Polyphase Mesozoic tectonics in the eastern part of the North China Block: insights from the Eastern Liaoning Peninsula massif (NE China)

Wei Lin (1) , Michel Faure (2) , Patrick Monié (3) , Qingchen Wang (1)

1 IGG - Institute of Geology and Geophysics [Beijing]
2 ISTO - Institut des Sciences de la Terre d'Orléans
3 Géosciences Montpellier

In Eastern China, the North China Block (NCB) has experienced a complex tectonic evolution during Late Palaeozoic to Mesozoic times. The unconformable sedimentary cover, which ranges in age from Neoproterozoic to Permian, underwent two tectonic episodes in Early Triassic and Cretaceous times. An early north–south compressional phase, D1, characterized by north-verging recumbent folds with east–west-trending axes and top-to-the-north ductile shear zones can be observed in a gabbroic pluton and the Neoproterozoic sedimentary host rocks. The available radiometric ages allow us to interpret this event as an Early Triassic back-thrusting related to the final stage of the collision between the North China and South China Blocks. During the LateMesozoic, an extensional event characterized by (1) half-grabens filled by continental terrigeneous red beds and lava flows, (2) low-angle detachment faults, (3) synkinematic granitic plutons, and (4) metamorphic core complexes is widespread in the Eastern Liaoning Peninsula. This extensional D2 event can be subdivided into a ductile deformation and a brittle deformation, corresponding to different expressions of crustal deformation. In every area studied in the Eastern Liaoning Peninsula, the ductile D2 deformation is characterized by a NW–SE-trending stretching lineation with a top-to-the-NWsense of shear.Mica and amphibole fromthe metamorphic country rocks, granodioritic or monzogranitic plutons and their mylonitized margins yield 40Ar/39Ar ages ranging from 130 to 120 Ma. These dates support fast cooling and exhumation rates coeval with the extensional tectonics. The brittle D2 deformation is responsible for the formation of high-angle normal faults marked by low-temperature cataclasites bounding half-grabens. During the Mesozoic, the tectonic regime of Eastern China experienced a significant inversion from compression to extension. The Eastern Liaoning Peninsula massif provides an example of this geodynamic transition.

Domaines: Tectonique; Milieux et Changements globaux

Wei Lin, Michel Faure, Patrick Monié, Qingchen Wang. Polyphase Mesozoic tectonics in the eastern part of the North China Block: insights from the Eastern Liaoning Peninsula massif (NE China). The Geological Society, London, Special Publications, 2007, 280, pp.153-169. ⟨10.1144/SP280.7⟩. ⟨hal-00134055⟩