滁州中生代火山岩LA-ICP MS锆石U-Pb年龄及其构造地质学意义  

LA-ICP MS Zircon U-Pb Ages of the Mesozoic Volcanic Rocks from Chuzhou Area and Their Tectonic Significances

作　　者：谢成龙[1] 朱光[1] 牛漫兰[1] 王勇生[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《地质论评》2007年第5期642-655,共14页Geological Review

基　　金：国家自然科学基金资助项目(批准号40672131;40603010)的成果。

摘　　要：详细的LA-ICPMS锆石U-Pb年代学研究表明,位于郯庐断裂（郯城—庐江断裂）带上张八岭隆起东侧边界上的滁州火山岩形成于早白垩世,具体年龄为132～116Ma,岩浆具有多期喷发的特点。该岩浆活动中132Ma的喷发年龄是郯庐断裂带上同期钙碱性岩浆最早出现的时间,代表了该断裂带上岩石圈伸展运动的开始时间。尽管滁州火山岩在构造位置上属于扬子克拉通,但岩浆岩中的古老锆石指示岩浆来源于古老的华北克拉通,这一现象可以用大陆碰撞后楔入模型来解释。该火山岩形成于中国东部岩石圈减薄的动力学背景之下,为岩石圈减薄及壳幔相互作用造成的早白垩世大规模岩浆活动的同期产物。与华北克拉通内部的同期火山岩年代学资料相比,断裂带上火山活动具有相对较早的开始时间和较长的演化历史,表明断裂带内岩石圈具有较克拉通内部强烈的减薄程度和长期的减薄历史,这一特点可能与郯庐断裂带于早白垩世初的大规模左行平移有关。Detailed LA-ICP MS zircon U-Pb geochronological data show that the Mesozoic volcanic rocks from Chuzhou area, which located on the east boundary of the Zhangbaling Uplift, were erupted during the Early Cretaceous, the forming ages varied between 132～116Ma, which show a characteristic of multi-stage eruption in a long period（16Ma）. 132 Ma is the earliest eruption age of the cal-alkaline magma within the Tan-Lu（Tancheng—Lujiang） fault zone, this age should represented the beginning of the lithosphere extensive movement beneath the fault zone. U-Pb dating of the ancient zircon indicate a source of the North China craton though these volcanic rocks were located on the Lower Yangtze block, this case support an interpretation of the crustal detachment model about the suturing of the North China and Yangtze craton. The lava occurred under a dynamic setting of the lithospheric thinning in Eastern China, and these rocks are ascribed to the lithospheric thinning and crust—mantle interaction as well as the large scale contemporary magmatism during the Early Cretaceous. Compared with the geochronology data of the contemporary volcanic rocks from the inner North China craton, the volcanic activity on the Tan-Lu fault zone was earlier and has a comparatively long history. This indicates an intense degree and a long period of the lithospheric thinning within the fault zone compared with inner craton, and this should ascribe to the large scale sinistral strike-slip shear of the Tan-Lu fault zone in the beginning of the Early Cretaceous.

关 键 词：滁州 中生代火山岩 LA-ICP MS 锆石年代学 郯庐断裂(郯城—庐江断裂)带 岩石圈减薄 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]