郯庐断裂带中桃源韧性剪切带剪切温压条件及锆石U-Pb分析  

P-T conditions and zircon U-Pb analysis of the Taoyuan ductile shear zone in Tan-Lu fault zone

作　　者：王微[1] 宋传中[1] 任升莲[1] 李加好[1] 张妍[1] 汪佩佩 胡达[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：《岩石学报》2016年第3期787-803,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41272222;41072161);博士点基金;中国地质调查局科研项目(1212011220243)联合资助

摘　　要：郯庐断裂带西侧的桃源韧性剪切带位于合肥市肥东县浮槎山的东麓,是郯庐断裂带的重要组成部分。左旋平移现象十分经典,走向北北东,垂直于大别造山带展布,带内大量发育高温糜棱岩。综合剪切带内基质的矿物组合、变形机制及电子探针分析结果,本文得出该韧性剪切带的变形温度为550～650℃,压力在0.5GPa左右,属高温中压变质环境,剪切深度大概在20km左右,后期抬升至地表。剪切带内不同岩石分别给出了～0.8Ga、～2.0Ga、～2.5Ga的锆石U-Pb基底年龄。推断0.8Ga和2.0Ga年龄具有华南板块的特征,而2.5Ga年龄岩石兼具有华南和华北板块的属性,仍无法判断其具体来自哪个板块。此外,剪切带内发育的同构造弱变形伟晶岩脉测得年龄为129Ma,指示郯庐断裂带肥东段在129Ma仍在进行左行剪切活动,但剪切强度已大幅衰减。The Taoyuan ductile shear zone is located in the eastern margin of the Fucha mountain in Feidong County. As a part of the Tan-Lu fault belt,it has been suffered sinistral ductile shearing. It is NNE-trending and perpendicular to the Dabie orogenic belt.Recently,the high-temperature mylonites were found in this belt. The mineral assemblages of matrix,deformation mechanism and the electron microprobe analysis together suggest the deformation temperature of the ductile shear zone is 550 ～ 650℃ and the pressure is about 0. 5GPa,which indicates a high-temperature medium-pressure metamorphic environment and equivalent to depth of 20 km,then exhume up to the surface later. In addition,zircon U-Pb ages in mylonites are focused on four groups： ～ 0. 8Ga, ～ 2. 0Ga and～ 2. 5Ga. The ～ 0. 8Ga and ～ 2. 0Ga are characteristic ages of the basement of the South China Plate; while ～ 2. 5Ga zircons maybe come from both the South China Plate and the North China Plate. Meanwhile,a syntectonic pegmatite vein in the ductile shear zone gave a 129 Ma age,which shows that the Tanlu ductile belt was still shearing in this period in Feidong segment,but the strength of the shearing had greatly attenuated.

关 键 词：郯庐断裂带 桃源韧性剪切带 变形环境 锆石U-PB年龄 

分 类 号：P542.3[天文地球—构造地质学] P597.3[天文地球—地质学]