward lateral extrusion these two blocks, perhaps driven collision Lhasa Eurasia.