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.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
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
