Late Mesozoic metamorphic core complexes: new constraints on lithosphere thinning in North China

摘要

Metamorphic core complexes (mcc's) are among the most prominent structural styles of lithosphere extension and thinning during late Mesozoic in North China. In this paper, the geometrical, kinematic and age characteristics of some of the mcc s, e. g.Liaonan, Waziyu (Yiwuliishan), Yunmengshan, etc., are discussed. Some common characteristics, such as kinematic polarity, geometric asymmetry, occurrence over a time span, scattered and isolated distribution, and progressive development, can provide direct constraints on the regional lithosphere extension and thinning in North China, which does not favor the prevailing plume model, a general de-lamination model or extensional collapse of overthickened orogenic crust. We argue that several aspects, suchas the kinematic polarity at depths during lithosphere extension, gradual break-up of lithosphere plate, relationship between magmatism and regional extension, and coeval activity of mcc's and Tan Lu fault, should be taken into consideration when constructing a more reasonable model for lithosphere extension and thinning in North China.