Late Mesozoic extensional tectonics of the Liaodong Peninsula massif:Response of crust to continental lithosphere destruction of the North China Craton  

作　　者：LIN Wei WANG QingChen WANG Jun WANG Fei CHU Yang CHEN Ke 

机构地区：[1]State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China [2]Graduate School of Chinese Academy of Sciences, Beijing 100049, China

出　　处：《Science China Earth Sciences》2011年第6期843-857,共15页中国科学（地球科学英文版）

基　　金：supported by the Innovative Project of the Chinese Academy of Sciences (Grant No. KZCX2-YW-Q05-05-03);the National Natural Science Foundation of China (Grants Nos. 90714007,40872142)

摘　　要：Unlike most Precambrian cratons that have thick sub-continental lithospheric roots,the Archean lithosphere beneath the North China Craton is thin (reduced from 200 km to about 80 km),and has been replaced by a geochemically juvenile lithospheric mantle.This is a unique regional geological event,which has attracted worldwide attention.In the North China Block,Late Mesozoic extensional tectonics is evident by low-angle detachment faults,syntectonic plutons bounded by ductile faults,metamorphic core complexes (MCC) and widespread Jurassic to Cretaceous half-grabens filled by continental terrigenous deposits and volcanic rocks.At a regional scale,these structures share the same NW-SE extensional direction,while maintaining their own individual kinematics.In other words,the MCC feature a top-to-the-NW sense of shear,and syntectonic plutons are typified by a top-to-the-SE shearing deformations.Geochronological results indicate that the extensional structures were formed between 130-120 Ma.These extensional events lead to magmatic rock emplacement,distributed at the footwall of the detachment faults.Two different exhumation stages can be identified based on regional structural and magmatic interpretation:a Jurassic slow or negligible exhumation and a Cretaceous fast one assisted by normal faulting.These two cooling stages correspond to distinct geodynamic processes that occurred during the Jurassic and Cretaceous.Extensional tectonics appear to have been insignificant before the Early Cretaceous,and the process may be demonstrated by partial melting of the crust.The second stage,dominated by an extensional regime,developed after ca 120 Ma,and is tentatively correlated with crustal extension caused by lithospheric removal of the North China Craton.Unlike most Precambrian cratons that have thick sub-continental lithospheric roots,the Archean lithosphere beneath the North China Craton is thin （reduced from 200 km to about 80 km）,and has been replaced by a geochemically juvenile lithospheric mantle.This is a unique regional geological event,which has attracted worldwide attention.In the North China Block,Late Mesozoic extensional tectonics is evident by low-angle detachment faults,syntectonic plutons bounded by ductile faults,metamorphic core complexes （MCC） and widespread Jurassic to Cretaceous half-grabens filled by continental terrigenous deposits and volcanic rocks.At a regional scale,these structures share the same NW-SE extensional direction,while maintaining their own individual kinematics.In other words,the MCC feature a top-to-the-NW sense of shear,and syntectonic plutons are typified by a top-to-the-SE shearing deformations.Geochronological results indicate that the extensional structures were formed between 130-120 Ma.These extensional events lead to magmatic rock emplacement,distributed at the footwall of the detachment faults.Two different exhumation stages can be identified based on regional structural and magmatic interpretation：a Jurassic slow or negligible exhumation and a Cretaceous fast one assisted by normal faulting.These two cooling stages correspond to distinct geodynamic processes that occurred during the Jurassic and Cretaceous.Extensional tectonics appear to have been insignificant before the Early Cretaceous,and the process may be demonstrated by partial melting of the crust.The second stage,dominated by an extensional regime,developed after ca 120 Ma,and is tentatively correlated with crustal extension caused by lithospheric removal of the North China Craton.

关 键 词：Liaodong Peninsula massif geometry and kinematics Late Mesozoic extensional tectonics destruction of the North China Craton 

分 类 号：P31[天文地球—固体地球物理学] P542.3[天文地球—地球物理学]