华北东部早白垩世花岗岩侵位的伸展地球动力学背景：激光^40Ar／^39Ar年代学证据

The extensional geodynamic setting of Early Cretaceous granitic intrusions in the eastern North China Craton:Evidence from laser ablation ^(40)Ar/^(39) Ar dating of K-bearing minerals.

早白垩世古道岭岩体位于华北克拉通东部的辽东半岛,主要由三种岩石组成,分别为庙岭变形闪长岩、万家岭片麻状花岗闪长岩和古道岭中粒二长花岗岩及其所含的细粒镁铁质包体。其中闪长岩和花岗闪长岩具有明显的变形组构,其片麻理方向与围岩万福糜棱岩相同,表明该岩体为同构造岩体。利用单颗粒激光^(40)Ar/^(39)Ar 年代分析方法测定的岩体不同岩相和糜棱岩中单矿物(角闪石、黑云母、钾长石)的^(40)Ar/^(39)Ar 年龄表明,古道岭岩体边缘相和围岩糜棱岩在早白垩世(120～113Ma)共同经历了变形、变质作用,揭示了在早白垩世时期该区的快速冷却(抬升)历史。这一地质事件遍布辽东半岛,乃至华北克拉通东部,并与华北克拉通东部大面积拉伸盆地的形成、大规模金成矿作用、A 型花岗岩的就位和变质核杂岩的形成同期,是华北东部早白垩世克拉通破坏和岩石圈强烈减薄作用的浅部地壳响应。

Early Cretaceous Gudaoling batholith, distributed in the Liaodong Peninsula, eastern North China Craton, is composed by three types of grantoids, deformed diorite at Miaoling, gnessic 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 ^40 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.