大别造山带岳西地区岩脉群锆石定年及意义  

ZIRCON AGE DATING FOR DIKES IN THE YUEXI AREA OF DABIE OROGEN AND ITS SIGNIFICANCE

作　　者：张媛媛[1] 闫峻[1] 刘晓强[1] 陈永康[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009

出　　处：《矿物岩石》2017年第1期49-56,共8页Mineralogy and Petrology

基　　金：国家重点研发计划(编号:2016YFC0600404)

摘　　要：大别造山带岳西地区分布有大量NNE走向的岩脉,其岩石类型多样,包括石英正长斑岩、花岗斑岩、石英闪长岩以及辉绿岩等。区内广泛发育中生代岩浆岩,以中酸性为主,伴有少量的基性岩。岩脉切穿区内广泛发育的岩浆岩,为燕山期岩浆活动最晚的产物。通过锆石LA-ICPMS定年方法得到石英正长斑岩、石英闪长岩和花岗斑岩3种类型的三件岩脉样品的年龄分别为127.1 Ma±4.5 Ma,127.5 Ma±1.9 Ma和127.4 Ma±2.5 Ma,这些岩脉的形成时代较为集中,其形成时代为早白垩世,代表了岳西地区中生代岩浆活动幕的结束。岳西地区岩脉群是郯庐断裂带左行走滑动力学体制下,岩浆沿剪张裂隙侵入形成,岩脉的形成时代指示郯庐断裂带南段中生代第三次左行走滑可能发生在127 Ma左右。NNE-striking dike swarm is widespread in Yuexi area of the Dabie orogen and these dikes consist of different rock types, including quartz-syenite porphyry, granite porphyry, quartzdiorite and diabase. It shows that the dikes cut through the Yanshanian intrusive bodies,indicating that the dikes formed in the latest stage of Yanshanian magmatic activity. LA-ICPMS zircon U-Pb dating yields weighted mean ages of 127.1 Ma±4. 5 Ma, 127.5 Ma±1.9 Ma and 127.4 Ma±2.5 Ma for the quartz-syenite porphyry, quartz-diorite and granite porphyry, respectively. Therefore, these dikes are generated during a short time span and formed in the early Cretaceous, represen- ting the termination of Mesozoic magmatism in this region. Owing to the sinistral strike-- slip movement of the Tan-Lu fault zone,the dike swarm in Yuexi area intruded along the shear--tensile cracks. The ages of these dikes indicate that the third sinistral strike-slip movement of the TLFZ might take place around 127 Ma.

关 键 词：岩脉 锆石U-PB年龄 岳西 大别造山带 郯庐断裂带 

分 类 号：P597.3[天文地球—地球化学]