沂沭断裂带早白垩世晚期伸展的低温年代学证据

沂沭断裂带(郯庐断裂带山东段)由4条断裂组成,其西部的两条分别称鄌郚—葛沟断裂和沂水—汤头断裂。横跨这两条断裂及夹持的中生代盆地,分别获得6个磷灰石裂变径迹数据,年龄分布在102~82Ma,封闭径迹长度集中在13.0~14.0μm。数据反演结果显示:隆起区在距今105~100Ma及约距今85Ma时有过两次快速冷却事件;这两条断裂所夹持的断陷区经历过快速沉降,达到最大古地温后,在距今85~60Ma快速抬升。结合区域地质背景资料,以及在沂沭断裂带附近南北向玄武岩脉及北西向断层的断层泥K-Ar年龄数据综合分析,认为沂沭断裂带在早白垩世晚期经历以伸展为主的左行张剪活动。

LOW-TEMPERATURE THERMOCHRONOLOGY EVIDENCE FOR EXTENSIONAL MOVEMENT OF THE YI-SHU FAULT ZONE IN LATE EARLY CRETACEOUS

The Yi-Shu fault zone(the Shandong sector of the Tan-Lu fault zone),could be divided into four faults,and named,in westward order,the Changyi-Dadian(F₁),the Anqiu-Lüxian(F₂),the Yishui-Tangtou(F₃) and the Tangwu-Gegou(F₄) faults.Six age data of apatite fission track(AFT),with samples collected from the profile across the F₃,F₄ and the Mesozoic basin sandwiched in between the both faults in northern part of the Yi-Shu fault zone,scattered from 102 Ma to 82 Ma and confined track length distributed between 13.0 and 14.0 μm.The inverse modeling resulted showed that there were two fast cooling episodes before 105～100 Ma and 85 Ma in uplift zone respectively.The AFT samples in basin underwent fast uplift during 85～60 Ma after it had been reached the deepest depth owing to fast sedimentation.After combining regional geology information and K-Ar age of two samples collected from the N-S-striking basaltic vein and the northwest-striking fault gouge near the Yi-Shu fault zone,the conclusions could be drawn that the Yi-Shu fault zone had been experienced two-stage evolution during Early Cretaceous: sinistral strike-slipping in early Early Cretaceous,and transtensional activation in late Early Cretaceous.Based on it,the related regional evolution in Crataceous was discussed in the paper.