The Kyonggi shear zone of the central Korean peninsula: Late orogenic imprint of the north and south China collision

The crustal-scale Kyonggi shear zone of central Korea has been identified a s a major boundary between the Precambrian Kyonggi massif in the south and the Imjingang belt in the north. The latter is an eastward extension of the Qinling-Dabie-Sulu collisional belt of China. Field observations and micro structural analysis indicate that the extensional shear zone evolved from a deep crustal ductile regime to a shallow crustal brittle regime, associate d with a rapid uplift of the Kyonggi massif following the Late Permian-Earl y Triassic collision between the Sine-Korean and Yangtze cratons. A Rb-Sr m uscovite age (226 +/- 1.2 Ma) of the mylonite suggests that the extensional ductile shearing occurred during the Late Triassic.