The extensional geodynamic setting of Early Cretaceous granitic intrusions in the Eastern North China Craton: Evidence front laser ablation Ar-40/Ar-39 dating of K-bearing minerals

Abstract

Early Cretaceous Gudaoling batholith,distributed in the Liaodong Peninsula,eastern North China Craton,is composed by three types of grantoids,deformed diorite at Miaoling,gnessie granodiorite at Wanjialing,medium-grained monzogranite and enclave at Gudaoling.The diorite and granodiorites have evidently gnessis structures,indicating that they had experienced ductile deformation. The directions of foliations and lineations are accordant with those of host mylonites at the lower plate of a normal fault,suggesting that the Gudaoling batholith is a syn-tectonic intrusion.Laser ablation ~(4o)Ar/~(39)Ar dating of K-bearing minerals (hornblende,biotite and K- feldspar) from each type of granitoid and mylonites gives a result that Gudaoling batholith and its host mylonites had experienced a deformation and metamorphism event during Early Cretaceous (120～113 Ma),showing a rapid cooling and exhumation history. This event in the Liaodong Peninsula,as well as east North China Craton are consistent with the timing of formation of pull-apart basins and metamorphic core complexes,large-scale gold mineralization and A-type granitic intrusions in the eastern North China Craton, which are shallow crustal response of destruction and lithospheric removal of east North China Craton.