辽宁丹东地区侏罗纪花岗岩的变形时代: ⁴⁰Ar/³⁹Ar年代学制约

Gneissic two-mica monzogranites are widespread in the southern Liaodong Peninsula, eastern China. The SHRIMP zircon U-Pb dating indicates that their emplacement ages are between 180 ∼ 157 Ma. The most remarkable characteristics of these granites are that these granites had experienced two stages of ductile deformation, i. e., the early NW-trending compression and later EW-trending extension. However, the deformation ages are still not constrained. In this paper we present UV laser ablation ⁴⁰Ar/³⁹Ar data of K-bearing minerals from the Heigou pluton, which is located at the southwestern of Dandong City, to study its deformation age and cooling history. Our results show that the Heigou pluton was deformed at ∼ 143 Ma and ∼ 121 Ma, respectively, during crustal compression and extension and subsequently cooled and exhumated from 121 Ma to 113 Ma. This indicates that the tectonic transition happened during 143 ∼ 113 Ma in the Liaodong Peninsula. Considering the regional tectonics, we present that the NW-trending compression was related to the subduction of Paleo-Pacific Plate beneath the Eurasia continent during Late Jurassic to Early Cretaceous, while the EW-trending extension was the result of the direction and speed transformation of the subduction of Paleo-Pacific Plate, lithospheric thinning and relaxation of compression.